{{PAGE_1}} LEVEL III · BIOMECHANICS

Unit B

Space Management in Preadolescent Children · Crossbites and Vertical Problems in Children · Concepts of Adjunctive Orthodontic Treatment · Adjunctive Orthodontic Treatment Procedures

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Space Management in Preadolescent Children
Crossbites and Vertical Problems in Children
Concepts of Adjunctive Orthodontic Treatment
Adjunctive Orthodontic Treatment Procedures

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1. Space Management in Preadolescent Children

Mixed Dentition Analysis Review

The most readily identifiable orthodontic problem in the early mixed dentition is dental crowding. Parents initially become concerned when the larger permanent incisors replace nicely aligned and spaced primary incisors in the early mixed dentition and crowding/malalignment is obvious. Parents want to know how this will impact the long-term alignment of the permanent teeth and usually seek advice from their family dentist initially. Family dentists should be able to:

Provide an answer based on their knowledge of dental development,
Perform a mixed dentition space analysis,
Interpret the results of the analysis, and
Suggest appropriate interventions.

The normal condition in the primary dentition is interdental spacing of the primary incisors (image 1). The primate spaces between the lateral incisors and canines in the maxillary arch, and between the canines and first molars in the mandibular arch of the primary dentition, provide space that is important in allowing alignment of the larger permanent incisors (image 2). As a general rule, children who present with crowded primary incisors will have major crowding problems in the permanent dentition (image 3). Spacing in the primary dentition is the norm. Perfectly aligned primary teeth with no spacing or crowded teeth are not normal.

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{{PAGE_4}} Image 1, Spacing of the primary incisors: Interdental spacing of the primary incisors, as in this child, is normal.

Image 2, Primate spaces in the primary dentition: The crowns of the developing permanent incisors lie lingual to crowns of the primary incisors.

Image 3, Crowding of the primary incisors: This child has significant crowding of the primary dentition, which is indicative of significant future crowding in the permanent dentition.

Mixed Dentition Transition

During the early mixed dentition the larger permanent incisors replace the smaller primary incisors, and the majority of children develop some degree of incisor crowding.

Graphs from Moorrees and Chadha (Angle Orthodontist 35, 1965) illustrate the amount of average crowding or spacing present in the incisor segments for males and females during the transition from the primary dentition to the early mixed dentition (Images 1-5). In each of these graphs, M represents the eruption of the permanent molar; I1 and I2 represent the eruption of the central and lateral incisor, and C the eruption of the permanent canine.

Prior to the eruption of the first permanent molars there is an average of about 2 mm of spacing in the maxillary incisor segment (images 1 and 2) and about 1 mm of spacing in the mandibular incisor segment (images 3 and 4). As the first permanent molars erupt, they drift forward, closing some of the interdental spacing found in the primary dentition. This is called the early mesial shift.

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{{PAGE_5}} As the larger permanent incisors erupt and replace the primary incisors, additional crowding occurs. In the maxillary arch, males (image 1) tend to have no incisor crowding, while most females (image 2) develop minor incisor crowding (<1 mm) when the permanent incisors erupt. In the mandibular arch both males (image 3) and females (image 4) appear to develop 2 mm of incisor crowding with the eruption of the lateral incisors. In all four cases, once the primary canines exfoliate this initial incisor crowding resolves.

Some parents may become quite concerned when the nicely aligned and spaced primary incisors are replaced by crowded and irregular permanent incisors in the early mixed dentition. This information can be used to reassure parents that some degree of initial crowding is quite normal in the early mixed dentition (image 5).

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{{PAGE_7}} Dental crowding is a function of two things: (1) the size of the teeth, and (2) the size of the dental arch supporting the teeth. Many parents are mystified when orthodontists or dentists suggest that extraction of teeth is required in young children who have not started their pubertal growth spurt and have a lot of growth potential remaining. Dentists must have a basic understanding of the growth and development of the dental arches to answer these concerns.

One can graphically summarize the dimensional changes in the maxillary and mandibular dental arches from ages 6-18 years. In the maxillary arch (image 1) there is a slight decrease in arch length and a slight increase in arch circumference (+1 mm). The maxillary incisors erupt into a more facial position, which increases arch length, but the loss of leeway space also reduces arch length. In the mandibular arch (image 2) there is a reduction in both arch length (-1 mm) and arch circumference (-4 mm) with a slight increase in canine and molar width. The mandibular incisors tend to upright over this period of time, which supplements effects due to the loss of leeway space.

In patients with moderate and more severe crowding, these average growth changes in the dental arches are insufficient to accommodate the larger teeth in both arches (image 3).

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{{PAGE_8}} Image 1, Growth changes in the maxillary arch.: Growth changes in the maxillary arch between 6-18 years of age.

Image 2, Growth changes in the mandibular arch.: Growth changes in the mandibular arch between 6-18 years of age.

Image 3, Comparison of maxillary & mandibular arch changes: Comparison of growth changes in the dental arches between 6-18 years of age.

Space Analysis Assumptions

In the early mixed dentition, we know that incisor crowding is very common, especially in the lower arch, and that future growth of the dental arches will most likely not accommodate a significant amount of dental crowding. The Mixed Dentition Space Analysis gives dentists some ability to predict future dental crowding (image 1).

As you recall from earlier courses, mixed dentition space analysis has a number of underlying assumptions:

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there is a reasonably good correlation between the size of the erupted mandibular incisors and the permanent canines and premolars
prediction tables are valid for your patient’s sex and ethnicity
all succedaneous teeth are present and developing normally
arch dimensions do not change appreciably during growth
molar position is stable.

Think about these assumptions before you begin the space analysis—for some patients all the assumptions are not correct, and you’ll have to take that into account as you interpret the results.

UNIVERSITY OF NORTH CAROLINA AT CHAPEL HILL SCHOOL OF DENTISTRY
SPACE ANALYSIS FORM
Patient's Name:			Date:
SECTION 1	AVAILABLE MANDIBULAR SPACE				SECTION 5	MANDIBULAR SPACE ANALYSIS
	Arch Segment Lengths	a:	______ mm	a. TOTAL SPACE AVAILABLE (from Section 1)	_______________________
	b:	______ mm	b. SUM OF MAND. INCISOR WIDTHS (from Section 2)	_______________________
	c:	______ mm	c. SUM OF LEFT CANINE & PREMOLARS (estimated below from mand. incisors)	_______________________
	d:	______ mm	d. SUM OF RIGHT CANINE & PREMOLARS (estimated below from mand. incisors)	_______________________
	TOTAL:	______ mm	e. TOTAL SPACE REQUIRED (b+c+d)	_______________________
		f. DISCREPANCY (a-e)	_______________________
SECTION 2	MANDIBULAR INCISOR WIDTH				SECTION 6	MAXILLARY SPACE ANALYSIS
#23 ______ mm		a. TOTAL SPACE AVAILABLE (from Section 1)	_______________________
#24 ______ mm		b. SUM OF MAX. INCISOR WIDTHS (from Section 4)	_______________________
#25 ______ mm		c. SUM OF RIGHT CANINE & PREMOLARS (estimated below from max. incisors)	_______________________
#26 ______ mm		d. SUM OF LEFT CANINE & PREMOLARS (estimated below from max. incisors)	_______________________
TOTAL:	______ mm	e. TOTAL SPACE REQUIRED (b+c+d)	_______________________
		f. DISCREPANCY (a-e)	_______________________
SECTION 3	AVAILABLE MAXILLARY SPACE				SECTION 7	SKELETAL JAW RELATIONSHIP
	Arch Segment Lengths	e:	______ mm	□ CLASS I □ CLASS II □ CLASS III
	f:	______ mm
	g:	______ mm
	h:	______ mm
	TOTAL:	______ mm
SECTION 4	MAXILLARY INCISOR WIDTH				SECTION 8	OCCCLUSION OF PERMANENT FIRST MOLARS
#7 ______ mm		RIGHT SIDE □ END-TO-END □ LEFT SIDE
#8 ______ mm		ANGLE CLASS I □ ANGLE CLASS II □ ANGLE CLASS III
#9 ______ mm
#10 ______ mm
TOTAL:	______ mm
						SECTION 9	MOLAR SHIFT (From end-to-end to Class I)
For Skeletal Class I only FIGHT SIDE + LEFT SIDE = TOTAL SHIFT ______ mm + ______ mm = ______ mm
						SECTION 10	LIP POSTURE (from Facial Profile Analysis)
ACCEPTABLE □ PROTRUSIVE □ RETRUSIVE
MANDIBULAR INCISOR POSITION (from Facial Profile Analysis and casts) ACCEPTABLE □ PROTRUSIVE □ RETRUSIVE
						INTERPRETATION OF NUMERICAL RESULTS (based on observations in Section 7 – 10)
To estimate the size of the unerupted canine and premolars in each quadrant (method of Tanaka and Johnston, J Am Dent Assoc 88:788, 1974): Mandibular quadrant: ½ the sum of the widths of the mandibular incisors, plus 16.5 mm. [ENTER ON LINE 5c and 5d ABOVE] Maxillary quadrant: ½ the sum of the widths of the mandibular incisors, plus 11.6 mm. [ENTER ON LINE 8a and 8d ABOVE]

Size of Unerupted Permanent Teeth

The UNC Space Analysis Form uses the Tanaka and Johnston space analysis procedure to predict the mesio-distal width of the unerupted canines and premolars. No radiographs or prediction tables are required to perform this analysis, an advantage over in other analyses. Upper and lower dental casts with erupted permanent incisors and a measuring device (i.e., Boley gauge) are all that are needed.

The first step in the Tanaka and Johnston space analysis is the measurement of the erupted lower incisors using a Boley gauge or dividers (image 1). The mixed dentition analysis (MDA) assumes that there is a correlation between the width of the lower incisors and unerupted canines and premolars in both arches.

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{{PAGE_10}} The width of the unerupted permanent canine and premolars in each buccal segment is determined by the following simple calculation:

Mandible: half the sum of the widths of the mandibular incisors + 10.5 mm Maxilla: half the sum of the widths of the mandibular incisors + 11.0 mm

The key assumption, of course, is that there is a good correlation between the size of the mandibular incisors and the unerupted canines and premolars. If there is an obvious discrepancy between the size of the mandibular centrals and laterals, as sometimes occurs, that would produce an over-estimate of the size of the unerupted teeth.

SECTION 2 MANDIBULAR INCISOR WIDTH #23: ______ mm #24: ______ mm #25: ______ mm #26: ______ mm TOTAL: ______ mm

Available vs. Required Space

The space available in the dental arch is determined by measuring the arch segments between the mesial surfaces of both first permanent molars (image 1). One must estimate an ideal dental arch where the teeth are arranged in a stable position in the alveolar bone. Using a Boley gauge or dividers, the arch segments are as follows:

Mesial of first permanent molar to mesial of primary canine
Mesial of primary canine to the mesial of the permanent central
Mesial of permanent central to mesial of primary canine
Mesial of primary canine to mesial of first permanent molar.

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{{PAGE_11}} The space required to accommodate the permanent teeth is determined in each arch by adding together:

The sum of the incisor widths (image 2)
The predicted widths of the unerupted left canine and premolars
The predicted widths of the unerupted right canine and premolars

Space discrepancy (crowding or spacing) is calculated in the mandibular arch (image 3) and the maxillary arch (image 4) by: Discrepancy = Total Space Available – Total Space Required

Image 1, Space Available in the maxillary and mandibular arch: The space available in the dental arch is determined.

Image 2, Incisor width in the maxillary and mandibular arch: The width of the four incisors in the maxillary and mandibular arches is recorded.

Image 3, Mandibular Space Analysis: The discrepancy (crowding or spacing) in the mandibular arch is calculated.

Image 4, Maxillary Space Analysis: The discrepancy (crowding or spacing) in the maxillary arch is calculated.

Considerations in Interpreting Results

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{{PAGE_12}} The endpoint of the analysis is a number for each arch that may be either positive (spacing) or negative (crowding). As you learned previously, these numbers have very limited significance when viewed alone. The practitioner must now refocus on other relationships to interpret the results for each individual patient. These relationships are included in sections 7-10 of the UNC Space Analysis Form (image 1) and include:

Lip posture
Lip competence
Incisor position
Skeletal jaw relationship
Future molar shift (leeway space)
Occlusal relationship of the 1st permanent molars

The facial profile analysis (image 2) is used to assess skeletal jaw relationship and lip posture. These relationships are used in sections 7 to 10 of the space analysis to interpret the results of the space analysis.

The results of the profile analysis are crucial in assessing crowding and incisor position. Protrusive lips, significant lip incompetence (>4 mm) and proclined incisors indicate dental crowding even if the teeth are aligned on the dental arches. These patients usually require extraction of permanent teeth to position the lips in acceptable positions, reduce lip incompetence, and upright the incisors in the alveolar bone. The profile view on the right shows lip and mentalis strain, while the view on the left shows lip incompetence (image 3). These relationships must be considered alongside the space analysis numbers.

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{{PAGE_13}} SECTION 7 SKELETAL JAW RELATIONSHIP (from Facial Profile Analysis) ☐ CLASS I: ☐ CLASS II: ☐ CLASS III

SECTION 8 OCCLUSION OF PERMANENT FIRST MOLARS RIGHT SIDE ☐ ANGLE CLASS I ☐ LEFT SIDE ☐ END-TO-END ☐ ☐ ANGLE CLASS II ☐ ☐ ANGLE CLASS III ☐

SECTION 9 MOLAR SHIFT (From end-to-end to Class I) For Skeletal Class I only RIGHT SIDE + LEFT SIDE = TOTAL SHIFT ___ mm + ___ mm = ___ mm TOTAL

SECTION 10 LIP POSTURE (from Facial Profile Analysis) ☐ ACCEPTABLE: ☐ PROTRUSIVE: ☐ RETRUSIVE MANDIBULAR INCISOR POSITION (from Facial Profile Analysis and casts) ☐ ACCEPTABLE: ☐ PROTRUSIVE: ☐ RETRUSIVE

Image 1, Interpretation of Numerical Results: Sections 7-10 of the UNC Space Analysis.

UNIVERSITY OF NORTH CAROLINA AT CHAPEL HILL SCHOOL OF DENTISTRY

FACIAL PROFILE ANALYSIS Draw the patient’s profile. Mark the position of each profile point relative to the imaginary vertical reference line, which is perpendicular to the visual axis or Frankfort plane, then connect your points to complete the profile drawing. For the drawing, the patient should be in, or very near, the terminal hinge position.

Frankfort Plane Porion (External Auditory Canal) Orbitale (Lower Rim of Orbit) Bridge of nose

Profile Points: Bridge of nose Tip of nose Base of upper lip Prominence of upper lip Upper-lower lip junction Prominence of lower lip Base of lower lip Soft tissue chin

What molar relationship is suggested by the profile? ________________ Is the Mandibular plane steep, moderate, or low in relation to the Frankfort plane? ________________ Summarize the lip posture. ________________ Summarize the skeletal jaw relationship in the antero-posterior and vertical planes. ________________

Image 2, UNC Facial Profile Analysis: The UNC Facial Profile Analysis assesses skeletal jaw relationship and lip posture.

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{{PAGE_14}} due to protrusive incisors.

Interpretation of Results

Now that you have completed a mixed dentition analysis and determined the amount of predicted crowding or spacing for a patient, how do you interpret the numbers and use the information in planning treatment?

When classifying generalized crowding (where the discrepancy numbers would be negative) the following clinical descriptions can be used:

0-2 mm/arch: mild crowding
2-4 mm/arch: moderate crowding
4 mm/arch: severe crowding
10 mm/arch: very severe crowding

The type of intervention depends on:

Amount of crowding (mild, moderate, or severe)
Location of crowding (localized or generalized)

Important questions should be considered:

Was there initially sufficient space, and loss of a primary tooth resulted in localized crowding?
Will a primary tooth have to be extracted, and will intervention to prevent space loss be required?
In mild cases of crowding, can the leeway space be used to align the teeth?

Types of Treatment for Space Problems

To effectively diagnose and treat space problems in the mixed dentition, dentists must be familiar with four terms:

Space maintenance
Space regaining
Space management
Serial extraction

The definition of each of these terms is based on the results of the mixed dentition analysis. The degree and location of crowding will determine which of the above strategies is employed in the mixed dentition.

The first three techniques are suggested for children in the mixed dentition with mild crowding, and serial extraction is suggested for children with severe crowding who will receive later treatment with a fixed orthodontic appliance. Using these techniques during the mixed dentition may simplify future

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{{PAGE_15}} comprehensive orthodontic treatment in the permanent dentition. Each one of these terms will be explained in separate sections of this module to help clarify the differences.

Children with more severe generalized crowding in the mixed dentition will need comprehensive fixed orthodontic treatment, involving arch expansion or extraction of permanent teeth, and may be best treated by an orthodontist.

Space Maintenance

In a patient with adequate space for the permanent teeth, space maintenance is the intervention used to prevent loss of space after extraction of a primary first or second molar. Once a primary molar is extracted, mesial drift and distal tipping of adjacent teeth will occur, reducing the space available for eruption of the underlying permanent premolars.

A number of factors must be evaluated prior to the initiation of space maintenance:

Space analysis should confirm that there is adequate space available.
When was the primary molar extracted? Space loss almost always starts immediately after the loss of a primary molar. If the tooth was lost more than 3 months previously, space loss probably has occurred, and then space regaining will be required rather than space maintenance.
When will the underlying permanent tooth erupt? If the permanent tooth will require more than 6 months to erupt, space maintenance will be required. Eruption charts give average values for the general population; one must remember that individual variation exists (image 1). Dental age as determined by assessing the general eruption schedule and root development (image 2) is more informative than chronological age. A permanent tooth normally erupts when 2/3 to 3/4 of root development is complete, and in general, a permanent tooth takes about 1 month to erupt through 1 mm of overlying bone. Extraction of primary teeth can also either accelerate or slow the eruption of underlying permanent teeth depending on root development.
Is there a permanent successor tooth present (image 3)? If not, long-term maintenance of the space for eventual prosthetic replacement may or may not be the best plan. This must be weighed against the possibility of closing the space orthodontically or forgoing space maintenance and allowing the permanent teeth to drift into the extraction site to close the space.

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{{PAGE_16}} Tooth eruption and development chart. Image 2, Incomplete root development: Eruption usually occurs when the root is 2/3rds to 3/4th complete. These erupting central incisors are at that stage. Image 3, Congenitally missing second premolar: Note that despite the congenitally missing 2nd premolar is missing, resorption of the mesial root of this 2nd primary molar has already begun. Removable vs. Fixed Space Maintainers A number of different types of space maintainers can be used after the loss of primary teeth. Generally the appliances can be classified as: Fixed (cannot easily be removed by the patient or adjusted in the mouth) (image 1) Removable (can be removed by the practitioner for minor adjustments or can be removed by the patient to allow easier access for oral hygiene)(image 2) With any type of appliance, adequate follow-up is crucial. Space maintainers are not an “insert it and forget it” type of treatment. All patients must be on a regular recall schedule and have adequate oral hygiene to ensure success. Patients with space maintainers are instructed to avoid hard, sticky, and chewy foods to decrease the chance of damage and loosening of appliances. Fixed appliances reduce the chance of failure, but

{{PAGE_17}} some children do not follow these suggestions very well and damage even the best-designed fixed space maintainers.

The adaptation of orthodontic bands on primary teeth, especially first primary molars, can be difficult. This reduces the effectiveness of fixed banded appliances on these teeth. But this is even more of a problem with removable appliances, since primary teeth do not have a pronounced height of contour that can be used to engage retentive elements such as wire clasps.

In general, fixed space maintainers are more effective in children than removable space maintainers.

Image 1, Fixed space maintainers: Crown-and-loop and band-and-loop appliances are examples of fixed space maintainers.

Image 2, Removable space maintainers: A removable appliance is an alternative design for bilateral space maintenance.

Fixed Space Maintainers

Fixed space maintainers require minimal cooperation by the patient (beyond not deliberately breaking them), and usually are preferred for that reason. There are several types:

Loss of a single tooth. Band and loop space maintainers are most commonly used after the extraction of a single primary first molar in the primary or mixed dentition (image 1). Bilateral band and loop space maintainers are indicated if both first primary molars are lost in an arch prior to the eruption of the permanent incisors. A variation of this appliance is the crown and loop space maintainer (image 2).
Loss of multiple teeth. If multiple primary teeth are lost and both the permanent incisors and first permanent molars have erupted, a lingual arch contacting the incisors (mandible) (image 3) or a lingual arch with a palatal button that does not contact the incisors (Nance appliance, maxilla) (image 4) can be used to prevent posterior space loss. Both appliances require the use of cemented orthodontic bands to attach the appliance to the 1st permanent molars. Variations of both appliances can be made to be removable by the use of special lingual attachments on the molars. The appliances can also include adjustment loops that can be activated to procline the incisors and tip the molars distally.

Lower lingual arches are contraindicated prior to the eruption of the permanent mandibular incisors. Remember, the permanent lower incisors tend to erupt lingual to the primary incisors. A lingual arch

{{PAGE_18}} that is contoured to the lingual surfaces of the primary teeth can impede the eruption of the permanent teeth (image 5).

Distal Shoe Maintainers

A distal shoe space maintainer is used in the primary dentition or early permanent dentition after the extraction of a 2nd primary molar before the 1st permanent molar has erupted (image 1). The goal is to prevent the first molar from drifting mesially as it erupts, which is likely to occur. If at all possible, the 2nd primary molar should be maintained through endodontic intervention (i.e., pulpectomy) even if the prognosis is guarded, because the intact tooth is a much better space maintainer than a distal shoe appliance.

Radiographs are used to construct the appliance, which uses a blade to engage the mesial surface of the 1st permanent molar to guide its eruption (Image 2). As the erupting permanent molar engages the blade, it is guided into the correct position in the arch. Distal shoe space maintainers can fail to

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{{PAGE_19}} guide the eruption of the first permanent molar. In this radiograph (image 3) the molar has drifted forward underneath the blade of the space maintainer and become positioned underneath the wire loop. The space maintainer must be removed and the tooth allowed to erupt into the mouth. Space regaining may then be used to reposition the tooth distally into a normal position.

Image 1, Distal shoe space maintainer: A distal shoe space maintainer designed to guide the eruption of the first permanent molar.

Image 2, Radiograph of a distal shoe space maintainer: Radiograph of a successful distal shoe space maintainer.

Image 3, Failure of distal shoe space maintainer: Failure of a distal shoe space maintainer. The appliance must be removed to allow the molar to erupt, and then it will be necessary to move it distally to re-open space for the 2nd premolar.

Removable Space Maintainers

The major indication for use of removable acrylic partial denture space maintainers is when multiple primary molars have been lost (image 1). In these cases, long spans of wire make band and loop space maintainers impractical, and unerupted or partially erupted permanent incisors make the use of a lingual arch problematic. Clasps are used to retain the appliances, and acrylic can be placed into the extraction sites to prevent tooth movement.

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{{PAGE_20}} The appliances allow ready access for oral hygiene in patients with a high caries rate. Compliance with wearing the appliance can then become an issue. If the appliance is not worn all the time, space loss will occur.

Flowchart for Space Maintenance Types

A structured sequence helps in the decision-making process when planning space maintenance in the primary and mixed dentitions, and a flow chart is the best way to understand the sequence.

The first part of the flow chart (image 1) deals with treatment options for loss of a single primary molar. The next part (image 2) shows the treatment options when there is loss of multiple primary molars, the first permanent molars are erupted, and the permanent incisors are not erupted. The last section of the flow chart illustrates treatment options when there is loss of multiple posterior permanent teeth and the first permanent molars and incisors are erupted (image 3).

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Space Regaining

Localized Space Loss

If space maintenance is not instituted after extraction of a primary tooth, space loss will occur during the next few months. Repositioning the teeth to regain space, not just space maintenance, is required to stabilize the situation. Up to 3 mm of space can be reestablished in a localized area with relatively simple appliances. Localized space loss greater than 3 mm constitutes a severe problem and is more difficult to manage.

In this case (image 1) localized space loss of about 3 mm has occurred in the maxillary arch after the premature loss of the upper left second primary molar. The first permanent molar has drifted forward into the extraction space and rotated mesio-lingually as it erupted. A removable acrylic appliance (image 2) was used to regain the space by distalizing the permanent molar with a wire spring that contacted the tooth on the mesio-buccal corner, to both distalize and de-rotate it. The space for the second primary molar was regained (image 3), and a fixed space maintainer (image 4) was placed to maintain the regained space. Space maintenance always is required after space has been regained, otherwise it will be quickly lost again. The sequence of steps in this space regaining treatment are shown together in image 5.

{{PAGE_23}} Image 1: Maxillary left 1st molar has drifted mesially after early loss of 2nd primary molar. Image 2: Removable space regaining appliance with a finger spring to move the molar distally. Image 3: Space has been opened with 3 months wear of the regaining appliance. Image 4: Band and loop space maintainer in place. Image 5: The sequence of space regaining

Appliances for Maxillary Space Regaining

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{{PAGE_24}} Image 1 illustrates an example of a simple single-tooth space regaining appliance that resembles a band and loop space maintainer. There are two coil springs on the wire loop, which is free to slide through the tubes attached to the orthodontic band. The springs are compressed when the appliances is cemented and apply a force to push the teeth apart.

Space regaining is easier in the maxillary than the mandibular arch, and removable appliances can be designed to utilize springs (image 2) or expansion screws (image 3) to reposition the teeth. At the same time these forces tend to dislodge the appliance, stressing the retention elements, which limits the amount of force that can be applied to the teeth. Removable appliances generally are designed to apply forces to a single point on a tooth surface resulting in tipping of the tooth and de-rotation if desired. As a majority of space loss manifests itself as tipping and rotation, these types of forces can be used with removable appliances to reposition teeth to their normal position.

If an expansion screw is used to regain space, the screw should be activated slowly (1/4 turn 2-3 times per week). When the screw is activated too quickly, the teeth will not move at the same rate as the screw is activated and the appliance may not seat correctly.

Extraoral forces can be applied to maxillary molars through the use of headgear. Unilateral space loss in the maxillary arch can be treated using an asymmetric headgear (image 4) in which the outer bow of the headgear on the side with space loss is longer than the unaffected side. A cervical pull neck strap is used along with the asymmetric outer bow to distalize the first permanent molar and upright the molar at the same time if mesial tipping is present, and the inner bow can be used for de-rotation.

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{{PAGE_25}} Image 1: Simple single tooth space regaining appliance. Image 2: Space regaining appliances with various wire spring designs. Image 3: Space regaining appliances with expansion screws, which must be activated very slowly. Image 4: An asymmetric cervical pull headgear to regain maxillary space unilaterally.

Mandibular Space Regaining

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{{PAGE_26}} In the mandibular arch, removable space regaining appliances are less efficient due to frequent problems with irritation of the lingual tissues, breakage, and lack of retention (image 1). They are recommended infrequently because poor compliance becomes a major problem.

More effective appliances in the mandibular arch are:

Active lingual arch
Lip bumper

A passive lingual arch is the best choice for space maintenance in the mandibular arch when multiple posterior teeth have been lost and the first molars have erupted. Lingual arches can also be designed to actively apply a distal force to the molars and procline the incisors, thus regaining space bilaterally in the mandibular arch. Adjustable loops of wire, fabricated into the posterior sections of the lingual arch, can be opened to expand the length of the lingual arch (image 2). Since lingual arches are usually constructed of heavy round steel wire that fits into lingual sheaths on the molar bands, large single activations generate excessive large forces. The loops must be opened only a little at the time, and this is done by the dentist after removing the lingual arch. It fits tightly enough that the patient cannot remove it.

A lip bumper (image 3) is attached to the lower first molars. It can be soldered or welded to the molar bands, or can be made to fit into tubes on the orthodontic bands (so the patient can remove it for meals and tooth brushing—which of course introduces compliance issues). The anterior portion of this heavy wire is coated with acrylic and is positioned off the labial surface of the teeth so it actively stretches the lower lip away from the teeth. The lip in turn puts force on the wire and the wire transfers the force to the molar teeth.

Both the active lower lingual arch and the lip bumper regain space by tipping the mandibular molars distally while proclining the incisors. With a lip bumper, even though the device does not touch the incisors, tongue forces procline the incisors when it eliminates lip pressure against them.

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{{PAGE_27}} Image 1: Removable mandibular space regaining appliance. Image 2: An adjustable lingual arch can be used for mandibular space regaining. Image 3: A lip bumper with an anterior acrylic shield.

Space Management

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{{PAGE_28}} In patients with generalized rather than localized crowding predicted to be less than 4 mm, space management uses leeway space to align the teeth. The mixed dentition space analysis shows the amount of crowding that could be alleviated if mesial shifting of the permanent molars were prevented.

Leeway space (image 1) is the difference in the mesial-distal widths of the teeth in the primary buccal segments (canine, first molar, and second molar) and the permanent buccal segments (canine, first premolar, and second premolar). The late mesial shift occurs with the exfoliation of the primary second molars around 11-12 years of age. Since the primary molars are larger than the premolars that replace them, the permanent first molars can move mesially with the loss of the primary second molars. In the majority of cases the leeway space is larger in the lower arch than the upper arch, which allows the lower molar to shift further anteriorly than the upper molar and establish a Class I occlusal relationship.

On average the leeway space per arch is:

Maxillary arch = 0.9 mm/quadrant
Mandibular arch = 1.8 mm/quadrant

These are average values, and there may be significant variations among individual patients. If leeway space is maintained, however, the average patient has nearly 4 mm of space in the mandibular arch that can be used for the relief of incisor crowding.

Treatment Steps in Space Management

In space management, prior to loss of the primary second molars a lingual arch is placed to prevent the late mesial shift (the mesial drifting of the permanent molars following exfoliation of the primary teeth). The lingual arch can also be activated slightly to tip the molars distally and the incisors facially, slightly expanding the arches to gain additional space. Image 1 shows a series of slides depicting space management in the late mixed dentition. Initially there is a mild amount of incisor crowding (image 1). A lingual arch is placed and the second primary molars are disked to increase the space available (image 2), which facilitates eruption of the first preolars and alignment of the anterior teeth. Once the premolars have erupted (image 3), the lingual arch can be removed and the incisors are relatively well aligned (image 4).

Disking primary canines as well as primary molars can also be used to provide space for alignment of the permanent teeth. A one-sided end-cutting diamond disk can be used to reduce the width of the primary canines and create sufficient space to allow the permanent incisors to realign in the early mixed dentition when a mild amount of crowding is present (image 5).

The mandibular leeway space allows the lower first permanent molars to shift mesially into a Class I molar relationship. If a lower lingual arch is placed to utilize the leeway space to align the permanent mandibular teeth, a Class I molar relationship may not result. In cases where a lower lingual arch is used for space management, headgear or other appliances may be required to distalize the maxillary molars to establish a Class I molar relationship.

{{PAGE_30}} Image 1: Moderate crowding in late mixed dentition child, with a small space discrepancy if mesial shift of the first permanent molars is prevented. Image 2: The incisors have been tipped facially with the lingual arch, and the mesial of the primary second molars have been disked to provide space. Image 3: After eruption of all the succedaneous teeth, the lingual arch can be removed. Image 4: The mandibular teeth now are in reasonable alignment.

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Early Loss of Primary Canines

A common sign of severe crowding in the early mixed dentition is early unilateral loss of a mandibular primary canine, which results in a shift of the dental midline (image 1). Initially there is inadequate space for the eruption of the permanent mandibular lateral incisor. As the incisor erupts it causes extensive resorption of the mesial surface of the primary mandibular canine, which causes increased mobility and early loss of the tooth. After the canine is lost unilaterally, the incisors are free to shift toward the side where the canine was lost.

In these cases it is best to extract the contralateral primary canine and place a lingual arch. This prevents the incisors from moving lingually and allows self-correction of the midline shift, which can occur if the incisors have not drifted too far laterally. A partial fixed appliance may be used to actively create space and correct the midline shift. A lower lingual arch can be used to maintain the leeway space in the mandibular arch while a fixed orthodontic appliance (first molar bands, bonded brackets on incisors—often called a 2x4 appliance) is used to align the mandibular incisors and correct the midline shift. The 2x4 appliance along with the LLA can be activated to create arch length by advancing the incisors and distally tipping the lower molars (image 2).

In the maxillary arch, early unilateral loss of a primary canine also is an indication for extraction of the contralateral one, but placement of a lingual arch to hold space usually is unnecessary.

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{{PAGE_32}} Image 1, Early unilateral loss of a mandibular primary canine: Early unilateral loss of a mandibular primary canine with a shift of the midline.

Image 2, Lingual arch and 2x4 appliance: A lower lingual arch and fixed 2x4 appliance used to align mandibular incisors.

Crowding >4 mm.

Patients with >4 mm of crowding/arch will require more extensive treatment and may best be referred to an orthodontist.

The critical treatment decision in these patients is whether to expand the dental arches to create space to align the teeth or to extract permanent teeth in each quadrant (usually, first premolars) to make room for the others. This subject is covered in detail in the Level IV teaching program To Extract Or Not To Extract, Part 1, which you will be studying in the near future. Expansion of the dental arches to create space must not cause excessive incisor protrusion, compromise alveolar bone support or periodontal attachment, or exceed the tolerance of the soft tissues (i.e., produce lip incompetence and protrusion).

Nonextraction treatment may require dental and/or skeletal expansion, distalization of posterior teeth, alteration of incisor position or angulation, and interproximal reduction (IPR) of tooth widths to provide additional space. A complete fixed appliance and 18-24 months of treatment time usually are necessary.

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Serial Extraction

In some children, potentially severe crowding is obvious (images 1-3), and the mixed dentition analysis quantified the space discrepancy as 7-8 mm in both arches. For this child, the mandibular lingual arch was placed to maintain leeway space to keep crowding from getting worse, in the hope that nonextraction treatment might be possible, and serial extraction was not done—but if the space discrepancy is large enough, intervention to gain sufficient space to align all the permanent teeth in a stable position will be futile.

Sequential extraction of primary teeth during the mixed dentition can reduce crowding and irregularity of the incisors, and if followed by extraction of first premolars in the late mixed dentition, can allow the permanent canines and second premolars to erupt through keratinized tissue into more normal positions in the alveolus at the appropriate time and in the correct sequence. Serial extraction can be defined as the orderly removal of selected primary and permanent teeth in a predetermined sequence to alleviate crowding.

Historically, serial extraction was developed in the hope of providing a way to treat severe crowding while eliminating the need for future appliance therapy. Time has shown that it does not result in ideal tooth positions or eliminate the need for future orthodontic treatment. The main advantages of serial extraction is that it potentially makes future orthodontic treatment less complicated and decreases periodontal problems due to eruption of teeth outside the dental arch. Perhaps it also improves long-term stability.

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Ideal Patient for Serial Extraction

The ideal patient for serial extraction should have:

Early mixed dentition with a large amount of predicted crowding, 8-10 mm of discrepancy per arch. If the amount of crowding is less than 10 mm, serial extraction alone is not recommended because more residual spacing and more uncontrolled tipping of the teeth will occur (image 1).
No skeletal disproportions.
Class I molar relationship.
Normal overbite. Serial extractions will deepen the bite.
No congenitally missing permanent teeth.

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{{PAGE_35}} Even in the ideal situation, a later phase of comprehensive orthodontic treatment is almost always required to correct the sequelae of serial extraction. In clinical practice where comprehensive follow-up treatment is available, patients with a discrepancy of 8 mm or more often are candidates for serial extraction.

Serial Extraction Sequence

The sequence followed during serial extractions is designed to allow the first premolars to erupt ahead of the canines so that the first premolars can be extracted early to allow eruption of the canines and second premolars. If severe crowding exists, the result is that in each quadrant, the canine and second premolar share the space vacated by the first premolar.

Normally, in the maxillary arch the first premolar erupts before the permanent canine, which is ideal for serial extractions. However in the lower arch, the first premolar erupts along with or after the permanent canine. This makes serial extractions in the lower arch trickier. If the primary 1st molar is extracted when the root of the underlying first premolar is approximately 1/2 to 2/3 developed, the eruption of the first premolar can be accelerated.

Step 1 of serial extraction sequence Primary canines are extracted first to allow the permanent incisors to align (image 1). A lower lingual arch may be placed to prevent the lower incisors from retroclining and deepening the bite prior to the eruption of the permanent canines.

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{{PAGE_36}} Step 2 of serial extraction sequence The first primary molars are extracted when the roots of the lower first premolars are about 2/3 formed and the crown is about to penetrate into the gingiva (image 2). This will accelerate the eruption of the first premolars so they erupt before the canines.

Step 3 of serial extraction sequence The first premolars are then extracted soon after they erupt. This allows the canine and second premolars to erupt into this space.

Serial Extraction Outcomes

Serial extraction is not a panacea for the treatment of severe crowding. In the vast majority of patients, future comprehensive orthodontic treatment is required to treat the tipping, residual spacing, and increased overbite that usually occurs after serial extraction. The advantage of serial extraction is that the comprehensive treatment usually is shorter and less complicated than if serial extractions had not been done.

In cases with very severe crowding, the amount of residual tipping and drifting may be minimal after serial extractions, as shown in this panoramic radiograph of a patient who had serial extractions but no orthodontic treatment (image 1). Even in this favorable situation, a period of fixed appliance treatment would improve both alignment and root positions.

The panoramic radiograph in image 2 also shows a favorable result of serial extraction, but you can see that one of the maxillary canines has been displaced facially because even with extraction in the quadrant of the dental arch, there was not quite enough room for it. Again, a period of fixed appliance treatment will be needed to finish the job.

Once the sequence of serial extraction has been initiated, a prudent dentist might repeat the mixed dentition analysis space analysis and/or refer the patient for an orthodontic consult prior to extracting the first premolars. As a general rule, extraction of the permanent teeth should not be done before arrangements for future fixed appliance treatment are in place.

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{{PAGE_37}} Image 1, Tipping and drifting of the teeth after serial extraction: Tipping of teeth is common after serial extraction. Image 2, Panorex of reasonable result after serial extractions: Reasonable results after serial extraction without orthodontic treatment.

Self-Test Referral

The self-test section of this program is designed to help you be sure you have understood the material.

Now that you have gone through the module, do the assigned reading in Contemporary Orthodontics(pages 147-184 in 5th ed.; pages 163-201, 4th ed.) Then take the self-test, and use it as a guide for further study and review.

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2. Crossbites and Vertical Problems in Children

Introduction: Skeletal versus Dental

Crossbite: Mandibular Shift?

A crossbite is the condition in which the anterior or posterior teeth occlude against the opposing teeth in an abnormal anteroposterior or transverse relationship, respectively. An anterior crossbite occurs when the maxillary incisors occlude lingual to the mandibular incisors (image 1). A posterior crossbite occurs when the maxillary posterior teeth occlude lingual to the mandibular posterior teeth (image 2). In either case a single tooth or multiple teeth may be in a crossbite relationship.

When assessing a crossbite, it is important to assess the patient’s occlusion in maximum intercuspation (MI) and centric relation (CR). A unilateral posterior crossbite is often due to a lateral shift from the point of initial contact (CR) (image 1), while an anterior crossbite can be due to a forward shift. A mandibular shift between CR and MI frequently makes the crossbite appear more severe.

Image 1, Anterior crossbite: Anterior and unilateral posterior crossbite, maxillary incisors lingual to mandibular incisors. The possibility of a mandibular shift from CR to MI should be evaluated carefully.

Image 2, Posterior crossbite: Bilateral posterior crossbite, maxillary molars lingual to the mandibular molars.

Crossbite: Skeletal vs. Dental

Remember that crossbites can be dental or skeletal in origin. A dental crossbite, by definition, exists because the teeth are displaced relative to their supporting bone. A skeletal crossbite exists because

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{{PAGE_39}} the jaw(s) are displaced relative to each other, and the teeth are reasonably well related to their supporting bone.

The definition is a bit tricky, because teeth that are displaced can create occlusal interferences that lead to a mandibular shift—but that’s still a dental crossbite with a mandibular shift, not a true skeletal crossbite caused by a distortion of the shape of the mandible. Prior to instituting any treatment, especially in anterior crossbites, it is important to determine the nature of the crossbite.

Dental Crossbites Dental crossbites arise due to displacement of teeth within the dental arch (image 1). Single or multiple teeth may be involved. These problems usually arise as the eruption path of a tooth or teeth is deflected because of crowding within the dental arch.

Skeletal Crossbites Skeletal crossbites tend to involve multiple teeth and are caused by the underlying position of the basal bone (image 2). Posterior skeletal crossbites are most commonly caused by a narrow maxilla but could also be due to an abnormally wide mandible. Significant posterior skeletal crossbites may be identified by significant incompatibility of the maxillary and mandibular arch forms. One arch may be V-shaped while the other is U-shaped, or one may be narrower than the other.

Anterior crossbites are a common finding in patients with Class III skeletal malocclusions whether due to maxillary deficiency (image 3) or mandibular excess.

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{{PAGE_40}} Image 1, Single tooth anterior crossbite: Example of an anterior dental crossbite involving a single tooth. Image 2, Anterior crossbite, skeletal Class III: Anterior crossbite involving multiple teeth due to a skeletal Class III malocclusion. Image 3, Lateral cephalometric radiograph - Class III skeletal relationship.: Lateral cephalometric radiograph of a Class III skeletal malocclusion due to maxillary deficiency.

Skeletal vs. Dental (cont.) The determination of whether the crossbite is skeletal or dental determines the degree of difficulty in treating it. If an anterior or posterior crossbite is dental in nature and involves a few teeth, treatment can usually be accomplished with simple appliances. On the other hand, skeletal crossbites are very difficult to treat and many times require orthognathic surgery to reposition the jaws to allow correct positioning of the teeth. Image 1 shows the results of a LeFort I maxillary advancement for correction of a Class III skeletal malocclusion in a patient who presented with a skeletal anterior crossbite.

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{{PAGE_41}} Anterior Crossbite

Assessment of Anterior Crossbite In the assessment of anterior crossbites it is critically important to differentiate a developing skeletal problem from a problem due only to displacement of the incisor teeth. The most common etiological factor of nonskeletal anterior crossbites is lack of space for the permanent incisors. Since the permanent tooth buds for the maxillary incisors develop palatally to the primary incisors, a shortage of space may force the permanent teeth to remain palatally. A space analysis should be done in these cases. If the developing crossbite is discovered before eruption is complete, adjacent primary teeth may be extracted bilaterally to create space and allow self-correction of the crossbite.

Pseudo-Class III Malocclusion Patients with a significant anterior shift of the mandible from CR to MI due to interferences caused by a dental anterior crossbite may appear to have a significant mandibular prognathism. It is very important to evaluate the patient’s occlusion and facial profile in CR and MI. An anterior dental crossbite with a significant anterior shift is called a pseudo-Class III malocclusion. These patients usually can be manipulated into an edge-to-edge incisor relationship in centric occlusion. When they shift forward into MI, the profile appears prognathic.

A pseudo-Class III malocclusion due to a forward shift is shown in image 1. The upper slide shows the occlusal relationship in CR in which the incisors are in an end-end relationship and the molars are in

{{PAGE_42}} a Class I relationship. In MI the patient postures the mandible forward to get the posterior teeth into occlusion. In this position the anterior teeth are in crossbite and the molars are in a Class III relationship. In a true skeletal Class III malocclusion, the patient has no significant anterior CR–MI shift, and the mandible cannot be positioned posteriorly.

Anterior Crossbite in Children

What is the rationale behind correcting anterior crossbites in children? If the crossbite is not too severe, and especially if it is due primarily to an anterior shift (i.e., is a pseudo-Class III), it is considered important to:

Allow normal jaw function by eliminating significant CR–MI functional interferences.
Establish normal interincisal contact. Lingually positioned incisors may interfere with lateral jaw excursions and cause significant abnormal incisal wear patterns that can compromise incisor esthetics.
Prevent periodontal involvement of the lower incisors (image 1). Significant dental compensations may also develop in response to the altered incisor positions. An anterior crossbite may force the mandibular incisors to be positioned more facially in the lower arch. If positioned too far facially the periodontal support of the lower incisors may be compromised due to loss of attached gingiva and gingival recession.
Allow correction of localized space loss.

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{{PAGE_43}} Space Considerations in Anterior Crossbite

It is crucial to evaluate the space required to correct an anterior crossbite prior to initiating treatment. Is there enough space present to accommodate the incisor? A maxillary incisor that is 7 mm wide cannot be moved into a space that is only 3 mm wide. Space may be created to allow alignment of the incisors and correction of the crossbite by:

Proclining the maxillary incisors
Extracting adjacent primary teeth
Reducing the mesial-distal width of the adjacent primary teeth

The patient shown in image 1 presents with an anterior crossbite due to rotated maxillary central incisor. There is inadequate space to derotate the central incisor and correct the anterior crossbite. The maxillary primary canines will have to be extracted to create space for the crossbite correction.

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{{PAGE_44}} Anterior Crossbite Treatment

After it has been determined that sufficient space exists to accommodate the teeth in crossbite, one must then determine how to move the teeth into the dental arch. If the maxillary incisors were deflected into a more palatal position during eruption, tipping them facially can, in the majority of cases, be used to correct the crossbite.

Relatively simple removable acrylic appliances (image 1) can be used to tip the maxillary teeth into the correct labial position. Adams clasps can be used for retention, while springs (20 mil stainless steel) can be designed to tip teeth labially. The addition of an anterior or posterior bite plane is usually not required in young children because the teeth are not in occlusion except during swallowing and parafunctional habits. The image on the left shows the spring being adjusted from the palatal side of the acrylic. The image on the right shows Adams clasps on the first molars while a labial bow contoured to the labial surface of the incisors extends between the distal surfaces of the canines.

Such appliances must be worn 24 hours/day to be efficient and effective. The finger spring can be activated 1.5–2 mm per month and will produce approximately 1 mm of tooth movement in that time. The most common problem with these types of removable appliances is lack of patient compliance. Poor appliance design and lack of adequate retention will greatly reduce compliance. Improper activation may also lead to inadequate untimely results.

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{{PAGE_45}} One inherent problem with removable appliances is that the forces applied by the finger springs will act to dislodge the appliance, which reduces the effectiveness of the applied forces. To counteract this, one must ensure that adequate retention is provided by clasps. Resin may be added to the lingual surfaces of the maxillary incisors to allow the finger spring to seat properly against the incisor rather than slide upward toward the incisal edge.

Anterior Crossbite Treatment (cont.)

Fixed orthodontic appliances can also be used to correct anterior crossbites. Fixed appliances reduce the need for patient compliance and provide a wider range of action and more continuous force application. One possibility in children is a cemented maxillary lingual arch with soldered finger springs or whip springs, which can be used to tip incisors labially to correct a crossbite. The appliance is easy to construct and can effectively align the anterior teeth (image 1).

A more frequently used fixed appliance for anterior crossbite correction consists of orthodontic bonds on the 4 maxillary incisors and bands on the 2 maxillary molars. This combination is commonly referred to as a 2 x 4 appliance (image 2). Fixed orthodontic brackets and arch wires can move the incisors in all three planes of space, but require skill in controlling unwanted movements. Movements such as tipping and torque are possible with fixed brackets, while removable appliances or springs on a lingual arch can only tip the incisors. Fixed appliances with bonded brackets are also more effective in creating space for crossbite correction and incisor alignment, because they can be used to move the teeth bodily if this is needed.

Retention of crossbite correction with a passive removable appliance is usually recommended for 2 months post-treatment to prevent relapse. If the overbite is sufficient to retain the incisor position after this time period, the passive retainer can be discontinued. If the overbite is insufficient, passive retainer use should be continued until positive overbite has been established. After correction with a fixed appliance (such as a 2 x 4 appliance), a passive retainer such as a Hawley retainer is

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{{PAGE_46}} recommended (image 3). If a removable appliance was used for correction, it can be modified to act as the passive retainer.

Image 1, Fixed lingual arch with soldered whip springs: A cemented lingual arch with soldered whip springs can also be used to correct an anterior crossbite.

Image 2, Fixed maxillary 2 x 4 appliance: A 2 x 4 appliance can efficiently correct an anterior crossbite.

Image 3, Hawley retainer: A Hawley retainer is the best choice to retain the correction of an anterior or posterior crossbite.

Treatment of Skeletal Anterior Crossbite

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{{PAGE_47}} True skeletal anterior crossbites are difficult to treat. Children in the primary or early mixed dentition who present with multiple anterior teeth in crossbite commonly have an underlying skeletal discrepancy. One must carefully evaluate the patient’s facial profile using facial form analysis. Interventions are skeletal in nature and may use growth modification techniques to improve the skeletal relationship. Reverse pull headgear (image 1) may be used in patients with maxillary deficiency in the early mixed dentition, while chin cup therapy has been used to help control mandibular growth in patients with mandibular excess (image 2). Chin cup appliances have limited success as they require an extended period of compliance and must be worn during the majority of the adolescent growth spurt to be effective.

A new and potentially more effective approach in the late mixed dentition after eruption of lower permanent canines is the use of Class III elastics to miniplates bonded to the maxilla and mandible (image 3). Bone screws to hold the miniplates are not stable until the alveolar bone has reached the stage of maturity seen at about age 11, when eruption of the canines would be expected, so that is the earliest time it can be used.

Patients with suspected skeletal anterior crossbites should be referred early in the mixed dentition for evaluation and possible treatment by an orthodontist.

A flowchart has been developed to help with evaluation and treatment of anterior crossbites (images 4 and 5) (see Contemporary Orthodontics, 5th ed., p. 412).

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{{PAGE_48}} Image 1, Reverse pull headgear: Reverse pull headgear or protraction headgear can be used to treat Class III skeletal malocclusions due to maxillary deficiency. Image 2, Chin cup appliance: Chin cup appliances can be used to treat Class III malocclusions due to mandibular excess, but true skeletal change beyond downward-backward rotation of the mandible is rarely achieved. Image 3, Class III elastics to miniplates: Light elastics to skeletal anchors can affect both maxillary and mandibular growth— but long-term outcomes have not yet been documented. Image 4, Flow chart for the treatment of anterior crossbites

{{PAGE_49}} Image 5, Flow chart for the treatment of anterior crossbites

Posterior Crossbite

Skeletal vs. Dental Posterior Crossbite

Posterior crossbites present as a narrow maxillary arch (image 1), a wide mandibular arch, or a combination of both. In the majority of cases, the problem is a narrow maxillary arch. The width of the maxillary arch and the inclination of the posterior teeth as viewed on study models can be used to help distinguish between a skeletal or dental posterior crossbite.

A dental posterior crossbite is due to lingual tipping of the posterior teeth in the transverse plane with an underlying maxilla of normal width (image 2). A posterior skeletal crossbite occurs when the transverse width of the maxilla is reduced while the maxillary posterior teeth may be tipped buccally to compensate for the narrow maxillary arch (image 3). Not only can posterior crossbites be solely skeletal or dental in nature, they can occur due to a combination of the two situations in which the maxillary teeth are tipped lingually and the skeletal maxilla is narrow—but this is rare; dental compensation for the skeletal problem usually occurs.

This differentiation is important, because two different treatment approaches will be used in each of these cases: tip the teeth buccally in dental crossbites and expand the maxillary width in skeletal crossbites.

  *Image 1, Skeletal Posterior crossbite: Bilateral skeletal posterior crossbite with a narrow, constricted and v-shaped maxilla.*
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  *Image 2, Posterior dental crossbite: A posterior dental crossbite can occur due to lingual tipping of the maxillary molars while the maxilla is of normal transverse width.*
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  *Image 3, Posterior skeletal crossbite: A posterior skeletal crossbite occurs when the transverse width of the maxilla is reduced, and the maxillary*
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{{PAGE_51}} lingual teeth may be tipped buccally to compensate.

Skeletal vs. Dental Posterior Crossbite (cont’d.)

Class III skeletal malocclusions usually present with a posterior crossbite as well as an anterior crossbite. The upper and lower jaws may be of normal transverse width, but due to the abnormal anteroposterior relationship, the lower arch appears relatively wider than the upper arch, and the patient presents with a posterior crossbite as well as an anterior crossbite. You should be very suspicious of an underlying Class III malocclusion in children who present with both a posterior and anterior crossbite. Image 1 shows a young boy in the early mixed dentition who shows such characteristics. His profile can be described as straight with a degree of maxillary deficiency. His occlusion reveals an anterior crossbite and a posterior crossbite.

Evaluation of Posterior Crossbite

Posterior crossbites in the mixed dentition are a common feature in children who have had prolonged thumb-sucking habits. Forces generated during a thumb-sucking habit can move the teeth and alter the shape of the maxillary arch. Increased tone of the buccinator muscles can constrict the maxillary arch (image 1). Because of the position of the thumb between the teeth, maxillary incisors usually are proclined (tipped forward) while mandibular incisors are retroclined. Posterior crossbites in children often appear to be unilateral in nature. Closer examination usually reveals that this results from a true bilateral constriction of the maxillary arch with a transverse shift of the mandible from CR to MI. These patients will also present with the mandibular dental midline deviated to the side in crossbite or the direction of the mandibular shift (image 2).

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{{PAGE_52}} Severe maxillary constriction can result in bilateral maxillary constriction without a functional shift. A true unilateral posterior crossbite can result from an intra-arch or jaw asymmetry. These problems are more complicated to treat and should be referred to an orthodontist.

Image 1, Thumb-sucking habit: Forces generated during a thumb- sucking habit can move the teeth and alter the shape of the maxillary arch.

Image 2, Bilateral posterior crossbite with a functional shift: Bilateral posterior crossbite with a functional shift, mandibular midline shifted to the right of the maxillary midline due to a functional shift of the mandible from CR to MI.

Treatment of Posterior Crossbite Crossbites caused by a mandibular shift should be treated as soon as they are discovered, even in the primary dentition if patient cooperation allows. Untreated mandibular shifts can result in:

Undesirable soft tissue growth modification
Dental compensation
Abnormal wear of the primary and permanent teeth
Reduced maxillary arch space required to align the teeth

In the primary and early mixed dentition, equilibration of the primary canines may eliminate interferences that result in a lateral shift into crossbite. More often the mandibular shift is due to bilateral maxillary constriction, and appliance therapy is used to expand the maxillary arch. Correction in the primary dentition is recommended if a mandibular shift is present and the child will cooperate with treatment. However if the permanent first molars are expected to erupt within 6 months, it is recommended that expansion be delayed until these teeth erupt and can be included in the treatment.

Removable Appliance Treatment Posterior crossbites can be treated with a number of appliances, both removable and fixed:

Removable split plate appliances

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W-arch appliance
Quad helix appliance
Rapid maxillary expander (RME)

Removable Split Plate Appliances (Image 1) These removable appliances use a split acrylic palate incorporating a wire spring or jackscrew for force generation to expand the maxillary arch. Compliance is essential for successful treatment. The forces generated by the appliance to expand the maxillary arch also tend to dislodge the appliance, which may further reduce compliance. Unless the expansion screw is turned very slowly, the appliance will not seat properly because the teeth have not had enough time to move between activations. As a result, these appliances are not as effective and successful as fixed appliances.

Lingual Arch Treatment

Quad Helix and W-Arch Appliances

The preferred appliances for correction of maxillary constriction in preadolescent patients are the quad helix (image 1) and W-arch (image 2) appliances. These lingual arch appliances are preferred in this age group, as the midpalatal suture is most likely open and heavy force is unnecessary to achieve dental and skeletal expansion.

Both appliances are constructed using 36 mil steel wire soldered to orthodontic bands cemented to the maxillary first permanent molars. The wire is positioned about 1 mm above the soft tissue to

{{PAGE_54}} prevent impingement. Both appliances generate approximately 2-4 pounds of force, which creates about 2 mm of slow expansion per month. The appliances are activated about 3-4 mm prior to cementation, which is roughly about 1/2 the facial lingual width of the permanent molar. It is recommended that both appliances should be removed and recemented to be accurately reactivated. Using these appliances, a posterior crossbite usually requires 2-3 months of active treatment followed by 3 months of retention utilizing the passive cemented appliance. The quad helix appliance, by virtue of the additional wire and helices, has increased range and springiness. The anterior helices may also act as a reminder to aid in stopping a thumb habit (image 1).

Mid-Palatal Suture Expansion

Maxillary expansion using high forces over a short period of time has been popular in the United States since the early 1960s and is known as rapid palatal (or maxillary) expansion (RPE or RME). Banded (image 1) or bonded (image 2) expansion screws are used to achieve this type of expansion in adolescent patients, whose mid-palatal suture has become so interdigitated that heavy force is needed to open it. The jackscrew is activated at a rate of 0.5 to 1.0 mm per day. Since the force generated between activations does not completely dissipate, cumulative forces of 10-20 lbs may be present during treatment. 10 mm or more of expansion can be seen in a period of 2-3 weeks. As the suture expands, a maxillary midline diastema usually occurs as the bony expansion carries the teeth apart. Whether they are attached to bands or are bonded, fixed palatal expansion appliances make adequate oral hygiene difficult and may interfere temporarily with normal speech.

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{{PAGE_55}} Image 1, Banded fixed palatal expander: Fixed expansion appliances with expansion screws can be attached to teeth with bands.

Image 2, Bonded fixed palatal expander: A bonded expander incorporates coverage of the occlusal surface of the teeth, thus opening the bite—which can be advantageous in a long face patient because it impedes eruption of posterior teeth.

Rapid Palatal Expansion

The theory behind rapid maxillary expansion is that if sufficient force is applied to the maxilla over a short period of time, the midsagittal suture will be opened quickly, resulting in maximum skeletal changes and minimal dental changes through tipping of the maxillary posterior teeth. The idea is that there would be not be enough time for tooth movement to occur and the teeth would move minimally relative to their supporting bone. In the short term this is true, but orthodontic tooth movement created by the stretched palatal mucosa allows skeletal relapse during stabilization and healing, so slower and rapid expansion produce similar long-term results.

Rapid palatal expansion not only opens the midpalatal suture of the maxilla, it affects structures higher up in the skeletal midface. The suture also opens wider and faster anteriorly due to buttressing of bone in the posterior maxilla (image 1).

Image 2 shows an occlusal radiograph of a maxilla prior to rapid palatal expansion. As the expansion screw is activated, the maxillary suture is opened producing a maxillary midline diastema (image 3). As the expansion continues, the palatal suture begins to fill in with new bone (image 4). After the expansion has stopped the palatal suture continues to fill in with more bone and the maxillary central incisors tip toward the midline, closing the midline diastema (image 5).

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{{PAGE_56}} Image 1, Effects of RPE on the skeletal midface: Rapid palatal expansion opens the midpalatal suture of the maxilla and affects structures higher up in the skeletal midface.

Image 2, Occlusal radiograph of pre-expansion maxilla: Maxilla prior to expansion with a rapid palatal expander.

Image 3, Effects of rapid palatal expansion: Maxillary suture has been opened producing a maxillary midline diastema.

Image 4, Effects of rapid palatal expansion: Palatal suture begins to fill in with new bone.

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{{PAGE_57}} Image 5, Effects of rapid palatal expansion: The palatal suture continues to fill in with more bone and the maxillary central incisors have tipped toward the midline, closing the midline diastema.

Slower Palatal Expansion

The same banded or bonded jackscrew appliances can be used for slow expansion by just increasing the interval between activation of the expansion screw. Slow expansion usually is done at the rate of 0.25 mm (one-quarter turn of the expansion screw) every other day. This produces a more physiological response at the midsagittal suture, where new bone is laid down at a rate more equal to the expansion of the suture.

In reality, rapid and slow expansion produce very similar long-term outcomes, because with rapid expansion orthodontic tooth movement continues after the skeletal expansion until bony stability is achieved. During this time the dental expansion is maintained, but the two halves of the maxilla move back toward each other, which is possible because at the same time the teeth move laterally on their supporting bone. With rapid expansion, the end result is about 50% skeletal and 50% dental expansion; with slow expansion the change is 50% skeletal and 50% dental from the beginning (image 1).

{{PAGE_58}} Regardless whether rapid or slow expansion is utilized to achieve skeletal expansion, a 3-4-month retention period with a removable or fixed retention appliance is needed to allow the suture to fill in with organized bone.

RAPID EXPANSION A Expansion (mm) Total Skeletal Dental 0 2 4 6 8 10 Weeks

SLOW EXPANSION B Expansion (mm) Total Skeletal Dental 0 2 4 6 8 10 Weeks

Slow Expansion for Young Children

Rapid palatal expansion is not recommended in young children. The midsagittal suture can be opened with moderate forces as generated by a W-arch or quad helix. If rapid palatal expansion is used in this age group, the risk of distorting the more pliable facial structures of the midface is markedly increased. In this 4-year-old girl, a jackscrew appliance activated daily was used to correct the posterior crossbite rather than a W-arch or quad helix appliance (image 1). The result was injury at the base of the nose (probably displacement of the vomer bone and bleeding in that area) and an obvious change in the width of her nasal bridge. It led to legal action against the dentist.

In preadolescent children (8-11 years old), a W-arch or quad helix appliance is recommended because the midsagittal suture still is patent enough that the lower forces generated by these appliances can deliver both dental and skeletal expansion. In late adolescence the suture is more organized and may require more force to achieve skeletal expansion. In these cases an RPE-type appliance may be require to achieve skeletal expansion. In adults, surgery is usually required to accomplish maxillary skeletal expansion, as the suture is highly organized and fused.

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Vertical Effects of Posterior Crossbite Correction

One must be aware that any forces applied to posterior teeth to correct a posterior crossbite have a vertical as well as a transverse vector that tends to open the bite anteriorly. This vertical vector tends to extrude the posterior teeth as well as tipping the lingual cusps downward. Both of these will result in a bite-opening effect. In patients with short lower face height and a shallow mandibular plane angle, this may have a positive effect. However, in patients with a steep mandibular plane and increased lower face height, such vertical changes will make the situation worse. One way to minimize these vertical effects during expansion is to use a bonded expander with bite blocks. Patients with complex transverse–vertical problems may best be treated with orthognathic surgery.

Images 1 and 2 are a flow chart has been developed to help with evaluation and treatment of posterior crossbites (See Contemporary Orthodontics, 5th ed., p. 408, Figure 11-21).

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{{PAGE_60}} Image 1, Posterior crossbite flow chart, part 1: Evaluation section of posterior crossbite flow chart Image 2, Posterior crossbite flow chart, part 2: Treatment plan section of posterior crossbite flow chart

Vertical Problems

Simple Anterior Open Bites: Thumbsucking

As with transverse problems, vertical problems can be dental or skeletal in nature. Vertical problems that are dental in nature may be easy to correct, while skeletal vertical problems may be very difficult to treat and may require surgical correction. Patients with complicated skeletal and dental vertical problems should be referred to orthodontists.

In the primary and mixed dentition, simple anterior open bites in children with good facial proportions are most commonly associated with prolonged thumb-sucking habits. The effects are related to the duration and intensity of the habit and can include:

Labial tipping of the maxillary incisors.
Lingual tipping of the mandibular incisors.
Reduced eruption of the incisors and overeruption of the posterior teeth.
Reduced maxillary intercanine and intermolar width.

Patients with a prolonged thumb habit usually present with increased overjet, reduced overbite (open bite), and a posterior crossbite.

These results are shown in a young boy who had a habit of sucking his right index finger (image 1). Due to the unilateral application of force to his incisors, he developed an increased overjet and anterior open bite that affected his right maxillary incisors only.

{{PAGE_61}} Thumbsucking (cont.)

The majority of children discontinue thumb-sucking habits before they reach school age. If the habit is stopped before the eruption of the permanent incisors, most of the dento-alveolar changes associated with the habit resolve spontaneously. However some children continue their habit after the incisors erupt. A sequence of inventions that may be used to help children discontinue thumb-sucking habits include:

Reminder therapy where a bandage is placed on the finger that is sucked.
Reward therapy, where a series of small daily rewards and a larger major reward are given to the child when the habit is not practiced over a period of time.
An elastic bandage wrapped around the elbow to prevent flexion of the elbow so that the finger cannot be sucked.
Appliance therapy, where a reminder appliance is cemented on the teeth.

For any of these methods to be effective, a child must wish to stop the habit. The intervention must not be perceived as punishment by the child. Appliance therapy requires a compliant patient who wishes to stop the habit, because noncompliant patients can easily distort or remove the appliances if they wish.

Appliance therapy uses a cemented maxillary lingual arch that has a crib constructed of soldered wire (usually 0.038”) on the anterior portion of the appliance. The anterior crib functions as a reminder and interferes with thumb position during sucking (image 1). The use of a habit appliance can result in spontaneous closure of an anterior dental open bite created by a thumb habit. These slides illustrate the before and after changes of a habit related dental open bite (image 2). Once the forces associated with the habit are eliminated, the oral musculature applies forces to the teeth to move them into more normal positions in the dental arch.

A flow chart has been developed to deal with treatment of oral habits (images 3 and 4) (see Contemporary Orthodontics,5th ed., p. 416, Figure 11-31).

{{PAGE_62}} Image 1, Cemented habit appliance: A cemented habit appliance can be cemented on the first permanent or primary molars. The anterior crib portion of the appliance acts as a reminder and interferes with finger position.

Image 2, Effects of habit appliance: The use of a habit appliance can result in spontaneous closure of an anterior dental open bite created by a thumb habit.

Image 3, Oral habits flow chart, part 1

Image 4, Oral habits flow chart, part 2

Open Bite in Adolescents In adolescents the major vertical problems are anterior open bite and anterior deep bite. At this age any vertical discrepancy tends to be more related to skeletal proportions rather than simple displacement of the teeth.

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{{PAGE_63}} Anterior Open Bite

Skeletal indicators of an anterior open bite include:

Increased anterior open bite
Steep mandibular plane
Excessive vertical growth of the maxilla
Downward rotation of the mandible
Excessive eruption of the posterior teeth

In young children anterior open bites are most commonly caused by thumb-sucking habits, and some resolution of the anterior open bite occurs with the discontinuance of the habit. In contrast, in adolescents open bites are rarely due solely to thumb habits, and discontinuance of the habit rarely results in spontaneous correct of the open bite. A severe open bite (image 1) usually has a skeletal component even if the patient continues thumb-sucking, the required orthodontic treatment can be quite complex, and the open bite may become progressively worse during the pubertal growth spurt.

Previously, tongue thrust swallowing (forward positioning of the tongue between the anterior teeth during swallowing) was thought to cause anterior open bite, and so-called “myofunctional therapy” was used to try to retrain the oral muscles so the bite would close. Contemporary research has shown that the tongue thrust is an adaptation of the tongue to an anterior open bite rather than a cause of it. Myofunctional therapy is not recommended as an effective treatment for tongue thrusting and anterior open bite.

Deep Bite: Dental vs. Skeletal

Anterior deep bite (excessive overbite) may result from excessive eruption of the mandibular incisors or from upward and forward rotation of the mandible that leads to a short face. The first of these would be described as a dental deep bite; the second would be termed a skeletal deep bite.

{{PAGE_64}} A deep bite due to over-eruption of the mandibular incisors often is seen in a patient with a Class II malocclusion and normal anterior face height (image 1) because when there is excessive overjet the lower incisors are free to erupt until they contact the palatal mucosa (images 2 and 3). Note the excessive curve of Spee in the lower arch. In adolescents who still have active vertical growth, the deep curve of Spee can be leveled by relative intrusion in which further eruption of the anterior teeth is prevented and the posterior teeth are allowed to erupt in response to further vertical growth.

Deep bite also can be due primarily to a short face related to upward-forward rotation of the mandible. This, of course, is a skeletal problem and is appropriately called a skeletal deep bite. It is discussed in more detail in the next screen.

An important concept: the objective of correcting a dental deep bite is to level the lower dental arch, which can be accomplished in a growing patient by impeding eruption of the lower incisors and allowing eruption of the posterior teeth. In a Class II patient it would be important to prevent an increase in anterior face height as this was done, because that would magnify any underlying mandibular deficiency. The mandible would rotate backward as well as downward.

To effectively treat adolescents with skeletal vertical problems—open bite or deep bite—one has to be highly aware of the two-dimensional aspects of the underlying problem and any treatment interventions. Because the treatment can be complex, referral to an orthodontist usually is prudent in these patients.

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{{PAGE_65}} Image 1, Class II patient, normal vertical: In this patient, a Class II malocclusion with a component of deficiency is present but the vertical facial proportions are normal—so her deep bite is dental, not skeletal. Image 2, Dental deep bite: Excessive overbite can be caused by excessive eruption in a Class II patient like this one, who has normal vertical facial proportions but a-p mandibular deficiency. Image 3, Lingual view: Note the excessive curve of Spee in the lower arch and the contact with the palatal tissues, both of which are due to over-eruption of the lower incisors.

Skeletal Deep Bite (Short Face)

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{{PAGE_66}} A child with a skeletal deep bite presents with a short face appearance (image 1). These children usually have:

Anterior deep bite (image 2)
Some mandibular deficiency
A Class II division 2 malocclusion
Reduced lower face height
Everted and prominent lips
Low mandibular plane angle
Long mandibular ramus (long posterior face height)
Decreased eruption of the maxillary and mandibular posterior teeth
Anteriorly directed growth pattern with upward and forward rotation of the mandible

Many of these children can be described as skeletal Class II with the mandible rotated upward and forward toward a Class I jaw relationship. One objective of treatment is to increase the eruption of the posterior teeth and have the mandible rotate downward to increase the lower face height. However as the mandible rotates downward the chin also rotates downward and backward, which may make the chin less prominent and make the Class II problem more severe.

Treatment of Skeletal Deep Bite

In growing adolescents, two approaches can be used to treat a Class II skeletal relationship and increase the eruption of the posterior teeth to improve vertical facial proportions and decrease overbite: cervical headgear and a deep bite functional appliance.

Cervical Headgear (Image 1) Cervical headgear will result in more eruption of the maxillary posterior teeth than the mandibular teeth. In patients with short face Class II relationships, excessive

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{{PAGE_67}} erupton of the maxillary teeth will increase the lower face height, but at the same time it will cause the mandible to rotate downward and backward, which at least partially negates the Class II growth modification effect of the headgear. The headgear does not control eruption of the incisors, which also is important in correcting the deep bite.

Deep Bite Functional Appliance (Image 2) Functional appliances offer the ability to improve the a-p jaw relationship while also controlling the vertical movements of the teeth during growth. Eruption of the maxillary posterior teeth and the incisors in both arches is blocked, while eruption of the mandibular posterior teeth is allowed. The effect is to level an excessive curve of Spee in the lower arch as face height is increased.

For this reason, the functional appliance usually is the appliance of choice in the treatment of deep bite Class II patients.

Skeletal Open Bite (Long Face)

Children with skeletal open bite present with a long anterior face height, which usually (though not always) is accompanied by anterior open bite. These children usually have:

Normal upper face
Overeruption of the maxillary and mandibular posterior teeth
Steep mandibular plane
Reduced posterior face height and increased anterior face height

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Downward and backward rotation of the mandible
Downward-directed growth
Downward tipping of the posterior maxilla

The goal of treatment is to prevent further downward growth of the posterior maxilla and prevent further eruption of the posterior teeth in both arches, so the mandible can rotate upward and forward to decrease the lower face height. To be effective, this growth modification must be used during active growth, which would mean that a protracted treatment time from the late mixed dentition to the completion of growth in postadolescence. For a skeletal open bite as severe as the one shown in image 1, surgical repositioning of the maxilla and chin is likely to be needed.

Orthodontic Treatment: High Pull Headgear

Several approaches to limiting vertical growth and improving skeletal open bite problems in less severely affected patients are possible. Because these techniques involve a thorough understanding of the underlying skeletal and dental relationships and involve advanced treatment mechanics, it is highly suggested that orthodontists provide the treatment when required.

High Pull Headgear to Maxillary Molars

A high pull headgear to bands on the maxillary first molars (image 1) provides a force to maintain the vertical position of the posterior maxilla and prevent eruption of these teeth. The headgear should deliver a force of 12 ounces per side and be worn 14 hours per day. The force vector will be determined by the relationship of the line of force between the outer bow of the headgear and the head cap (image 2). If this line of force runs through the center of resistance of the maxillary molar (near the trifurcation of the molar roots), the tooth will not tip as it moves posteriorly and upward. If the line of force does not run through the center of resistance, tipping in either the clockwise or counterclockwise direction will occur, depending on whether the force vector is above or below the center of resistance. Distal tipping (clockwise) of the molar will tend to open the bite and rotate the

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{{PAGE_69}} mandible downward, further increasing the face height, so this must be avoided, and a short outer bow (but not too short) is required.

High Pull HG to Maxillary Splint 2. High Pull Headgear to a Maxillary Splint A more effective approach to treating children with excessive vertical development is to use an acrylic occlusal splint with an attached high pull headgear (image 1). With this combination, a vertical force can be applied to all the maxillary teeth, which provides better control of excessive maxillary vertical growth and controls the eruption of all the maxillary teeth. A long-face child who displays an excessive amount of maxillary gingiva below the upper lip line would be a good candidate for this type of treatment.

One drawback of this approach is that the appliance does not control the eruption of the mandibular posterior teeth, which are free to continue to erupt. If the mandibular molars erupt, the bite opens further as the mandible rotates downward and backward, increasing the vertical face height.

As with all interventions that rely on growth modification, long-term treatment during the entire active phase of growth will be required to successfully maximize the treatment result.

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{{PAGE_70}} Note that the force vector when using a high pull headgear and a maxillary splint is different from a high pull headgear attached to the maxillary molars only. In the combination appliance the entire maxilla is deemed to be a single unit with a single center of resistance (image 2). This center of resistance is deemed to be located between the apices of the maxillary premolars. The line of force should be directed through this point in an upward and backward direction. This would mean that a high pull headgear with a short outer bow bent upward would be required.

Image 1, High pull headgear to a maxillary splint: A high pull headgear can be used to apply force to the entire maxilla through the use of a maxillary splint. Image 2, Force application using a HPHG and maxillary splint: The high pull headgear and maxillary splint combination applies an upward and backward force to the entire maxilla.

Functional Appliance with Bite Blocks

3. Functional Appliance with Bite Blocks

Another treatment alternative is a functional appliance that includes posterior bite blocks so that the mandible is rotated beyond the freeway space, which (at least theoretically) generates force from the stretched muscles to inhibit eruption of the posterior teeth and prevent vertical descent of the maxilla. The appliance can also be designed to reposition the mandible anteriorly depending on the degree of mandibular deficiency present.

With this appliance, the anterior teeth are allowed to erupt while the posterior teeth are restricted. This will result in closure of the open bite when the appliance is removed. In long-face patients

{{PAGE_71}} without an open bite, all teeth would be covered by the acrylic to apply an intrusive force to all the teeth.

Appliances of this type do lead to closure of anterior open bites, but the change is primarily from eruption of the incisors, not from upward-forward rotation of the mandible—so there is only a small if any effect on the growth pattern.

Headgear to Functional Appliance

4. High Pull Headgear to Functional Appliance with Bite Blocks

The ultimate approach to controlling the pattern of growth in patients with skeletal open bite would be a combination of high pull headgear to restrict vertical growth and a functional appliance with posterior bite blocks to control eruption of the teeth (images 1 and 2). The high pull headgear applies a vertical force to the whole maxilla as headgear to a splint does, and the functional appliance with bite blocks) controls eruption of the mandibular and maxillary posterior teeth while allowing eruption of the incisors.

In spite of all that, recent studies have shown that there is remarkably little effect on the long face growth pattern from even this combination of headgear and functional appliance. The bottom line: none of the types of treatment that have been advocated for patients with skeletal open bite of any severity really are effective in controlling the excessive vertical growth.

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{{PAGE_72}} As we have discussed briefly in the previous material on use of temporary anchorage devices, it now is possible to intrude maxillary posterior teeth, and this does offer a possibility for controlling excessive eruption of posterior teeth. Could bone plates be used to prevent undesired downward growth of the maxilla? Perhaps—but the long-term stability of intruding maxillary posterior teeth still has not been established, and bone plates to restrict growth have had almost no evaluation of any type as of the end of 2012.

Vertical Problems: the Bottom Line

As the dentist responsible for patients with deep bite or open bite problems, what should you expect? Some reasonable conclusions:

thumbsucking is the major cause of most open bites in children, and treatment to extinguish this habit—in a child who wants to stop—is indicated in those whose thumbsucking extends into the elementary school years.
open bite that persists probably has a skeletal component. Treatment of these patients is complex and difficult, and for those with a severe long face / open bite problem, the prognosis is poor.
deep bite is strongly related to overjet, so most Class II children with normal face height will also have a dental deep bite that will need to be corrected during orthodontic treatment.
in contrast to skeletal open bite, functional appliance treatment to correct short face/ deep bite problems is reasonably effective, and damage to the tissues palatal to the maxillary incisors and/or the gingiva in the lower incisors from an impinging overbite is an indication for treatment during the mixed dentition.
management of patients with a combination of a-p and vertical problems is complex enough to indicate referral to an orthodontist in most instances.

Self-Test Referral

The self-test section of this program is designed to help you be sure you have understood the material. Read pages 576-480, 403-412, 536-540, 514-523 (5th ed.) or pages 284-287, 437-443, 498-

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3. Concepts of Adjunctive Orthodontic Treatment

Goals of Adjunctive Treatment

Definition of Adjunctive Treatment

Adjunctive orthodontic treatment, by definition, is “tooth movement carried out to facilitate other dental procedures that are aimed at controlling disease and restoring function.”

Although adjunctive treatment could be needed in children, for all practical purposes it is treatment for adults who have lost teeth and/or supporting bone to dental disease. Some tooth positions and dental relationships are not conducive to long-term oral health, so that occlusal function contributes to destruction of the occlusion. This is referred to as “pathologic occlusion.” An example would be the loss of gingival tissues lingual to the upper incisors from a deep, impinging overbite.

If signs of pathologic occlusion exist, or if restorations needed for other problems would compromise the maintenance of oral hygiene or overly stress the periodontal support apparatus, tooth movement should become part of an overall treatment plan.

For this patient, there are two possibilities for replacement of the missing mandibular first molars. One is a complete orthodontic fixed appliance supported by bone plates or screws to bring the second and third molars mesially and close the space; the other is opening the space for replacement of the first molars (with implants or bridges), which requires repositioning the tipped mandibular second molars, to both improve the periodontal health of the second molars and provide space for adequate restorations.

The problem with closing the space is that it requires complex and prolonged orthodontic treatment, probably over more than 2 years, because remodeling of cortical bone would be required and the roots of the molars would have to be brought mesially further than the crowns. In the lower arch, leaving the molars tipped mesially creates a periodontal situation that is difficult to manage.

In contrast, the orthodontic component of a replacement treatment plan is straightforward and reasonably quick. What is needed is distal tipping of the second molars. The replacement plan, therefore, usually is the more practical and better choice.

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{{PAGE_75}} Goals of Adjunctive Treatment

Adjunctive treatment implies limited orthodontic goals, improving a particular aspect of the occlusion rather than comprehensively altering it.

The goals of adjunctive treatment are to

facilitate restorative treatment by positioning the teeth so more ideal and conservative techniques (including implants) can be used.
improve periodontal health by eliminating plaque-harboring areas and improving the alveolar ridge contour adjacent to the teeth.
establish favorable crown-root ratios and position the teeth so that occlusal forces are transmitted along the long axes of the teeth.
do this while maintaining or improving dental and facial esthetics.

The treatment methods discussed in this module and presented in more detail in the Adjunctive Treatment Procedures module, typically involve a partial fixed appliance and are completed in less than 6 months. Such treatment can be (and often is) carried out in the context of family/restorative practice.

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Adjunctive Treatment: Types of Tooth Movement

Possible tooth movements in adjunctive treatment include

mesial or distal movements of specific crowns, roots, or both
correction of the axial inclination of drifted teeth
correction of the buccolingual position of certain teeth
correction of rotations
extrusion of selected teeth

Although intrusion of teeth can be an important part of comprehensive treatment for adults, it should be avoided as part of adjunctive treatment because of its technical difficulty and the possibility of root resorption and/or loss of control of tooth positions. As a general rule for adjunctive treatment, teeth that are excessively elongated are best treated by reduction of crown height, which has the added advantage of improving the crown-root ratio in patients who have experienced loss of alveolar bone.

For example, when a mandibular molar is to be uprighted (image 1), it is usually necessary to reduce its occlusal surface to avoid occlusal interferences (image 2). Reducing the crown also changes the crown-root ratio in a favorable direction (image 3).

{{PAGE_77}} Image 1, pre-uprighting: Uprighting a tipped molar increases the crown height while it reduces the depth of the mesial periodontal pocket.

Image 2, progress: Reducing the height of the crown usually is necessary to avoid occlusal interferences and allow the uprighting to occur.

Image 3, crown height reduction: Reduction of crown height is particularly desirable if bone support is lacking, because it improves the crown-root ratio.

Adjunctive vs Comprehensive/Complex Treatment

In this patient (image 1), a fractured lower incisor created an esthetic problem because it was obvious when she smiled, and the malpositioned tooth was difficult to restore properly. Five months of adjunctive orthodontic treatment aligned the upper and lower incisors, and then an ideal restoration was placed (treatment details are shown in the module Adjunct Treatment Procedures). To her, the orthodontics was an important part of solving an esthetic problem that the fractured tooth created. Adjunctive treatment can be indicated to improve dental esthetics as well as to improve function and/or control health problems.

In adults with periodontal and restorative problems that are complex enough to require more than 6 months for the orthodontic phase of therapy, coordinated ortho/perio/restorative treatment by a team of dentists usually is needed.

Whether one or several practitioners are involved, adjunctive orthodontics must be coordinated carefully with the periodontal and restorative treatment. Orthodontic treatment for TM dysfunction should not be considered adjunctive. Complex adjunctive treatment is considered in more detail in the Level IV module with that title.

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{{PAGE_78}} Diagnosis / Treatment Planning

Diagnosis: Data Base—Problem List Any treatment plan must be based on adequate diagnosis. Planning for adjunctive treatment requires two diagnostic steps:

Collecting an adequate data base of information
Developing a comprehensive but clearly stated list of the patient’s problems These are precisely the same steps needed in evaluation of any potential orthodontic patient (see the modules Essentials of Orthodontic Diagnosis, and Concepts of Treatment Planning). The problem list, of course, includes all the patient’s problems, not just those directly related to orthodontics. Comprehensive diagnosis, in the sense that no problems have been overlooked, is the key to developing appropriate solutions to problems that may involve several branches of dentistry.

{{PAGE_79}} Orthodontic Diagnosis

Diagnosis: Data Base—Problem List (cont.)

The interview and clinical examination parts of the diagnostic evaluation are the same, whatever the type of orthodontic treatment. Diagnostic records for adjunctive orthodontic patients, however, differ from those for children in several ways:

Individual intraoral radiographs usually are needed to supplement the panoramic radiograph (image 1).
The U.S. Public Health Service guidelines for radiographic evaluation of dental pathology should be followed in determining exactly what radiographs are needed (click on image 2 to see the summary of these recommendations).
Cephalometric radiographs may not be needed.
- The guideline is that serial cephalometric evaluation is required to evaluate changes due to growth or to major changes in tooth position. Nongrowing adults whose treatment will involve repositioning of only some teeth, therefore, do not require a cephalometric radiograph.
Articulator-mounted casts are more likely to be needed.
- This is the case if extensive restorative procedures are planned, or if there are signs of pathologic occlusion.

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{{PAGE_80}} U.S. Public Health Service Guidelines: Dental Radiographic Examination for Pathology

Condition	Recommended radiographs
Regular dental care No previous caries No obvious pathology History of fluoridation	Panoramic film only
Previous caries Obvious caries	Add bitewings
Deep caries Periodontal disease	Add periapicals, affected area only

Image 1, radiographs: For patients with periodontal disease, additional intraoral detail radiographs are required.

Treatment Planning

For patients receiving adjunctive orthodontic treatment, the treatment plan must specify the solutions to the patient’s various problems and the sequence in which treatment procedures will be carried out.

The sequence of treatment is guided by two principles:

Pathologic problems must be brought under control before the orthodontic phase of treatment begins (image 1).
Permanent restorations and definitive perio procedures should be deferred until after the final occlusion has been developed (image 2).

The first step in treatment planning, therefore, is to separate pathologic problems from occlusal problems.

Once these problems have been identified, they are brought under control. The sequence of treatment then is orthodontic tooth movement to establish the occlusion and finally the definitive perio/restorative treatment. Maintenance of the restorations and continued disease control is required long term.

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{{PAGE_81}} Patient Consultation The same scheme used for comprehensive orthodontic treatment applies also to adjunctive patients. The approach is best described as an organized way to seek the plan that provides optimal benefit to the patient. Possible solutions to the various problems are considered, starting with the most important one, interactions and practical considerations are reviewed, and alternative treatment possibilities are outlined. At a meeting with the patient, the doctor’s role is to evaluate the alternative treatment possibilities and present them as clearly and objectively as possible. The goal is to get the patient to understand the alternatives. After the patient and doctor agree on the treatment plan concept, its details are established.

Diagnostic Evaluation, Adjunctive Ortho Patient

Let’s examine this process in the context of a specific patient. Fred, age 30, was concerned primarily about the appearance of his maxillary incisors, because of the midline space (central diastema) and the small size of the laterals (image 1). He particularly didn’t like “the gap in my smile.”

Fred had spaces in both the upper and lower arches. Three first premolars and the mandibular left canine had been extracted previously. Overjet was slightly excessive, but the posterior occlusion was essentially normal (image 2).

The panoramic radiograph showed good dental health despite the spacing in the arches, so there was no indication for intraoral radiographs (image 3).

Did you notice the facial asymmetry, with the nose somewhat off to the left and the chin off to the right? Note in the pan that the right condyle is smaller than the right one and there is a more pronounced antegonial notch on the right side, indicating a lack of condylar growth on that side. Both those findings suggest an old condylar fracture that healed well. The deviation of the nose probably also is the result of old trauma. Is the asymmetry a problem? Not unless he is aware of it as a problem, and he was not. Is further loss of the smaller condyle likely? Probably not, unless he has experienced early signs of degenerative arthritis—and he had not.

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{{PAGE_83}} Diagnostic Evaluation, Adjunctive Ortho Patient (cont.)

As with all patients, the diagnostic data base is derived from three sources:

Interview—which made it clear that his concern was almost entirely the appearance of his maxillary incisors
Clinical examination—which revealed no problems with oral health, jaw function, or facial esthetics (despite the mild mandibular and nasal asymmetry, which were not perceived as problems by the patient)
Analysis of diagnostic records—in this case, primarily the dental casts, which revealed small lateral incisors midline diastema mildly excessive overjet dental midlines not coincident

The mild overjet was not really a problem—but it would have to be considered when correction of the diastema and small lateral incisors was planned. It would be important to keep the maxillary dental midline coincident with the middle of the face, rather than focusing on making it coincident with the mandibular dental midline.

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{{PAGE_84}} DATA BASE

Interview Clinical Exam Analysis of Diagnostic Records

concern: appearance of maxillary incisors good health of oral hard and soft tissues good lip support, facial proportions midline diastema, small max laterals spaces at mandibular extraction sites mild overjet

PROBLEM LIST spaces both arches, especially maxillary central diastema small maxillary lateral incisors

Possible Solutions / Patient Conference

There were two possible solutions to the problem of spacing in both arches:

Comprehensive orthodontics to close spaces and obtain alignment in both arches that was as ideal as possible
Treatment of the maxillary arch only, accepting the spaces in the mandibular arch

For the problem of the small maxillary lateral incisors, the only treatment would be restorations to build up them up to normal size (or choose not to correct the problem, which would leave him with compromised dental esthetics).

How do you choose between the possibilities?

Remember, you don’t, the patient does. It is the doctor’s role to present the possible solutions and discuss their pros and cons with the patient so that he can make an informed decision.

In this case, Fred chose the shorter and less expensive approach of treating the maxillary arch only, but wanted the small laterals built up as part of the overall approach.

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Treatment Plan Concept / Details

At this point, the treatment plan concept should be clear. For Fred, it was treatment for the maxillary arch only, to close the maxillary central diastema, keeping the maxillary dental midline about where it was, and open space so that the lateral incisors could be built up. The essence of informed consent is that the patient and the doctor(s) agree at this point.

The treatment plan details are for the doctor(s) and show how the concept is to be implemented:

bonding of edgewise .022 slot brackets for the maxillary arch, back to 2nd premolars only
elastomeric chains to close the central diastema, then compressed coil springs to open space for build-ups of the lateral incisors
slight retraction of the central incisors as needed to get the space correct for ideal proportions of the lateral incisors
removal of excessive gingival tissue in the maxillary midline, and repositioning of the frenum, if needed
composite build-ups of the lateral incisors
maxillary retainer

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{{PAGE_86}} Tx Plan Concept Tx Plan Details

CONCEPT Treat maxilla only:

close diastema
open space adjacent to lateral incisors
retract maxillary centrals slightly to adjust space for best build-ups of laterals
perio / restorative treatment after ortho

DETAILS Orthodontics: bond maxillary arch, .022 edgewise bkts elastomeric chain to pull central incisors together compressed coil springs to open space adjacent to lateral incisors

Perio / Restorative: consider frenotomy if poor tissue reaction composite build-ups

Treatment Progress Treatment was implemented as planned. The maxillary arch was bonded, but only to the 2nd premolars (which simplified the appliance and avoided the problem of attachments to the crown on one maxillary first molar) (image 1). Elastomeric chain on an steel arch wire that provided 0.003-inch clearance between the wire and the bracket, so that the teeth could slide along the wire, was used to close the excess space, slightly retracting the upper incisors as this was done (image 2). Note the use of multiple segments of the chain, with a 2-unit segment initially from the mesial bracket of one central incisor to the mesial bracket of the other. A continuous chain would have produced too much force. There was no attempt to correct the dental midline, which might have made the facial asymmetry more apparent. After the diastema was closed, compressed coil springs were used to open space for build-ups of the lateral incisors (image 3). When a maxillary central diastema is closed, tissue reaction in the midline is possible, and the patient should be told that a frenotomy procedure may be needed. In this case, it was not. Composite build-ups were done immediately after the orthodontic appliance was removed (image 4), and a retainer was placed. Treatment time, as planned, was 6 months.

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{{PAGE_87}} Image 1, pre-treatment: Age 30, prior to treatment. Image 2, space closure: Space closure with elastomeric chains. Image 3, positioning laterals: Positioning laterals with compressed coil springs. Image 4, treatment completed: Restorations completed. Image 5, treatment sequence: Overview of steps in treatment. Treatment Progress (cont.) Level III Biomechanics — Unit B · 87 / 142

{{PAGE_88}} Fred was pleased with the improvement in his smile esthetics (image 1), and lip support was unchanged (image 2). To a trained eye the facial asymmetry is still noticeable, but all faces have some asymmetry, and if Fred remained more asymmetric than most people, neither he was not even aware of it, and almost certainly his friends and associates also had never noticed it. Although the comprehensive treatment that would have been required for ideal occlusion was not done, the treatment solved his problem.

Should the lower arch have been treated? There was no esthetic problem related to the spaces there, his oral health was good despite the spaces, and there was no problem with functional occlusion. So the judgment was that there was no compelling reason to treat the lower arch.

It often is the case that adjunctive orthodontics focuses—quite appropriately—on a specific aspect of the dental occlusion rather than comprehensive correction of a malocclusion.

Image 1, smile change: Change in smile esthetics with treatment. Image 2, post-treatment facial: Fred, age 31, at completion of treatment.

Biomechanical Considerations

Effects of Reduced Periodontal Support

Because adjunctive treatment often involves adults who have experienced periodontal disease, an important consideration in developing the detailed plan for adjunctive orthodontic treatment is the amount of bone support for the teeth.

When bone loss has occurred, a periodontally involved tooth differs from a normally supported tooth in two important ways:

A decrease in the volume of the periodontal ligament also occurs (image 1).This means that the normal force against the crown produces greater pressure in the PDL—so lighter forces are required when bone loss has occurred.

Remember that it’s the pressure in the PDL that affects blood flow and leads to the biologic responses that allow tooth movement. The goal, obviously, is to use whatever force is needed to

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{{PAGE_89}} produce the optimal pressure. For example, suppose you were trying to move a premolar bodily. The typical force to do that, producing close to the ideal pressure in the PDL, is 100 grams. But if half the alveolar bone support has been lost, 100 grams would produce twice the ideal pressure, because the force is being expressed over half the PDL volume. If bone loss has occurred, the force has to be reduced from what it would have been with a normal tooth. Otherwise pressure in the PDL would be too large.

Effects of Reduced Periodontal Support (cont.)

When bone loss has occurred, a periodontally involved tooth differs from a normally supported tooth in two important ways:

A decrease in the volume of the periodontal ligament also occurs
When force is applied, the center of resistance of the root will be further from the crown—so relatively larger moments are needed to control root position.

Remember that a force against the crown of a tooth creates a moment (MF), because the force on the crown is at a distance from the center of resistance, which is near the midpoint of the part of the root that is within supporting bone. For our typical normal premolar, a 100-gm force creates a 1000 gm- mm moment because it is 10 mm to the center of resistance.

To control root position, a couple (two forces equal in magnitude and opposite in direction) must be applied to the crown, creating a moment (MC) that counteracts the moment of the force. A couple

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{{PAGE_90}} creates a pure moment—no net force to move the tooth, just a moment to rotate it. The couple usually is created by a wire that crosses a bracket on the crown at an angle, so that one corner of the bracket is lifted up while the other is pushed down. In the normal condition, a 1000 gm-mm MC is needed to cancel out the 1000 gm-mm MF, and then bodily movement will occur. But when half the bone support has been lost, the distance to the center of resistance increases to 15 mm, and with 100 gm force, a 1000 gm-mm MC would be inadequate and the tooth would tip (image 1). After loss of half the supporting bone, therefore, bodily movement would require a 50-gm force and a 750 gm-mm moment of the couple, to balance the 750 gm-mm moment of the force (image 2).

Image 1, moments: Bone loss increases the distance from the crown (and an orthodontic force on it) to the center of resistance.

Image 2, corrected for bone loss: With loss of half the bone, half the force and a relatively larger moment are required.

Appliance Considerations: Fixed vs Removable

Can you use a removable appliance for adjunctive orthodontics, or is a fixed appliance required? For adults receiving adjunctive orthodontics, as a general rule, removable appliances rarely are satisfactory, for four reasons. With acrylic removable appliances that incorporate springs for tooth movement:

It is impossible to obtain both a force, which generates a moment, and the moment of a couple to counteract the moment of the force, with a single spring (image 1), so control of root position is lacking. A couple is much easier when you can pull as well as push. That requires a fixed attachment.
It is difficult to correct rotations at the same time a crown is repositioned, for the same reasons: two points of contact are needed to rotate a tooth without displacing it (image 2). The direction of tooth movement is always at right angles to the initial contact of a fingerspring on a removable appliance. Applying a fingerspring to the mesiolingual angle so that the rotation of the premolar would improve also carries the tooth buccally, whether or not that is desirable.

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{{PAGE_91}} 3. At best, the removable appliance is worn only part of the time. Interrupted forces, those that are there when the appliance is in place but drop to zero when it is removed, can move teeth but are not as effective as continuous forces. 4. Discomfort and interference with speech and mastication are greater than with a carefully designed and placed fixed appliance.

Do the same limitations apply to clear aligners, like those used with Invisalign? The top 3 items in the above list apply in the same way. With Invisalign you can not rotate teeth or move them bodily unless you bond fixed attachments to the teeth so the aligner can get a better grip (image 3), and the aligners are not worn all the time. Clear aligners are easier for adults to tolerate than acrylic plates, however.

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{{PAGE_92}} Image 1, spring for distal tipping: With a finger spring from a removable appliance, the tooth would tip distally, because there is no moment to control root position. Image 2, spring for attempted rotation: Adjusting the point of application of the spring could produce some rotation, but the tooth also would be displaced facially. Image 3, Clear aligner over fixed attachment: For rotation, extrusion or bodily movement of teeth, clear aligners require fixed attachments on the teeth.

Appliance Considerations: Fixed vs Removable (cont.)

One situation in which an acrylic removable appliance may have an advantage is in a patient with multiple missing teeth. With a fixed appliance that has long unsupported spans of wire between teeth, distortion of the arch wire can become a problem, and irritation of the cheek can also occur. These problems are avoided with a removable appliance that has acrylic between separated teeth.

In addition, with a removable appliance, some reaction forces from tooth movement can be spread over adjacent supporting tissues, such as the palatal vault and alveolar mucosa. Major tooth

{{PAGE_93}} movements, however, will still be very difficult with a removable appliance. The anchorage value of supporting tissues is minimal.

In the patient shown here, a removable appliance was preferred to reposition the second molar before fabrication of a removable partial denture, because of the multiple missing teeth and the long span between the incisors and the molar. A spring-loaded screw against the molar was used instead of a fingerspring to provide better control of the amount of activation.

Fixed Appliance Considerations: Bracket Placement

The position of fixed appliance brackets, like the twin edgewise brackets typically employed in adjunctive orthodontics, affects the type of movement that will occur for each tooth when a wire connecting the brackets is placed.

Often the primary goal of adjunctive treatment is to upright a molar, using the premolars and canine as anchorage. If the anchor teeth are not perfectly aligned, and brackets are placed on the anchor teeth in the ideal position near the center of the crown, a straight piece of wire connecting the brackets creates forces and moments to ideally position these teeth, which can decrease their anchorage value (image 1).

If the goal is to upright a molar but to use the premolars and canines just as anchorage without repositioning them, it would be better to place the brackets on the anchor teeth so that a straight

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{{PAGE_94}} segment of wire would not displace them (image 2). The effect on the anchor teeth with the different bracket positions is compared in image 3. Where do you put the brackets for adjunctive orthodontics with a partial fixed appliance? It depends on exactly what tooth movement you’re trying to accomplish.

Summary, Adjunctive Orthodontic Concepts

Adjunctive orthodontics differs from comprehensive/complex orthodontics in several important ways:

The goals of treatment are to solve specific problems for the patient, usually related to control of periodontal disease and long-term maintenance of the teeth or positioning teeth to facilitate restorative and prosthodontic treatment, not to produce ideal dental occlusion.

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{{PAGE_95}} Diagnostic records are likely to include additional radiographs, and articulator-mounted dental casts are needed more frequently. Treatment usually involves only part of the dentition and is completed in 6 months or less. Fixed appliances are preferred but often the brackets are placed to limit the movement of anchor teeth instead of repositioning them to an ideal position.

Self-Test Referral

The self-test section of this program is designed to help you be sure you have understood the material. Read pages 362-369, 621-627 in Contemporary Orthodontics,5th ed, (or pages 411-417, 633-639, 4th ed) then take the test, and use it as a guide for further study and review.

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{{PAGE_96}} 4. Adjunctive Orthodontic Treatment Procedures

Molar Uprighting

Molar Uprighting

One of the most frequently used adjunctive orthodontic procedures is the uprighting and distal movement of a mesially tipped permanent second molar to allow placement of a properly contoured restoration.

Early loss of permanent first molars is much less common now than previously, but fluoridation does not protect against pit and fissure caries, and deep occlusal decay in these teeth can occur before patients are even aware of it. If a first molar must be extracted, mesial drift of the permanent second molar can be expected. The younger the patient when the tooth was removed, the more drift is likely to occur, but even in adults, second molars drift mesially when first molars are lost.

In the mandibular arch, the second molar typically tips mesially, and often spaces develop between the premolars as these teeth drift distally into the extraction site (image 1). Periodontal inflammation and bone loss often occur on the mesial of the tipped second molar. In the maxillary arch, the second molar usually rotates mesiolingually and tips mesially, while spaces open between the premolars. This makes replacement of the missing tooth difficult, but periodontal problems are much less frequent than in the mandibular arch.

Periodontal problems on the mesial of a tipped mandibular second molar occur for two reasons: (1) the area beneath the tipped mesial portion of the crown is difficult to clean and inherently unhealthy, and (2) occlusal forces are not directed along the long axis of the tooth. If a bridge or implant is placed without correcting the position of the tooth, both factors increase the likelihood of periodontal breakdown that may cause the restoration to fail.

The advantages of uprighting the tipped molar and closing spaces between the premolars are better periodontal health and a better long-term prognosis for restorations placed in this area. It is possible to fabricate a bridge without uprighting a tipped abutment molar, but it is very difficult to make a good one (image 2), and the long-term success of an implant-supported crown adjacent to a tipped molar also can be compromised.

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{{PAGE_97}} Image 1, loss of first molar: Typical mesial tipping of mandibular second molar after loss of first molar. Image 2, bridge on tipped abutment: Bridge on tipped abutment: periodontal health is compromised.

Molar Uprighting (cont.)

When a mandibular second molar has tipped mesially into an old first molar extraction space, the best treatment usually is to extract the third molar and upright the second molar by tipping it distally. This provides space for an appropriately contoured replacement tooth and places occlusal forces more along the long axis of the teeth.

If restorations (crowns/onlays) are needed in what would be the bridge abutment teeth (as they often are), replacing the missing first molar with a bridge pontic can be the best procedure (see images). If restorations are not needed, an implant is often preferred.

The bridge or implant stabilizes the dental occlusion and serves as a permanent retainer to maintain the tooth positions.

For this patient (image 1), the lower second molar was tipped distally after the third molar was extracted (image 2), creating an ideal arrangement for placing a bridge or implant. On the postuprighting radiograph, note the new bone that has filled in on the mesial of the second molar (image 3).

A view of implant-supported crowns to replace missing first molars (in a different patient) can be seen in image 4.

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{{PAGE_98}} Image 1, pretreatment occlusion: Dental relationships prior to molar uprighting. Image 2, post-uprighting occlusion: After molar uprighting, before restorations.

Image 4, implant-supported molar crowns: Crowns on implants now replace missing first molars for this patient.

Considerations in Molar Uprighting

Three things must be kept in mind when this type of molar uprighting is the plan:

Extraction of the third molar is necessary if significant distal movement of the second molar is to be obtained. If both the second and third molars are to be retained, the technique for uprighting is different (see below).
Adequate anchorage for the uprighting must be obtained. This means that fixed attachments on the molar, canine, and both premolars are necessary, and better control is obtained when a fixed lingual arch from canine to canine is placed (image 1). Typically, a band is placed on the molar to be uprighted (but a bonded tube can be used), bonded brackets are placed on the facial surface of the premolars and canine, and a bonded lingual wire is used to stabilize the position of the canines.
Reduction of the occlusal surface of the molar is necessary as it uprights, to control occlusal interferences (image 2). This also improves the crown-root ratio and decreases stress on the

{{PAGE_99}} periodontium.

Image 1, fixed appliance for uprighting: Fixed appliance for molar uprighting: band on molar, bonded brackets on premolars and canines, and a bonded canine-to-canine lingual arch.

Image 2, reduction of uprighted molar: Reduction of the occlusal surface of the molar improves the crown-root ratio.

Fixed Appliance for Molar Uprighting

The first step in molar uprighting is to place a fixed appliance, either bands or bonded attachments, on the molar and the anchor teeth.

Bonded brackets on the premolars and canine are almost always preferred now. Exactly how they should be placed is determined by the extent to which movement of these anchor teeth is desired (see the Concepts of Adjunctive Treatment module). Marks on the teeth (which can be made intraorally after enamel etching in preparation for bonding) help in orienting the bracket as desired (image 1).

Either a bonded tube (image 2) or a band carrying a welded tube (image 3) can be used on the molar. A bonded tube can be broken off during treatment, so a band is more trouble-free, but the band margins should not extend into periodontally sensitive areas. The more severe the periodontal problems, the more likely a bonded tube would be preferred.

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{{PAGE_100}} Image 1, orientation marks: Orientation marks help in bonding brackets in the correct location.

Image 2, molar uprighting appliance: Band on molar, with bonded attachments on anchor teeth—note the bonded lingual arch.

Image 3, banded molar: Bonded tube on molar, bonded brackets on canine and premolars.

Step 1 in Mandibular Molar Uprighting

The sequence of treatment requires three steps. The first step to upright the molar, correcting malalignment of the premolars and canines at the same time.

This can be done in three ways: with

a flexible rectangular wire placed in both the premolar brackets and the molar tube (image 1).
a continuous wire that spans the old extraction site and an auxiliary spring (image 2). This requires two tubes on the molar, one used for the auxiliary spring and the other for the main arch wire. It is convenient to have two tubes available routinely on a molar to be uprighted, so that an auxiliary spring can be used if desired.
a wire in the brackets of the anchor teeth that does not span the old extraction site, and an auxiliary uprighting spring (image 3).

The choice is determined by how much change is desired in the position of the anchor teeth, and how severely the molar is tipped. A continuous flexible wire implies that the molar is only mildly tipped. After initial alignment of the anchor teeth, an auxiliary spring often facilitates uprighting the molar, so the first two ways frequently are combined.

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{{PAGE_101}} An auxiliary spring with a separate anchor segment of rigid wire is indicated when the molar is severely tipped, so that a continuous flexible wire cannot be fitted into both the attachments on the anchor teeth and the molar tube. With this approach, the anchor teeth should be stabilized with a rigid wire before the auxiliary spring is activated.

Image 1, continuous flexible wire: Continuous flexible wire for alignment/uprighting. Image 2, continuous wire plus auxiliary spring: Auxiliary uprighting spring with continuous wire. Image 3, anchor segment plus auxiliary spring: Auxiliary spring with separate anchor segment.

Step 2 in Mandibular Molar Uprighting

The second step in a typical molar uprighting case is to further open the space of the missing first molar, closing any space between the premolars and moving the second molar more distally. Often it is as important to move the second premolar mesially, closing spaces between the premolars, as it is to move the molar further distally.

This is accomplished with a compressed coil spring over a rigid wire (images 1 and 2). The wire must not fit too tightly in the brackets and molar tube, because it must be able to slide in the attachments. For sliding to occur, there must be at least 0.002 inch clearance between the wire and the attachments—so .020 wire would be the largest that should be used with a .022 edgewise appliance. Often .018 wire is rigid enough, and the additional clearance would facilitate sliding.

{{PAGE_102}} Reactivation of the spring can be accomplished by adding a split section of tubing over the arch wire to further compress the spring (image 3). It is not necessary to remove the spring to activate it in this way.

Image 1, compressed coil, diagram: Compressed coil spring to open space for replacement of the missing molar and close spaces between premolars.

Image 2, compressed coil, intraoral: Compressed coil spring over continuous arch wire.

Image 3, re-activation of coil: Adding a split spacer as shown in the diagram reactivates the spring without having to remove the wire.

Step 3 in Mandibular Molar Uprighting The third and final step in a typical molar uprighting case is a fixed retainer to maintain the teeth in position until either a bridge or implant can be placed. This can be done either with a wire for that purpose in the attachments (images 1, 2), or with a wire bonded into shallow intracoronal preparations after the orthodontic appliance has been removed (images 3, 4). In either case, the bridge or implant will serve as a permanent retainer, and it should be placed as soon as possible. Long delays in placing the permanent retainer can lead to problems.

{{PAGE_103}} The two types of fixed retainer are shown diagrammatically in image 5. If retention is continued more than a few weeks, the bonded intracoronal retainer is preferred.

Mesial Root Movement in Mandibular Molar Uprighting

It is much more difficult to move the root of the second molar mesially than to tip the crown distally, but if the third molar is not extracted, some mesial root movement is needed.

This is typically accomplished with a loop in a rectangular arch wire segment. The wire is shaped initially as shown in image 1. When it is placed into the molar tube, a moment is created to tip the crown distally and bring the root mesially (image 2). If the wire is pulled through the distal of the tube and bent over (image 3), the effect is to create a force to prevent the crown from tipping distally. Then the effect is to close the space and bring the root of the second molar mesially—if the premolars are tied together to provide adequate anchorage.

If the molar to be uprighted is severely rotated and tipped, a modification of a loop wire, with the wire inserted into the distal of the molar tube as shown in image 4, can be helpful.

The major advantage of moving the roots of a lower second molar forward is to improve the periodontal condition between the 2nd and 3rd molars. As we have noted previously, this root movement is difficult because remodeling of cortical bone usually is required, and the advantage of retaining the 3rd molar versus removing it and tipping the 2nd molar distally must be evaluated carefully.

Maxillary Molar Uprighting

A similar approach can be taken to uprighting a mesially tipped maxillary second molar. In the upper arch, the additional anchorage of a canine-to-canine lingual arch is not needed (and would be highly irritating to the tongue if used).

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{{PAGE_105}} As they drift mesially, upper molars tend to tip less than lower molars but rotate more. The details of the uprighting appliance always must be modified to deal with the specific clinical situation. Loops in rectangular wire, or a superelastic continuous wire, can be used to tip an upper molar distal or activated to bring the root mesially.

This patient, who had lost both upper first molars and one second premolar, needed uprighting of both second molars in preparation for restorations. On the right side, moving the roots of the molar mesially would be desirable so as not to increase the already large space. On the left side, tipping the molar distally to increase the space and improve its inclination was the appropriate goal.

Image 1, occlusal view: Occlusal view, missing maxillary molars.

Image 2, radiograph, right side: Radiograph, right side: missing first molar and 2nd premolar.

Image 3, radiograph, left side: Radiograph, left side: missing first molar.

T-Loops in Uprighting

For this patient, T-loops were used bilaterally.

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{{PAGE_106}} On the left side, after the loop was activated by placing it into the tube on the molar, the end of the wire was bent over so that the crown could not move distally and the roots would move mesially. This is the same type of activation shown in the drawing below, of activating a lower molar uprighting appliance to bring the roots mesially. On the right side, the end of the loop was not bent over, and then the activation was expressed by tipping the crown distally and opening the space. When a couple is placed against the crown of a tooth, the crown will move more than the root unless movement of the crown is restrained. Thus a T- loop can be used to move either the crown or the root, depending on how it is attached.

Image 1, uprighting right side: Uprighting maxillary 2nd molar, mesial root movement: wire activated with end bent over at back of molar tube to restrain distal movement of the crown.

Image 2, uprighting left side: Uprighting maxillary 2nd molar, distal crown tipping: wire activated with molar tube free to slide distally along the wire.

Fixed Retainers

At the completion of the molar uprighting, which required four months for this patient, fixed retainers in the form of bonded wires were placed (images 1-4).

Retainers of this type are tolerated by patients much better than a palate-covering maxillary removable retainer, and for that reason are much more effective in maintaining the position of the teeth until final restorations can be placed.

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Evaluation of Maxillary Molar Uprighting

Image 1, left side: Fixed retainer bonded into small occlusal preparations, left side. Image 2, right side: Bonded fixed retainer, right side. Image 3, occlusal view: Occlusal view, bilateral fixed retainers. Image 4, drawing of fixed retainer: Diagram, intracoronal fixed retainer.

For this patient, bridges were placed bilaterally after the maxillary molar uprighting was continued. As part of the restorative phase of treatment, root canal therapy was performed for the right molar and second premolar abutment teeth.

Note that as planned, the space on the left side was opened as the crown of the molar tipped distally, while the inclination of the right molar was improved, but the space remained the same size as the roots moved mesially.

The benefit of the orthodontic treatment was to improve the periodontal prognosis of the abutment teeth, both by creating a better gingival environment and by placing masticatory stresses more along the long axis. Note particularly the improved bone contour on the mesial of the maxillary left 2nd molar.

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Further Considerations in Molar Uprighting

Root Paralleling in Molar Uprighting

Because research has shown that in the upper arch, healthy alveolar bone can exist even if the second molar and second premolar roots are not parallel, closing space in the upper arch also is more feasible than in the lower arch. The crowns can be brought together with having to move the roots further than the crowns, i.e., the space can be closed without the necessity of paralleling the roots. Almost always, not as much tooth movement is required either to open space in the upper arch (or close it) when a first molar was lost previously.

For this patient who had lost both the upper and lower left first molars years before, uprighting the mandibular second molar by tipping it distally after extraction of the third molar, but closing the molar extraction space in the upper arch, was the treatment plan. That was feasible because the upper molars could be left at a mesially tipped inclination that would not be compatible with periodontal health in the lower arch.

Molar Uprighting with Posterior Crossbite Correction

For this patient, who wanted replacement of a missing lower molar, the situation was complicated by a crossbite relationship of the molars in that quadrant. Note (image 1) that the lower second molar was rolled to the lingual, and the upper second molar was tipped facially, so there was a complete buccal crossbite of those teeth.

For this man (age 50), the anterior deep bite was not a problem esthetically, and since his periodontal condition was good (i.e., he was tolerating the anterior deep bite from the perspective of periodontal health), there was no necessity to totally correct the occlusion. His problems were the missing lower first molar, the mesially and lingually tipped lower second molar, and the molar crossbite. Adjunctive orthodontic treatment appropriately would focus on correcting the occlusion so that a satisfactory restoration for the missing tooth would be possible.

One approach to correction of a molar crossbite of this type is the use of a “through the bite” or cross-elastic, running from the mesial of the lower molar to the facial of the upper molar. A cross-elastic to correct the more common lingual crossbite is illustrated in image 2. Because elastics of this type tend to extrude the teeth as well as move them faciolingually, they must be used carefully, but they can be quite effective.

Molar Uprighting with Posterior Crossbite Correction (cont’d.)

Image 1, posterior crossbite / tipped molar: Buccal crossbite of second molars, lower molar uprighting needed to allow replacement of missing lower first molar.

Image 2, cross elastics: Drawing of cross-elastic to correct posterior crossbite.

Uprighting of the lower second molar was done in the usual way, tipping the crown distally with a flexible arch wire. In addition, a rubber band from a button on the lingual of the lower molar (image 1) to a hook on the facial of the upper molar (image 2) was used to tip the upper molar lingually and the lower molar facially.

An elastic of this type is called a cross-elastic because it crosses through the occlusion. The force was about 100 gm when the jaws were in their postural position. Reduction of the cusp height of both teeth was necessary to allow the crossbite correction. Normal occlusion on the lower second molar bridge abutment was achieved.

With the upper molar brought lingually and the lower molar moved facially as well as uprighted, it was possible to bring the posterior teeth into good occlusion (image 3), and a fixed bridge was placed with the abutment teeth out of crossbite (image 4). The amount of change created by the combination of uprighting the lower molar and lingual movement of the upper molar can be seen in the composite view (image 5).

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{{PAGE_111}} This patient could tolerate some extrusion during crossbite correction that was compensated by reducing the cusp height of the teeth—but not every crossbite patient could, so cross-elastics cannot be used for all crossbite conditions.

{{PAGE_112}} Image 1, lower band with lingual button: Lower arch, uprighting with fixed appliance, lingual button on lower molar for attachment of cross-elastic.

Image 2, upper band with facial hook: Molar uprighting in lower arch, buccal hook on upper molar band for attachment of cross-elastic.

Image 3, orthodontic treatment completed: Crossbite corrected, upper molar band removed.

Image 4, bridge in place: Bridge in place, molar uprighted and crossbite eliminated. In this situation, retention of the crossbite correction is needed, and the bridge also serves as a permanent retainer.

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Molar Uprighting: Summary and Conclusions

Molar uprighting can improve the periodontal prognosis for teeth adjacent to the missing tooth or teeth, and facilitate restorative procedures. Some important considerations to remember:

a partial fixed appliance almost always is the best method—removable appliances are largely ineffective because they are limited in the type of tooth movement they can produce and are difficult for the patient to tolerate
in the mandibular arch, a bonded canine-to-canine lingual wire increases the anchorage value of a premolars-canine anchorage unit—but this is rarely indicated in the maxillary arch
if a molar to be uprighted is not severely tipped, a continuous flexible archwire segment (usually NiTi wire) is effective
greater tipping of the molar usually is managed best with the use of an auxiliary uprighting spring
crossbite correction with cross-elastics can be done simultaneously with uprighting, but long-term retention is likely to be needed—and a fixed bridge with two abutments is a permanent retainer
mesial root movement to close space can be managed with a T-loop archwire segment, and is easier to accomplish in the maxillary arch, where root inclination is not as critical as in the mandibular arch

Forced Eruption

Indications for Forced Eruption

If a tooth has a defect in the cervical third of the root (from fracture, resorption, decay or periodontal problems), extensive crown lengthening would be necessary to gain access for treatment. Poor esthetics and adverse changes in the crown-root ratio are likely problems.

For many patients, controlled extrusion (forced eruption) is an excellent alternative. It improves endodontic access and can allow crown margins to be placed on sound tooth structure while maintaining the gingival contour. Although a tooth with a single tapering root is the ideal candidate for extrusion, multirooted teeth also can be managed in this way.

The distance of extrusion is determined by

the location of the defect relative to the alveolar crest
space for placement of the restoration margin (1 mm)
allowance for the gingival attachment (2 mm)

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{{PAGE_114}} For this patient, the crown of a maxillary first premolar fractured beneath a restoration, leaving a defect extending 2 mm below the alveolar crest (images 1 and 2). To prepare this tooth for a new crown, 5 mm extrusion would be needed: 2 mm to reach the defect, 1 mm to place the restoration margin, and 2 mm allowance for the gingival attachment.

Forced Eruption

Extrusion requires relatively light force (50-100 grams). Too much force can produce tissue damage and ankylosis. A tooth can be extruded at a rate up to 1 mm/week without biologic damage, so a few weeks of treatment time almost always is sufficient.

For this patient, to extrude the damaged premolar, a button was bonded on its occlusal surface, and edgewise brackets were bonded on the adjacent canine and second premolar (image 1). A segment of rectangular wire with a loop that faced downward initially was rotated into position and tied to the button, creating a force of approximately 100 grams to extrude the premolar (image 2). It elongated about 5 mm in as many weeks (images 3 and 4).

Compare the change in position of the fractured tooth over that period of time (image 5). Note that when a tooth is extruded, both bone and gingival tissue tend to come with it.

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{{PAGE_115}} Image 1, appliance set-up: Bonded button on fractured tooth, brackets on adjacent teeth.

Image 3, 5 weeks later: Extrusion completed, 5 weeks later.

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{{PAGE_116}} Table: | Image 5, change in position: Change in position with extrusion—note the change in gingival contour as well as the change in tooth position. | |

Forced Eruption (cont.)

With the extrusion completed, the brackets and button were removed, and the now-passive spring was bonded directly to serve as a fixed retainer (image 1). An extruded tooth should be held in its new position at least 4 weeks, until the rebound tendency from stretched gingival and periodontal tissues subsides.

Because gingival tissues tend to follow the extruding crown, usually it is necessary to perform a gingivoplasty before a new crown can be placed (image 2). This is much less extensive than a crown-lengthening procedure without the extrusion, however.

At that point a new crown can be placed, with a better crown-root ratio and better gingival contours than would have been the case without the extrusion (images 3 and 4).

Inter-Arch Elastics for Forced Eruption

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{{PAGE_117}} Sometimes the anchorage for extrusion can be the teeth in the opposite dental arch. This 60-year-old patient fractured off the facial surface of a mandibular first molar, with the fracture line extending subgingivally.

For extrusion of the fractured molar, the maxillary premolars and first molar were bonded, placing the brackets so that a straight wire would fit passively (image 1). The occlusal surface of the fractured tooth was reduced to provide space for extrusion. Then a button was bonded to the fractured lower molar, and a light elastic was used to extrude the tooth (image 2) until the fracture line was accessible. After 4 weeks (image 3), the fracture line was far enough above the alveolar crest that a crown with proper margins could be fabricated.

The force from an interarch elastic is not as constant as from a spring on a fixed appliance. Anything about an orthodontic appliance that can be removed will be—the elastic will not be worn all the time, even by a highly cooperative patient. So the rate of extrusion is less predicable with this method, but it can work very well for a fractured molar.

Image 1, appliance set-up: Button bonded to fractured molar, maxillary segment for anchorage.

Image 2, extrusive elastic in place: Interarch elastic for extrusion, 100 gm force.

Image 3, 4 weeks later: Extrusion completed, 4 weeks later.

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{{PAGE_118}} Forced Eruption to Maintain Bridge Abutment Tooth

For this patient in her 60s, the bridge in the maxillary left quadrant was failing, and the canine abutment had cervical decay that extended subgingivally (arrow in image points to the subgingival carious area).

The plan was to

section the bridge, maintaining the molar crown that was the distal abutment of the bridge while removing the pontic and the canine crown
restore the canine temporarily
fabricate a new crown after it was extruded to the point that proper margins could be placed

Extruding the canine would also provide a better crown-root ratio, but the damaged tooth would not be an adequate abutment for a long-span replacement bridge, so an implant in the premolar area to replace the bridge pontic also was planned.

Forced Eruption to Maintain Abutment Tooth (cont.)

The other maxillary teeth were used as anchorage. A tube was bonded to the crown on the molar, brackets were bonded to the incisors and the other canine, and a button was bonded to the temporary amalgam restoration in the canine. A flexible nickel-titanium wire was used to generate the extrusive force (images 1 and 2). As the canine extruded, amalgam from the core of the previous crown was ground away to keep the tooth out of occlusion, and the button was rebonded at a higher level.

After 8 weeks, the button could be bonded on the root surface, and the tooth was extruded to its final position, with the old amalgam core completely removed (image 3). It was held there for a month

{{PAGE_119}} before the orthodontic appliance was removed. Total elongation was about 6 mm, with treatment time of 3 months.

The panoramic radiograph near the completion of the restorative treatment (image 4) shows the elongated canine with a temporary crown in place and implants replacing the bridge pontic and the right lateral incisor.

Remember that patients with this type of adjunctive orthodontic treatment must be seen every 1-2 weeks to reduce the occlusal surface of the tooth being extruded, control inflammation, and monitor progress. Stabilization for 3-6 weeks after extrusion is completed allows for reorganization of the PDL and minimizes relapse.

Forced Eruption: Summary and Conclusions

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{{PAGE_120}} Forced eruption as an adjunctive orthodontic procedure:

is indicated as a way to make restoration of fractured teeth possible
usually requires a partial fixed appliance (an exception using magnets in attraction can be seen in Module 23, Biology of Orthodontic Treatment)
should be done using relatively light force (50-100 gm)
occurs at a rate of about 1 mm per week
often requires recontouring the gingiva, and sometimes requires recontouring alveolar bone, after the tooth movement is completed.

One theory of forced eruption has been that it should be done very quickly (in a few days) with heavy force, so that bone and gingiva would not follow the movement of the remaining part of the tooth. This is undesirable because it injures the periodontal support apparatus of a tooth that already has been damaged. That is too high a price to pay for avoiding recontouring of the tissues before a final restoration is placed—and recontouring often is required anyway.

Maxillary Incisor Alignment

Appliances for Maxillary Incisor Alignment

Another frequent indication for adjunctive orthodontics is to prepare for restoration of maxillary incisors. Cosmetic dentistry in this region—for example, the placement of veneers on discolored or fractured teeth—is facilitated by properly aligning the teeth initially.

There are two ways to accomplish this:

bonded brackets, flexible arch wires, and coil springs over the wire to reposition the teeth (image 1); or
a series of transparent plastic aligners (image 2).

At this point, brackets and wires remain the most cost-effective approach. For modest degrees of tooth movement, plastic aligners are a feasible (but expensive) alternative.

{{PAGE_121}} Image 1: Clinical photo of upper dental arch with bonded brackets, wire, and coil springs to open space for build-ups of lateral incisors. Image 2: Clinical photo of a transparent plastic aligner held in hand, made by resetting teeth on a dental cast with small movements, used as an alternative for minor tooth movements.

Maxillary Incisor Alignment, Fixed Appliance

Ed was age 47 when he asked his dentist if it was possible to put crowns on his upper incisors to close the large central diastema (image 1), which he had never liked. The result of that, however, would be a pair of the world’s largest central incisors, hardly an esthetic improvement.

He was told that what he really needed was repositioning of the incisors to distribute the space equally among them, then esthetic restorations with build-ups of all four maxillary incisors would be possible. He accepted that plan, which called for placing a fixed appliance on his upper arch only. The estimated orthodontic treatment time was about 6 months. The treatment objective was to partially close the large central diastema (images 2, 3) by bringing the central incisors closer together, opening space mesial and distal to the lateral incisors as this was done, and then to restore all four maxillary incisors.

Although his lower incisors were mildly irregular (image 4), this was not a problem, either from the point of periodontal maintenance or esthetics, and no treatment for the lower arch was planned.

His periodontal health was good, so disease control measures before beginning orthodontic treatment were not necessary. But remember that any pathologic processes must be brought under control before orthodontics begins.

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  *Image 1, smile: Ed, age 47, pretreatment.*
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  *Image 2, diastema: Ed, age 47, pretreatment.*
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  *Image 3, upper arch: Occlusal view, upper arch: large central diastema, small incisors.*
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  *Image 4, lower arch: Occlusal view, lower arch: mild crowding, no problem.*
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Fixed Appliance Treatment

For Ed, first molars were banded, and brackets were bonded on all other maxillary teeth except the upper left second premolar. It had a ceramic crown that would be difficult to bond and was not really

Level III Biomechanics — Unit B · 122 / 142

{{PAGE_123}} needed as part of the anchorage unit.

Coil springs on a light steel arch wire were used to obtain the desired spacing of the incisors, which had been determined by the restorative dentist. This was achieved in 5 months. The soft tissues in the midline tolerated the partial closure of the diastema well—but sometimes diastema closure leads to enough tissue reaction to require periodontal surgery. Ed did not need that, though he had been warned that it might be necessary.

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{{PAGE_124}} Image 1, frontal view: Repositioning completed, 5 months treatment. Image 2, right lateral: Repositioning completed, 5 months treatment. Image 3, left lateral: Repositioning completed, 5 months treatment. Image 4, maxillary occlusal: Repositioning completed, 5 months treatment. Image 5, progress composite: Repositioning completed, 5 months treatment.

Fixed Appliance Treatment (cont.)

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{{PAGE_125}} When the appliance was removed after 5 months, a thermoplastic suckdown retainer was placed immediately to maintain the teeth in position until the restorations could be placed (image 1). This retainer looks just like a plastic aligner (shown in this program in the next few screens), and is identical except that it holds the teeth in position rather than moving them a little. Before the build-ups are done, it is important to evaluate tooth-lip relationships (image 2). For best smile esthetics in this case, it was apparent that slight lengthening of the central incisor crowns was needed, in addition to closing the interproximal spaces. For Ed, composite plastic build-ups for the four upper incisors were completed a few weeks later (image 3). It is critically important to coordinate the completion of the orthodontics and the restoration of the repositioned teeth. Unless the restorations are placed immediately after the appliance is removed (which often is the best plan), a retainer must be placed immediately, otherwise the teeth will drift.

Image 1, completion of treatment: Ready for appliance removal, suckdown retainer to be placed immediately.

Image 2, tooth-lip relationships: 4 weeks later, tooth-lip relationships just prior to composite build-ups.

Image 3, build-ups completed: Same day, build- ups completed.

Retention After Completion of Restorations

Ed was very pleased with the change in his smile esthetics (image 1). Restorations alone, without repositioning the incisors first, would not have been nearly as successful.

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{{PAGE_126}} When a maxillary central disastema is closed, there always is a tendency for it to reopen because the gingival circumferential fiber system is interrupted in the region of a large diastema. Like many adults, Ed did not tolerate a palate-covering maxillary retainer and much preferred a fixed retainer.

There are two ways to make a fixed retainer to hold central incisors together. The first type (image 2), consisting of a rigid bar, is both less effective (more likely to break) and less physiologic (splints the teeth too much).

The better way, bonding the teeth together with a piece of flexible wire, which was done for Ed, is shown in image 3. He will need a retainer of this type indefinitely.

Image 2, rigid bonded retainer: Fixed retainer, rigid wire: less satisfactory.

Image 3, flexible bonded retainer: Fixed retainer, flexible wire: preferred.

Maxillary Incisor Alignment, Removable Aligner

An alternative for incisor alignment is a series of plastic aligners. This approach is less effective when space closure is needed (and so wouldn’t have worked as well for Ed, the case immediately above). It is better suited for the correction of mild crowding.

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{{PAGE_127}} Removable Aligner Treatment For this patient, a series of 16 aligners was fabricated using computer technology (image) (at a laboratory cost of $1500). The plan was for the patient to wear each aligner all the time for 2 weeks, then switch to the next one.

In this case, treatment time was just under one year, as opposed to the theoretical 32 weeks, because compliance with wearing the appliance all the time left something to be desired. The treatment sequence depends on completing the movement created by any aligner before proceeding to the next one.

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Removable Aligner Treatment (cont.)

The result of treatment was satisfactory alignment of the incisors, as well as correction of the premolar positions.

The last aligner would continue to be worn as a retainer full-time for at least 3 months, then just at night. Maintaining perfect alignment long-term would require long-term retention, and the last aligner would eventually have to be replaced with a new retainer. With multiple teeth involved, a plastic suckdown retainer, essentially identical to the last aligner, would be the best choice.

Mandibular Incisor Alignment

Indications for Mandibular Incisor Alignment

Another indication for adjunctive orthodontics is crowding of lower incisors that poses a restorative problem, creates tissue irritation, or is needed to help control periodontal disease.

A key question with crowded lower incisors that require orthodontic alignment is whether extraction of one lower incisor and space closure, or opening space for alignment and restoration of the tooth, is the best plan. The more severe the crowding, the better the final occlusion would be with extraction of one tooth.

Let’s look at a patient in whom restoration of a fractured lower incisor was quite difficult because of malalignment. She wanted something done about the fractured crown, both because of its appearance and because the fractured edge was irritating.

Should the fractured tooth be extracted and the space closed, or should space be opened for better alignment and a successful restoration?

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{{PAGE_130}} Image 1: Sara, age 60, fractured lower incisor = restorative problem. Image 2: Sara, age 60, fractured lower incisor = restorative problem.

Planning for Mandibular Incisor Alignment

From the perspective of dental esthetics, three lower incisors versus four is not an important issue, but the lower incisors are exposed more in older patients than in younger ones because the upper and lower lips sag downward with aging. So alignment of these teeth can become more important with increasing age.

In addition, in adults, loss of lip support if the incisors are retracted during space closure can increase facial wrinkles and subtly make the patient look older. For esthetics, it’s better to increase lip support than decrease it. Because of the esthetic sensitivity, mandibular incisor alignment can be considered the most difficult and potentially troublesome type of adjunctive treatment.

Note that Sara has mild crowding in the upper arch and more severe crowding in the lower arch. There is a deep bite anteriorly. The maxillary incisors are upright and tipped lingually in a mild Class II, division 2 pattern (although the molar relationship is Class I). She has a fixed bridge replacing a lower premolar and extensive good-quality restorations. She expects the best in dental care.

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{{PAGE_131}} Image 1, frontal view: Sara, age 60, fractured lower incisor = restorative problem. Image 2, right lateral: Sara, age 60, fractured lower incisor = restorative problem. Image 3, left lateral: Sara, age 60, fractured lower incisor = restorative problem. Image 4, maxillary occlusal: Mild maxillary incisor crowding, central incisors tipped lingually. Image 5, mandibular occlusal: More severe mandibular incisor crowding.

Planning for Mandibular Incisor Alignment (cont.) Level III Biomechanics — Unit B · 131 / 142

{{PAGE_132}} At age 60, some loss of lip fullness is to be expected (image 1). Sara’s facial proportions and jaw relationships are normal. The appearance of the fractured tooth is a concern, but facial esthetics is not. On the other hand, treatment certainly shouldn’t make her look worse or older.

The panoramic radiograph (image 2) shows extensive restorations (inlays, onlays, and crowns) in good condition, with a fixed bridge replacing a missing mandibular left premolar.

Alveolar bone levels appear normal in both the panoramic radiograph and in recent bitewings (which are needed for patients with restorations—see the radiographic guidelines in Concepts of Adjunctive Treatment). Clinical examination confirmed no evidence of active periodontal disease.

For this patient, either of the treatment approaches (extract the fractured incisor and close space, ending up with three lower incisors; or expand the arches to allow the fractured tooth to be aligned) would change the position of the incisor(s) and affect lip support. So a cephalometric radiograph and tracing (images 3 and 4) are needed to evaluate the esthetic impact of treatment.

Cephalometric analysis confirms that jaw relationships are within normal limits but with a mild skeletal Class II pattern. There is some retrusion of upper incisors (a mild Class II division 2 pattern), and a normal relationship of the mandibular incisors to the chin.

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{{PAGE_133}} Frontal/profile views: normal facial proportions, no esthetic problem.

Panoramic radiograph, extensive previous restorative treatment.

Cephalometric radiograph.

Cephalometric tracing: mild Class II division 2 pattern.

Treatment Options: the Patient Decides

For Sara, extracting one lower incisor and closing the space would deepen the bite and could lead to tissue damage lingual to the upper incisors. In addition, lip support from the teeth would decrease, which has an aging effect. On the positive side, there would be no need to restore the fractured tooth and no worry about maintaining the restoration long term.

The alternative treatment would be expansion of the lower arch to make room for the fractured incisor, so that it could be restored properly. It would be necessary to correct the lingual tipping of the upper incisors to gain enough overjet to expand the lower arch, so alignment of the upper incisors

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{{PAGE_134}} would be necessary. This would slightly increase lip support and improve dental and facial esthetics. Treatment time would be about the same with both approaches.

Computer predictions help patients understand the esthetic impact of changing jaw or tooth position (image 1). Sara was shown computer image predictions of the effect on her profile of the alternative treatment possibilities, so she could choose between them. This, of course, is her decision—both morally and legally, she is entitled to make the decision.

As the predictions show, for Sara the esthetic impact on the profile of either treatment plan would be subtle, but increased lip fullness makes you look younger—which is as desirable at age 60 as age 40. Smile esthetics also would be better with arch expansion and alignment of the teeth in both arches. Since her primary motivation was esthetics, Sara preferred arch expansion rather than extraction and space closure.

The plan, therefore, was a bonded fixed appliance for both arches. Because of the deep bite, only the upper arch was bonded initially, and the upper incisors were tipped facially to create some overjet. Then the lower arch was bonded, and space was opened so that the crowded incisors could be aligned. Since major tooth movement was not required in the upper arch, clear brackets were satisfactory for treatment and were more esthetic.

Treatment Completion

{{PAGE_135}} The orthodontic treatment required 6 months. As anticipated, expansion of the maxillary incisor segment gave space to expand the mandibular incisor area, and produced excellent occlusion and incisor function. The rotated mandibular right canine was not corrected because a preliminary set-up of the teeth showed that there was not quite enough space to allow this.

She was referred for restoration of the fractured lower incisor immediately after braces were removed, and wore plastic suckdown retainers in both arches until the restoration could be accomplished. Then a clip-on lower retainer was used, and the suckdown retainer for the upper arch was continued at night for a few months.

{{PAGE_136}} Image 1, frontal view: Sara, completion of orthodontic and restorative treatment. Image 2, right lateral: Sara, completion of orthodontic and restorative treatment. Image 3, left lateral: Sara, completion of orthodontic and restorative treatment. Image 4, maxillary occlusal: Sara, completion of orthodontic and restorative treatment. Image 5, mandibular occlusal: Sara, completion of orthodontic and restorative treatment. Level III Biomechanics — Unit B · 136 / 142

{{PAGE_137}} Post-Treatment Esthetics

Dental and facial esthetics were satisfactory after restoration of the incisor, which took place a few weeks after the orthodontic appliance was removed (images 1-4). In this case, both better occlusion and better esthetics were accomplished with arch expansion rather than extraction of the fractured incisor, at the cost of one more restoration to be maintained. Treatment time would have been the same or longer with extraction, and the cost of the two possible orthodontic approaches also would be quite similar.

It came down to understanding what the patient wanted, offering her alternatives that she understood, and letting her make an informed decision (see Concepts of Adjunctive Treatment).

It is interesting to compare the computer image prediction, which was based on predicted changes in incisor position on the cephalometric tracing, to the real profile posttreatment (image 5).

Computer image predictions are not perfect, but if done carefully can be quite close to reality. It’s one thing to explain to a patient what the effect of treatment is likely to be, and something else to show them a picture. Patients like the feeling of better communication that seeing the predictions provides, and there is minimal risk that they will think the reality is not as good as the prediction.

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{{PAGE_138}} Image 1, frontal, smile: Sara, facial appearance at completion of treatment. Image 2, frontal, relaxed: Sara, facial appearance at completion of treatment. Image 4, profile, relaxed: Sara, facial appearance at completion of treatment.

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Retention After Mandibular Incisor Alignment

Whenever incisors are repositioned in adults, retainers are needed. Sara had a suckdown upper retainer (similar to the removable aligner, but passive) and an acrylic-wire clip-on lower retainer.

For Sara, the lower retainer will be worn just at night, indefinitely. It has two purposes:

maintaining the lower incisor alignment, and
controlling the overbite, as the facial aspect of this retainer is contoured to do.

After the teeth have stabilized initially, preventing the bite from deepening also will maintain the alignment of the upper incisors, so an upper retainer is not needed long term. She discarded it after 4 months.

{{PAGE_140}} Mandibular Incisor Alignment (cont’d.)

Comparison of smile esthetics from before to after treatment shows the improvement that was achieved.

Note that there were two components to the esthetic change:

restoration of the fractured incisor, and
improved lip support.

Adjunctive treatment to change incisor positions must always take both into account.

In modern dentistry, adjunctive orthodontic treatment offers the possibility of better management of other dental problems. For that reason, adjunctive orthodontics for adults is a rapidly growing part of clinical treatment.

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Conclusions

Mandibular incisor alignment in adults:

is one of the more difficult adjunctive treatment procedures.
in a patient with severe incisor crowding and a fractured or endodontically-involved incisor, extraction and space closure can be the most effective treatment.
non-extraction alignment of less severely crowded lower incisors often requires repositioning of the upper incisors as well,
whatever the type of treatment in an adult, long-term retention will be needed. Initially, a suckdown retainer can be satisfactory; in the long-term, either a clip-on removable retainer or a bonded lingual flexible wire performs better

Summary of Adjunctive Treatment

Summary: Molar Uprighting, Crossbite Correction

There are five major types of adjunctive orthodontic treatment for adults:

Uprighting of drifted molars to facilitate restorations
Distal tipping of crowns—the preferred method in the lower arch, and usually in the upper arch as well; requires removal of third molar if second molar is to move significantly distally
Three steps: align/upright: active, flexible arch wires; with or without auxiliary spring consolidate space: coil spring on rigid wire retention: bonded intracoronal wire
Mesial movement of roots—difficult but possible, more feasible in the upper arch because root paralleling is not as critical; allows retention of third molar
Correction of posterior crossbite, also to facilitate restorations
Cross-elastics are effective, if some extrusion of the teeth can be tolerated
The alternative is an active arch wire (see Chapter 20, Contemporary Orthodontics)

Summary: Extrusion, Maxillary Incisor Alignment

The five major types of adjunctive orthodontic treatment for adults: 3. Extrusion of fractured teeth, an alternative to crown-lengthening surgery that may produce an esthetic problem 4. How far do you have to extrude? enough movement to bring the fracture line to the surface an additional 1 mm for placement of the gingival margin of the restoration an additional 2 mm for gingival contours 5. Requires a bonded attachment (usually a button rather than a bracket) on the tooth to be extruded

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{{PAGE_142}} 6. Anchor teeth can be adjacent (usually preferred) or in the opposite arch (requires use of vertical elastics) 7. Alignment of maxillary incisors, usually to redistribute spaces in preparation for build-ups 8. Fixed appliance with bonded brackets and coil springs: the usual method 9. Removable aligners: a new method involving computer-generated casts on which a sequence of aligners can be made

Summary: Mandibular Incisor Alignment

The five major types of adjunctive orthodontic treatment for adults: 5. Alignment of mandibular incisors, usually for the correction of crowding 6. One possibility: extraction of one incisor and space closure may or may not be compatible with good occlusion reduces lip support, may tend to make the patient look subtly older 7. The other possibility: arch expansion likely to require treatment of both the upper and lower arch esthetic considerations are the key in this decision 8. This is the most difficult and potentially troublesome of the adjunctive procedures

Adjunctive orthodontics is an increasingly important of comprehensive treatment for adults, with the potential to improve periodontal health and improve the quality of restorative dentistry.

Self-Test Referral

The self-test section of this program is designed to help you be sure you have understood the material. Read the section on adjunctive treatment in adults in Contemporary Orthodontics (5th ed., pages 627-637; 4th ed., pages 639-651). Then take the self-test, and use it as a guide for further study and review.

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Quartz 4

Explorer

Level III Biomechanics - Unit B__formatted_raw__v1

Contents

1. Space Management in Preadolescent Children

Mixed Dentition Analysis Review

Mixed Dentition Analysis Review

Interpretation of Results

Types of Treatment for Space Problems

Space Maintenance

Space Maintenance

Fixed Space Maintainers

Space Regaining

Localized Space Loss

Treatment Steps in Space Management

Early Loss of Primary Canines

Crowding >4 mm.

Serial Extraction

Serial Extraction

Ideal Patient for Serial Extraction

2. Crossbites and Vertical Problems in Children

Introduction: Skeletal versus Dental

Crossbite: Mandibular Shift?

Crossbite: Skeletal vs. Dental

Posterior Crossbite

Skeletal vs. Dental Posterior Crossbite

Skeletal vs. Dental Posterior Crossbite (cont’d.)

Evaluation of Posterior Crossbite

Mid-Palatal Suture Expansion

Slower Palatal Expansion

Slow Expansion for Young Children

Vertical Effects of Posterior Crossbite Correction

3. Concepts of Adjunctive Orthodontic Treatment

Goals of Adjunctive Treatment

Definition of Adjunctive Treatment

Adjunctive Treatment: Types of Tooth Movement

Treatment Planning

Diagnostic Evaluation, Adjunctive Ortho Patient

Treatment Plan Concept / Details

Fixed Appliance for Molar Uprighting

Mesial Root Movement in Mandibular Molar Uprighting

Maxillary Molar Uprighting

Evaluation of Maxillary Molar Uprighting

Further Considerations in Molar Uprighting

Root Paralleling in Molar Uprighting

Molar Uprighting with Posterior Crossbite Correction

Molar Uprighting with Posterior Crossbite Correction (cont’d.)

Molar Uprighting: Summary and Conclusions

Forced Eruption

Indications for Forced Eruption

Maxillary Incisor Alignment

Appliances for Maxillary Incisor Alignment

Maxillary Incisor Alignment, Fixed Appliance

Retention After Completion of Restorations

Removable Aligner Treatment (cont.)

Mandibular Incisor Alignment

Indications for Mandibular Incisor Alignment

Planning for Mandibular Incisor Alignment

Treatment Options: the Patient Decides

Retention After Mandibular Incisor Alignment

Conclusions

Summary of Adjunctive Treatment

Summary: Molar Uprighting, Crossbite Correction

Summary: Extrusion, Maxillary Incisor Alignment

Graph View

Table of Contents