02 - 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 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.

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.

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 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:

1. Allow normal jaw function by eliminating significant CR–MI functional interferences.
2. 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.
3. 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.
4. Allow correction of localized space loss.

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.

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.

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 tomove 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 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

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).

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
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.	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.
Image 3, Posterior skeletal crossbite: A posterior skeletal crossbite occurs when the transverse width of the maxilla is reduced, and the maxillary 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).

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
• 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 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).

Image 1, Quad helix appliance: A cemented quad helix appliance with four wire helices, which were opened slightly before the appliance was cemented into position.	Image 2, W-arch appliance: A W-arch appliance, which also is expanded slightly before cementation, also can be used to correct a posterior crossbite. It is not as springy as a quad-helix, so would require more activations to correct a more severe crossbite.

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.

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).

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.
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).

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.

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.

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).

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.

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).

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.

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.

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.

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)

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.

Image 1, Short face (skeletal deep bite) patient: Note the reduction in lower face height and prominence of the chin relative to the lower lip, which often is seen in this facial pattern. A deep bite and a Class II division 2 malocclusion also are present.	Image 2, Intraoral views, same patient: The lower incisors contact the palatal tissues behind the upper incisors—note the inflammation around the maxillary right central incisor.

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.

1. 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 eruption 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.

2. 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.

Image 1, Cervical pull headgear: Cervical pull headgear used in the correction of a short face vertical deficient patient.	Image 2, Functional appliance: Functional appliance used in the correction in a short face patient. Note that the lower incisors and maxillary posterior teeth are capped to impede their eruption, while the mandibular posterior teeth are free to erupt.

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
• 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.

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

Image 1, High pull headgear to the maxillary molars: The high pull headgear applies an upward and backward force to maxillary molars through the inner and outer bows of the appliance.	Image 2, Force application using a high pull headgear: The effect on the maxillary first molar of high pull headgear with force vectors above, through or below the center of resistance of the tooth.

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.

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 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.

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, 498-502, 559-564, 534-542 (4th ed), then take the self-test, and use it as a guide for further study and review.

Copyright 2013, UNC Dept. of Orthodontics

Self-Test

Instructions

1. View the teaching program.
2. Use the mouse to mark the correct answer(s) to each question.
3. Review the feedback from the program—it will tell you if you’re right or wrong, and why.

Reading: Contemporary Orthodontics, 3rd edition, pages 63-64, 216-217, 220-221, 231-233, 435-447, and 491-508.

Question 1

The correction of anterior crossbites in children is recommended to

a. prevent periodontal involvement of the lower incisors.

b. eliminate significant CR-MI interferences.

c. correct localized space loss.

d. prevent abnormal incisor wear patterns.

1. a and b
2. b and c
3. a, b, and d
4. a, c, and d
5. all of the above ✓

Correct

That’s right; all of these are reasons why the correction of anterior crossbites in children is recommended. 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. The correction may also allow normal jaw function by eliminating significant CR–MI functional interferences that may interfere with lateral jaw excursions and cause abnormal incisal wear patterns that can compromise incisor esthetics. Single tooth crossbites are commonly due to localized space loss, the space must be regained first to allow the incisor to be repositioned in the dental arch.

Incorrect

No, that’s wrong. All of these are reasons why the correction of anterior crossbites in children is recommended. 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. The correction may also allow normal jaw function by eliminating significant CR–MI functional interferences that may interfere with lateral jaw excursions and cause abnormal incisal wear patterns that can compromise incisor esthetics. Single tooth crossbites are commonly due to localized space loss, the space must be regained first to allow the incisor to be repositioned in the dental arch.

Question 2

Patients with a pseudo-Class III malocclusion

1. invariably have an underlying Class III skeletal relationship.
2. have a significant anterior shift from CR-MI due to an anterior crossbite. ✓
3. cannot be manipulated into an end-to-end incisor relationship in CR.
4. usually present with maxillary skeletal retrusion.
5. cannot be treated with orthodontics alone and must be treated with surgery.

Correct

That’s right. 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 skeletal crossbite. An anterior dental crossbite with a significant anterior shift is called a pseudo-Class III malocclusion. It is very important to evaluate the patient’s occlusion and facial profile in CR and MI. These patients usually can be manipulated into an edge-to-edge incisor relationship in centric occlusion prior to shifting forward. When these patients shift forward into MI, facial profile analysis reveals an apparent mandibular prognathism due to the anterior shift of the mandible. Orthodontic treatment of the crossbite eliminates the CR-MI shift and the apparent skeletal discrepancy.

Incorrect

No, that’s wrong. 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 skeletal crossbite. 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 prior to shifting forward. Orthodontic treatment of the crossbite usually eliminates the CR-MI shift and the apparent skeletal discrepancy. In a true skeletal Class III malocclusion, the patient has no significant anterior CR-MI shift and the mandible cannot be positioned posteriorly.

Question 3

Which of the following is not a usual component of a removable appliance to correct an anterior dental crossbite?

1. Finger spring
2. Adams’ clasps
3. Bite plane
4. Labial bow
5. Palatal expansion screw ✓

Correct

That’s right, a palatal expansion screw is not a usual component of removable appliances used to correct an anterior crossbite. Palatal expansion screws are more commonly used in removable appliances to correct a posterior crossbite. Finger springs are commonly used to tip incisors into the correct position. Adams’ clasps on posterior teeth provide retention, while a labial bow contoured to the labial surfaces of the incisors provides a stop for the incisor as it is advanced. Bite planes may be used to open the occlusion to allow forward movement of the incisor during correction.

Incorrect

No, that’s wrong. A palatal expansion screw is not a usual component of removable appliances used to correct an anterior crossbite. Palatal expansion screws are more commonly used in removable appliances to correct a posterior crossbite. Finger springs are commonly used to tip incisors into the correct position. Adams’ clasps on posterior teeth provide retention while a labial bow contoured to the labial surfaces of the incisors provides a stop for the incisor as it is advanced. Bite planes may be used to open the occlusion to allow forward movement of the incisor during correction.

Question 4

A) Children with skeletal anterior crossbites due to mandibular excess can easily be treated with growth modification, because (B) Once the crossbite is corrected, future skeletal growth doesn’t affect the treatment result.

1. A true, B true, A and B related
2. A true, B true, A and B not related
3. A true, B false
4. A false, B true
5. A and B false ✓

Correct

That’s right, both statements are false. Children with skeletal anterior crossbites due to mandibular excess are very difficult to treat with growth modification. The chin cup appliance has been designed to restrict the forward growth of the mandible but has limited success because it requires an extended period of compliance and must be worn during the majority of the adolescent growth spurt to be effective. If the patient has not completed all of his or her mandibular growth, future mandibular growth tends to undo the treatment and the anterior crossbite reappears. The end result is that the patient outgrows any early correction of the underlying skeletal problem.

Incorrect

No, that’s wrong. Both statements are false. Children with skeletal anterior crossbites due to mandibular excess are very difficult to treat with growth modification. The chin cup appliance has been designed to restrict the forward growth of the mandible but has limited success because it requires an extended period of compliance and must be worn during the majority of the adolescent growth spurt to be effective. If the patient has not completed all of his or her mandibular growth, future mandibular growth tends to undo the treatment and the anterior crossbite reappears. The end result is that the patient outgrows any early correction of the underlying skeletal problem.

Question 5

(A) Young children with both anterior and posterior crossbites may have an underlying Class III skeletal malocclusion, because (B) Significant AP discrepancies between the maxilla and mandible may also present as a posterior crossbite even though jaw width is normal.

1. A true, B true, A and B related ✓
2. A true, B true, A and B not related
3. A true, B false
4. A false, B true
5. A and B false

Correct

That’s correct, both statements are true and related. Class III skeletal malocclusions usually present with an anterior crossbite as well as a posterior crossbite. The upper and lower jaws may be of normal transverse width but due to an abnormal anteroposterior relationship, present as an anterior crossbite as well as a posterior crossbite. The AP discrepancy prevents the normal interdigitation of the U-shaped maxillary and mandibular dental arches in both planes of space. You should be very suspicious of an underlying Class III malocclusion in children who present with both a posterior and anterior crossbite.

Incorrect

No, that’s wrong, both statements are true and related. Class III skeletal malocclusions usually present with an anterior crossbite as well as a posterior crossbite. The upper and lower jaws may be of normal transverse width but due to an abnormal anteroposterior relationship, present as an anterior crossbite as well as a posterior crossbite. The AP discrepancy prevents the normal interdigitation of the U-shaped maxillary and mandibular dental arches in both planes of space. You should be very suspicious of an underlying Class III malocclusion in children who present with both a posterior and anterior crossbite.

Question 6

A child in the mixed dentition presents with a left posterior crossbite and a mandibular midline shifted to the left in MI. Both dental arches appear symmetric. Your most probable diagnosis would be

1. pseudo-Class III malocclusion.
2. left unilateral posterior dental crossbite.
3. unilateral mandibular crowding on the left side.
4. bilateral posterior crossbite with a functional shift to the left. ✓
5. asymmetry of the mandibular ramus on the left side.

Correct

That’s right. Posterior crossbites in children often appear to be unilateral in nature, but closer examination usually reveals that the majority of these result 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. A true unilateral posterior crossbite due to an intra-arch or jaw asymmetry is less common in children.

Incorrect

No, that’s wrong. Posterior crossbites in children often appear to be unilateral in nature, but closer examination usually reveals that the majority of these result 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. A true unilateral posterior crossbite due to an intra-arch or jaw asymmetry is less common in children. Pseudo-Class III malocclusions result in predominately anterior crossbites.

Question 7

Which of the following appliances is recommended to correct a posterior dental crossbite in a preadolescent patient?

1. Quad-helix appliance ✓
2. Hyrax appliance
3. Rapid palatal expander
4. Haas appliance
5. Mini-expander

Correct

That’s correct. Of these choices, the quad-helix is preferred because the midpalatal suture is most likely open and heavy-force application is unnecessary to achieve dental and skeletal expansion. All the other choices are examples of appliances that use rapid palatal expansion and unnecessarily heavy forces to expand the palate.

Incorrect

No, that’s wrong. You have chosen an appliance that uses rapid palatal expansion techniques and unnecessarily heavy forces to expand the palate. Of these choices, the quad-helix is preferred because the midpalatal suture is most likely open and heavy-force application is unnecessary to achieve dental and skeletal expansion. All the other choices are examples of appliances that use rapid palatal expansion and unnecessarily heavy forces to expand the palate.

Question 8

(A) Rapid palatal expansion is indicated for the treatment of skeletal crossbites in late adolescence because (B) The mature palatal suture is highly organized and the bone is well interdigitated and nearly fused.

1. A true, B true, A and B related ✓
2. A true, B true, A and B not related
3. A true, B false
4. A false, B true
5. A and B false

Correct

That’s right. Both statements are correct and related. The palatal suture becomes well organized and highly interdigitated in late adolescence. As this occurs, more force is required to expand the suture, and a jackscrew as employed in rapid palatal expansion is recommended to accomplish the skeletal expansion at this age.

Incorrect

That’s wrong. Both statements are correct and related. The palatal suture becomes well organized and highly interdigitated in late adolescence. As this occurs, more force is required to expand the suture, and a jackscrew as employed in rapid palatal expansion is recommended to accomplish the skeletal expansion at this age.

Question 9

One must be cautious when correcting posterior crossbites in children with

a. a shallow mandibular plane.

b. a steep mandibular plane angle.

c. decreased lower anterior face height.

d. increased lower anterior face height.

1. a and c
2. b and c
3. a and b
4. a and d
5. b and d ✓

Correct

That’s right. One must be cautious when correcting posterior crossbites in children with an excessive vertical growth component. Forces applied to posterior teeth to correct a posterior crossbite have a vertical vector as well as a transverse vector that tends to alter vertical relationships. 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 that uses bite blocks.

Incorrect

No, that’s wrong. One must be cautious when correcting posterior crossbites in children with an excessive vertical growth component. Forces applied to posterior teeth to correct a posterior crossbite have a vertical vector as well as a transverse vector that tends to alter vertical relationships. 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 that uses bite blocks.

Question 10

Which of the following is most likely to be found in a child with a long-standing thumb-sucking habit?

1. Proclined mandibular incisors
2. Deep overbite
3. Reduced overjet
4. Posterior crossbite ✓
5. Undererupted posterior teeth

Correct

That’s right. Children with a long-standing thumb-sucking habit usually present with a posterior crossbite. The other findings are quite unlikely. Lingually directed forces usually retrocline or upright the lower incisors. The upper incisors are proclined by the thumb resulting in an increased overjet. Overeruption of the posterior also causes an anterior open bite.

Incorrect

No, that’s wrong. Children with a long-standing thumb-sucking habit usually present with a posterior crossbite. The other findings are quite unlikely. Lingually directed forces usually retrocline or upright the lower incisors. The upper incisors are proclined by the thumb resulting in an increased overjet. Overeruption of the posterior also causes an anterior open bite.

Question 11

(A) Successful treatment of thumb-sucking habits can be accomplished with dental appliances such as a fixed thumb crib because (B) Crib appliances are very successful in noncompliant patients.

1. A true, B true, A and B related
2. A true, B true, A and B not related
3. A true, B false ✓
4. A false, B true
5. A and B false

Correct

That’s right, the first statement is true, but the second statement is false. Dental appliances such as a fixed thumb crib act as a reminder and can be effective in patients stopping a thumb-sucking habit. For these appliances to be effective, a child must wish to stop the habit—any intervention must not be perceived as punishment by the child. Appliance therapy requires a compliant patient who wishes to stop the habit since noncompliant patients can easily distort or remove the appliances if they wish.

Incorrect

That’s wrong. The first statement is true, but the second statement is false. Dental appliances such as a fixed thumb crib act as a reminder and can be effective in patients stopping a thumb-sucking habit. For these appliances to be effective, a child must wish to stop the habit—any intervention must not be perceived as punishment by the child. Appliance therapy requires a compliant patient who wishes to stop the habit since noncompliant patients can easily distort or remove the appliances if they wish.

Question 12

Anterior deep bite patients usually

a. present with over-erupted mandibular incisors.

b. present with a flat mandibular curve of Spee.

c. are treated by increasing lower face height.

d. require a downward rotation of the mandible during treatment.

1. a and c
2. b and d
3. a, b, and c
4. b, c, and d
5. a, c, and d ✓

Correct

That’s right. Deep bite patients usually present with overerupted mandibular incisors. This overeruption of the mandibular incisors is often seen with a Class II malocclusion because when there is excessive overjet, the lower incisors are free to erupt until they contact the palatal mucosa. This also results in a deep curve of Spee in the lower arch, not a flat curve of Spee. Deep bite patients also tend to have a decreased lower face height due to an upward and forward growth of the mandible. Treatment is usually aimed at creating a downward rotation of the mandible to increase lower face height.

Incorrect

No, that’s wrong. Deep bite patients usually present with overerupted mandibular incisors. This overeruption of the mandibular incisors is often seen with a Class II malocclusion, because when there is excessive overjet the lower incisors are free to erupt until they contact the palatal mucosa. This also results in a deep curve of Spee in the lower arch, not a flat curve of Spee. Deep bite patients also tend to have a decreased lower face height due to an upward and forward growth of the mandible. Treatment is usually aimed at creating a downward rotation of the mandible to increase lower face height.

Question 13

Patients with vertical excess (the long face syndrome) usually present with

1. increased upper face height.
2. steep mandibular plane angle. ✓
3. decreased anterior face height.
4. increased posterior face height.
5. superiorly positioned posterior maxilla.

Correct

That’s right. Patients with vertical excess or long face syndrome usually present with a steep mandibular plane angle, but the other characteristics are not characteristic of this condition. The upper face height may be normal, while there is usually a decreased posterior face height and increased anterior face height. The posterior maxillary plane is usually inferiorly positioned, which causes the mandible to rotate downward and backward thus further increasing the anterior face height.

Incorrect

No, that’s wrong. Patients with vertical excess or long face syndrome usually present with a steep mandibular plane angle, but the other characteristics are not characteristic of this condition. The upper face height may be normal, while there is usually a decreased posterior face height and increased anterior face height. The posterior maxillary plane is usually inferiorly positioned, which causes the mandible to rotate downward and backward thus further increasing the anterior face height.

Question 14

Nongrowing patients with a combination of severe vertical excess and a Class II relationship are best treated with

1. high pull headgear.
2. high pull headgear with a maxillary splint.
3. functional appliance with bite blocks.
4. high pull head gear to a functional appliance with bite blocks.
5. orthognathic surgery. ✓

Correct

That’s right. Orthognathic surgery is required to achieve optimum dentofacial relationships in nongrowing patients with severe vertical excess and Class II skeletal relationships. In growing patients, growth modification using a high pull headgear to a functional appliance with bite blocks may reduce the skeletal disproportions but rarely is successful in the more severely affected individuals. For them, orthognathic surgery may the best treatment option.

Incorrect

No, that’s wrong. Orthognathic surgery is required to achieve optimum dentofacial relationships in nongrowing patients with severe vertical excess and Class II skeletal relationships. In growing patients, growth modification using a high pull headgear to a functional appliance with bite blocks may reduce the skeletal disproportions but rarely is successful in the more severely affected individuals. For them, orthognathic surgery may the best treatment option.