Quartz 4

Unit Self-Test

34 min read

Level IV Clinical Treatment — Unit B Self-Test

Module 1: To Extract or Not To Extract Part 2

Question 1

Which of the following would be considered camouflage treatment?

a. Retraction of protruding upper incisors

b. Retraction of protruding lower incisors

c. Retraction of both upper and lower incisors

d. Midpalatal expansion (sutural expansion) of a narrow maxillary arch to treat posterior crossbite

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

Correct

That’s right, retraction of protruding upper incisors is typical camouflage for skeletal Class II problems; retraction of protruding lower incisors could be camouflage for skeletal Class III. Retraction of incisors in both arches implies correction of crowding/protrusion in patients who don’t have a jaw discrepancy, so that isn’t camouflage. Neither is sutural expansion of a narrow maxillary arch, because if the midpalatal suture opens, the maxilla is widened and the skeletal discrepancy is corrected.

Question 2

Which of the following are appropriate times for orthodontic camouflage?

a. preadolescence

b. adolescent growth spurt

c. late adolescence

d. early adult life

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

Correct

That’s right, camouflage treatment isn’t indicated until after the adolescent growth spurt is over, or nearly over. It’s acceptable in late adolescence and in adults, but not in children who still have a lot of growth left. Growth modification, avoiding the displacement of teeth that is typical of camouflage, should be attempted first in growing children.

Question 3

Which of the following are appropriate extraction patterns for Class II camouflage?

a. one lower incisor

b. upper first premolars

c. upper first and lower second premolars

d. upper and lower first premolars

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

Correct

That’s right, upper first premolar extraction, alone or in combination with lower second premolar extraction (usually) or lower first premolar extraction (occasionally) is used for Class II camouflage. Extraction of one lower incisor implies Class III, not Class II camouflage.

Question 4

(A) The major reason patients seek correction of Class II or Class III problem is to improve jaw function, because (B) Incisor contact is difficult to achieve in Class II and impossible in Class III.

  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 false, but the second is true. Some patients seek treatment primarily to improve function, and it’s true that normal incisor function is lacking in Class II and Class III patients. But the great majority who bring their children for treatment or seek it themselves as adults have concerns about their appearance. When protruding upper incisors and a deficient chin cause you to be judged stupid until proved otherwise, and a sunken-in midface and prominent lower jaw makes you a witch, concerns about facial appearance are much more than just vanity.

Question 5

Patients are likely to judge their camouflage treatment as a failure if

a. incisors are retracted too much, affecting facial appearance.

b. incisors are not retracted enough, so that excess overjet remains.

c. extraction spaces are not closed.

d. vertical problems are not corrected.

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

Correct

That’s right, all these factors probably would lead patients to judge their camouflage treatment a failure. The most significant ones, however, are those that affect facial appearance. If you sought treatment to improve your appearance and the effect was to improve your dental occlusion while making facial appearance worse, you would be justifiably upset.

Question 6

Why are computer simulations of treatment outcomes used for postadolescent camouflage and surgery patients, but not for younger patients?

  1. Growth prediction is almost impossible ✓
  2. Younger patients are too immature to choose appropriately
  3. Parents of younger children object to prediction techniques
  4. Predictions are just as useful in younger patients

Correct

That’s right, computer simulations of treatment effects, in the absence of growth, can be accurate enough to be useful clinically, but in children with skeletal problems, the combination of growth and treatment is almost impossible to predict accurately. If prediction worked for younger patients, it could be quite useful in helping patients and parents choose among alternatives, but simulations have to be at least reasonably accurate or they’re just misleading.

Question 7

Which of the following are reasons for many fewer Class III than Class II patients treated with extraction for camouflage?

a. Fewer Class III patients in the population

b. Retracting the lower incisors tends to make the chin more prominent

c. Class III patients often have a large nose, and extraction for camouflage may make it look bigger

d. On a percentage basis, as many Class IIIs as Class IIs have camouflage

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

Correct

That’s right, the first 2 items are reasons for the lower number of Class III patients: there are fewer of them, and a large chin is difficult to camouflage. The size of the nose is a factor in Class II camouflage but is not particularly relevant for Class III patients. The percentage of Class III patients who have camouflage is lower than Class II because retracting the incisors often makes the chin look even stronger. A prominent chin is a major concern for Class III patients. They don’t want it made even more prominent by retracting the lower incisors.

Question 8

Orthodontic camouflage isn’t a good idea for patients with a long face, open bite problem. Why? Which of the following are correct?

a. Elongating the incisors to close the bite often makes facial appearance worse

b. Retracting the incisors does not shorten excessive face height although it may reduce the extent of the open bite

c. Attempts at camouflage may make the nose and chin more prominent

d. No need to try camouflage, open bite often corrects itself spontaneously

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

Correct

That’s right. Elongating the incisors often makes facial appearance worse rather than better by exposing too much of the teeth (and often the gingiva as well) beneath the lips, and changing the a-p position of anterior teeth does not reduce excessive face height. There is little effect on the nose and chin, however. Although open bite tends to correct itself in young children with normal jaw relationships, self-correction almost never occurs in adolescents. For the girl in this image, the upper teeth already are too far below the lip line for good facial esthetics. Elongating them further, with or without extraction, might close her open bite but would damage rather than improve facial esthetics. She is a candidate for surgery.

Question 9

To what extent does camouflage treatment correlate with the development of TMD?

  1. High positive correlation, increases the chance of TMD
  2. Low positive correlation, slightly increases the chance of TMD
  3. Little or no correlation ✓
  4. Low negative correlation, slightly decreases the chance of TMD
  5. High negative correlation, decreases the chance of TMD

Correct

That’s right, a number of studies have shown little or no correlation between camouflage treatment and the development of TMD.

The good news is that like most orthodontic treatment, camouflage doesn’t cause TMD. The bad news is that like most orthodontic treatment, camouflage also doesn’t cure TMD.

Question 10

What’s the best advice from the family dentist to a 16-year-old who asks about the possibility of orthodontics to correct her protruding upper incisors?

  1. You need treatment to try to make your lower jaw grow—it’s not too late.
  2. At this point, you’ll need braces on all your teeth and will have to have some teeth removed.
  3. If you really want to look better, you’ll probably have to have an operation on your jaw.
  4. At this point, you need a complete diagnostic evaluation to decide what type of treatment would be best. ✓

Correct

That’s right, a complete diagnostic evaluation is needed, including photographs and cephalometric radiographs that can be put into a computer program to allow simulation of possible outcomes. At age 16, correcting the problem by modifying growth almost surely wouldn’t work, but there’s no way to know about camouflage versus surgery without further information. If it’s a borderline situation, having the patient and parents view computer simulations to help them make the decision is the modern approach.

Module 2: Special Considerations in Orthodontics for Adults

Question 1

What is the percentage of adults in the orthodontic patient pool in the United States at present?

  1. 5%
  2. 10%
  3. 15%
  4. 20% ✓
  5. 25%

Correct

That’s right, as of 2000 about 20% of all orthodontic patients were adults. The percentage was down from the 25% of 1995, but the absolute number of adults seeking treatment has remained at the 1995 level, so it’s still a significant proportion of the total orthodontic treatment pool.

Question 2

Which of the following are characteristics of the group of adults who seek treatment to improve their present situation?

a. Younger, usually between 20 and 40

b. Want comprehensive treatment

c. Motivation usually is psychosocial

d. Often concerned about visibility of braces

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

Correct

That’s right, all these are characteristics of the group of adults who seek treatment to improve their present situation. They tend to be younger, want comprehensive treatment, have a primarily psychosocial motivation, and often are willing to pay extra for braces that are less visible, such as ceramic brackets, lingual brackets, or the clear plastic aligners advertised as “invisible braces.”

Question 3

Which of the following are characteristics of the group of adults who seek treatment to maintain their teeth and their dental health?

a. Older, usually over 30

b. Want treatment for specific problems

c. Motivation usually is psychosocial

d. Often concerned about visibility of braces

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

Correct

That’s right, the first two statements describe the patients whose goal is to maintain their dentition, but the last two do not. These patients tend to be older and want treatment for specific problems that require a multidisciplinary dental approach rather than comprehensive orthodontic treatment. They are motivated by health concerns more than psychosocial ones and usually are not concerned about the visibility of orthodontic appliances once they decide they need treatment.

Question 4

Which of the following statements accurately describe the prevalence of perio problems in patients with severe malocclusion?

a. Periodontal pocketing is more prevalent than mucogingival problems at all ages.

b. The prevalence of mucogingival problems peaks at about age 40, then declines.

c. By age 25, the majority of patients with severe malocclusion have evidence of mucogingival problems.

d. For patients with severe malocclusion, the prevalence of periodontal pocketing doubles between the early 30s and the early 40s.

  1. none of the above ✓
  2. a and b
  3. a, b, and c
  4. b, c, and d
  5. all of the above

Correct

That’s right, for patients seen in the dentofacial clinic where those with very severe malocclusion are evaluated, none of these statements are correct. The data show that mucogingival problems are more prevalent than pocketing below age 25. The prevalence of mucogingival problems peaks in the early 20s, not at age 40, and declines in the late 20s. At age 25, about one-third of dentofacial patients have evidence of mucogingival problems, but it never becomes a majority. The prevalence of pocketing is about the same (nearly two-thirds of the patients) in the age 33-39 and over 40 age groups—the rapid increase in perio problems is over by the mid-30s.

Question 5

(A) Stripping of gingival tissues away from the facial surface of incisors is a particular risk when nonextraction orthodontic treatment is performed because (B) Expansion of the arches to obtain space moves the teeth facially and stresses the gingival attachment.

  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, these statements are true and related. When the arches are expanded in nonextraction treatment, the teeth have to be moved facially. Then stripping of the gingival tissues is a risk, even more in adults than in children. This is a major limitation of how much the dental arches can be expanded to bring teeth into alignment.

Question 6

What is optimal force for tipping a tooth to a new position when half the alveolar bone support has been lost?

  1. 10 grams
  2. 25 grams ✓
  3. 50 grams
  4. 75 grams
  5. 100 grams

Correct

That’s right, when half the alveolar bone has been lost, half the periodontal ligament area over which force would be distributed has also been lost, so the optimal force would be half the amount for tipping with normal bone support (50 grams), or 25 grams.

Question 7

For a premolar to be moved bodily after half the alveolar bone support had been lost, how would the ratio between the force to move the tooth and the moment to control root position be affected?

  1. No effect on this ratio
  2. Increased force relative to the moment
  3. Increased moment relative to the force ✓
  4. Necessary to double the moment, otherwise the tooth would tip
  5. Effect unpredictable, would depend on the shape of the root

Correct

That’s correct. The force would need to be reduced from what would be used with normal bone support, but because bone loss increase the distance from the point of force application to the center of resistance of the root, the moment would have to be increased relative to the force.

Question 8

(A) Adults tend to tolerate the irritations of orthodontic treatment better than children because (B) Almost all adults have a higher pain tolerance.

  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 of these statements are false. As a rule, adults don’t tolerate the irritations of orthodontic treatment as well as children, and it’s not true that older patients necessarily have a higher tolerance for orthodontic pain. One of the modern pain-relieving agents is needed routinely for adults at the beginning of treatment, and the addition of a mild tranquilizer can help some of the more severely affected adults—something that’s almost never needed with children.

Question 9

What amount of force would be required to intrude a pair of elongated maxillary central incisors?

  1. 10 grams
  2. 20 grams ✓
  3. 50 grams
  4. 75 grams
  5. 100 grams

Correct

That’s right, the correct force for intrusion of a single tooth would be 10 grams, so for two central incisors 20 grams would be needed. The only way to obtain the precisely calibrated force necessary for this type of tooth movement is to use an auxiliary spring to deliver the force just to those two teeth. A continuous arch wire must not be used.

Question 10

Why should an elongated maxillary third molar be extracted before orthodontic treatment begins?

  1. Probable periodontal disease around such a tooth
  2. Periodontal breakdown likely to develop during orthodontics
  3. Occlusal interference from its position likely to complicate treatment ✓
  4. No reason to extract it if it’s healthy

Correct

That’s right, an elongated maxillary third molar, even if healthy, is likely to cause occlusal interferences as tooth movement proceeds. That would be the major reason for removing it, especially in the maxillary arch where retained third molars are less likely to lead to periodontal problems. But in the orthodontic treatment of adults, removal of upper and lower third molars before the orthodontics begins usually is needed to minimize the chance of problems of some type.

Question 11

Which of the following characteristics would be needed in a bracket/wire appliance to torque the roots of central incisors lingually?

a. Rectangular arch wire that nearly fills the bracket slots

b. Torsional force of 75 grams per tooth

c. Precious metal wire material

d. Ceramic, not metal, brackets

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

Correct

That’s right, the first two statements describe a torquing arch wire, but precious metal is not necessary and is obsolete in modern usage, and metal rather than ceramic brackets would be preferred. Depending on the size of the bracket and therefore the dimensions of the wire to fill the bracket slot, a modern torquing wire would be either stainless steel or beta-titanium (nearly pure titanium). Ceramic brackets look better, but everything else about them is a disadvantage, not an advantage. That’s why metal brackets are preferred when torque is needed.

Question 12

When restorative build-ups of incisors are needed in an adult patient to bring small teeth to normal size and allow proper alignment/occlusion, at what point in treatment should this be done?

  1. Before any orthodontics begins
  2. Immediately after initial alignment is obtained
  3. Near the end of orthodontics, with slightly excessive space provided ✓
  4. Immediately after the orthodontic treatment is completed

Correct

That’s right, the best integration of the orthodontic and restorative phases of treatment is obtained by doing the build-ups near the end of the orthodontic treatment, with the teeth close to their final position but with slightly excessive space provided for the convenience of the restorative dentist. This allows ideal contouring of the restorations, and then the residual space can be closed in the final months of the orthodontic treatment. The alternative is to wait until the orthodontics is completed, but it can be difficult to have just the right amount of space available in that circumstance.

Question 13

For a patient with severe malocclusion and periodontal disease, at what point would orthodontic treatment be indicated?

  1. As soon as possible, to facilitate the perio treatment
  2. As soon as initial perio treatment is completed
  3. When active disease has been eliminated
  4. When perio control has been established and can be maintained ✓
  5. Not until at least one year after periodontal disease has been eliminated

Correct

That’s correct, orthodontics should not begin until perio control has been established and can be maintained. Control of the perio problems must be maintained throughout any orthodontic treatment. Beginning orthodontics before that time risks exacerbation of periodontal breakdown—but there is no need to wait for a year after control has been established.

Question 14

(A) Gingival surgery to section the elastic gingival fibers is important in maintaining the correction of severe rotations because (B) These fibers are the major cause of relapse after rotation correction.

  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, these statements are both true and related. Stretched elastic gingival fibers cause relapse after correction of rotations unless they are sectioned and allowed to heal with the tooth in the correct position, so this adjunctive perio surgical procedure is important when rotations have been corrected.

Question 15

What is the relation of exposure of gingiva on smile to the decision to use canines as replacements for missing lateral incisors?

  1. Exposure of gingiva on smile is acceptable, but not exposure with lips relaxed.
  2. Successful canine substitution requires reshaping the crown.
  3. Gingival surgery to change the contours often is needed for canine substitution.
  4. Canines look more like laterals if their greater crown height is not observed. ✓
  5. There is no relationship, shape of crown is the key.

Correct

That’s correct. Because of their greater crown height, it is very difficult to make canines look like laterals if the entire crown height is observed on smile. But if the lip line is low and only part of the crown is seen even on smile, that makes canine substitution more esthetic. Dental esthetics are particularly important on smile, and exposure during smiling, not at rest, is the important criterion.

Question 16

Surgery to move the chin forward improves facial esthetics in which of the following ways?

a. Decreases the appearance of a weak chin

b. Improves throat form and throat length

c. Decreases the amount of wrinkles in the lower face

d. Makes the nose look less prominent in the face

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

Correct

That’s right, moving the chin forward improves facial esthetics in all these ways. Not only does it make the chin itself more prominent, it improves throat form and throat length and stretches the skin in that area so that the amount of wrinkles in the lower face decreases. The nose always is viewed in relation to the chin, so making the chin more prominent decreases the relative prominence of the nose.

Module 3: Complex Adjunctive Treatment

Question 1

Which of the following are appropriate treatment sequences for a patient with complex problems?

a. Extractions/endo/perio/restorative/orthodontics/restorative

b. Endo/perio/restorative/extractions/orthodontics

c. Perio/restorative/extractions/endo/orthodontics

d. Restorative/endo/extractions/perio/orthodontics/maxillofacial surgery

e. Extractions/perio/endo/restorative

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

Correct

That’s correct, all these sequences are appropriate. Treatment to bring disease under control is the first stage of treatment and should precede any orthodontics. The sequence of procedures within that stage varies with the patient’s particular needs. The biggest pathologic problem gets treated first. And of course complex treatment doesn’t have to involve orthodontics or postorthodontic restorative and perio, so the final sequence also would be quite appropriate if no correction of malocclusion or no postorthodontic treatment was required.

Question 2

Which of the following are likely benefits from including orthodontics in complex treatment?

a. Improved self-esteem

b. Better long-term prognosis for fixed restorations

c. More successful endodontics

d. Control of TMD

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

Correct

That’s right, the first two statements are correct, the other two are not. Improved self-esteem is an important benefit that often encourages patients to change their expectations for job and social success after treatment. The long-term prognosis for crowns, bridges, and other definitive restorations is better when the position of the teeth allows them to be made more ideally. But orthodontics has nothing to do with the success of endodontic treatment, which should be completed if needed before orthodontics begins, and orthodontics cannot be expected to control TMD (although it can perhaps help as part of a more comprehensive plan for TMD).

Question 3

Which of the following statements correctly describe the relationship of endodontic to orthodontic treatment in the treatment of complex problems?

a. Endo treatment always precedes orthodontics.

b. Endo treatment may increase the chance of root resorption during later orthodontics.

c. Endo treatment involving apical surgery should be avoided if orthodontics is planned.

d. For teeth with a doubtful pulpal prognosis, orthodontic treatment can increase the chance that endo will be required.

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

Correct

That’s right, b and d are correct, but a and c are not. It’s true that for teeth with a doubtful pulpal prognosis, orthodontics may be the “last straw” so that endodontic treatment is required. In that situation the patient must be warned of this possibility, but endodontics after the orthodontics has started sometimes is necessary, so it doesn’t always precede the orthodontics. Some evidence suggests that endodontically treated teeth are more prone to root resorption. The type of endodontic treatment doesn’t affect later orthodontics, so if apical surgery is required to bring infection under control, later orthodontics is still possible.

Question 4

What is the optimum time after the completion of orthodontics before definitive restorative treatment should begin?

  1. As soon as possible ✓
  2. After initial orthodontic retention is completed
  3. Six months, to allow the occlusion to settle into final position
  4. 12 months, to be sure no further occlusal changes will occur

Correct

That’s right, definitive restorative treatment should begin as soon as possible. If changes in the occlusion occur before the permanent retainers (the definitive restorations) are placed, they are likely to be for the worse, not the better. In adjunctive treatment, there is no possibility that tooth positions will become stable after an initial period with full-time retainers, so there really isn’t any period of “initial orthodontic retention” or “final settling of the occlusion.” As a general rule, the longer the delay between orthodontics and the final restorations, the greater the chance of problems.

Question 5

What is the most important aspect of esthetic replacement for a single missing maxillary lateral incisor?

  1. Crown form of the replacement tooth
  2. Gingival exposure of the replacement tooth
  3. Appropriate size for the replacement tooth
  4. Symmetry of the replacement tooth with the natural lateral ✓
  5. Orientation of the crown to obtain natural appearance

Correct

That’s correct, all of these things are important, but symmetry, making the replacement tooth as much as possible like the natural one, is the most important aspect of esthetic replacement of a single lateral. For that reason, closing the space on one side only often is not the best plan, because it’s so hard to achieve symmetry when that is done.

Question 6

Which of the following are major contributors to the difficulty in closing an old mandibular first molar extraction space?

a. Large mesial root movement of the second molar

b. Loss of alveolar bone in the old extraction site

c. Periodontal problems distal to the second molar

d. Occlusal interferences that inhibit uprighting

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

Correct

That’s right, a and b are correct, c and d aren’t. Uprighting a mandibular second molar by bringing its roots mesially is difficult under the best of circumstances because of the distance they would have to be brought forward. Loss of alveolar bone in the old extraction site makes it even harder, because as the ridge atrophies and becomes narrower, remodeling of cortical rather than medullary bone is required to allow the tooth to move. Periodontal problems distal to the second molar and occlusal interferences during the tooth movement can be important in patient management but don’t affect the difficulty of closing the space.

Question 7

Which of the following is the major advantage of an implant to replace a maxillary lateral incisor versus a fixed bridge?

  1. Better gingival esthetics
  2. Better crown form is possible
  3. Better crown esthetics for central and canine ✓
  4. Less total cost

Correct

That’s correct. The greatest advantage of an implant is that it makes it unnecessary to prepare the adjacent central incisor and canine as bridge abutments, and it takes great skill to make abutment crowns that look as good as unprepared natural teeth. Of course, if the potential abutment teeth need restoration anyway, this might tip the balance toward a bridge pontic, which can have gingival esthetics and crown form as good as an implant. Although the cost of implants is decreasing, the cost of an implant replacement would be more than that of a bridge under most circumstances.

Question 8

What would be the effect on overjet of orthodontic treatment to bring the roots of maxillary second molars forward?

  1. Reduce it ✓
  2. No effect
  3. Increase it
  4. No way to predict, depends on the force system used

Correct

That’s right, the force system to bring maxillary second molar roots forward would have a reciprocal effect on the maxillary anterior teeth, pulling them back; so it’s predictable that overjet would decrease.

Question 9

In a patient with a Class II deep bite malocclusion, how would mandibular advancement surgery facilitate replacement of missing anterior teeth?

a. Correct the deep bite

b. Allow correct incisor function

c. Make canine-protected occlusion possible

d. Decrease any posterior buccal crossbite tendency

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

Correct

That’s right, all of these are correct. Mandibular advancement would correct the deep bite (if the mandible were rotated down as it was advanced, as it is in a deep bite patient). That would allow correct incisor function and make canine-protected occlusion possible. Since bringing the mandible forward makes it wider relative to the mandible, this also would decrease any posterior buccal crossbite tendency. If there is no buccal crossbite prior to mandibular advancement, one goal of the orthodontic treatment that accompanies this surgery is to control lingual crossbite after the advancement.

Question 10

Which of the following is the major problem when brackets are bonded to prosthetic teeth and these are tied to an arch wire to replace missing teeth during orthodontic treatment?

  1. Not good esthetically
  2. With a rigid arch wire, excessive function on these pontics can displace other teeth
  3. Pontics are not stable when a flexible arch wire is being used ✓
  4. TMD becomes more likely

Correct

That’s right, the biggest problem is that the pontics are not stable when a flexible arch wire is being used. A heavy rectangular wire is needed to hold them. They are very realistic, so esthetically they are quite good. Excessive function, even with a rigid wire, simply isn’t a problem, and their use has no relationship to TMD.

Module 4: Orthodontic Retention

Question 1

Which of the following are major reasons for orthodontic retainers after the end of active treatment?

  1. Imperfect occlusion
  2. PDL reorganization incomplete
  3. gingival fiber reorganization incomplete
  4. unfavorable growth
  5. a and b
  6. c and d
  7. a, b and c
  8. b, c and d ✓
  9. all are major reasons

Correct

That’s correct; b, c and d is the right answer. Imperfect occlusion is not a reason for orthodontic retention (thought it might be a reason for more thorough treatment), because the occlusal relationships have little to do with post-treatment stability. Despite what some clinicians have claimed, a patient who has a perfect result needs retainers just as much as one whose occlusion is improved but not perfect. The other things on the list are the major reasons for retention.

Question 2

When passive arch wires are left in place as retainers after active tooth movement has stopped, how long does it take for the PDL to reorganize?

  1. 2-3 months
  2. 4-6 months
  3. 7-9 months
  4. at least a year
  5. an indefinitely long time ✓

Correct

That’s right. The time would be indefinitely long, because PDL reorganization proceed very far as long as teeth are splinted together by archwires, and it is incomplete when the braces are removed no matter how long passive archwires have been in place. Reorganization of the PDL requires that a tooth can be displaced in function relative to the ones next to it, which is what happens during normal function.

Question 3

How long does it take for gingival elastic fibers to completely remodel after a severely rotated tooth has been repositioned?

  1. 2-3 months
  2. 4-6 months
  3. 7-9 months
  4. at least a year
  5. an indefinitely long time ✓

Correct

That’s right, #5 is the correct answer. Gingival elastic fibers take a long time to remodel when they have been stretched a lot, and the greatest amount of stretching of those fibers occurs when a severe rotation is corrected. Remodeling of gingival fibers does begin while archwires are holding the teeth in position, but it isn’t complete even after a year of archwire retention and another year of being held by a retainer. For that reason, a surgical fiberotomy procedure often is needed to prevent re-rotation.

Question 4

(A) Mandibular wisdom teeth routinely should be removed at the end of orthodontic treatment, because (B) pressure on the other teeth as they try to erupt is a major cause of lower incisor crowding.

  1. A true, B true, related
  2. A true, B true, 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. There are indications for removal of third molars, but that doesn’t have to be done routinely, and pressure from third molars is not the main reason for crowding of lower incisors in the late teens.

Question 5

Which of the following are ways in which growth in the late teens affects the stability of a corrected malocclusion?

  1. forward mandibular growth
  2. downward rotation of the mandible
  3. decrease of the mandibular plane angle
  4. downward growth of the maxilla
  5. a and b
  6. a, b and c
  7. b, c and d
  8. a, b and d ✓
  9. all are major reasons

Correct

That’s right, the correct answer is #4, a, b and d. A small decrease of the mandibular plane angle usually occurs during normal adolescent growth, but this has little or no effect on the stability of the corrected malocclusion, especially if the treatment ended at the end of the adolescent growth spurt. In contrast, downward growth of the maxilla that causes downward rotation of the mandible is a major cause of anterior open bite, and forward growth of the mandible is the major cause of late incisor crowding, and if extreme leads to mandibular prognathism and a severe Class III malocclusion.

Question 6

What is the minimum length of time for full-time (except while eating) retainer wear after correction of alignment problems?

  1. 3 months ✓
  2. 6 months
  3. 7-12 months
  4. one year
  5. an indefinitely long time

Correct

That’s correct. 3 months is the minimum time, because PDL reorganization takes that long. Beyond 3 months, gingival elastic fibers are the main threat to alignment, and their effect can be controlled with part-time wear. But of course that schedule presumes that the dental arches have not been over-expanded and incisors have not been moved too far labially—if that’s not the case, permanent retention will be needed.

Question 7

(A) Retention time for adults often can be shorter than it is for adolescents because (B) adults take their treatment more seriously and are more compliant with the retainer schedule.

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

Correct

That’s right. Both statements are true but they have no cause-effect relationship. The major reason that adults often have shorter retention times than adolescents is that they do not need prolonged retention to control growth, while adolescents do. Compliance with retainer wear has nothing to do with the speed of reorganization of tissues. Age does—the older you are, the slower you recover from most things, so PDL reorganization probably is a bit slower in adults.

Question 8

For which of the following do you need 2-point contact of the retainer with the tooth to maintain tooth position? Correction of …

  1. rotation
  2. a-p alignment
  3. vertical alignment
  4. space closure
  5. a and b
  6. a, b and c
  7. b, c and d
  8. a, b and d
  9. a, b, c and d ✓

Correct

That’s right, a retainer needs at least 2-point contact for all of these. One-point contact allows tooth position to change in all of these ways even if a retainer is worn.

Question 9

What is the greatest problem in using a suck-down lower retainer to maintain incisor alignment?

  1. compliance ✓
  2. poor control of rotations
  3. poor control of vertical alignment
  4. poor control of facio-lingual alignment
  5. poor control of space closure

Correct

That’s right, the greatest problem is compliance. A lower suckdown is less comfortable than an upper one, and patients don’t wear them as well for that reason. It’s true that suckdowns do not control vertical position as well as facio-lingual position, but vertical control is adequate if the patient wears it, and control of both rotations and space closure is good.

Question 10

What is the greatest disadvantage of a suckdown retainer for the maxillary arch?

  1. compliance
  2. poor control of rotations
  3. poor control of vertical alignment ✓
  4. poor control of facio-lingual alignment
  5. poor control of space closure

Correct

That’s correct, the answer is #3. A maxillary retainer often needs to control both alignment and overbite. An acrylic palate-covering retainer makes it easy to arrange a bite plate lingual to the upper incisors to keep the lower incisors from erupting, while a suckdown retainer maintains alignment but does not offer the same control of lower incisor eruption. If maintenance of alignment is all that needed, a suckdown retainer is a good choice.

Question 11

(A) When a heavy wire is used as a fixed retainer for the lower incisors, it is important to bond it to every tooth because (B) If it’s bonded to multiple teeth, it won’t come off if the bond breaks on one tooth.

  1. A true, B true, related
  2. A true, B true, 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 false and the second statement is true. When a heavy wire is used as a fixed lower canine-to-canine retainer, it should be bonded only to the canines so that the incisors are not splinted together and can function normally. It’s true that if a fixed retainer is bonded to all the incisors, it won’t come off if the bond to one incisor breaks—but that’s a major disadvantage of bonding to multiple teeth, because tooth decay under a broken bond can develop quickly.

Question 12

Which of these characteristics are the major disadvantages of a canine-to-canine clip-on retainer?

  1. So small it’s easy to lose
  2. So small it’s easy to bend out of shape
  3. Poor control of vertical alignment
  4. Poor control of space closure
  5. a only ✓
  6. b only
  7. a and b
  8. c and d
  9. a, c and d

Correct

That’s correct, the small size that makes it so easy to lose is a major disadvantage of a canine-to-canine clip-on; the other characteristics are strengths rather than weaknesses. The clip-on design resists distortion well, gives good a-p and vertical control of incisor position, and excellent control of space closure.

Question 13

Which of these characteristics is the most important cause of the difficulty in keeping a maxillary central diastema closed?

  1. large width of the space
  2. excessive fibrous tissue between the teeth
  3. abnormal contour of the teeth
  4. abnormal elastic fiber arrangement ✓
  5. abnormal root structure of the teeth

Correct

That’s right, the biggest problem is an abnormal elastic fiber arrangement—the elastic fibers do not cross the midline as they normally do, so there is nothing to keep the space closed. It is true that there often is a wide space and usually there is excessive fibrous tissue between the teeth that needs surgical removal, but the space can be closed without great difficulty. Both the crowns and roots of the teeth are normal and do not affect treatment and retention.

Question 14

(A) After a maxillary central diastema is closed, a bonded lingual retainer is the best choice because (B) a removable retainer clips the teeth tightly.

  1. A true, B true, related
  2. A true, B true, 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, but the second statement is not why a bonded retainer is the best choice. The space between the maxillary incisors after a central diastema has been closed usually pops open a little every time a removable retainer is removed, and then the teeth are pushed back together when the retainer is re-inserted. That means the teeth are continually jiggled back and forth. This keeps them from tightening up as the PDL is reorganized and may lead to root resorption—so a fixed retainer is more physiologic as well as more esthetic.

Question 15

(A) The most likely mechanism by which high-intensity light accelerates tooth movement (if it does) is increased blood flow because (B) light chills the tissues it affects and cold is known to facilitate healing. These statements are:

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

Correct

That’s right, A is true and B is false. Light energy is known to heat tissues, heating tissues is known to increase blood flow, and increased blood flow seems to facilitate tooth movement, so A is the most likely mechanism at present—though the mechanism is not understood.. Even though correctly-timed cold can facilitate healing after injury, light doesn’t chill tissues, so B is incorrect. What is the real mechanism for tissue-penetrating light? That’s still unknown.

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