Quartz 4

Unit Self-Test

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Level IV Clinical Treatment — Unit A Self-Test

Module 1: Why Do We Do Orthodontics

Question 1

Which of the following attributes of treatment are important when health care is structured around the quality of life paradigm?

a. Prevention of disease

b. Neuromuscular adaptation and function

c. Self-esteem

d. Positive social interaction

  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 important from the perspective of quality of life. Putting the emphasis on broader aspects of quality of life doesn’t mean that prevention of disease is not important or that neuromuscular adaptation should receive less emphasis. The quality of life paradigm does say that it’s incorrect to assume that if you don’t have a specific disease, everything is fine. Good health and absence of disease are not necessarily synonymous.

Question 2

Why, in the mid-20th century, did the emphasis in orthodontics change toward stability of the result from the previous emphasis on ideal occlusion?

a. Relapse toward crowding after expansion of the dental arches

b. Return of deep bite tendencies

c. Return of incisor protrusion

d. Concern about esthetics

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

Correct

That’s right, the shift toward emphasizing stability was based on concern about relapse in dental relationships, not on concerns about esthetics. The assumption remained for a time that if the occlusion were maintained at a near-ideal level, esthetics would take care of itself, and the risk of impaired esthetics if incisors were retracted to improve stability was not recognized at first. Experience showed that there was a potential risk to esthetics with excesive incisor retraction, just as there is with excessive protrusion. This led to the current emphasis on tooth position and jaw relationships as important factors in facial esthetics.

Question 3

(A) For most patients, the primary motivation for orthodontic treatment is concern about dental/facial esthetics because (B) Diminished self-esteem nearly always is due to discrimination related to esthetic problems.

  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 one is false. Those who seek orthodontic treatment often do so because of concern about facial esthetics, but low self-esteem is by no means always a part of the problem, and self-esteem problems can arise from many causes other than dental and facial appearance. Adolescent and adult patients who seek treatment, in fact, tend to score higher on self-esteem and related psychological scales than those with similar esthetics who don’t seek treatment. It appears that you have to have reasonably high self-esteem to seek treatment. Those with low self-esteem tend to feel that treatment wouldn’t do any good anyway.

Question 4

Which of the following are reasons why orthodontic treatment for patients with malocclusion can improve the prognosis for their periodontal disease?

a. Crooked teeth are harder to keep clean

b. The biologic response to orthodontics includes stimulation of the immune system

c. Improved occlusion can decrease the force felt by some vulnerable teeth during bruxism

d. The presence of orthodontic appliances tends to change the bacterial flora in a desirable way

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

Correct

That’s right, orthodontics can improve the prognosis for some patients by making it easier to keep the teeth clean and by decreasing the force felt by vulnerable teeth during bruxism. Although bacterial and immune phenomena are the major determinants of periodontal disease, orthodontics doesn’t affect the immune system or bacterial flora, at least in ways that decrease the risk of periodontal problems.

Question 5

(A) Poor masticatory efficiency is highly correlated with malocclusion because (B) The occlusal surfaces of the teeth must fit together precisely for efficient mastication.

  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 false. It seems reasonable that severe malocclusion should decrease masticatory efficiency, but even a weak correlation between the type of occlusion and masticatory efficiency has not been established. Patients with severe malocclusion often learn not to try to eat some things in public, not so much because they can’t but because it is hard for them to be socially acceptable while doing so. During mastication occlusal contact of the teeth is rare, so if normal jaw movements are possible, it may not make much difference exactly how the teeth would fit if they were in contact.

Question 6

What is the chance that TMD symptoms will accompany posterior crossbite with a shift?

  1. 1 in 10
  2. 1 in 6 ✓
  3. 1 in 4
  4. 1 in 2
  5. unpredictable, no relationship established

Correct

That’s right, there’s about a 16% chance, or 1 in 6, that TMD symptoms will accompany a posterior crossbite with a shift, given a 0.4 correlation coefficient between the two conditions. That is the highest correlation between any type of malocclusion and TMD, but it isn’t very high. Another way to say the same thing is that the data indicate that 5 times out of 6, TMD will not become a problem for a crossbite patient.

Question 7

(A) The chance that a Class III patient will have TMD symptoms is directly related to the severity of the Class III malocclusion because (B) Severe Class III patients have to shift their jaw on closure.

  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 false. In fact, patients with mild Class III problems are more likely to have TMD symptoms, probably because they have to shift to avoid incisor intereferences. Patients with severe Class III don’t have incisor interferences and don’t have to shift on closure. So there’s an inverse relationship between Class III severity and TMD, not a direct one.

Question 8

What’s the chance that a child with Class II malocclusion will be teased because of his or her protruding teeth?

  1. 10-15%
  2. 20-30%
  3. 40-50% ✓
  4. 50-70%

  5. 75%

Correct

That’s right, nearly half of Class II children report being teased by other children about their protruding teeth; that is more than we would like but not quite the majority. If the teeth protrude badly enough, adults are likely to assume that child isn’t very smart and may treat him or her accordingly. That isn’t teasing, but it can be psychologically damaging.

Question 9

(A) Patients often are reluctant to admit that they are seeking treatment because of concerns about dental/facial appearance because (B) They think physical and functional problems are more likely to impress doctors.

  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. For sure, patients often are reluctant to admit esthetic concerns. Why that’s true varies, but often it relates to the feeling that psychosocial concerns shouldn’t be admitted, especially since the doctor probably wouldn’t take them seriously anyway.

Module 2: To Extract or Not To Extract Part 1

Question 1

Which of the following are major reasons for tooth extraction in orthodontic treatment?

a. Protruding upper incisors

b. Protruding lower incisors

c. Severely crowded incisors

d. Impacted maxillary canines

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

Correct

That’s right, the major reasons for extraction are severe crowding and protrusion of incisors that creates lip separation at rest and lip strain on closure. Protruding incisors in both arches, of course, are just another outcome of lack of space to accommodate the teeth in the dental arches. Impacted canines rarely are an indication for extraction.

Question 2

Which of the following is an indication for expansion of the arches to deal with crowding of the incisors?

  1. < 3 mm crowding
  2. < 5 mm crowding
  3. < 7 mm crowding
  4. any could be correct ✓

Correct

That’s right, the decision to expand the arches can’t be made just from the degree of crowding. Any of those measurements might be consistent with a decision to expand the arches (or to extract). Because crowding and protrusion are aspects of the same thing, it’s necessary also to determine whether incisor protrusion is masking the space discrepancy. To do that, you have to look at the patient.

Question 3

(A) Full and everted lips indicate excessive protrusion of incisors because (B) The position of the incisors determines the amount of lip support provided by these teeth.

  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 and the second one is true. Excessive incisor protrusion is indicated by the combination of two things, full and everted lips and lip separation at rest with strain on closure. Lip fullness varies greatly with racial and ethnic characteristics, but when lip separation at rest is present, that is viewed as a problem. The teeth are too prominent only when you have to strain to close your lips over them.

Question 4

How does the percentage of orthodontic patients with premolar extraction at present (at a reasonably typical location, like UNC) compare to the percentage with premolar extraction in 1950?

  1. Much lower
  2. A little lower
  3. About the same ✓
  4. A little higher
  5. Much higher

Correct

That’s right, the percentage now and 50 years ago is about the same. Premolar extraction was introduced in the 1940s and 1950s as a way to improve the stability of results of orthodontic treatment, peaked in popularity in the 1960s, and its use has declined since then.

Question 5

Which of the following are reasons for the decline in the percentage of patients with premolar extraction to treat crowding/protrusion?

a. Effects on facial esthetics

b. Instability even after extractions

c. Introduction of bonded brackets to replace bands

d. Considerations of treatment efficiency

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

Correct

That’s right, all these factors contributed to the decrease in the number of patients having premolar extraction. As time passed, it was realized that retracting the incisors too much can affect facial esthetics unfavorably. Extraction treatment decreases the chance of long-term instability but does not eliminate it. Bonded brackets remove the need for interproximal space for band material and make nonextraction treatment easier, and nonextraction treatment tends to take less time and effort.

Question 6

What is now considered the minimum percentage of patients with Class I crowding/protrusion who would need extractions rather than expansion?

  1. 5%
  2. 10% ✓
  3. 26%
  4. 50%
  5. 65%

Correct

That’s right, the best current estimate of the minimum extraction percentage (by McNamara in 2002, who extracts only when it is absolutely necessary), is 10%. That is based on his survey of consecutive patients in his practice. On the other extreme, no one any longer advocates extraction in more than 50%, though extraction percentages often were higher than that in the 1960-85 period.

Question 7

Which of the following are ways by which arch expansion in patients with Class I crowding/protrusion can improve dentofacial esthetics?

a. Increasing the prominence of the incisors

b. Increasing the amount of lip support

c. Decreasing the width of buccal corridors

d. Altering the width of the alar base of the nose

  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 3 items affect tooth-lip-cheek relationships and dentofacial esthetics, but moving the teeth does not affect the width of the base of the nose (it takes surgery to do that). Esthetic effects must be considered from both the frontal and lateral views of the face and are not limited to the effect on the incisors, although those are the most visible teeth.

Question 8

Which of these choices is the major way extraction would affect long-term stability?

  1. Decreasing tongue pressure
  2. Disrupting the gingival fiber network
  3. Decreasing lip/cheek pressure ✓
  4. Decreasing bite force against the teeth

Correct

That’s right. Extraction has the potential to decrease pressure by the lips and cheeks against the dentition, if the incisors are retracted. If it affected tongue pressure at all, retracting the incisors would increase it. There’s little or no effect from extraction with space closure on either the gingival fiber network or bite force.

Question 9

On long-term recall, how does incisor irregularity with nonextraction (expansion) patients compare to patients who had early (serial) extraction?

  1. Much greater
  2. A little greater ✓
  3. About the same
  4. A little less
  5. Much less

Correct

That’s right, the existing data indicate that irregularity on long-term recall tends to be a little greater in nonextraction patients and that 70% of long-term serial extraction patients have only minimal incisor crowding. But the differences are smaller than was expected at the height of enthusiasm for extraction to prevent relapse into crowding.

Question 10

What’s the current recommendation as to the best time to start treatment of patients with moderate crowding/protrusion?

  1. Primary dentition, so that permanent teeth erupt in the correct position
  2. Early mixed dentition, to take maximum advantage of growth
  3. Late mixed dentition, to maintain leeway space when 2nd primary molars are lost ✓
  4. Early permanent dentition, to keep treatment time to a minimum

Correct

That’s right, beginning treatment in the late mixed dentition, so that leeway space can be maintained when 2nd primary molars are lost, is now considered the best time to start treatment. Even if primary teeth are moved, permanent teeth do not necessarily erupt where their predecessors were located, so that doesn’t work. For Class I crowding/protrusion, changes in jaw relationships are not necessary, and early treatment has not been shown to be more effective than later treatment in obtaining alignment of the teeth. If leeway space is lost before treatment begins, treatment time is likely to be increased rather than decreased.

Question 11

Which one of the following statements about the limits of arch expansion for stability is incorrect?

  1. Dimensions of the upper arch are more important than the lower ✓
  2. Incisors can be advanced 2 mm in most patients
  3. Intercanine expansion of any magnitude is unstable
  4. Expansion of 2-3 mm per side in the premolar-molar region is acceptable

Correct

That’s right, it’s the lower arch whose dimensional changes are the key to evaluating likely stability. In the lower arch, as a general rule, the incisors can be advanced 2 mm in most patients, but more than that is likely to be unstable. Expansion across the mandibular canines is unstable, but 2-3 mm expansion per side in the lower premolar-molar regions is acceptable.

Question 12

For an adult considering orthodontic treatment, which of the following would be most likely to help her understand the esthetic implications of arch expansion versus extraction?

  1. Informed consent booklet
  2. Dental cast set-up, showing the tooth movement in each instance
  3. Computer simulation of profile change ✓
  4. Discussion with another patient who had the same kind of treatment

Correct

That’s right. Of the items on the list (all of which could be helpful), computer simulations are particularly important in helping patients understand the esthetic impact of alternative treatment approaches, and most likely to be helpful in making the decision. This is a good illustration of the adage that “a picture is worth a thousand words.” Computer simulations can be quite accurate in nongrowing individuals, but it is very difficult to accurately predict growth, so the simulations are much more useful for adults.

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