Quartz 4

Unit Self-Test

15 min read

Level II Diagnosis — Unit A Self-Test

Module 1: Malocclusion Definition and Prevalence

Question 1

What were the primary goals of orthodontic treatment prior to the 20th century?

  1. alignment of irregular incisors
  2. correction of occlusal discrepancies
  3. improvement of dental / facial appearance
  4. 1 only
  5. 1 and 2
  6. 2 and 3
  7. 1 and 3 ✓
  8. all the above

Correct

That’s right. In the early days of orthodontics, the focus was on the appearance of the teeth and their effect on the appearance of the face. The goal was an improvement in both. Treatment was done with “regulating appliances”.

Question 2

What were the primary goals of orthodontic treatment in the early 20th century?

  1. alignment of irregular incisors
  2. correction of occlusal discrepancies
  3. improvement of dental / facial appearance
  4. 1 only
  5. 1 and 2 ✓
  6. 2 and 3
  7. 1 and 3
  8. all the above

Correct

That’s correct. With the development of the concept of occlusion, the focus of treatment became correction of the molar relationship occlusal discrepancies, but the teeth also were brought into alignment relative to the line of occlusion and this corrected other occlusal discrepancies. From Angle’s perspective dental and facial appearance were automatically taken care of when the occlusion was corrected.

Question 3

What are the primary goals of orthodontic treatment now?

  1. alignment of irregular incisors
  2. correction of occlusal discrepancies
  3. improvement of dental / facial appearance
  4. 1 only
  5. 1 and 2
  6. 2 and 3
  7. 1 and 3
  8. all the above ✓

Correct

That’s right. At present there is a strong focus on improvement of dental / facial appearance, but alignment of irregular incisors and correction of occlusal discrepancies also are primary goals. You can’t obtain the greatest improvement of dental / facial appearance unless you correct alignment and occlusal relationships along with soft tissue proportions and tooth-lip relationships.

Question 4

What is NHANES-III?

  1. American system for prioritizing treatment need
  2. Third national study of the HANES approach
  3. Epidemiologic survery of health needs of US population ✓
  4. Method for enhancing the outcomes of treatment

Correct

That’s right. NHANES-III was the third major survey of the health needs of the US population, carried out in the 1990s. It included a section on dental needs, and provided the best data available for the prevalence of characteristics of malocclusion, broken down by the three major population sub-groups (European descent, African descent, Mexican-American).

Question 5

What percentage of the American population have severe or extreme irregularity of their incisors?

  1. 15% ✓
  2. 20%
  3. 25%
  4. 33%
  5. 50%

Correct

That’s correct. About one-third of the population have little or no incisor crowding and irregularity, so two-thirds have crooked teeth, but only 15% have severe or extreme irregularity. The others don’t reach that level of irregularity. With irregularity that severe, it is difficult to align the teeth without having to extract one or more teeth to make room for alignment of the others.

Question 6

What percentage of the American population have overjet severe enough to predispose them to problems in social interaction?

  1. 4% ✓
  2. 8%
  3. 12%
  4. 16%
  5. 20%

Correct

That’s correct. Overjet of 7 mm generally is considered the point at which social-interaction problems related to the protruding upper incisors are almost certain to be encountered. 7-10 mm is rated as severe, and >10 mm as extreme. The NHANES-III data show that 3.8% of the population are in the 7-10 mm category, and 0.3% >10, so the correct answer is 4%.

Question 7

How does the prevalence of severe or extreme deep bite in the US population compare to the prevalence of severe or extreme open bite?

  1. severe / extreme deep bite more than 5 times as prevalent ✓
  2. severe / extreme deep bite more than twice as prevalent
  3. deep and open bite prevalence is about the same
  4. severe / extreme open bite more than twice as prevalent
  5. severe / extreme open bite more than 5 times as prevalent

Correct

That’s right. Severe or extreme deep bite is more than 5 times as prevalent as severe or extreme open bite (17% vs 3%). In part this reflects the larger number of whites and Mexican-Americans than blacks in the total population, because severe open bite is much more prevalent in blacks—but even in blacks, severe deep bite is more prevalent.

Question 8

What’s the biggest single reason that leads people to think they need orthodontic treatment?

  1. increased risk of periodontal breakdown due to malocclusion
  2. increased risk of trauma to the teeth
  3. difficulty in chewing and eating
  4. TMD or increased risk of developing it
  5. difficulty or potential difficulty with social interactions ✓

Correct

That’s right. The biggest single reason for orthodontic treatment is to overcome or prevent problems with social interactions because of dental and facial appearance. All the others are valid reasons for treatment, and for some patients they’re the main reason for treatment—but for most people, treatment is primarily for psychosocial reasons, not function or disease / trauma.

Question 9

(A) A moderately severe dentofacial problem may lead to more severe psychosocial problems than an extremely severe one because (B) negative responses are more obvious and consistent for the less severely affected individual.

  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. Negative responses are more consistent for the more severely affected individual. The less severely affected individual often encounters inconsistent responses—sometimes those protruding incisors seem to make a big difference, sometimes they don’t. That creates anxiety about social interactions and can have more severe psychosocial effects than consistent negative responses.

Question 10

When financial constraints on orthodontic treatment are removed, as when comprehensive orthodontic treatment is a benefit of working at a generous employer, approximately what percentage of the workers who are told by their dentist that they need treatment actually seek it?

  1. ~90% ✓
  2. ~80%
  3. ~70%
  4. ~60%
  5. varies, depending on the patient’s or parent’s goals for the future

Correct

That’s right, if it’s essentially free, about 90% go ahead with orthodontic treatment when it’s recommended. There aren’t a lot of employers generous enough to offer dental treatment including comprehensive orthodontics to all their employees and their family—but it has happened. In that circumstance, the company’s dentists tell about 55% of the employee group that they need orthodontic treatment and would benefit from it, and 50% accept treatment. 50/55 = 90.9%.

Question 11

What percentage of children from families who are just above the poverty level receive orthodontic treatment?

  1. 5%
  2. 10% ✓
  3. 15%
  4. 25%
  5. 50%

Correct

That’s right, about 10% of those who are just above the poverty level receive treatment (or did at the time of NHANES-III). Since third-party payment by Medicaid or other third-party programs would have funded only a small fraction of this, it is apparent that many families with limited discretionary income are willing to use much of it for orthodontic treatment that they expect to improve their child’s chances of long-term success.

Module 2: Known Causes of Malocclusion

Question 1

What is the most frequent location for a supernumerary tooth?

  1. Maxillary midline ✓
  2. Maxillary lateral incisor area
  3. Maxillary posterior quadrants
  4. Mandibular anterior area
  5. Mandibular posterior area

Correct

That’s right, a supernumerary tooth can appear almost anywhere, but this occurs most frequently in the maxillary midline. A tooth in that location is called a mesiodens.

Question 2

What has happened to the number and size of teeth during primate evolution?

  1. both have decreased ✓
  2. size has decreased but number has remained the same
  3. number has decreased but size has remained the same
  4. in the human lineage, both have stayed the same

Correct

That’s correct. Both the number and size of the teeth have decreased. At present, the variability and frequent absence of third molars and upper lateral incisors suggests that from an evolutionary perspective, these teeth may be on their way out.

Question 3

(A) A scar of the lip after an injury is likely to lead to protrusion of the incisors because (B) the scar changes the pattern of soft tissue pressure against the incisor 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 but the second is true. A lip scar would tend to increase lip tightness and push the incisors lingually, not make them more protrusive.

Question 4

Which of the following are characteristic of fetal alcohol syndrome, caused by exposure to high levels of alcohol during embryonic development?

  1. underdeveloped maxilla and midface
  2. Class III malocclusion
  3. long and abnormally shaped upper lip
  4. 1 only
  5. 1 and 2
  6. 1 and 3
  7. 2 and 3
  8. 1, 2, and 3 ✓

Correct

That’s right, all of these are facial characteristics of FAS. It leads to an underdeveloped maxilla and midface, Class III malocclusion, and a long and abnormally shaped upper lip.

Question 5

Which of the following types of malocclusion is most likely to be an inherited problem?

  1. severe incisor crowding
  2. maxillary and midface deficiency
  3. maxillary protrusion
  4. mandibular and chin deficiency
  5. mandibular and chin protrusion ✓

Correct

That’s correct. Mandibular protrusion (prognathism) has a strong inherited component, much more than the other conditions listed. The protruding “Hapsburg jaw” of the European royal family has persisted for hundreds of years, but mandibular prognathism is characteristic of many other families as well.

Question 6

(A) The highest rate of malocclusion is found in modern cities because (B) the mixture of populations in these genetic melting pots leads to inheritance of mismatched jaws and 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 correct. The first statement is true but the second one is false, not the correct explanation. Independently inherited tooth and jaw characteristics do not account for the increase in malocclusion as populations have become more urban.

Question 7

Which of the following is not a possible outcome of trauma that displaces a primary maxillary central incisor at age 6?

  1. an enamel defect in the middle of the crown of the permanent central ✓
  2. dilaceration of the root of the permanent central
  3. drift and partial space closure when the primary tooth is lost and the permanent tooth fails to erupt
  4. ankylosis of the permanent central

Correct

That’s right. The other items are possible, but the crown of the permanent central has formed by age 6, so an enamel defect in the middle of the crown isn’t a possible outcome (although that could happen with trauma at an early age).

Question 8

How strong is the relationship between ankylosis of a primary molar and the development of malocclusion?

  1. very strong, usually happens
  2. strong, often happens
  3. weak, rarely happens ✓
  4. not at all, never happens

Correct

That’s right, ankylosis of a primary molar rarely leads to the development of malocclusion, but sometimes a problem arises because of drift of the permanent teeth in the vicinity—so there’s a weak relationship.

Question 9

In modern urban populations, what percentage have such severe malocclusion that it can be considered handicapping?

  1. <0.5%
  2. 1%
  3. 5% ✓
  4. 10%
  5. 25%

Correct

That’s right, about 5% of modern urban populations have malocclusion that is considered handicapping because of its effect on normal function and/or social interactions.

Question 10

Which of the following conditions is most frequently associated with multiple congenitally missing teeth?

  1. fetal alcohol syndrome
  2. ectodermal dysplasia ✓
  3. cleft lip and palate
  4. hemifacial microsomia
  5. all are frequently associated with this problem

Correct

That’s right. Ectodermal dysplasis is so strongly associated with multiple congenitally missing teeth that a child who is missing most of the teeth should be evaluated for ectodermal dysplasia even if that diagnosis has not been made previously.

Question 11

Modern research suggests that at least what percentage of malocclusion is due to environment rather than inherited factors?

  1. <10%
  2. 25%
  3. 50% ✓
  4. 75%

  5. 90%

Correct

That’s right, twin studies show that at least 50% of malocclusion cannot be explained by inherited factors, and some researchers suggest that the figure for environment causation is considerably higher.

Question 12

What is the most likely cause of a unilateral posterior crossbite in a child?

  1. hereditary factors
  2. trauma to one condyle leading to reduced growth on that side
  3. overgrowth of the condyle on one side
  4. bilateral narrowing of the maxilla related to thumb sucking ✓

Correct

That’s right, the great majority of apparent unilateral crossbites in children are due to bilateral narrowing of the maxilla due to thumb sucking, and a functional shift so the teeth are in normal occlusion on one side and crossbite on the other.

Module 3: Equilibrium Theory and the Etiology of Malocclusion

Question 1

The best evidence is that environmental factors explain at least what percentage of malocclusion?

  1. <10%
  2. 25%
  3. 50% ✓
  4. 75%

  5. 90%

Correct

That’s right, twin studies indicate that no more than 50% of malocclusion can be attributed to heredity, so at least 50% of malocclusion must be attributed to environmental causes, and it may be greater.

Question 2

(A) Under most circumstances, the teeth are in a position of equilibrium because (B) tongue and lip pressures against the teeth are in balance.

  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 even though the second one is false. The teeth are in a position of equilibrium, but the equilibrium isn’t defined just by tongue and lip forces.

Question 3

During swallow, how does tongue pressure against the incisors usually relate to lip pressure?

  1. 2-3 times greater ✓
  2. about 60% greater
  3. about the same
  4. about 50% less
  5. 2-3 times less

Correct

That’s correct. Tongue pressure against the incisors during swallowing usually is 2-3 times greater than lip pressure, so they don’t balance.

Question 4

(A) The dental equilibrium is explained by a balance of resting tongue and lip pressures against the teeth because (B) the dental apparatus is designed to resist forces of short duration.

  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, the first statement is false but the second one is true. Although only resting pressures have a long enough duration to affect the equilibrium, they don’t balance, and so don’t explain the equilibrium.

Question 5

What is the threshold for force duration to produce tooth movement?

  1. <1 hour
  2. 4-8 hours ✓
  3. about 12 hours
  4. 18-20 hours

Correct

That’s correct. The duration threshold is somewhere between 4 and 8 hours, probably at about 6 hours.

Question 6

(A) Tongue thrust swallow has little or no effect on the position of the teeth because (B) the duration of the pressure during swallowing is too short to have an effect.

  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. The statements are true and related. Tongue thrust swallow doesn’t push the teeth around because the pressure during each swallow lasts for only one second, so hundreds of swallows per day produce only a few minutes of pressure.

Question 7

(A) The mode of respiration can be an etiologic factor in malocclusion because (B) respiratory mode affects posture and thereby changes resting pressure.

  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 statements are true and related. Respiratory mode can be significant for malocclusion, and almost certainly its’ because posture and thereby resting pressures are affected.

Question 8

To what extent do you have to be a mouthbreather instead of a nasal breather to produce significant effects on your dental occlusion?

  1. 10-20%
  2. 20-50%
  3. 50-75%

  4. 75%

  5. nobody knows ✓

Correct

That’s right, although we know there’s a relationship between the percentage of nasal vs oral respiration and effects on malocclusion, at this point nobody knows what the threshold percentage is.

Question 9

What happens to head posture when the nose is abruptly closed off?

  1. head tilts up
  2. mandible drops down
  3. tongue assumes lower posture
  4. 1 only
  5. 1 and 2
  6. 1 and 3
  7. 2 and 3
  8. 1, 2, and 3 ✓

Correct

That’s right, When the nose is abruptly closed off, head posture changes as the head tilts up and the jaw goes down, and tongue posture changes too.

Question 10

(A) Long face adults have about the same biting force as normal children because (B) the long face grop fail to gain biting strength during adolescence.

  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 statements are true and related. Why the long face group fail to gain strength in the masticatory muscles at puberty remains a mystery, but the long face condition can be recognized before muscle strength becomes abnormal.

Question 11

(A) Measuring biting force is an important diagnostic procedure for children with growth problems because (B) bite force is the major determinant of how much face height the patient will develop.

  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. Measuring bite force isn’t an important diagnostic procedure, because its role in determining fact height is modest at best.

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