01 - Malocclusion Definition and Prevalence

Changing Goals of Orthodontic Treatment

Purpose of This Module

This module discusses the concept and characteristics of malocclusion, introduces the classification of malocclusion, and reviews the epidemiologic data for the prevalence of types of malocclusion. At its conclusion you should be able to discuss the:

• 21st century goals of orthodontic treatment
• Epidemiology of malocclusion
• Prevalence of the major characteristics of malocclusion
• Need and demand for orthodontic treatment

The Concept of Malocclusion

Crowded, irregular and protruding teeth have been a problem for some individuals for most of human history. The first efforts to correct this go back to at least 1000 BC, and as dentistry developed in the 18th and 19th century, a number of devices to “regulate” the teeth came into use. This treatment was focused entirely on aligning irregular and crowded teeth, and thereby improving the appearance of the teeth and face. In an era when an intact dentition was a rarity, little attention was paid to bite relationships, and the details of the way upper and lower teeth contacted each other was considered unimportant.

It was necessary to consider how the teeth should fit together when prosthetic replacement of missing teeth was planned. The term “occlusion of the teeth” was introduced to describe this, and concepts of prosthetic occlusion appeared in the late 1800s. Edward Angle, the “father of modern orthodontics”, is credited with most of the development of the concept of occlusion of the natural dentition. He provided the first clear and simple definition of normal occlusion, invented the term malocclusion to describe deviations from normal occlusion, and developed the first useful classification of malocclusion.

Angle’s Characteristics of Normal Occlusion

Angle’s postulate was that the maxillary first molars were the “key to occlusion” because of their position at the base of the zygomatic arch, and that the mesiobuccal cusp of the upper first molar should occlude in the buccal groove of the lower first molar. If this molar relationship existed, and if the teeth were aligned along a smoothly curving “line of occlusion”, then normal occlusion would result. This statement, which is correct unless there are aberrations in the size of the teeth, brilliantly simplified normal occlusion.

Angle’s line of occlusion passes through the central fossae of the maxillary posterior teeth and across the cingulum of the upper canines and incisors. The same line runs along the buccal cusps of the mandibular posterior teeth and the incisal edges of the lower canines and incisors. The line thus specifies the occlusal and interarch relationships of the teeth, once the molar relationship has been established.

Angle’s Classification of Malocclusion

Having described normal occlusion, Angle then was able to specify three classes of malocclusion based on the first molar relationship:

Class I: normal relationship of the first molars, but line of occlusion incorrect because of incorrectly aligned teeth

Class II: lower molar distally positioned relative to upper molar; line of occlusion not specified

Class III: lower molar mesially positioned relative to upper molar; line of occlusion not specified

Note that the Angle classification has four classes: normal occlusion and the classes of malocclusion. Normal occlusion and Class I malocclusion share the correct molar relationship but differ in the way teeth relate to the line of occlusion. The line of occlusion may or may not be correct in Class II and Class III, but the molar relationship is incorrect.

Image 1: Normal occlusion	Image 2: Class I malocclusion
Image 3: Class II malocclusion	Image 4: Class III malocclusion

Goals of Treatment: from Angle to the Present

By the early 1900s, the goal of orthodontic treatment had evolved beyond the alignment of irregular teeth to the correction of malocclusion. This led to less emphasis on the appearance of the teeth and face—Angle’s view was that if the dental occlusion was correct, dental and facial esthetics also would be ideal. Unfortunately, as time passed it became clear that even an excellent occlusion was not an excellent orthodontic treatment result if it was achieved at the expense of proper tooth-jaw relationships and facial proportions.

The advent of cephalometric radiology, which came into routine clinical use in orthodontics in the mid-20th century, made it clear that many Class II and Class III malocclusions resulted from jaw relationships, not just from malposed teeth. A small mandible relative to the maxilla came to be called a skeletal Class II malocclusion because it almost required a Class II molar relationship, and a large mandible relative to the maxilla became skeletal Class III. Correction of jaw as well as tooth relationships (which might require jaw surgery as well as orthodontics) became a goal of treatment.

In the early 21st century, occlusion still is important, but achieving correct relationships of oral and facial soft tissues, rather than focusing just on teeth and bone, has become a primary goal of treatment. It’s not just teeth any more. This is a paradigm shift—a change in the conceptual basis for treatment.

Goals of Treatment: from Angle to the Present (cont.)

The images with this screen outline the difference between the goals of treatment in the 20th century, dominated by Angle, and the 21st century shift toward the “soft tissue paradigm”, which offers a broader view of treatment goals than just the correction of malocclusion.

Image 1	Image 2
Image 3	Image 4
Image 5

Treatment in the Soft Tissue Paradigm Era

Because of Angle’s emphasis on the antero-posterior position of the teeth and jaws, profile photographs and lateral cephalometric radiographs received the greatest emphasis in orthodontic diagnosis until quite recently. But for this girl, treated by David Sarver and colleagues in the early 2000s, the frontal facial views show both the initial problem and the effects of treatment much more clearly.

When they sought treatment at age 11, this girl and her parents were concerned about her facial appearance and especially her “no teeth” appearance when she smiled. On smile, she exposed only 1 mm of her malformed maxillary incisors (image 1). To say that she had an Angle Class I malocclusion would be accurate but remarkably unhelpful, because the major problems were her short lower face and tooth-lip disproportions, neither of which are specified when a patient is classified Class I.

Her orthodontic treatment focused on increasing face height and positioning the malformed teeth for temporary restoration (image 2) and later permanent restoration. The favorable effect on her facial growth can be seen in the cephalometric superimposition (image 3)—another thing you will learn a lot more about in this course.

At age 18 (image 4), permanent laminates were placed on the anterior teeth, which would not have been possible without the increase in face height and balance that was created by modern orthodontics. Coordinated orthodontic / restorative or prosthetic treatment is done much more frequently now because it produces better results.

Image 1	Image 2
Image 3	Image 4

Epidemiology of Malocclusion

Population Studies: Dental Crowding / Malalignment

Several studies of the prevalence of malocclusion were undertaken between 1930 and 1965, using the Angle classification. The results varied tremendously: the prevalence of malocclusion in the United States was reported as anywhere between 35% and 95% of the population. The problem was a lack of consensus as to how much deviation from Angle’s normal (really ideal) occlusion could be tolerated before an individual was judged to have malocclusion. The conclusion was that the Angle classification just couldn’t be used for population studies.

More recently, studies in most developed countries have used specific characteristics of malocclusion to obtain information about their prevalence. As part of the NHANES-III study, a large-scale evaluation in the 1990s of the health of the white (European descent), black (African descent) and Mexican-American population groups in the United States, the alignment of the teeth was calculated by the irregularity index (image 1). This is the total of the distances between incisor contact points, so it allows a quantitative measurement of the extent of incisor irregularity.

The irregularity data, without differentiating the three population sub-groups, are shown in image 2. Note that one-third of the total population have at least moderately irregular (usually crowded) incisors, and nearly 15% have severe or extreme irregularity.

Image 1: Measurements to calculate the irregularity index.	Image 2: US population percentages for degrees of incisor irregularity, NHANES-III.

Population Studies: Overjet

Overjet is defined as the horizontal overlap of the incisors (image 1). Normally the upper and lower incisors are in contact, with the upper incisors ahead of the lower only by the thickness of their incisal edges, i.e., normal overjet is 2-3 mm. Excessive overjet correlates with Class II molar and jaw relationships. If the lower incisors are in front of the upper incisors, this is reverse overjet, which correlates with Class III molar and jaw relationships.

Overjet is a better indicator of Class II and Class III problems than is the molar relationship that Angle described, and it now is used in population studies instead of molar relationship. Data for overjet in the American population are shown in image 2. Note that only one-third of the population have ideal overjet, and another one-third have only slightly increased overjet. Moderate overjet (5-6 mm) is found in 10%. Overjet of 7 mm or more can create severe problems. This affects about 5% of the American population.

Increased overjet associated with Class II is much more prevalent than reverse overjet associated with Class III. Reverse overjet of -3 mm or more represents a severe problem. There is a significant racial difference in the prevalence of reverse overjet: up to 5% of people of Asian origin have severe or extreme reverse overjet, versus 0.5% for African-Americans blacks and 0.3% for Americans of European descent.

Image 1: Overjet is defined as the distance from the facial incisal edge of the lower central incisor to the lingual incisal edge of the upper central incisor. Ideally, it is 1-2 mm.	Image 2: US population percentages for overjet, NHANES-III.

Population Studies: Overbite / Open bite

Overbite is defined as the amount of vertical overlap of the incisors (image 1). Normally the lower incisal edges contact the lingual surface of the upper incisors at or above the cingulum, i.e., normal overbite is 1-2 mm. In open bite, there is no vertical overlap, and the vertical separation (in negative numbers) is measured to quantify its severity.

Data for overbite and open bite are shown in image 2. Half the population have an ideal vertical relationship of the incisors. Note that moderate and severe deep bite are much more prevalent than moderate and severe open bite, but extreme deep bite is only slightly more prevalent than extreme open bite.

Image 1: Measurements for overbite and open bite.	Image 2: Population percentages, overbite and open bite.

Population Studies: Changes with Age

Changes in the prevalence of ideal alignment, severe crowding, excess overjet and open bite by age group are shown in this graph. As age increases, note the increase in crowding and the decrease in ideal alignment, and the decrease in severe overjet. As we will see later in this course, these changes are related to mandibular growth. As you can see, open bite prevalence is not affected and stays the same.

Population Studies: Racial / Ethnic Differences

There are only modest differences in incisor irregularity between the three American racial groups studied in NHANES-III. Two differences in antero-posterior and vertical facial and dental proportions are worth noting:

1. Deep bite is much more prevalent than open bite in the population as a whole, but vertical relationships vary greatly between racial groups. Average open bite is significantly larger in African-Americans than the other groups (image 1). More clinically relevant, severe open bite is 5 times more prevalent in African-Americans. The average deep bite is significantly larger in those of European descent, and severe deep bite is nearly twice as prevalent.
2. In the three major groups in the NHANES-III study, severe reverse overjet is found in less than 1% of the population—but in people of Asian descent, up to 5% have severe reverse overjet (image 2).

Image 1	Image 2

Population Studies: Summary

The key points to remember from modern population studies of malocclusion:

• About half the population have well-aligned teeth or slight irregularity, while about 15% have irregularity severe enough that either major expansion of the dental arches or extraction of a permanent tooth in each quadrant of the arch is likely to be needed if the teeth are to be aligned.

• With increasing age, incisor irregularity gets worse and the number of people with ideal alignment decreases.

• 15% of the US population are Class II, and about half of these individuals have overjet severe enough to predispose them to problems in social interactions.

• Open bite is much more prevalent and deep bite less prevalent in African-Americans.

• Class III and reverse overjet are much more prevalent in those of Asian descent.

• Other racial / ethnic differences are modest and unimportant.

Problems due to Malocclusion

Malocclusion: Types of Problems

Protruding, irregular or maloccluded teeth can cause three types of problems for patients:

1. Psychosocial problems due to discrimination because of dental and/or facial appearance
2. Problems with oral function difficulties in jaw movement (muscles not well coordinated, pain) temporomandibular joint dysfunction problems with mastication, swallowing or speech
3. Greater susceptibility to trauma, periodontal disease or tooth decay

These are listed in the general order of their importance. Let’s consider them one at the time.

Psychosocial Problems

Studies have confirmed what you’d probably think anyway, that severe malocclusion is likely to be a social handicap and a threat to self-image and self-esteem. Every time you meet someone new, they size you up based largely on your facial appearance. The caricature of a stupid person always includes protruding upper incisors (image 1), so if your front teeth stick out, you’re not expected to be very smart. A girl or woman with a deficient midface and prominent lower jaw is a witch (image 2), expected to be unpleasant and perhaps even dangerous. A tall, skinny, long face man probably has no education or social skills, and is not to be taken seriously until he proves otherwise. And so on… there are a lot of caricatures along these lines.

Fortunately, as others get to know you better, the appearance of your face and teeth becomes less important, but it’s not a trivial handicap to have to overcome negative first impressions all the time—it affects your whole adaptation to life. This places the concept of handicapping malocclusion in a larger and more important context. “It’s just cosmetic, no big deal” misses the problem in a major way. If it affects your interaction with others, it is a big deal because it decreases your quality of life and your chance to succeed in life.

Why do parents seek treatment for their children? Why do adolescents and adults seek treatment for themselves? The major reason is to lessen or remove a psychosocial handicap that can have a major effect on their ability to get ahead in the world.

Image 1: Caricature of a stupid person - note the malocclusion.	Image 2: Witches almost always have prominent chins.

Psychosocial Problems (cont.)

McGregor’s studies of the effect of a disfiguring dental or facial condition offer an interesting insight into its psychosocial effect. An individual who is grossly disfigured can anticipate a consistently negative response. An individual with an apparently less severe problem, such as a deficient chin or protruding incisors, sometimes is treated differently because of this and sometimes not.

It seems to be easier to cope with a defect if the response of other people is consistent than if it isn’t. Unpredictable responses create anxiety and can have a major impact on self-image and interaction with others.

Psychosocial Problems: the Effect of Self-Esteem

An individual’s self-esteem also makes a difference in how much a dentofacial abnormality affects him or her. As the chart shows, there are several possible responses to the same level of abnormality. You have met individuals who try so hard to overcome negative responses that they succeed despite what would seem a severe handicap. Some others with a similar condition adapt and accept a level of discrimination. Some begin to use the abnormality as a reason not to try, or literally fight back against what they see as persecution. It’s interesting that one way to improve the chance that a prisoner will not be back in prison after release is to treat a facial deformity while he or she is there.

Psychosocial Problems: Who Seeks Treatment?

The variety of responses to apparently similar levels of dentofacial abnormality mean that something that is not a problem to some individuals can be a major problem, or a problem but only a minor one, for others.

When the patient shown in these photos sought treatment as an adult (image 1), she said her major reason was that she was tired of people staring at her when she went out to dinner, and finally now she could afford treatment. But she held a good job, was married, had a positive attitude toward life, and expected that treatment would make an acceptable situation better—not that it would finally allow her to succeed. She had already made a great effort to succeed despite her handicap.

In fact, people who seek treatment for problems like this tend to score higher on psychologic scales of satisfaction and optimism than the general public. Those who see themselves as hopeless failures are less likely to seek treatment than those with a positive attitude who are sure they would benefit from it.

Both her dental and facial appearance were greatly improved by retraction of her protruding upper incisors and augmentation of her deficient chin (by a lower border osteotomy of the mandible to move her chin forward) (image 2). Five years after treatment (image 3), she held a much more responsible job—one that she was capable of handling before treatment, but almost surely would never have obtained because of her appearance.

Image 1: Age 29, Pre-treatment	Image 2: Age 31, Completion of treatment
Image 3: Age 36, 5-year recall

Problems With Oral Function

It seems obvious that poor dental occlusion would make it more difficult to chew your food normally. Some people with a severe malocclusion do report difficulty in eating, and say they can eat better after orthodontic treatment—but the great majority of those who seek orthodontic treatment report no problem with eating. When there is a problem due to malocclusion, it’s often more that it’s difficult to be socially acceptable while managing your food, and so you avoid eating in public and learn to avoid certain foods that are hard to manage. Pizza is an excellent example—can you bite cleanly through the crust and not get any of the filling on you? That’s really difficult if you have an open bite or excess overjet.

Would a severe malocclusion make you more likely to develop temporomandibular pain / dysfunction (TMD)? Usually, no. If there is a relationship, it’s a weak one, and there’s an important link to stress. It’s probably true that if you have a dental occlusion that requires you to shift your jaw when you bring your teeth together, and that you react to stress by clenching and grinding your teeth, you are at greater risk of TMD. There’s little or no evidence that’s also true for other types of malocclusion.

Can malocclusion lead to difficulties in swallowing and speech? Perhaps, but that’s rare. The ability of individuals with extreme malocclusion to speak normally is impressive, and almost always they also can swallow normally—although the adaptive tongue position needed to do this can look abnormal. We’ll review this later in some detail later in the course.

So is improving oral function a major reason for orthodontic treatment? Yes, for some patients, but not for most of them.

Problems With Injury and Dental Disease

Are you more likely to suffer injury to your dentition, or to develop dental disease, if you have malocclusion?

Protruding upper incisors and excess overjet produce a greater risk of injury to the teeth during childhood than normal overjet. There is about 1 chance in 3 that a child with untreated Class II malocclusion and excessive overjet will experience trauma to the upper incisors, but usually the result is only minor chips in the enamel. Most accidents that damage the teeth are associated with normal activity, not sports—but mouthguards for contact sports definitely can reduce damage to the teeth.

Extreme overbite can lead to damage to the tissues lingual to the upper incisors and/or labial to the lower incisors, and can even cause loss of the affected teeth. Soft tissue damage is an indication for orthodontic treatment.

Are you more likely to develop caries because your teeth are irregular and hard to clean? Although that sounds reasonable, there is no evidence that poor alignment of the teeth is a significant risk factor for caries.

Are you more liable to develop periodontal disease for the same reason if you have crooked teeth? Perhaps, but other factors, like how well you take care of your teeth and how good your immune system is, are much more important. The conclusion of an extensive study published in 2008 is that there is no evidence to support the claim of a periodontal health benefit from orthodontic treatment.

The bottom line: malocclusion can lead to increased risks to dental health, but this is the least likely of our three major reasons for orthodontic treatment.

Need and Demand for Orthodontics

Population Estimates of Need for Orthodontic Treatment

We now have good estimates of the prevalence of various characteristics of malocclusion. How does that relate to need for treatment?

If you consider only the severity of malocclusion as an indicator of need, there are two possible approaches. The first is to score each of the characteristics (irregularity, overjet, etc.) and add up the score. That has been tried but for all practical purposes just doesn’t work. If you have a little bit of several characteristics, you may get a high score when they’re added up, but that doesn’t relate well at all to how much you really need treatment.

The second approach is to accept the idea that the severity of the worst characteristic of a malocclusion is the major indicator of treatment need. For instance, if you have 10 mm overjet, that in itself is an indicator that you need treatment, and mild vs moderate irregularity of incisors is almost irrelevant. This approach now is used in many countries, in the form of the IOTN (Index of Treatment Need) system for grading treatment need. Patients can quickly be placed in one of 5 grades, from grade 1 “no need” to grade 5 “extreme need”. Children in grades 4 and 5 get priority for treatment, and perhaps financial help in obtaining it. The IOTN grades are shown in the attached charts.

Pay particular attention to the characteristics of grades 4 and 5, which are considered definite indications for treatment. Does that mean nobody in grade 3 needs treatment? No, because the psychosocial effect varies—and a child with real problems socially related to the appearance of his or her teeth needs treatment even if the malocclusion is not graded as severe.

Image 1: Characteristics of IOTN grades 1 and 2.	Image 2: Characteristics of IOTN grade 3.
Image 3: Characteristics of IOTN grade 4	Image 4: Characteristics of IOTN grade 5.

Population Estimates of Need for Orthodontic Treatment (cont.)

It is possible to take the data from NHANES-III for characteristics of malocclusion, and calculate the percentage of the major population groups in the US with IOTN scores that indicate mild, moderate and severe treatment need.

This graph shows the calculated IOTN grades for adolescents (age 12-17) in the major American population groups. Note that about 15% of the white and Hispanic (Mexican-American) groups are IOTN grades 4 or 5, indicating definite treatment need, while 20% of the black population are in this category. Moderate treatment need, grade 3, occurs in approximately another one-third of the white and black groups, and over 40% of the Hispanic group.

Population Estimates of Psychosocial Need for Treatment

How do the IOTN grades relate to the psychosocial aspect of need for treatment? You can’t assume a close coordination between severity of some aspect of malocclusion and its impact on appearance.

To deal with this, an “Aesthetic Component” of IOTN now has been added (note the British spelling, they developed it). It consists of a series of photos of the teeth. A dental appearance like photos 1-3 (image 1) is considered to indicate no need for treatment; photos 4-7 (image 2) are borderline; and photos 8-10 (image 3) indicate definite treatment need.

How the teeth are perceived is very much affected by the soft tissue frame in which they are presented to the world. So these pictures of teeth alone can be misleading, but at least adding the Aesthetic Component does acknowledge that how it looks and the effect of dental and facial appearance on social interactions is important in evaluating treatment need.

Image 1: IOTN esthetic scale 1-3, no need for treatment	Image 2: IOTN esthetic scale 4-7, borderline need
Image 3: IOTN esthetic scale 8-10, need treatment

Demand for Treatment in the USA

By no means do all those who are classified as needing treatment actually seek it. Some do not feel they really need it or do not want to accept it. Others agree that they need treatment but can’t afford it or can’t obtain it.

More parents and children in urban/suburban areas than rural areas think that they need treatment. As this graph shows, family income is a major determinant of how many receive treatment. This reflects two things, one obvious and the other perhaps not so obvious. Obviously, high income families can more easily afford orthodontics. But it’s also true that a good dental / facial appearance is more important if you want to achieve more prestigious social positions and better-paying occupations. The higher the aspirations for the child, the more likely the parents are to seek orthodontic treatment, and upper income parents tend to have higher aspirations.

Although every state supports at least some orthodontic treatment for low-income children through its Medicaid program, this pays for very little of the total treatment that is done. Note in the graph that even in the lowest income group, more youths and adults receive treatment than Medicaid or other third-party sources cover. The amount of treatment that is done for the lower income segments of the population reflects the importance that many of these families place on it. It’s widely accepted that if you really want John or Susie to get ahead in the world, you need to get those teeth fixed—and much of what little discretionary income exists for low-income families is used for orthodontics surprisingly often.

Demand for Treatment in the USA (cont.)

The effect of financial constraints on orthodontic treatment is seen most clearly by the response when treatment is largely or completely covered by third-party plans, so that the cost of treatment no longer is a factor in deciding whether to seek it. In one such setting where comprehensive dental care including orthodontics was provided, the dentists recommended treatment for 55%, and 50% accepted it.

It seems likely that as money is available to support it, demand for treatment will reach at least the 35% level at which parents readily recognize a need for treatment. The NHANES-III data show that even in the 1990s, 35-50% of the children in more affluent areas were receiving orthodontic treatment.

It is interesting that demand for treatment among adults has greatly increased over the last 30 years. A survey of orthodontic practitioners in 2010 showed that, on average, nearly 30% of orthodontic patients were adults (age 19 or older). Wearing braces as an adult now is more socially acceptable than it was not so long ago, though no one really knows why. Older adults (over age 40) now have orthodontic treatment in conjunction with other types of dental treatment, because it now is widely accepted that better periodontal / restorative / prosthetic results can be achieved by improving the dental occlusion as part of the treatment.

Summary

Summary

Important points from this teaching program:

Angle classification:

• 4 classes, not 3 (normal occlusion, 3 malocclusion)
• molar relationship plus line of occlusion

Extended Angle classification:

Jaw relationship that predisposes to molar relationship

Modern goals of treatment

• soft tissue proportions / tooth-lip relationships
• jaw relationship
• dental alignment / occlusion

Summary (cont.)

Irregularity index (NHANES III data)

• 33% crowded incisors, 15% very crowded
• gets worse with increasing age

Overjet (NHANES III data)

• one-third severe or negative
• <1% Class III except Asian 5%

Overbite / open bite (NHANES III data)

• deep bite more frequent than open bite in total population
• severe deep bite more prevalent in those of European descent
• severe open bite much more prevalent in African-Americans

Reasons for orthodontic treatment

• psychosocial: discrimination, self-esteem
• oral function: mastication, swallowing, speech
• injury / disease

Summary (cont.)

Need for treatment determined by IOTN method: Most severe characteristic

IOTN grades for US population:

• 15% of whites and Mexican-Hispanic have severe malocclusion
• 20% of African-Americans have severe malocclusion

IOTN aesthetic component is based on view of teeth only, no facial component

Dentists vs parents:

• dentists: 55% need = all IOTN grade 3, some grade 2
• parents: 35% need = all IOTN grades 4-5, some grade 3

Demand for treatment:

• affected by patient perception of problem, socio-economic status
• 50% want treatment if no financial constraint
• high demand from lower income groups: perception that orthodontics is important for future success of child

Referral to Self-Test

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

Now that you have gone through the module, do the assigned reading in Contemporary Orthodontics(pages 2-18, 99-103 and 133-145 in the 5th ed.; pages 2-22, 111-119, 145-158 in the 4th ed.) Then take the self-test, and use it as a guide for further study and review. Be sure you understand the correct answer to all questions that you didn’t get right on your first try.

Copyright 2013, UNC Dept. of Orthodontics

Self-Test

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”.

Incorrect

No, that’s wrong. 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.

Incorrect

No, that’s wrong. 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.

Incorrect

No, that’s wrong. 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).

Incorrect

No, that’s incorrect. 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.

Incorrect

No, that’s incorrect. 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%.

Incorrect

That’s wrong, you’ve over-estimated the number of severe Class II malocclusions as characterized by overjet. 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.

Incorrect

That’s wrong. 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.

Incorrect

No, that’s wrong. 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.

Incorrect

No, that’s wrong. 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%.

Incorrect

No, that’s wrong. 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.

Incorrect

No, that’s incorrect. 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.