{{PAGE_1}} LEVEL IV · CLINICAL TREATMENT

Unit A Why Do We Do Orthodontics · To Extract or Not To Extract Part 1

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Why Do We Do Orthodontics
To Extract or Not To Extract Part 1

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Why Do We Do Orthodontics

Goals of Treatment

Introduction to Level IV

You have been through Level III, in which the goal was to teach you how to provide orthodontic treatment for patients whom you would manage in a typical family practice. There is a hierarchy for clinical knowledge:

Knows: the background for clinical decisions (Levels I and II)
Does: selected clinical procedures (Level III). No practitioner can do everything for everybody, so we all provide selected clinical procedures and refer patients to others for treatment that we do not provide.
Understands: the basis for treatment of more complex treatment (Level IV), so that you can make appropriate referrals for treatment that you do not provide. You will, of course, make your own decisions about the scope of your practice in the future—which may include more or less orthodontics than what you were taught to do in Level III. But whether you are in family practice or a different specialty practice, you will find yourself needing answers to questions about orthodontics and working with orthodontists in treatment of patients who have complex problems that require a multi-disciplinary approach. The goal of Level IV is to provide a level of understanding of orthodontic practice that will enable you to work effectively and efficiently with orthodontists.

The Paradigm for Health Care: Quality of Life vs Disease Control

A discussion of the goals of orthodontic treatment has to begin with a review of the goal of health care more generally. A paradigm is defined as shown in the graphic—and the health care paradigm has changed in recent years. After scientific discovery of the cause of many diseases, it was generally accepted for many years that the major objective of health care was the control if not the elimination of disease. A disease-free life, it was thought, would be the ideal.

But consider the possible impact of controlling disease on other aspects of life. What do you do if the cure is worse than the disease? To put the problem in a dental context, to what extent would you prescribe extensive gingival surgery to treat periodontal problems if it greatly impaired the patient’s appearance and affected his or her ability to keep a job?

It has become clear that the impact of any treatment on the quality of life must be considered. In the modern paradigm, the goal of health care is to obtain for the patient the best quality of life, taking into account the balance between the physical and psychosocial aspects of health.

{{PAGE_4}} Paradigm: a set of shared beliefs and assumptions that represent the conceptual foundation of an area of science or clinical practice

Health care paradigm changes:

early-mid 20th century Disease control NOW Quality of life

Goals of Orthodontic Treatment

At one level, it is easy to state the goals of orthodontic treatment. We would like to give the patient the best possible:

dental and facial esthetics
dental occlusion
stability of the result

But that leaves two questions:

How do you judge what is best?
What do you do if the goals are incompatible, for example, if the best esthetics would not give the best occlusion and/or stability?

A bit more than 100 years ago, when Norman Kingsley (who was a noted sculptor as well as dentist) began the development of orthodontics in America, the only reason for orthodontic treatment was to improve esthetic problems by aligning the incisor teeth. Alignment of irregular teeth had been done occasionally for that purpose all the way back to at least the 2nd century A.D.

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{{PAGE_5}} The goals of orthodontics: the best possible

Kingsley, late 19th century

dental / facial esthetics
occlusion
stability of the result

Goals of Orthodontic Treatment, Early 20th Century

Around the turn of the 20th century, Edward Angle, the “father of modern orthodontics”, defined ideal occlusion. It is interesting that the very concept of ideal (normal) occlusion is only a little more than 100 years old.

Having defined ideal occlusion, Angle then was able to define malocclusion as deviations from the ideal. He distinguished three major classes of malocclusion based on the molar relationship. So the Angle classification has four categories: ideal occlusion and Class I, II, and III malocclusion.

Not surprisingly, Angle felt that the major goal of orthodontic treatment was to perfect the dental occlusion. Philosophically, he held that everyone had the potential to be ideal. In his view, the best facial esthetics always accompanied ideal occlusion of all 32 teeth, and he maintained that if the occlusion were perfected, function would cause the teeth to stay in that idealized relationship.

You can still hear echoes of that view in modern dentistry. For instance, some dentists still claim that proper occlusion will maintain teeth in a new position—which is clearly not the case. Occlusion has remarkably little to do with stability.

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{{PAGE_6}} The goals of orthodontics: the best possible

dental / facial esthetics
occlusion
stability of the result

Angle, early 20th century (Callout pointing to ‘occlusion’)

Goals of Orthodontic Treatment, Mid-20th Century

Angle felt that it was never necessary to extract teeth to obtain space for proper alignment and occlusion of the others. Expansion of the dental arches was always his treatment approach. You already know, from our previous review of equilibrium principles, that if the dental arches are expanded too much, the teeth are likely to be unstable and too prominent.

By the middle of the 20th century, it was apparent that if Angle’s prescriptions for treatment were followed, relapse was highly likely for many patients. Tweed in the United States and Begg in Australia independently developed methods of treatment—ironically, adapting Angle’s orthodontic appliance in each instance—to allow proper positioning of teeth after premolar extraction. The goal was to obtain better stability of the result and to overcome esthetic problems created by excessive dental protrusion.

But the problem was that this compromised the occlusion to some extent (it’s not ideal occlusion if some teeth are missing), and could affect facial esthetics for the worse as well as the better.

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The goals of orthodontics:

the best possible

dental / facial esthetics
occlusion
stability of the result

Tweed, Begg mid-20th century

Goals of Orthodontic Treatment Now

In these early years of the 21st century, in both restorative dentistry and orthodontics, there is an increased emphasis on dental and facial esthetics (image 1). At this point, the goal of treatment still is the best possible esthetics, occlusion, and stability—but if these are incompatible, the best approach now is often to optimize esthetics and accept some compromise in occlusion and stability (permanent retention required). Why?

In the modern age, there are three reasons for doing orthodontics—listed here in their order of importance (image 2):

primarily, to help patients overcome psychosocial handicaps created by discrimination based on facial appearance
additionally, to improve function of the teeth and jaws
occasionally, to improve oral health

Remember that patients seek orthodontic treatment usually and restorative treatment frequently to improve their quality of life. Quality of life, of course, is very much affected by psychosocial handicaps related to dental and facial appearance (though of course if can also be affected by function and health).

That means it isn’t enough to just replace missing teeth, or to bring the teeth into ideal alignment and occlusion without considering the esthetic outcome (image 3). If the dental and facial esthetics are

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{{PAGE_8}} not satisfactory, it’s not satisfactory treatment—because then the desired improvement in quality of life would not achieved.

The goals of orthodontics, now: the best possible

dental / facial esthetics (Esthetic restorative dentistry)
occlusion (Modern orthodontics)
stability of the result

Why does it make sense to emphasize esthetics? Why do we do orthodontics?

primarily, to help patients overcome psychosocial handicaps
additionally, to improve function
occasionally, to improve oral health Patients seek orthodontic treatment largely to improve their quality of life

Why does it make sense to emphasize esthetics? Why do we do orthodontics?

primarily, to help patients overcome psychosocial handicaps If the esthetic outcome isn’t satisfactory, it’s not successful treatment Patients seek orthodontic treatment largely to improve their quality of life

Health Effects

Reasons for Treatment: Health

Let’s look further at the reasons for orthodontic treatment, beginning with the health effects. What’s the relationship of malocclusion and oral disease?

Hard tissue lesions: little or no relationship There’s simply no evidence that tooth decay is more likely if teeth are not well aligned (image 1).
Periodontal disease: a weak relationship In general, oral hygiene, bacterial types, and immune status are the major factors in whether periodontal disease develops—but there is some evidence that patients with severe malocclusion are

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{{PAGE_9}} more likely to develop periodontal problems. Perhaps this is because good hygiene is more difficult to achieve.

Did the malocclusion (images 2, 3) have anything to do with this man’s development of periodontal disease (image 4)? Probably only to the extent that it discouraged him from taking care of his teeth. There is some evidence that the “bad bugs” related to periodontal disease are more prevalent around malaligned teeth, but malalignment makes it harder to keep the teeth clean and the bacterial flora under control—it doesn’t make it impossible. So motivation is important.

At age 47, as it became apparent that he was in great risk of losing all his teeth, this man wanted treatment to save them if possible.

Orthodontics and Periodontal Health (cont.)

Periodontal disease: a weak relationship

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{{PAGE_10}} Despite this, orthodontics can be an important part of the treatment plan for an adult with periodontal problems. For instance, uprighting a tipped molar often improves the health of the tissues around it (see the program on Adjunctive Orthodontics for more information). A vulnerable tooth that is subjected to occlusal trauma can be stabilized better if other teeth are positioned to take some of the force during bruxism. Successful control of advanced periodontal disease is more likely if the teeth are aligned and brought into more normal occlusion.

This patient decided he wanted to save his teeth and wanted the malocclusion corrected as part of the overall treatment plan. The first step in complex treatment of this type is to bring the periodontal disease under control, and the patient has to demonstrate the motivation to make that possible. The perio treatment includes scaling, curettage, gingivectomy/gingivoplasty—whatever is necessary to stop the progression of the disease (images 1 and 2).

With periodontal disease under control, orthodontics is quite feasible even when severe bone loss is present. Coordinated orthodontic and periodontic treatment can make it easier to manage the periodontal problems. For this patient, splinting of the teeth after they were brought into alignment (note that one lower incisor was extracted and space was closed) was part of the long-term plan (image 3).

{{PAGE_11}} Image 1: Clinical photo showing dental malocclusion and periodontal issues after initial scaling/clean-up. Image 2: Clinical photo illustrating gingivectomy and extensive curettage required before orthodontic treatment. Image 3: Clinical photo depicting splinting of teeth at completion of active orthodontics, with braces visible on upper and lower arches.

Third Molars in Post-Orthodontic Patients

What to do about third molars that often do not have enough space to totally erupt is an important question for most patients in late adolescence, whether or not they have had orthodontic treatment. You already know that third molars really can’t be blamed for the development of lower incisor crowding in late adolescence—that is much more a response to late mandibular growth than pressure exerted by third molars that are trying to erupt. Are there health considerations in the decision to retain or extract third molars? Yes, there are.

Third molars can be put into three categories: (1) those that erupt and become a functional part of the dental arch; (2) those that erupt into the mouth, but are only partially exposed and are not in occlusion; (3) those that have not entered the oral cavity.

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{{PAGE_12}} Those in the first category usually are not a problem, with one important exception. They are more likely to be seen in individuals who have large jaws, particularly a large mandible, and therefore in those who have a skeletal Class III tendency or bimaxillary protrusion. Extraction of third molars before surgery to reposition the mandible may be needed.

Those in the third category produce health risks related to the bacterial flora around them and development of chronic inflammation; those in the third category are a lesser health risk but may become cystic and damage other teeth or produce significant bone lesions (image 4). Follow-up radiographs to monitor their status are needed if they are retained.

Let’s look more closely at the second category, for which new information about the effects of chronic inflammation and about their role in the development of periodontal disease has changed recommendations for their management.

Partially Erupted Third Molars

Partially erupted third molars, particularly mandibular third molars, are problematic because when the crown of the tooth breaks through the soft tissue and is exposed to the oral environment, bacteria can and do penetrate deeply along the crown. Even though periodontal bone loss does not occur quickly when this happens, an increased probing depth is found, and this is a hospitable area for the anaerobic bacteria that now are now known to be the cause of periodontal disease. The result is that periodontal disease tends to develop initially around third molars and spread anteriorly from there, and that chronic inflammation in this area can be the source of cardiovascular disease and complications of pregnancy. You have, of course, learned about this in other courses, so we do not need to go that again—but we do need to provide recommendations about management of partially erupted third molars.

Is orthodontic treatment related to partially erupted third molars? It seems logical that expansion of the dental arches to correct crowding of the anterior teeth would decrease space for third molars, and that if the second molars move mesially during orthodontic space closure, this would increase space. Extraction of first molars is rarely done for orthodontic purposes, but major mesial movement of the second and third molars does occur after first molar extraction in children or adolescents, and functional third molars in occlusion often is the outcome. Extraction of second premolars tends to bring the molars forward, though not nearly as much as first molar extraction. The extent to which it decrease partial exposure of third molars has not been documented—it helps somewhat, but often not enough.

Should partially erupted third molars be extracted routinely? What about watchful waiting to see if they will eventually come into occlusion? The current guidelines:

removal of exposed 3rd molars decreases the chances of early periodontal disease
if a partially erupted 3rd molar is retained, monitoring that includes probes for evaluation of the bacterial flora is needed
an episode of pericoronitis is an indication for extraction
recovery after 3rd molar extraction is faster and less problematic in teen-agers

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{{PAGE_13}} Function

Orthodontics and Function There are two aspects to the relationship between dental occlusion and function: (1) Masticatory Efficiency It is difficult to demonstrate that patients with normal occlusion can chew and eat better than those with malocclusion, although it is obvious that patients with severe malocclusion have difficulty in eating many foods. Perhaps this difficulty comes from the fact that occlusion as dentists view it really does not come into play during eating. The upper and lower teeth almost never contact each other during chewing. So if normal jaw movements are possible and the jaws and teeth are reasonably well related, perhaps the details of occlusion do not matter very much for mastication. But some patients comment that they can eat better after orthodontic treatment. It makes sense that correcting severe deviations from the normal relationships would make a difference. We can’t yet measure improvements in masticatory efficiency—there are no good tests. But there’s another aspect of being able to chew better: often patients with severe malocclusion learn that there are some things they can’t eat in a socially acceptable way, and they avoid eating those things when other people are around. For instance, pizza often offers a challenge is you have an open bite or large overjet. Perhaps what we need is an evaluation of how patients feel about eating pizza (or other things) in public and what reactions they get from others when they do, not an evaluation of how many chews it takes to get to the point that swallowing is OK.

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{{PAGE_14}} Mastication: Good dental occlusion → good chewing efficiency (?)

Remember: almost no occlusion while chewing

Patients tell us they can chew and eat better after treatment. We can’t measure it—but it’s important to do so, to document this benefit

TM Joint Function and Malocclusion

(2) TMD/Occlusion

What’s the relationship between TM pain/dysfunction and malocclusion? That, too, is a difficult question to answer, for the same reason: Remember that there is almost no occlusion during mastication. The teeth are brought lightly together at the end of most swallows, but otherwise are separated. Occlusion, as viewed by bringing dental casts together, is only a minor part of normal function with the natural teeth.

Occlusal relationships, therefore, become important in the etiology of TM dysfunction only to the extent that patients clench and grind their teeth, and neuromuscular adaptation to the occlusion during bruxism determines whether pain develops. In the absence of parafunctional activity, TM pain/dysfunction related to the occlusion simply does not develop. Perhaps the way to look at it is that some arrangements of the teeth make it easier to hurt yourself by bruxing and grinding than others.

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Occlusion / TM joint function:

TM pain / dysfunction = problem of neuromuscular adaptation to occlusion

Remember: almost no occlusion while chewing

TMD text: “If patients could accept the simple advice, ‘Let your teeth alone’, there would be no need for this book.”

Occlusal goal: arrange the occlusion to minimize the chance of injury during bruxism

Effects of a Lateral Shift

There is a relationship between some types of malocclusion and TMD.

The strongest correlation is with crossbite with a lateral shift. The correlation coefficient between the two conditions is about 0.4. If you square any correlation coefficient, you get the chance of successfully predicting one thing from the presence of the other. What’s the chance that TMD will be found when there is a crossbite and lateral shift? The correlation coefficient is 0.4: (0.4) squared = 0.16, so there is a 16% chance that a patient with a crossbite and lateral shift will have symptoms of TMD. It works in reverse, too, so there also is a 16% chance that a patient with TMD will have a crossbite with a lateral shift.

Does having a crossbite with a shift predispose you to TMD? Yes, but remember that if you have such a crossbite, there is only 1 chance out of 6 that you have or will develop TMD and 5 chances out of 6 that you won’t.

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{{PAGE_16}} TMD and Other Types of Malocclusion The correlation coefficients are even lower for other types of malocclusion. The coefficients are about 0.3 for Class III and Class II deep bite, meaning there’s only about a 10% chance of correctly predicting that TMD will develop in a patient with these malocclusions. Perhaps this reflects the fact that some (but by no means most) individuals with either of these malocclusions have to shift to avoid incisor interferences when they bring their teeth together. It’s pertinent that the severity of Class III malocclusion is inversely related to the prevalence of TMD (image 1). With a mild Class III, incisor interferences are likely to force a shift on closure, whereas a severe Class III puts the incisors beyond occlusal contact. It makes sense, therefore, that patients with mild Class III who are forced to shift on closure are more likely to develop TMD symptoms than those with severe Class III, who don’t have to shift. For several other types of malocclusion, some investigators report a weak correlation with TMD; others do not find a relationship. Anterior open bite falls into this category of controversy. If there is a relationship to TMD, it is very weak (image 2). Perhaps the best way to look at it is this: Some types of malocclusion make it easier to generate muscle spasm and pain/dysfunction by clenching and grinding your teeth. No matter how good your occlusion is, you can still hurt yourself with parafunctional activity if you do it enough. So perfect occlusion decreases the chance of TMD but doesn’t eliminate it. And if you don’t clench and grind, it’s easier to tolerate a malocclusion that predisposes you to TMD without developing it.

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{{PAGE_17}} TMD and Malocclusion: The Bottom Line Orthodontic treatment changes the occlusion, but it neither causes nor cures TMD. With orthodontic treatment, preexisting TMD often gets better—the sore teeth created by treatment takes all the fun out of clenching and grinding. But you can’t count on long-term improvement—if the patient goes back to bruxism, the TMD is likely to recur. TMD may develop after orthodontic treatment, but it’s hard to be sure whether the treatment had anything to do with it. Certainly it is possible that orthodontic treatment could create an occlusion that would lead to a shift on closure, or a greater awareness of the occlusion that would predispose a patient to bruxism. The best evidence that this rarely happens is that the chance of developing TMD as you get older is the same whether you had orthodontic treatment or didn’t. The bottom line: As a general rule, orthodontics doesn’t cause TMD—and it doesn’t cure it.

Psychosocial Effects

Psychosocial Impact of Malocclusion Now let’s examine the psychosocial impact of malocclusion. In a sense, we already took that into account in thinking about chewing efficiency in the context of how other people react if you have trouble managing some kinds of food. Let’s look at the reaction to your facial appearance. What difference does your facial appearance make, really? Begin by understanding that every time you meet a new person, their first impression is based largely on your facial appearance. He or she looks like … a good person, a hard case, whatever. We all size people up in that way, instinctively. Fortunately, as people get to know each other better, appearance isn’t so important, but it’s a considerable handicap to have to overcome an unfortunate

{{PAGE_18}} appearance every time you meet somebody new.

What do you think of the person in this image? Just based on her appearance, you will immediately have some ideas about what you’d find if you met her. ![[whyortho_20.webp|Initially, you would assume about this person [what?] …]]

Effect of Protruding Incisors

Three caricatures drive home the point:

(1) Protruding upper incisors suggest that you’re an idiot.

You can’t draw a proper idiot without giving him protruding teeth—like Zero in the comics, for example (image 1). If you want him to look smarter, you’ll have to correct those teeth.

What’s your initial reaction to this girl (image 2) and young woman (image 3)? You’re likely to assume that neither is very smart, because their dental appearance suggests that—but that’s not correct, for either one.

The caricature associated with protruding upper incisors creates a social handicap that’s hard to overcome. It’s a terrible problem to have to convince every new person you meet that you’re not stupid.

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{{PAGE_20}} Effects of Dental Appearance and Chin Prominence

Three caricatures drive home the point: (2) Bad teeth (decayed, broken, missing, obviously crowded, or protrusive) suggest that you’re from a lower socioeconomic class, probably aren’t well educated, and don’t take good care of yourself.

The patient we looked at in Section 2 of this module wanted treatment more to keep from being judged unfavorably than to improve his health, though both were reasons for treatment. In an adolescent, crowded and irregular incisors can create a social problem at a time in life when it’s particularly difficult to cope successfully (images 1, 2). This boy’s complaint: “I try not to smile and show my teeth.” That reflect his awareness of possible social discrimination based on dental/facial appearance.

(3) Chin prominence (strength) means a lot. In a male, a strong chin is associated with a more powerful personality, while a weak chin is associated with general weakness and doubtful intelligence (your upper incisors will protrude, of course, if your mandible is deficient). When you first met him, would you expect the boy in image 3 to be a leader in his group? Not likely. It’s hard to be elected class president if you have a weak chin. In a female, a strong enough chin makes you a witch. This girl’s chin (image 4) isn’t that strong, but it detracts, makes her look as if she might be unpleasant, unhappy, hard to get along with. Bottom line: It’s not just your teeth, it’s jaw proportions as well.

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  Image 1: Poor dental appearance implies neglect.
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  Image 2: Protruding/irregular incisors imply poor socioeconomic status as well as questionable intelligence.
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  Image 3: A weak chin in males implies general weakness.
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  Image 4: A strong chin in females implies an unpleasant level of aggressiveness.
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{{PAGE_22}} Social Limitations What’s the benefit of treatment? Click on the icon and consider the impact of this clip from the classic movie Casablanca:

Would the girl have looked like that (and become a movie star), without braces on her teeth at an early age? Probably not. A nice idea to have planted in the public mind in 1943.

Clip from Casablanca. https://proffit-instruction.netlify.app/Modules/whyortho/video/25.mp4

Psychosocial Benefit of Treatment Let’s be sure you understand the psychosocial problem that malocclusion can create for a child or an adult:

Stereotypes determine long-term performance to a surprising degree. Children placed into a classroom labeled as low- or high-performing tend to perform at the predicted level—so if you’re thought to be stupid, you’re likely to conform to the prediction.
Nearly half the Class II children report being teased at school about their protruding teeth. “Yeah, yeah, Buck-toothed dummy!”
Both incisor irregularity and incisor protrusion are predictors of teasing.
The effect on self-esteem created by this type of social discrimination also affects future performance.

The more you’re treated as if you are stupid, the more you may come to believe that it’s not worth trying to do better—and people don’t achieve more than they try to accomplish.

Benefit of Treatment (cont.) This man returned at age 50, 20 years after treatment (which in his case involved orthodontics and orthognathic surgery) to say, “Now I have my own successful business—and without the treatment I would never have had the confidence to quit my job years ago and go out on my own. I’m so grateful for what it did for me.”

The bottom line regarding psychosocial effects of malocclusion: Dental and facial appearance is not “just esthetics,” it affects your whole life. Because the psychosocial handicap of an unfortunate facial appearance is the biggest problem for most orthodontic patients, it’s the major reason for orthodontic treatment.

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{{PAGE_23}} Image 1: Age 29, prior to treatment.

Image 2: Age 50, 20 years after treatment was completed.

Summary: Quality of Life So why do we do orthodontics? To help a patient with his or her particular problem.

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{{PAGE_24}} The goal of treatment should be to provide the greatest possible benefit to that particular patient— which means, of course, that what is most important to the individual patient should receive the emphasis. That might be esthetic improvement to help with psychosocial problems, improved occlusion to solve functional problems, or an improvement in oral health. Is esthetics the most important thing? For some patients, generally the majority, yes, but certainly not for all. Orthodontics represents particularly well the type of health care that focuses on improving the quality of life, not on controlling or preventing disease. Not surprisingly, it has become increasingly valued worldwide as the health care paradigm has changed to emphasize quality of life.

Self-Test Referral

The self-test section of this program is designed to help you be sure you have understood the material. Before you take the self-test, read the assigned material in Contemporary Orthodontics (5th ed., pages 50-64; 4th ed, pages 58-70). Then use the self-test as a guide to further study of this important material.

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2. To Extract or Not To Extract Part 1

Background

Reasons for Orthodontic Extraction

There are two reasons for extracting teeth in orthodontic treatment:

correction of crowding/protrusion
camouflage of jaw discrepancy

As a general rule, extraction for crowding/protrusion is done for patients with Class I malocclusion, i.e., no skeletal problem. Extraction for camouflage is done for patients with Class II or (less frequently) Class III problems.

It is important to keep the purpose of extractions in mind. Because some patients with a skeletal problem (mandibular deficiency, for instance) also have crowded teeth, extractions for crowding/protrusion sometimes are needed in patients who also have a Class II or Class III problem. The same extraction space can’t be used to correct crowding and again for camouflage, so crowded teeth in a Class II or Class III patient can greatly limit the possibility for camouflage.

This program focuses on crowding/protrusion in patients with normal jaw relationships (Class I malocclusion). Part 2 of To Extract or Not to Extract reviews extraction for camouflage of skeletal problems.

Crowding and Protrusion: Aspects of the Same Thing

An important concept: crowding and protrusion are really two different aspects of the same thing. If there isn’t enough room for the teeth:

either they remain upright and become crowded and irregular
or they align themselves on the arc of a larger circle and protrude

Both of the patients shown here have the same amount of room for the teeth in the lower jaw. Note the crowding in both arches for the patient in image 1. Even with this degree of crowding, some protrusion also may be present. You wouldn’t know until you looked at the patient’s face.

In image 2, the lower incisors are aligned, and there is moderate crowding in the upper arch. The incisors are aligned because, although the patient had had no treatment, they protruded forward during growth, at the expense of the lip. The prominence of the roots of the lower incisors suggests protrusion, but you would have to look at the face to evaluate how protrusive they are.

The important point: if there’s not enough room for the teeth, soft tissue characteristics of individual patients determine whether they’re crowded, are protrusive, or have some aspects of both.

Facial Impact of Protrusion

How do you evaluate protrusion when you look at the patient’s face? It’s hard to see from the frontal but can be observed in oblique and profile views.

An important guideline:

The teeth are too protrusive if:

the lips are separated at rest, and
strained and everted on closure

This is the face that goes with the intraoral picture of protrusion that you just saw. In the oblique view, with the lips relaxed, note that the lips are separated at rest. More than 4 mm lip separation at

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{{PAGE_27}} rest is excessive.

In the profile view, with the lips together, you can see that the lips are both strained and everted. Eversion refers to the prominence of the lip relative to its base. For the upper lip, that is the base of the nose; for the lower lip, it is the sulcus between the lip and chin. Lip eversion and lip protrusion are the same thing. Our terminology is that protrusion of the incisors is reflected in eversion of the lips.

Remember that both of these findings, lip separation at rest and strain/eversion on closure, must be present to make the diagnosis of excessive incisor protrusion. Prominent, protrusive, or everted lips can be present as a soft tissue characteristic that is not due to protrusion of the incisors.

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{{PAGE_28}} Oblique view: >4 mm lip separation at rest is excessive.

Profile view: Note the lip strain on closure and lip protrusion.

Combined views: Combination of lip separation at rest and lip strain on closure indicates excessive incisor protrusion.

Extraction for Crowding/Protrusion The purpose of extraction in the treatment of crowding/protrusion, of course, would be to:

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{{PAGE_29}} provide space to align crowded teeth without protruding them, or provide space to retract protruded teeth to a normal relationship with the lips and jaw or perhaps something of both (though, as we have already noted, the same space can’t be used twice to obtain both alignment and retraction)

Conversely, expansion of the arches—aligning the teeth without extraction—would be the best treatment if the teeth were retruded, not providing enough lip support.

You’d have to look at the face, not just the teeth, to determine that as well. These two patients illustrate the extremes in lip support from the teeth.

The woman in image 1 has too little lip support, so her profile is concave. Her lips are thin and lack normal prominence. Her incisors are retrusive, not prominent enough for best esthetics. Appropriate treatment for her would be to move the incisors facially—certainly they should not be retracted any further.

The woman in image 2 has a convex profile, with prominent lips that are separated at rest. Though you can’t see it here, her lips also are strained on closure. She has protrusive incisors, especially relative to her chin, and in orthodontic treatment, she would be a candidate for premolar extraction so that the incisors could be retracted.

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{{PAGE_30}} Extraction Percentages over Time

Dentists’ opinions about extraction for crowding/protrusion have changed dramatically over time.

Early in the 20th century, as orthodontics developed, expansion of the arches was the usual treatment. By mid-century, extraction of first premolars was used frequently to provide space for alignment and/or retraction of canines and incisors. By the end of the century, expansion again was used more often than extraction.

This graph shows data from the graduate orthodontic clinic at UNC and illustrates the shift from expansion to extraction and back again. The percentage of patients treated in the clinic who had extraction of first premolars, the typical extraction pattern used to treat Class I crowding/protrusion, increased sharply in the late 1950s, then slowly declined over the next 30 years. The same type of change occurred in most American locations, although the increase in extraction percentages occurred earlier in many areas.

CHANGES IN THE EXTRACTION PERCENTAGE, 1953-1998 EXTRACTION OF FOUR 1st PREMOLARS

PERCENT OF PATIENTS 50 40 30 20 10 0 1953 1958 1963 1968 1973 1978 1983 1988 1993 1998 (p<.001)

Reasons for Increase in Extraction Percentage

Why did extraction replace expansion as the usual treatment, at least for a while? The reason is critically important in understanding the whole issue of extraction versus arch expansion (nonextraction) in orthodontic treatment of crowding/protrusion:

It was a search for stability of the result.

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{{PAGE_31}} By the mid-20th century, both doctors and patients observed that all too often after the arches were expanded to correct crowding of the teeth, relapse occurred. Prominent orthodontists reported that after premolar extraction, relapse problems disappeared. The increasing use of bands on all (instead of just some) of the teeth to provide more precise orthodontic tooth movement also had an effect on the expansion/extraction decision. Although each band is quite thin, the cumulative effect of band material at every contact point can be several millimeters of arch length. So fully banded treatment tended to mean a higher percentage of patients with extractions. But the big reason for extraction was to improve the chance that once the teeth were straight, they would stay straight and not relapse into crowding.

Reasons for Decrease in Extraction Percentage

Why did the pendulum swing back toward nonextraction (expansion) more recently? There are several reasons:

Retracting incisors too much can harm facial esthetics in some patients, and the first (small) decrease in the extraction percentage in the late 1960s probably was related to a better appreciation of this problem.
Research data in the 1970s, from long-term (>10 year) recall of patients treated for Class I crowding, showed that relapse into crowding still occurred in some patients even after extraction.

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{{PAGE_32}} That reduced the enthusiasm for extraction as a guarantee of long-term stability. 3. In the 1980s, bonding of attachments largely replaced banding (typically, except for molars), and band space no longer was a major consideration. This made it possible to align crowded teeth without so much protrusion—so the number of extraction cases decreased further. 4. In the 1990s, some practitioners linked premolar extraction—wrongly—to the development of TMD. Those claims, though false, led to a widely reported lawsuit and a more defensive approach by some practitioners. 5. Finally, most clinicians agree that it is more difficult and takes longer to treat extraction cases well, which tends to reduce enthusiasm for extraction in borderline cases. The interesting result: a complete cycle, so that the extraction percentages in 1955 and 1995 were the same. In the first decade of the 21st century, as you can see, extraction percentages have remained at about the same level.

Current Spread in Extraction Percentages There was an interesting public debate in the late 1990s between two longtime friends who practice in Texas and differ on the indications for extraction. Both kept up with the percentage of extractions in their practices for a year—more than 200 consecutively treated patients for each. Both felt that the great majority of their patients had a satisfactory outcome from treatment.

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{{PAGE_33}} The extraction advocate had a 50% extraction rate (for all types of cases, not just crowding/protrusion); the nonextraction advocate had a 20% rate. Probably extractions in 5-10% of the patients were for camouflage, not crowding/protrusion. So for Class I patients, the expansion advocate was extracting premolars in 10-15%, the extraction advocate in 40-45%.

Those numbers probably illustrate the bounds for extraction at present and outline the area of debate. It appears that extraction or expansion is a clear-cut decision for two-thirds of the patients, i.e., both doctors would treat them the same way, while one-third perhaps could be treated either way.

Further evidence on the minimum extraction percentage was presented recently by an advocate of expansion who reported that 10% of a large sample of his patients required extraction to prevent excessive protrusion.

The bottom line: not all patients can be expanded successfully. Judicious extractions are necessary for some patients and may facilitate treatment in others.

Scientific Knowledge: Extraction Effect on Jaw Function

Let’s look at what we know about the extraction decision and the three important aspects of orthodontic treatment outcomes, starting with the impact of premolar extraction and jaw function. What difference does it make if your premolars are present or absent, in terms of occlusion and jaw function?

{{PAGE_34}} Does it affect how well you can eat? Almost surely not—there’s no evidence at all to support the idea that you need 8 premolars for normal mastication.

Are you more likely to develop TM dysfunction if your first premolars have been extracted? That claim, as we have noted, was made in the 1990s, without any scientific data to support it, and it has been totally refuted by research. It is interesting that the dentists who offered this idea were quite prepared to extract second molars instead. No explanation was offered as to why first premolars were vital components of the dental occlusion and second molars were not.

The bottom line: the presence or absence of premolars has little or no effect on function, and premolar extraction does not lead to TM joint dysfunction.

Esthetics Extraction to Improve Facial Esthetics The esthetic effect of extraction has been debated for a long time. In the early 20th century, concerns were expressed about esthetic problems created by too much protrusion, and this remains a potential problem to this day. If the arches are expanded too much to correct crowding of the teeth, there are two problems: the result tends to be unstable, and the excessive protrusion of the incisors is unesthetic.

{{PAGE_35}} This patient sought retreatment after expansion of her crowded dental arches because she and her parents didn’t like the way it looked. After premolar extraction allowed retraction of the protruding teeth, she was elected Miss Alabama. It’s a dramatic illustration that too much protrusion damages esthetics and retracting teeth to correct protrusion can improve it. (Courtesy Dr. David Sarver)

After initial treatment: Age 16, after orthodontic expansion of both arches that resulted in excessive protrusion. After retreatment: Age 17, after retreatment with premolar extraction and retraction of incisors. Profile change: Profile views before/after retraction of protruding incisors. As Miss Alabama: Age 18, Miss Alabama.

Expansion to Improve Facial Esthetics

By the same token, as you have seen already, lack of lip support also can decrease profile esthetics. In evaluating esthetics, however, it isn’t enough to look just at the profile. What really counts is what the smile looks like. Changing the width of the dental arches can improve smile esthetics for some patients—and of course, if the arches were expanded too much, also could make smile esthetics worse.

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{{PAGE_36}} This girl’s narrow upper arch, which contributed to moderate crowding, also gave her wide buccal corridors, i.e., too much space between the cheeks and the teeth when she smiled. Note the esthetic improvement from transverse expansion that also created enough space to allow the teeth to be aligned without excessive protrusion of the incisors.

Extraction versus Expansion: Effect on Esthetics

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{{PAGE_37}} Exactly how do expansion and extraction affect esthetics? By changing the prominence of the teeth. All other things being equal, expanding the arches would move the incisors facially and make them more prominent, and extracting would have the opposite effect. Obviously, this could be controlled to some extent by how much the expansion moved the posterior teeth laterally rather than forward and by how extraction spaces were closed (with more or less retraction of the incisors versus forward movement of the posterior teeth).

This diagram indicates the amount of change that might occur in typical treatment of crowding/protrusion. If you were close to the maximum amount of acceptable protrusion before treatment, expansion could move you outside the acceptable range. If you were too retrusive initially, expansion would move you into the acceptable range. If you were near the center of the acceptable range, expansion would simply leave you esthetically acceptable, as you were to start with.

Extraction, of course, would move you in the other direction. For some patients, extraction would be necessary to move into the esthetically acceptable range; for some others, extraction would definitely be contraindicated because it would move the patient outside the acceptable range; and for others, the esthetic outcome would be to leave the patient acceptable, as he or she was before treatment.

How can two doctors disagree about the need for extraction, when both insist (correctly) that the esthetic outcomes are satisfactory? Because of the expansion/extraction decision is not critical for esthetics in many patients, who stay in the acceptable range either way.

CLASS I CROWDING FIRST PREMOLAR EXTRACTIONS ESTHETICS

How Many Need Extraction for Esthetics?

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{{PAGE_38}} How many patients would need extraction for esthetics? One recent and extensive data set, from patients treated by Dr. James McNamara, who used extractions only when it was deemed absolutely necessary, shows a 10% extraction rate. This suggests that at least 10% need extraction to be treated without being moved outside the acceptable range in the direction of too much protrusion.

How many crowded patients would be moved outside the esthetically acceptable range in the other direction, by extraction? There are no data, but perhaps the same 10-15% estimate would be a good guess as to the number who would be esthetically unacceptable with premolar extraction.

The bottom line: the effect on esthetics is a critical consideration in the extraction versus expansion decision for some (but by no means all) patients with crowding/protrusion. It is better to treat without extractions if this is possible, so the number of patients for whom there is an esthetic limitation from too much expansion is the important thing to remember.

CLASS I CROWDING FIRST PREMOLAR EXTRACTIONS ESTHETICS FLAT LIPS FULL LIPS ACCEPTABLE

McNamara, AAO Early Treatment Conference, Feb. 2002: 51 of 520 consecutive cases had premolar extraction because they were becoming too protrusive

Stability Extraction and Stability The same thinking applies to the relationship between extraction and stability, but it’s a bit more complicated.

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{{PAGE_39}} The orthodontists of the mid-20th century, when the extraction percentage increased, made an assumption about stability that was based on clinical observations, not on carefully collected data. The assumption was that moving the patient toward full lips by expanding the arches caused increased pressure by the lips and cheeks, which promoted relapse, and that flattening the lips by making the teeth less prominent reduced lip-cheek pressures and made the tooth position more stable.

Stability is not that simple, but it seems reasonable that extraction would be:

critical for stability in some patients who were borderline initially, i.e., who already had as much prominence of the teeth as the lips and cheeks would tolerate,
wouldn’t make much difference for others,
and might actually make some patients less stable because lip-cheek pressure would be too low relative to tongue pressure.

That concept is expressed in a diagram similar to the one for esthetics.

CLASS I CROWDING FIRST PREMOLAR EXTRACTIONS

STABILITY FLAT LIPS MORE STABLE? FULL LIPS LESS STABLE? ACCEPTABLE Extraction Nonextraction

Greater Stability in Extraction Cases? We know now that many patients have relapse into crowding of teeth after orthodontic treatment. Especially, lower incisors tend to become irregular long-term no matter what was done during treatment in adolescence. Because lower incisor crowding occurs in nearly everyone in their late

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{{PAGE_40}} teens and early twenties, even in those who naturally had nicely aligned incisors up to that time, it is not surprising that incisor crowding can happen after orthodontic treatment.

It’s clear that some extraction patients experience relapse. That doesn’t mean that relapse isn’t an even bigger problem after arch expansion. Unfortunately, there are no good data to document the chance of relapse into crowding with the alternative forms of treatment.

The difficulty in obtaining good data for treatment outcomes is that you have to carefully follow patients for a long time, and that’s hard to do. How many patients treated in early adolescence can be brought back for 10-year recall? Not all, for sure, and there is a chance that the ones who respond to recall are those who are unusually proud of their treatment outcome or unusually critical of it.

Nevertheless, there is some evidence that extraction helps with stability, as for instance the findings that on long-term recall, nonextraction cases have the highest irregularity and that patients who had serial extraction have relatively low irregularity. But the relationship is not nearly as clear-cut as was thought at one time.

Little, AAO Early Treatment Conference, Feb. 2002: Poorest stability in collected long-term cases was in the nonextraction group

STABILITY

FLAT LIPS MORE STABLE?

FULL LIPS LESS STABLE?

ACCEPTABLE

Boley, AAO Early Treatment Conference, Feb. 2002: On 5-year recall, 70% of serial extraction cases had <3.5 mm irregularity

Why Should Expansion Be More Successful Now?

An important question is, “If nonextraction treatment led to so many relapse problems years ago, why should we expect it to be more successful now?”

There are two answers. The first is that if you can keep the first permanent molars from shifting forward so that the leeway space is available, research data show that about 70% of the Class I

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{{PAGE_41}} crowded patients would have enough room to align the rest of the teeth. Leeway space, of course, is the difference in size of the second primary molars and second premolars. Is it possible to maintain the leeway space? Yes, in most instances, so the ideal time to treat most children with crowding/protrusion problems is to start at the very end of the mixed dentition, just as the second primary molars are ready to exfoliate. Maintaining leeway space minimizes the need for arch expansion, so this approach would be expected to be more stable long-term. Of course, there still would be the normal tendency for lower incisors to become crowded toward the end of growth. The second answer is that transverse expansion of the dental arches has been shown to be more stable than antero-posterior expansion. Perhaps you could say that the cheeks are more tolerant than the lips when the teeth are moved facially. So in current treatment, transverse expansion is emphasized, and protrusion of the incisors is not as great as it would have been if all the expansion were in the incisor region.

Why should we think expansion would be more successful (i.e., more stable) now than fifty years ago?

done differently? MAINTAIN LEEWAY SPACE

Gianelly, AAO Early Treatment Conference, Feb. 2002: Boston Univ. sample: 70% of Class I crowded patients have enough space if leeway space is maintained

Leeway space: Maintaining leeway space allows about 70% of Class I crowding patients to be corrected without arch expansion.

Why should we think expansion would be more successful (i.e., more stable) now than fifty years ago?

done differently? MAINTAIN LEEWAY SPACE TRANSVERSE EXPANSION, NOT ANTERO-POSTERIOR

is transverse expansion more stable than a-p expansion? Good evidence suggests that it is

Transverse expansion: Transverse expansion limits incisor protrusion.

Ways to Produce Transverse Expansion

There are three ways to produce transverse expansion:

arch wires
passive devices to hold lips/cheeks away
opening of the midpalatal suture

Arch wires can be expanded to increase the circumference of the dental arch, and can be manipulated to create more or less of the total expansion transversely or anteriorly.

Passive devices that hold the lips away from the lower incisors can and do result in more prominence of the incisors, because of the change in the balance between tongue vs. lip forces that this produces.

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{{PAGE_42}} There is no evidence to show that this type of change in tooth position is more stable than changes created by orthodontic tooth movement. Stability, after all, is determined by the lip pressure after the device is removed, and the extent to which the lips change when these devices are used is debatable.

The current favorite approach is to open the midpalatal suture to widen the maxilla, then use arch wires to expand the mandibular arch, but no data exist to show that this method gives better results long-term.

Moderate transverse expansion by any of these methods seems to be acceptable.

Palatal expander, frontal: Bonded appliance in place, to expand across midpalatal suture. Palatal expander, occlusal: Bonded appliance with jackscrew to expand across midpalatal suture.

How Much Expansion Can Be Tolerated?

Perhaps the most important question of all, from the perspective of stability, is: “How much expansion can be tolerated?”

Orthodontists often have compared individual patients to population averages and decided how much to move teeth based on what it would take to make the patient more like the average. For stability after treatment, that doesn’t work. The lower arch is the key, and you must look not at the original arch dimensions but at the amount of change that would be produced by treatment. Let’s look again at a slide you saw in Level III in the discussion of equilibrium effects on the dentition. The best evidence suggests that:

the lower incisors can be moved forward 2 mm, if they’re not already protrusive
very little if any expansion across the canines is stable
2-3 mm expansion across the premolars and molars is tolerated

The combination of 2 mm forward movement of incisors and 2-3 mm transverse expansion can provide a 6-7 mm increase in arch length for most patients. Beyond that, although further expansion is possible, stability becomes a real concern.

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{{PAGE_43}} EXPANSION LIMITS FOR STABILITY If incisors already are protrusive, any forward movement usually is unstable.

Summary/Conclusions What Do You Do with the Child with Class I Crowding/Protrusion? So what do you do with the child in your practice who has Class I crowding and perhaps some protrusion as well? Three thoughts: be sure that treatment starts in the late mixed dentition, so that leeway space will be available if needed. Don’t wait until all the permanent teeth erupt—but there’s no advantage for most children to start before the late mixed dentition. With very few exceptions, enthusiasm for treating 8-year-olds for crowding is not supported by evidence. be sure that dental and facial esthetics are considered on both sides of the extraction/nonextraction decision. For some children, extraction is the only way to get good esthetics. For others, expansion is the only way. be sure that expansion/extraction decisions are made in the context of the amount of change for an individual patient, not from comparing his or her arch dimensions to some population average. Stability, after all, is a function of the change produced within an individual patient.

{{PAGE_44}} What Do You Do with the Adult with Class I Crowding/Protrusion?

An adult who is concerned about Class I crowding almost surely is concerned about the dental and/or facial esthetics but may also hope that TM pain-dysfunction would disappear if the occlusion were better. In that case, there also are three thoughts to keep in mind:

fortunately, orthodontic treatment almost never is the primary cause of TMD. Unfortunately, orthodontics also rarely corrects it. So orthodontics to treat TM joint problems should be approached with great caution.
often, the best esthetic outcomes in adults will require permanent retention
computer simulations of treatment outcomes can help adults understand the esthetic implications of treatment decisions in a way they can’t from words

Let’s look at an adult in whom computer simulation of probable outcomes was important in deciding on extraction or nonextraction treatment.

Computer Simulations

This woman was concerned about mildly crowded upper and more severely crowded lower incisors, especially the lip irritation that the lower incisors produced. She admitted that she hoped to improve her appearance by getting treatment at age 45. Her lip support, as seen in the profile view (image 1) reflected the thinning of lips that occurs with increasing age.

Using computer-generated simulations of the profile effects of treatment, she was told that her teeth could be aligned with the extraction of one lower incisor, with a slight flattening of her profile and somewhat more thinning of the lips (image 2), or she could be treated by expanding the arches (image 3) but then would benefit from augmentation genioplasty (image 4) to obtain better chin-lip balance and stability. The technique for simulating the profile effect of treatment is reviewed in more detail in part 2 of “To Extract or Not to Extract?” on extraction for camouflage.

What do you think she said on seeing these?

“Oh, if that’s all the difference it makes, go ahead and extract the tooth.”

For her, both extraction and expansion were feasible treatment plans, and the esthetic impact of the treatment was important. She would have had more lip fullness and a better smile with expansion, but only she could decide if the more complex treatment would be worth it. After all, it’s the patient’s decision, and computer simulation of the facial effects of treatment helps significantly in obtaining true informed consent that is based on understanding the treatment alternatives.

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{{PAGE_45}} Summary In summary, important points to remember are:

For patients with Class I crowding/protrusion, both esthetics and stability are important considerations in planning orthodontic treatment—but jaw function and TMD are not.

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If extraction is planned, usually four first premolars are removed, because this provides the greatest flexibility in aligning the incisors and obtaining appropriate lip support. Other extractions occasionally are preferred.
Evaluation of esthetics requires consideration of both frontal (smile) tooth-lip-cheek relationships and lip support at rest. Excessive lip separation at rest and lip strain on closure are indications for retraction of the incisors. Lack of lip fullness is an indication for bringing them forward.
Stability is affected by the amount of change within the dental arches, particularly when the arches are expanded.
For perhaps 30% of patients, excellent results can be obtained by either arch expansion or appropriate extractions.
With either approach, controlling the position of the incisors is the key. Extraction is acceptable esthetically if the incisors are not retracted too much, and may improve stability; expansion is acceptable for stability if not overdone and may have esthetic advantages.
Computer image simulation of treatment effects can help adults understand the implications of the extraction/nonextraction decision (but this works only for adults, because growth in children is so unpredictable).