Answers in search of questioners.
Given a need for treatment (itself a topic that could occupy the experts for a day or two but that probably would be discussed before an empty hall), the next logical question is when? Early or late? Clearly, the timing of many of the treatments to be discussed at this meeting probably would generate little controversy. Indeed, I would argue that the main controversy--and perhaps the reason for the full lecture hall--surrounds the treatment of Class II malocclusion. To be more precise, the controversy surrounds not the occasional early intervention for a specific reason but, rather, the routine treatment of Class II malocclusions with some sort of 2-stage, functional and fixed appliance combination, commonly with expansion and without extraction.
Will you treat early? If the answer is no, the alternative late treatment, commonly begun at the end of the mixed dentition stage and featuring E-space conservation and some sort of maxillary distalization, would seem to be in order. This approach has been referred to by William Proffit as the gold standard against which other approaches must be judged. In other words, if you wish to treat in some other way, you must seek evidence that it is superior to a single phase of late mixed-dentition treatment.
If your investigation convinces you that early treatment is better, then you will need to ask yet another series of simple questions to determine what form this early treatment will take. Which jaw will your early treatment target? Treatments aimed at the midface are out of fashion, perhaps because they generally require cooperation and commonly are said to target the wrong jaw. Moreover, lurking in the fringes of organized dentistry is a vocal minority claiming that backward-pushing mechanics cause temporomandibular dysfunction. Unfortunately, if you examine these various assertions and assumptions, you will find a general lack of supporting data. Indeed, there is a growing body of evidence that the end results of treatments aimed at the midface are indistinguishable from those that are designed to "grow" mandibles.
If, on the other hand, you are drawn to the conclusion that treatments should be aimed at the mandible, you must answer a simple question: Why?
It will be difficult to muster convincing support for the argument that you must treat the mandible because a Class II malocclusion is a disease of an underdeveloped mandible: young children, both Class I and II, tend to have relatively small mandibles. The young also are short and ungainly. Time and the normal pattern of growth and development presumably will ameliorate all of these deficiencies. In other words, will Class II patients still have small mandibles at maturity? If you conclude that the mandible really is the material cause of the Class II malocclusion, then it would be appropriate to ask whether any treatments effectively target it. Specifically, are you going to employ 1 or more of the so-called functional appliances? To answer yes, you must first ask why. What do you hope to accomplish and is there any proof that what you hope for is possible?
Our Association, in calling for early screening (which, of course, leads to early treatment), has published a laundry list of potential benefits. However, public service announcements often are more akin to wishful thinking than to a meaningful guideline for a rational practice. Perhaps the most common biological reason for using functional appliances is to augment mandibular growth. It is argued that, much like the United States Army, these treatments let Class II patients be all that they can be. Unfortunately, long-term studies indicate that the only lasting effect is in the midface, not in the mandible. This surprising result has led some influential clinicians to argue for earlier treatments, and others, for later. Both tactics apparently are designed to preserve the extra growth that is said to occur in the functional stage of 2-phase treatments. But what if there is no extra growth? What if functional appliances serve only to produce a "Sunday bite" that is slowly made permanent by the excess mandibular growth commonly seen even in Class II patients? In this case, functional appliances might be seen to work but not to confer any special benefits to offset the extra time and cost of multiphase treatments. Therefore, functional appliances would not constitute a substitute for surgery, as often is claimed. Supporters might argue that even if functional appliances cannot "grow mandibles" (to put it bluntly), they might minimize the need for premolar extraction.
How can this be achieved? Growth is a powerful, seemingly magical word, but it is difficult to see how growth can create space for a crowded, protrusive dentition. Bone does not grow interstitially, and the teeth tend to come forward on their bases. The mandible has no sutures, so there is no surface at which arch perimeter can be created. Distalization is not only poor English, but it is also exceptionally difficult to achieve. Therefore, the only option is arch development, a treatment that when called "expansion" was discredited as unstable and unreliable.
In the upper jaw, extra perimeter can be created, at least in theory, by rapid maxillary expansion. However, the effectiveness of this form of development remains to be seen. Dentoalveolar and basal expansion ultimately have to answer to the envelope of motion of the lips, cheeks, and tongue. Accordingly, the clinician interested in nonextraction treatment will seek evidence of long-term, clinically significant increases in arch perimeter. Failing that, the potential benefits of early growth-modification Class II treatments shrink to the potential of a favorable psychologic impact and the prevention of incisor fracture.
Clearly, some patients suffer psychologically because of their protrusive incisors; they would benefit emotionally from treatment. Moreover, there is at least some evidence that early incisor retraction might reduce the risk of fracture. But are these occasional benefits enough to support what amounts to an orthodontic growth industry? If the answer is yes, then early treatment might well be an appreciable benefit for the Class II patient; however, if the answer is no, then we must make a decision. The basic tenets of evidence-based dentistry state that decisions for individual patients must be based on the best available evidence. Accordingly, some specific Class II patients probably would benefit from early intervention. In contrast, if there is no generalized biological rationale, a decision to treat most Class II patients early might still make sense when it is a condition of referral from the family dentist.
What about the biological questions? I would argue that they could and should form the basis of yet another early treatment symposium, this time aimed at referring dentists whose notions about the benefits of early treatment have done so much to shape and constrain contemporary orthodontic practice.
Presented at the International Symposium on Early Orthodontic Treatment, February 8-10, 2002; Phoenix, Ariz.
Lysle E. Johnston
Reprinted from: Am J Orthod Dentofacial Orthop 2002;121:552-3
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|Author:||Johnston, Lysle E.|
|Publication:||American Academy of Gnathologic Orthopedics Journal|
|Date:||Dec 1, 2006|
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