Class II Therapy and Compliance
It seems to me, as I go about my daily professional tasks, that the most difficult and persistent problem I have to deal with is the distalization of upper molars. I suspect this is true in most practices, because most of us accept the Angle Class I occlusion as a goal and do our best to achieve it. As the years have passed and we have learned more about the nature of occlusion, we have begun to understand why achieving a Class I molar relationship is so difficult.
The classic study by Harris and Behrents of some untreated patients from the original Bolton group has helped us recognize nature's role in promoting and maintaining a Class II malocclusion.1 Essentially, they found the pattern of growth and eruption to be directed so as to encourage any pre-existing Class II tendency. In other words, Class II malocclusions become significantly more Class II as time goes by. The therapist is thus obliged to correct not only what nature has already done, but what it seems likely to continue in the future.
As if this weren't enough, we have come to realize that many of the orthodontic forces we use can extrude molars, open the bite, and make Class II therapy even more difficult. Schudy showed several years ago that any excess vertical alveolar growth or molar eruption only compounds an extant Class II relationship.2
Some orthodontists conclude that it isn't nice to fool Mother Nature, and they simply remove the upper bicuspids, correct the cuspids to Class I, and leave the molars in Class II. This may be a reasonable approach in some cases, but quite often extractions are ruled out by upper-lip esthetic requirements.
McNamara found that fewer than 30% of Class II patients in a group of 8-to-10-year-olds displayed truly protrusive maxillae.3 Most of the Class II cases in this group had mandibular retrusions, excessive anterior face height, or a combination of the two. Johnston has suggested that an older group might show fewer mandibular retrusions and more maxillary protrusions,4 but the actual percentages are not critical. What is important is that we distinguish the cause of the Class II in each individual case. If cephalometrics has taught us anything, it is how to determine the type of Class II malocclusion we are dealing with, so that we can fashion our treatment based on reasonable assumptions.
For example, patients with protrusive maxillae can benefit from the use of traditional therapies such as Kloehn or directional headgears and Class II elastics. But with retrusive mandibles or excess anterior vertical dimensions, such treatment can accentuate vertical dentoalveolar development, move A point distally, and flatten the profile. Even when patients cooperate to the fullest, elastics and headgears require several months of action before any tangible improvement appears.
This brings into focus what I consider the most severe limitation of the permissive therapies: patient compliance. Readers have chided me in the past for admitting my inability to motivate patients to wear proven appliances, but judging from the hundreds of conversations I've had with orthodontists, I am not alone in this respect. Within the past decade, new approaches to Class II therapy have been developed to overcome the need for compliance--the Herbst appliance, the Hilgers palatal expander, the Jasper Jumper, and the Gianelly Neo Sentalloy archwire, to name a few.
The article in this month's JCO by Jones and White introduces another such appliance. From my personal experience, the Jones Jig is one of the most effective and reasonable methods of correcting Class II molar relationships with a minimum of patient cooperation. Besides eliminating compliance as a factor, it offers several advantages over traditional therapies:
The Jones Jig is not a universal appliance; like any system, it has its limitations. If Class II treatment requires the distalization of A point, as in a bimaxillary protrusion, then one should not expect the jig to work like a Kloehn headgear. If a Class II correction requires the advancement of lower incisors, the Jones Jig alone won't suffice. Nor should one expect the elevation of lower molars for improvement of a hypodivergent face, because the jig doesn't normally depend on lower anchorage. That doesn't prevent the clinician from adding a lower lingual arch or even a lower bonded appliance and Class II elastics. Still, when the Jones Jig is used alone, it produces definite, discrete movements that are limited almost entirely to the teeth to which it is attached.
The good news is we now have more effective mechanisms available than ever before to help us achieve Class I molar relationships, even with non-compliant patients. The bad news is that many orthodontists continue to use therapies that are not only inefficient, but contraindicated. I know some clinicians who treat nearly every Class II malocclusion with a Kloehn headgear, and they achieve marvelous dental results. However, even though many of their patients don't need a reduction in maxillary convexity, that is what they often get. Equally misguided are the practitioners who are so enamored of accelerated mandibular growth that they use a Herbst appliance even with a bimaxillary protrusion, which the Herbst can't hope to correct.
It all comes back to diagnosis. If one identifies the major contributors to the Class II condition early on, then one can decide which therapy offers the best chance to correct those problems. A cookbook approach to treatment planning may be simple, but diagnostic accuracy is bound to suffer. We still have to treat patients one at a time in a highly specific manner, and that is one of the few things about orthodontics that should never change.