Muscle Strength & It’s Influence on Orthodontic Mechanics

When treating orthodontic patients, it is critical to always remember the most important principle of orthodontic treatment. That is, the same brackets, bands, and wires may and probably will produce different treatment responses in different patients. Most of these differing responses occur in the vertical dimension. Throughout this article, I will continually emphasize the importance of vertical control in orthodontic treatment. In fact, controlling the vertical dimension is the most important aspect of orthodontic treatment.

This leads us to the next most important principle of orthodontic treatment, which is the worst mistake that can be made when treating an orthodontic patient is to allow the bite to open in a patient who already has open bite tendencies. The reason this is so important is that no matter the severity of the open bite (and whether it is dental or skeletal), it is typically corrected (unless orthognathic surgery is done) with purely dental movement. Indiscriminate bite opening can lead to aesthetic problems such as excess gingival display, excessive down and back mandibular rotation (which, because the mandible opens on an arc, can result in a retrognathic, class II appearance), and, as a result, poor facial aesthetics. Dr. Sassouni’s studies (more on that later) pointed out that the poorest aesthetic results occur in patients with long faces. Since this can be a very poor outcome, we obviously want to avoid this. One of the best ways to avoid it is not to treat open bite patients. Bjork stated in his studies (again, more on that later) that approximately 15% of patients have weak muscled, open bite tendencies. So this is a big part of the 25% of cases that the typical general dentist should avoid.

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