Occlusal plane alteration in orthognathic surgery--Part II: Long-term stability of results.
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Alteration of the occlusal plane may be indicated in patients who present with either low occlusal plane (LOP) facial type or the high occlusal plane (HOP) facial type. Surgical alteration with double jaw surgery to increase or decrease the occlusal plane angulation may be required to achieve optimal functional and esthetic results. This study evaluated the stability of results in two groups of patients. Group 1 consisted of 14 patients who underwent surgical increase of the occlusal plane angulation with a postsurgical follow-up average of 23 months. The average surgical increase in occlusal plane angulation was 5.6 degrees. Several anatomic landmarks were evaluated relative to stability of results. Postsurgical changes that were statistically significant included a postsurgical anterior facial height change (-0.8 mm), ramus height change (-0.3 mm), and a change in mandibular plane angle (-0.5 degrees). These changes were due, in part, to the removal of the occlusal splint allowing some autorotation of the mandible superiorly and settling in of the occlusion. There was no significant change in any of the other parameters evaluated. Group 2 consisted of 27 patients, with a mean follow-up of 21 months, that had an average surgical decrease in occlusal plane angulation of 8.8 degrees with double jaw surgery. There was an 8 mm advancement of the mandible at point B, and a 10 mm advancement at pogonion. The maxilla was moved 3 mm superiorly at point A, and the maxillary first molar showed no significant vertical movement. The postsurgical changes demonstrated no statistically significant horizontal movement of the mandible.(ABSTRACT TRUNCATED AT 250 WORDS)