OCCLUSAL PLANE ALTERATION IN ORTHOGNATHIC SURGERY .1. EFFECTS ON FUNCTION AND AESTHETICS

The angular relationship of the occlusal plane and Frankfort horizonta l (occlusal plane angle, normal value 8 degrees +/- 4 degrees) is very important, in both diagnosis and treatment planning, but is usually i gnored. Surgical alteration of the occlusal plane may influence presur gical orthodontic mechanics and surgical technique and design, but may offer significant benefits relative to the patient's functional and e sthetic results. Candidates for surgical alteration of the occlusal pl ane angulation include the low occlusal plane (LOP) facial type and th e high occlusal plane (HOP) facial type. Correction of the LOP facial type by downward and backward (clockwise) rotation of the maxillomandi bular complex has been a well accepted technique. Upward and forward ( counter-clockwise) rotations of the maxillomandibular complex for corr ection of the HOP facial type has not been supported as an acceptable treatment modality. However, we have demonstrated that upward and forw ard rotations are stable with proper treatment planning, appropriate p resurgical orthodontics, proper execution of the surgery, and in the p resence of healthy and stable temporomandibular joints. This article w ill discuss the clinical characteristics of the LOP and HOP facial typ es, the specific anatomic changes with alteration of the occlusal plan e, the presurgical orthodontic goals, and the surgical techniques for downward and backward and upward and forward repositioning of the maxi llomandibular complex. Cases are presented to demonstrate the applicat ion of this treatment approach.