Occlusal plane alteration in orthognathic surgery--Part I: Effects on function and esthetics.

The angular relationship of the occlusal plane and Frankfort horizontal (occlusal plane angle, normal value 8 degrees +/- 4 degrees) is very important, in both diagnosis and treatment planning, but is usually ignored. Surgical alteration of the occlusal plane may influence presurgical orthodontic mechanics and surgical technique and design, but may offer significant benefits relative to the patient's functional and esthetic results. Candidates for surgical alteration of the occlusal plane angulation include the low occlusal plane (LOP) facial type and the high occlusal plane (HOP) facial type. Correction of the LOP facial type by downward and backward (clockwise) rotation of the maxillomandibular complex has been a well accepted technique. Upward and forward (counter-clockwise) rotations of the maxillomandibular complex for correction of the HOP facial type has not been supported as an acceptable treatment modality. However, we have demonstrated that upward and forward rotations are stable with proper treatment planning, appropriate presurgical orthodontics, proper execution of the surgery, and in the presence of healthy and stable temporomandibular joints. This article will discuss the clinical characteristics of the LOP and HOP facial types, the specific anatomic changes with alteration of the occlusal plane, the presurgical orthodontic goals, and the surgical techniques for downward and backward and upward and forward repositioning of the maxillomandibular complex. Cases are presented to demonstrate the application of this treatment approach.