SKELETAL CHANGE AT SURGERY AS A PREDICTOR OF LONG-TERM SOFT-TISSUE PROFILE CHANGE AFTER MANDIBULAR ADVANCEMENT

Purpose: This study examined the time course of hard and soft tissue c hanges after mandibular advancement surgery and the association betwee n skeletal changes as a result of surgery and subsequent soft tissue c hanges. Patients and Materials: Subjects were enrolled in a randomized clinical trial of rigid versus wire fixation after sagittal split ram us osteotomy, with cephalometric data obtained before orthodontics, im mediately before surgery and at 8 weeks, 6 months, 1 year, and 2 years postsurgery, This early report describes changes in 20 Caucasian fema le subjects who had completed all phases of the study; these were not segregated by fixation method, Cephalometric changes were referenced t o a cranial base coordinate system, Differences in soft and hard tissu e changes among time intervals were examined using analysis of varianc e; the associations between immediate surgical change in chin landmark s and subsequent short- and long-term soft and hard tissue changes wer e examined using linear regression analysis. Results: Soft and hard ti ssue mandibular structures were positioned anteriorly and inferiorly d uring surgery; the horizontal and vertical hard tissue mandibular chan ges were stable for 2 years after surgery (P >.30), as were the vertic al soft tissue changes (P >.08), There was horizontal relapse of the l ower lip and the inferior sulcus (P <.03) by 8 weeks; no horizontal re lapse was detected in soft tissue chin points for up to 2 years after surgery, The time course of changes in osseous pogonion was more stron gly predicted by the amount of surgical osseous chin change than were changes in soft tissue chin projection.Conclusions, Prediction of chan ges in soft tissue chin projection after mandibular advancement surger y is less certain as time from surgery increases and less certain than the prediction of changes in bony chin projection.