Soft-tissue and dentoskeletal profile changes associated with mandibular setback osteotomy

Abstract

The aims of the present retrospective cephalometry study were (1) to describe the interrelationships of the soft-tissue and dentoskeletal profiles after total mandibular setback osteotomies and (2) to detect whether there were any cephalometric variables that could contribute to an accurate prediction of the surgical effect on the soft-tissue profile. The presurgical and postsurgical lateral cephalograms of 50 consecutively treated patients (37 females and 13 males) were used; these patients had received combined orthodontic-surgical management of mandibular prognathism by means of a bilateral vertical ramus osteotomy with an extraoral approach. At the time of surgery, their ages ranged from 17 to 41 years. Lateral cephalograms with the teeth in habitual occlusion taken before and approximately 1 year after surgery were available for all patients. A computerized cephalometric appraisal, named profile analysis, was developed and used, including variables corresponding to sagittal and vertical relationships of skeletal and soft-tissue profiles, incisal relationships, soft-tissue thickness, and lip morphology. The statistical elaboration of the data was made by means of paired t test, Pearson's product-moment coefficient correlation, and multiple regression analyses. The assessment of the results disclosed that considerable facial changes and improvement took place after the surgical procedure. The skeletal and soft-tissue facial profiles were straightened and the posture of the lips was improved. The normal incisal relationship achieved became influential on the soft tissues overlying both incisors and led to a better lip competence and posture. Posterior movement at points B and Po was accompanied by reductions ranging from 91% to 103% of the corresponding soft tissues. The presence of both significant correlation coefficients (p less than 0.05) and high r square values (greater than 0.70) in the multiple regression analysis for the osseous tissue variables N-B and N-Po, alone or together with the overjet and S-N-B angle, respectively, reflected their high prediction value with regard to the sagittal relationship of the lower lip, its thickness, and the soft-tissue thickness at the chin area. The findings of Pearson's product-moment coefficient correlation also indicated that the operative changes of the thickness of the upper lip, the lower lip, and the soft tissue at the chin region are influenced by the initial preoperative thickness of the area.