Primary Mandibular Deficiency Dentofacial Deformities: Occlusion and Facial Aesthetic Surgical Outcomes.

[PURPOSE] The purpose of the present study was to document the malocclusion and facial dysmorphology in primary mandibular deficiency (PMD) subjects with chronic obstructive nasal breathing before treatment and the outcomes after bimaxillary orthognathic, genioplasty, and intranasal surgery.

[PATIENTS AND METHODS] A retrospective cohort study of PMD subjects undergoing bimaxillary, chin, and intranasal surgery was implemented. The predictor variables were grouped into demographic, anatomic, operative, and longitudinal categories. The primary outcome variables were the initial postoperative occlusion achieved at 5 weeks postoperatively (T) and that maintained long-term more than 2 years after surgery (T). Six occlusion parameters were assessed: overjet, overbite, coincidence of dental midlines, Angle classification, molar vertical, and transverse positions. A second outcome variable was the facial esthetic results. Photographs were analyzed to document 7 facial contour characteristics.

[RESULTS] Forty subjects met the inclusion criteria. Their age at surgery averaged 32 years (range 13 to 63). The study included 25 females (63%). The findings confirmed that the occlusion after initial surgical healing (T) met the objectives for all parameters in 39 of the 40 patients (98%). Most patients (35 of 40; 88%) achieved and maintained a favorable occlusion for each parameter in the long-term (mean 5 years, 3 months). Subjects requiring counterclockwise rotation of the maxillomandibular complex were more likely to a have recurrent anterior open bite in the long-term. Facial contour deformities on presentation included weak chin (80%), deep labiomental fold (90%), everted lower lip (100%), short neck-to-chin length (88%), obtuse neck-to-chin angle (85%), weak mandible angles (93%), and "bunching" of the neck soft tissues (85%). Before surgery, 88% of the subjects exhibited a minimum of 5 of the 7 facial deformities. Correction of all 7 facial deformities was confirmed in 86% of the subjects in the long-term.

[CONCLUSIONS] Most PMD subjects achieved and maintained a corrected occlusion in the long-term. In the untreated subjects, a "facial type" was identified. Orthognathic surgery proved effective in correcting the associated facial dysmorphology in most patients.