Title

Hemimandibular Elongation: Is the Corrected Occlusion Maintained Long-Term? Does the Mandible Continue to Grow?

Document Type

Article

Publication Date

2-1-2017

Abstract

Purpose The purpose of this study was to assess for the maintenance of a corrected occlusion and ongoing mandibular growth in a group of patients younger than 26 years with hemimandibular elongation (HME) who underwent bimaxillary orthognathic reconstruction. Materials and Methods We conducted a retrospective cohort study of HME patients operated on by a single surgeon at 1 institution between 1999 and 2013. At a minimum, all patients underwent Le Fort I and bilateral sagittal ramus osteotomies. Study exclusions included patients aged 26 years or older; those with clefts, craniofacial disorders, or tumors; and those with a history of temporomandibular joint or orthognathic surgery. The study variables included age, gender, side of condylar hyperactivity, premolar extractions, extent of mandibular deformity and malocclusion, planned surgical change, and longitudinal follow-up. The outcome variables studied were the achievement and maintenance of a corrected occlusion and the occurrence of continued mandibular growth after surgery. We compared the occlusion at intervals including the following: before surgery (T1), 5 weeks postoperatively (T2), and either 6 to 24 months after surgery (T3) or more than 2 years after surgery (T4). Anterior occlusion assessment included evaluation of overjet, overbite, and dental midline position. Posterior occlusion assessment included the Angle classification, first molar vertical position, and first molar transverse position. If the corrected anterior occlusion remained stable and no posterior open bite occurred, then no clinically significant condylar hyperactivity and/or ongoing mandibular growth was judged to have occurred. Results Seventy-six consecutive patients met the inclusion criteria. Age at operation averaged 18 years (range, 14.5 to 25 years), and the study included 44 female patients (58%). T3 patients (10 of 76, 13%) had documentation of occlusion at a mean of 19 months after surgery. T4 patients (66 of 76, 87%) had documentation of occlusion at a mean of 5 years 8 months after surgery. Only 1 of the 76 study patients (1%) was judged to have clinically significant ongoing mandibular growth after reconstruction. For all other patients, a corrected anterior occlusion was maintained long-term, and a posterior open bite did not develop in any. In 7 of the 76 patients (9%), there was a recurrent posterior crossbite by 1 year after completion of orthodontics but without the need for retreatment. An association was confirmed between mandibular setback and long-term posterior malocclusion even with simultaneous maxillary advancement (P =.05). Conclusions In HME, a favorable occlusion can be reliably achieved and maintained long-term in most cases using standard bimaxillary orthognathic technique. The need for mandibular setback, even in the presence of simultaneous maxillary advancement, proved to be a factor in the recurrence of long-term posterior malocclusion, although the risk remains low. The results clarify that in patients with HME, by use of the described techniques and timing for surgery, there is no need for an ablative open joint procedure to arrest condylar growth.

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