Biomechanical evaluation of a T-shaped miniplate fixation of a modified sagittal split ramus osteotomy with buccal step, a new technique for mandibular orthognathic surgery.

OBJECTIVE: The purpose of this study was to biomechanically evaluate the stability of a T-shaped miniplate fixation of a modified sagittal split ramus osteotomy (MSSRO) with buccal step and to compare it with single or double-parallel straight miniplates fixing a standard sagittal split ramus osteotomy (SSRO). STUDY DESIGN: Eighteen Synbone mandibular replicas were used in the study and divided into 3 groups. Standard SSRO was applied in the first and second groups, and the third group was cut for MSSRO with buccal step. After 7 mm of advancement, fixation modalities for the 3 groups included a single straight miniplate, double-parallel straight miniplates, and a T-shape miniplate, respectively. Each model was secured in a jig and subjected to vertical load on the anterior teeth. RESULTS: The T miniplate group showed a significantly higher value for stability than the group with a single straight miniplate. There was no significant difference in stability between the T miniplate and the double-parallel straight miniplate groups. CONCLUSION: For mandibular advancement surgery of 7 mm in a laboratory environment, a T-shaped miniplate used with MSSRO and buccal step as a combination significantly optimize the resistance and stability of the fixation compared with a standard SSRO fixed with a single straight miniplate.

Evaluation of skeletal stability after surgical-orthodontic correction of skeletal open bite with mandibular counterclockwise rotation using modified inverted L osteotomy.

PURPOSE: To evaluate the surgical-orthodontic stability of treating skeletal open bite patients with mandibular ramus osteotomies using a modified inverted L osteotomy (M-ILO) and counterclockwise rotation of the mandible stabilized with rigid fixation. PATIENTS AND METHODS: In a retrospective review, 12 patients with skeletal open bites (8 females, 4 males) who received mandibular M-ILO in the period 2004-2007 at Tohoku University Hospital were studied. Lateral cephalograms were taken immediately before surgery (T1), immediately after surgery (T2), and at 1 yr after surgery (T3). Cephalometric analysis for point B, pogonion, menton, and mandibular plane angle was obtained at the designated time intervals. RESULTS: Mandibular counterclockwise rotation showed stability for point B, pogonion, and menton referred to X-Y coordinate, and for mandibular plane angle. The mean value for each variable was compared between T2 and T3. No statistically significant change was observed for all variables. CONCLUSIONS: With a well-positioned maxilla, skeletal open bite can be successfully treated using M-ILO. Mandibular counterclockwise rotation showed stability at 1 yr after surgery.