A CBCT Study on Positional Change in Mandibular Condyle According to Metallic Anchorage Methods in Skeletal Class III Patients After Orthognatic Surgery

Purpose: This study was to evaluate the postoperative stability of the mandibular condyle according to the number of screws in the proximal segment using cone beam computed tomography (CBCT).

Patients And Methods: Thirty patients diagnosed with skeletal class III malocclusion and underwent sagittal split ramus osteotomy (SSRO) were enrolled in this study. In Group A, 4 screws and a 4-hole miniplate were used for the internal fixation of an osteotomy and 3 screws, only 1 screw in the proximal segment, and a 4-hole miniplate were used in Group B. We digitally measured anteroposterior, supero-inferior, and mediolateral positions and angles of the long axis of the mediolateral poles in CBCT scans pre-operatively, within 1 week postoperatively and 3, 6 months after surgery.

Results: The condylar head angle in the axial plane showed consistent and significant changes. The condylar head angle in the coronal plane decreased in both groups, which shows that condylar heads bent inward. In the axial plane, Group A showed statistically significant differences while Group B did not in early stage (T0-T1-T2). The change in distance between condylar heads shows that these have moved outward in both groups.

Conclusion: The results show that a fixation method using 3 screws with a 4-hole miniplate did seemed preferable and may give some flexibility for condylar heads to be positioned in physiologic position during postoperative phase.