Determination of The Mandibular Center of Rotation and Assessment of Association between Cephalometric Indices and Its Location

Following maxillary impaction, the mandible rotates around a center. Inaccurate determination of mandibular rotation can have profound effects on orthognathic surgical treatment planning and final surgical outcome. The present study determined the relationship between the cephalometric characteristics of candidates for maxillary impaction surgery using sagittal and vertical locations of the center of rotation of the mandible.

In a descriptive and cross-sectional trial, 36 candidates for LeFort I maxillary impaction surgery were selected. Two lateral cephalograms were obtained in open and closed mouth positions. The center of rotation of the mandible was determined by the Reuleaux technique. Cephalometric measurements of the patients with the determined center of mandibular rotation locations (regions 1 and 4 of the coordinate axis) were done and the results were subjected to the student t-test.

The center of mandibular rotation was located in region 1 of the coordinate axis in 17 (50%) and in 17 (50%) in the 4th region of the coordinate axis. Statistically significant differences existed regarding the MP-SN (p<0.006), CO-GO (p<0.006), and CO-GN (p<0.04) at two regions of 1 and 4 for the center of rotation of the mandible in the coordinate axis.

With the decreased length of the ramus and increased inclination of the plane, the center of rotation of the mandible tended to be situated at region 1 of the coordinate axis, and together with the increased length of the ramus and decreased plane inclination, the center of mandibular rotation tended to be located at region 4 of the coordinate axis.