Mobility of the mandible following advancement and maxillomandibular or rigid internal fixation: an experimental investigation in Macaca mulatta.

This study examined the postsurgical range of mandibular motion following sagittal advancement osteotomy in Macaca mulatta when either maxillomandibular or rigid osseous fixation were used. Seventeen adult female Macaca mulatta underwent sagittal advancement osteotomy of approximately 4 to 6 mm. Six had 6 weeks of maxillomandibular fixation and eleven had rigid osseous fixation with no maxillomandibular fixation. Mandibular range of motion was measured by the change in the angle of the posterior aspect of the mandibular ramus from a closed-mouth and an open-mouth cephalogram. Parametric tests were used to statistically analyze the results. The results of this investigation showed that the animals who did not undergo maxillomandibular fixation maintained a greater range of motion in the early postsurgical period and obtained preoperative mobility by 12 weeks postsurgery. The animals who underwent six weeks of maxillomandibular fixation showed statistically significant decreases in range of motion when compared to the rigid fixation group at each period of time postsurgery, with significant reductions from preoperative values at 12 weeks postsurgery.