Azita Tehranchi - Associate professor, Dental Research Center, Dept. of Orthodontics, Shahid Beheshti University of Medical Sciences, Tehran, Iran
Hossein Behnia - Professor, Dept. of Oral & Maxillofacial Surgery, Dental School, Shahid Beheshti University of Medical Sciences, Tehran, Iran
Majid Heidarpour - Post graduate student, Dept. of orthodontics, Dental School, Shahid Beheshti University of Medical Sciences, Tehran, Iran
Bahman Toutiaee - MA, Engineering Dept., Iran Center for Dental Research
M. Javad Khosropour - Orthodontist, Private Practice, Tehran, Iran

Aim: Analyzing the changes made during distraction osteogenesis (DO) in asymmetric mandibles Materials and methods: This study was performed on a three dimensional model of a desiccated mandible, based on a finite element method. The distraction devices were placed with an angle of ۹۰, ۶۰ or ۳۰ degrees to the oblique surgical cut. The directions of the pins were such that the ۳۰ and ۶۰ degree pins were placed in a counterclockwise direction relative to the perpendicular pin. The distractors were opened for ۱۵ and ۳۰ mm. The amount and direction of movement of proximal and distal segments and the displacement of pogonion were evaluated in all three planes of space.Results: In the distal segment, the maximum change in pogonion was seen in ۳۰ degree angle. In the proximal segment, if the distraction device was used with ۹۰ degree angle, the condylar process rotated in the clockwise rotation. In ۳۰ degree angle, this process rotated in a counterclockwise direction and the minimum rotation was seen in ۶۰ degree angle.Conclusion: If gonial angle is to be augmented in a downward direction maximally, the angle of distraction device to the surgical cut is critically important (that is, it should be perpendicular to surgical cut). By use of perpendicular mode, ramus slops more posteriorly. It is better to use the distraction pin with a thirty degree angle if the ramus needs to be uprighted. The oblique surgical cut, irrespective of the distraction pin angle, increases the anterior facial height.

Distraction Osteogenesis, mandibular asymmetry, mandibular lengthening, finite element method