Three-dimensional analysis for prediction and assessment of mandibular movement in orthognathic surgery in the ramus

A new method (Three-Dimensional (3-D) Analysis of Mandibular Movement) was developed to evaluate the movement of the mandible during surgery and in postoperative years, in three dimensions. The analysis was done with the aid of preoperative cephalograms and preoperative, predicted and postoperative dental models. The method consisted of measuring the amount and direction of the movements of defined points on the dental models and displaying the movement of other bony landmarks in the cephalometric tracings by coordinate transformation. All the calculations for the coordinate transformation were performed with the aid of a micro-computer. The results of an analysis with the method in two cases indicated that it is quite useful in determining the operative procedure as well as in evaluating the postoperative stability of the mandible, because in addition to the vertical and antero-posterior movement, it enables us to see the lateral movement of the mandible.