[Study on the simulation in planning for orthognathic surgery by using a personal computer].

This study was made in order to develop and evaluate three-dimensional simulation programs in planning for orthognathic surgery by using microcomputer system. Microcomputer system is composed of CPU (NEC, PC-9801), high resolutional color display, color printer, image scanner, and MOUSE. This simulation is composed of four procedures. 1. Data input Three-dimensional coordinate data on tracing obtained from CT films is inputted. One data file is made from one outline of structures. 2. Three dimensional reconstruction A control file is made to arrange data files constructing structures. 3. Simulation This procedure is composed of cutting and movement. The horizontal projection of mandible is displayed. After cutting simulated orthognathic surgery is designed, new data files and new control file are made. A movement consists of parallel translation and rotation. A movement data is combined with movements designed on each of three projections. 4. Three-dimensional graphic display Three-dimensional graphics of the mandible before and after a simulation for orthognathic surgery are displayed by perspective views with treated hidden lines and accurate pictures (COSMOZONE 2SA, NIKON). These simulation programs were carried out with the asymmetrical patient. The simulation was supposed that the operation was combined with sagittal splitting osteotomy of the right mandibular ramus and body ostectomy of the left lower first premolar part. Three-dimensional graphics of the mandible before and after the simulation were presented. Its three-dimensional mandibular position and form after orthognathic surgery were predicted. These three-dimensional simulation programs may be important procedure, when a treatment planning in asymmetrical prognathic case is discussed.