Reliability of bimaxillary surgical planning with the 3-D orthognathic surgery simulator

Functional and esthetic dysgnathia surgery requires accurate planning and precise surgical technique. Programs that simulate such surgery have thus become increasingly important. These are useless, however, when there is no technique for reproduction of surgical planning in the patient. This can be mediated by a surgical model. The present study investigates the accuracy resulting from use of the 3-D orthognathic surgery simulator (3-D OSS) in reproducing planned patient treatment. Eighteen patients with Angle Class III malocclusions who required bimaxillary surgery were evaluated. Planning criteria depended on the orthognathically intended occlusion and the jaw position simulated in the dentofacial planner, which predicted a harmonious profile. Model planning was carried out in the 3-D OSS. The accuracy of surgical reproduction was determined by cephalometric comparison of the postoperative cephalograms and computer simulation images. There were horizontal repositioning errors of 0.61 +/- 0.45 mm to 0.78 +/- 0.52 mm at the maxillary reference points (posterior nasal spine, anterior nasal spine, point A, and incision superius). Analysis of the positioning precision attained vertically was of the same order of magnitude, with values between 0.57 +/- 0.46 mm and 0.85 +/- 0.71 mm. Less precision was achieved in the mandible. The mean horizontal variation observed at incision inferius (0.91 +/- 0.51 mm) was still within the range of values for the maxilla, but an increase in the error to 1.61 +/- 0.79 mm was registered caudally to menton. The attained position of the maxilla did not vary significantly from the planned position (P < or = 0.05). Use of the orthognathic surgery simulator allowed precise implementation of the planned surgery. The model planning proved to be very helpful in preparing difficult bimaxillary operations.