Abstract
The study aimed to compare the accuracy of soft tissue changes by manual prediction and digital prediction using computer software for mandibular advancement surgery. The subjects were 15 patients （2 males and 13 females, mean age 24.6 years） with mandibular retrusion who underwent sagittal split ramus osteotomy. XY coordinates of five soft tissue measurement points at the time of initial examination （T0）, before orthognathic surgery （T1）, and at the end of post-orthodontic treatment （T2） were calculated by manual prediction （MP value） and prediction using Dolphin Imaging software （version 11.0; GC ORTHOLY, Tokyo） （IS value）. Differences between predicted and actual coordinate values were compared using Bland-Altman analysis to examine systematic errors. Pog moved an average of 3.77mm forward. The results of the Bland-Altman analysis showed proportional errors of the upper lip at T2-T1 in both MP value and IS value, and fixed errors were observed in the X coordinate of the lower lip. Although the errors in the chin area were smaller than those in the lip area, it was clear that the IS value had fixed errors. Both methods may predict the postoperative lower lip more anteriorly than it actually is, while digital prediction may predict the chin area more anteriorly. Thus, care should be taken not to overestimate the soft tissue changes.
