Thesis (M.Sc.) - Cairo University - Faculty of Oral and dental medicine - Department of Oral and Maxillofacial Surgery

The aim of this study was to evaluate the reliability of software soft tissue prediction and establishing a ratio between the volumetric change of hard tissue and soft tissue to improve the prediction reality. Computer-guided genioplasty was done for 7 patients with a retruded chin followed by 6 months postoperative to evaluate the results. Materialize Mimics software was used for the simulation and 3- Matic software was used for guide designing and computing the comparison between the actual and simulated soft tissue.it was also used in evaluating the volumetric changes and assessment of soft tissue changes around the chin segment.This study found that the software accuracy was 92.86% as the average for the all- simulation accuracy percentage that ranged from -2 to 2 mm and the mean of absolute error was 0.169. The areas of the largest error range were identified at the sub-mental area and the chin tip with a mean of error equal to 7.14%. Results also gave a new ratio of 1:0.7 with a new perspective regarding the volumetric soft tissue response after genioplasty. This ratio is applicable only for the chin soft tissue. By studying the effect of chin advancement on the other soft tissue zones, it was found that the lower cheeks and the lower lip got changed more than the upper cheek and the sub-nasale with the upper lip. Besides, A strong correlation equal to 0.732 was found between the lower lip and chin changes, while a weak one was found between the lower lip and the zone of sub-nasale with upper lip changes. In conclusion, there is a discrepancy between the actual soft tissue changes and the virtual simulation specifically in the submental and chin tip changes, the effect of soft tissue varied in a negative and positive direction, and it did not follow the same pattern as the hard tissue changes after genioplasty

Issued also as CD