Gender Differences in Soft-Tissue Profile Changes Following Double Jaw Surgical Correction of Mandibular Prognathism in Taiwanese

The purpose of this study was twofold: (1) to analyze the soft-tissue changes after simultaneous maxillary LeFort I multiple segmental osteotomies and the mandibular ramus sagittal split osteotomy procedures in Taiwanese patients that will allow for the improved predictability of soft-tissue responses in double-jaw surgery cases, and (2) to determine whether there were gender differences between males and females. The data from this study suggested that when simultaneous two-jaw surgery was performed to correct severe mandibular prognathism, there was a tendency for the soft-tissue responses to be similar to those seen in only single mandibular setback procedures. In this study, the soft/hard-tissue change ratio of lower lip (LI) to mandibular incisor (Iii) change was 1.04:1, 0.93:1 ratio of inferior labial sulcus (ILS) to point B movement for men and women, 0.90:1 (male) and 1.06:1 (female) ratio of soft-tissue pogonion (POS) to hard-tissue pogonion (Pog) The prediction of upper lip changes was deeply affected by the mandibular setback, although strong correlations were found between the changes of the upper incisor and the four upper softtissue parameters SN (subnasale), SLS (superior labial sulcus), LS (labrale superius), and STS (stomion superius) . The reason might be attributed to the freeing of the upper lip previously trapped by the protrusive lower incisors; the soft/hard-tissue ratio between LS and Pog was found to be 0.15 for men and 0.34 for women. The average ratios of soft-tissue to hard-tissue change appear to show a gender difference between some measurements, which suggests the need for different ratios when the results of orthognathic surgery are being predicted.