A prospective study of soft- and hard-tissue changes after mandibular advancement surgery: Midline changes in the chin area.

INTRODUCTION: The purpose of this research was to prospectively determine the ratio of 2 soft-tissue landmarks, pogonion (sPg) and menton (sMe), to their hard-tissue counterparts (Pg and Me) in the sagittal and vertical directions for mandibular lengthening surgeries. METHODS: We drew a sample from the prospective Orthognathic and Orthofacial Surgery Research study, consisting of patients who underwent surgical mandibular lengthening (alone or in combination with maxillary osteotomy) without genioplasty. We digitized landmarks using Facewizz software and determined the relationships between the hard- and soft-tissue changes by correlation analysis. RESULTS: Pearson correlation test showed a significant correlation between the type of surgery and the sPg:Pg and sMe:Me ratios. The sPg:Pg ratio was 87% for mandibular lengthening only and 102% for mandibular lengthening in combination with maxillary surgery. The sMe:Me ratio was 85% and 96% for upward and downward movements, respectively. CONCLUSIONS: The average ratios presented in this study for the pogonion and menton can aid in preoperative planning by providing estimates for soft-tissue behavior. Further stratifications will be possible after the Orthognathic and Orthofacial Surgery Research database is enriched with more inclusions.