Evaluation of chin morphology after two-jaw orthognathic surgery: A retrospective study using stereophotogrammetry

Background: The mandibular advancement or setback achieved by bilateral sagittal osteotomy can generate significant changes in the soft tissues of the mandible and chin. This was a retrospective study of patients who underwent bimaxillary orthognathic surgery in the Oral and Maxillofacial Surgery Residency Training Program, School of Dentistry of Ribeirão Preto, University of São Paulo. Objective: The aim of this study was to retrospectively evaluate changes in chin morphology in patients with orthognathic surgery of two jaws using Three-dimensional (3D) photography. Based on inclusion and non inclusion criteria, 11 records including 9 women (81.1%) and 2 men (18.9%), with a mean age of 33.5 years, were incorporated in the study. 3D images were analyzed with Vectra M3® software (Canfield Scientific, Fairfield, NJ, USA), after marking reference points on the face, determining linear measurements, and performing area and angle calculations. We analyzed 3D photographs obtained preoperatively (T0), 6 months (T1), and 1 year (T2) after surgery. Results: Chin height (Li-Me) and surface (Li-Me) demonstrated an average increase of 9.2 mm and 8.8 mm, respectively, after 6 months. In addition, chin prominence (Go-Pg), chin-to-neck distance (C-Gn), and lower jaw area increased on average by 12.1 mm, 15.0 mm, and 34.6 mm2, respectively, after 6 months. However, the mentolabial angle (Li-Si-Pg) decreased on average by 18.8° after 6 months. All results remained stable after 12 months. Conclusion: In conclusion, 3D photography was very useful for the evaluation of facial soft-tissue changes after orthognathic surgery. Our study demonstrated a decrease in mentolabial angle and increases in chin prominence, chin height and surface, chin-to-neck distance, and lower jaw area.