Lower face widening in mandibular osteotomies: Is the increase in osseous and cutaneous bigonial distance correlated with mandibular advancement?

Mandibular osteotomies are known to widen the mandibular angles by increasing the bigonial distance (BGD). Previous studies have highlighted the relationship between the extent of mandibular movement and the increase in BGD, both for cutaneous bigonial distance (CBGD) and osseous bigonial distance (OBGD). However, the relationship between changes in OBGD, CBGD and mandibular advancement remains to be fully established. The aim of this study was to compare changes in OBGD and CBGD using adapted three-dimensional examination techniques in patients who underwent mandibular osteotomies. Preoperative and postoperative computed tomography scans and stereophotogrammetry were used to measure mandibular advancement, OBGD and CBGD before and after surgery. Of the 77 patients included, 93.5 % underwent bilateral sagittal split osteotomy, and 79.2 % had received patient-specific guided surgery. Of these, 53 patients had mandibular advancement and 24 underwent mandibular setback. In all cases, a significant increase in both OBGD and CBGD was found after surgery. The extent of mandibular advancement was significantly associated with a greater increase in both OBGD and CBGD.