Comparison of lingual cortical thickness, mandibular ramus thickness, and pattern of cancellous bone distribution at the mandibular ramus between skeletal class I and class III in Thai samples

Abstract

Objective: Medial osteotomy forms an essential part of bilateral sagittal split ramus osteotomy, a technique commonly used in orthognathic surgery. The purpose of this study was to evaluate and compare the lingual cortical thickness (LCT), mandibular ramus thickness (MRT), and pattern of cancellous bone distribution (CBD) at the mandibular ramus between skeletal classes Ⅰ and ⅠⅠⅠ in a Thai sample group. Methods: Ninety cone-beam computed tomography scans of Thai patients with skeletal classes I and III were used to measure LCT and MRT and to evaluate the CBD pattern (types 1–6) at three levels: at the lingula and 3 and 6 mm above the lingula. The results were compared between patients with skeletal classes I and III. Results: LCT at the lingula level in patients with skeletal class III was significantly greater than that in those with skeletal class I. At other levels, LCT and MRT were not significantly different. The type 1 CBD pattern was most commonly found in skeletal classes I (73 %) and III (68 %). As the level above the lingula increased, the amount of cancellous bone was reduced, and LCT and MRT were thinner in both groups. Conclusions: The only significant difference between skeletal classes I and III was LCT at the lingula level. The CBD patterns of both patient groups were similar. At the higher level, LCT, MRT, and existence of cancellous bone decreased in both groups.