Sagittal split ramus osteotomy-related biomechanical properties

Sagittal split ramus osteotomy (SSRO) is one of the most common maxillofacial operations, and the technique relies on a directed fracture involving different biomechanical variables. The aim of this study was to find out the biomechanical characteristics involved during each step of sagittal split osteotomy. We sampled eight fully dentate human mandibles and used the right side for hardness tests and the left side for a traction-to-fracture test within an unfinished SSRO. Right sides were sampled in five parts underlying the corticotomy course and tested with a hardness testing automatic machine. The mean hardness measures ranked to 21.5HV (Hardness Vickers Unit): 17.8HV; 27.4HV; 22.7HV; 28.7HV; for the lingual, diagonal, vestibular, full ramus, and full body samples, respectively. Left sides were cut using Epker's technique, and split with an electromechanical testing machine. The higher values reached before fracture in the traction-to-fracture tests ranked to 99.1N/6.7mm; 137.2N/10.8mm; 36.2N/4.2mm; 93.0N/7.3mm; 74.0N/8.1mm; 78.1N/4.5mm; 90.9N/10.6mm; and 64.7N/4.1mm, respectively, for specimens I, II, III, IV, V, VI, VII and VIII. This study provides to our knowledge the first biomechanical characteristics of SSRO and proposes a reproducible method for evaluation.