Biomechanical in vitro evaluation of three stable internal fixation techniques used in sagittal osteotomy of the mandibular ramus: A study in sheep mandibles

Among the osteotomies performed in orthognathic surgery,the sagittal osteotomy of the mandibular ramus (somr) is the most common,allowing a great range of movements and stable internal fixation (sif),therefore eliminating the need of maxillomandibular block in the postoperative period. objectives: the purpose of this study was to evaluate the biomechanical resistance of three national systems used for sif in somr in sheep mandibles. material and methods: the study was performed in 30 sheep hemi-mandibles randomly divided into 3 experimental groups,each containing 10 hemi-mandibles. the samples were measured to avoid discrepancies and then subjected to somr with 5-mm advancement. in group i,2.0x12 mm screws were used for fixation,inserted in an inverted l pattern (inverted l group). in group ii,fixation was performed with two 2.0x12 mm screws,positioned in a linear pattern and a 4-hole straight miniplate and four 2.0x6.0 mm monocortical screws (hybrid group). in group iii,fixation was performed with two 4-hole straight miniplates and eight 2.0x6.0 mm monocortical screws (mini plate group). all materials used for sif were supplied by osteosin - sin. the hemimandibles were subjected to vertical linear load test by kratos k2000mp mechanical testing unit for loading registration and displacement. results: all groups showed similar resistance during mechanical test for loading and displacement,with no statistically significant differences between groups according to analysis of variance. conclusion: these results indicate that the three techniques of fixation are equally effective for clinical fixation of somr.