Evaluation of the bending strength of rigid internal fixation with absorbable and metallic screws in mandibular ramus sagittal split osteotomy: in vitro study Avaliação da resistência à flexão da fixação interna rígida, com parafusos absorvíveis e metálicos, na osteotomia sagital do ramo mandibular: estudo in vitro

The aim of this study was to evaluate, in vitro, the bending strength of internal fixation with absorbable and metallic screws in mandibular ramus sagittal split osteotomy in sheep hemimandibles. The screws were inserted as lag screws, with an inverted "L" configuration, and the set was submitted to bending strength tests. The load and displacement of the peak and final load averages were, respectively, 18.45 kgf, 8.19 mm and 14.38 kgf for Group I, and 16.67 kgf, 6.73 mm and 13.98 kgf for Group II. The results were submitted to statistical analysis by Student’s t test and by the Pearson correlation analysis. The groups showed no statistically significant differences, indicating the feasibility of both for osteosynthesis in mandibular ramus sagittal split osteotomies.<br>O objetivo deste estudo foi avaliar, in vitro, a resistência à flexão da fixação interna, através do uso de parafusos absorvíveis e metálicos, na osteotomia sagital do ramo em hemimandíbulas de carneiros. Os parafusos foram inseridos como "lag screw", com configuração em "L" invertido e o conjunto submetido ao teste de resistência à flexão. As médias da carga e do deslocamento do pico e da carga final do Grupo I foram de 18,45 kgf, 8,19 mm e 14,38 kgf, e do Grupo II de 16,67 kgf, 6,73 mm e 13,98 kgf, respectivamente. Os resultados foram submetidos à análise estatística pelo teste t de Student e pela análise de correlação de Pearson. Os grupos exibiram diferenças estatisticamente não significativas, indicando a viabilidade de ambos para a osteossíntese em osteotomias sagitais do ramo mandibular

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