title: Biomechanical in vitro evaluation of three stable internal fixation techniques used in sagittal osteotomy of the mandibular ramus: a study in sheep mandibles.
abstract: 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.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the biomechanical resistance of three national systems used for SIF in SOMR in sheep mandibles.
  
  
  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.
  
  
  CONCLUSIONS
  These results indicate that the three techniques of fixation are equally effective for clinical fixation of SOMR.
authors.affiliation: Oral and Maxillofacial Surgery, Bauru School of Dentistry, University of São Paulo, Bauru, SP, Brazil. le_benetti@yahoo.com.br
authors.forename: Leandro Benetti de
authors.initials: LB
authors.lastname: Olivera
authors.forename: Eduardo
authors.initials: E
authors.lastname: Sant' Ana
authors.forename: Antonio José
authors.initials: AJ
authors.lastname: Manzato
authors.forename: Fábio Luis Bunemer
authors.initials: FL
authors.lastname: Guerra
authors.forename: G William
authors.initials: GW
authors.lastname: Arnett
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001863:Bone Screws; D005593:Fracture Fixation, Internal / Q000379:methods*; D019248:Jaw Fixation Techniques; D008334:Mandible / Q000033:anatomy & histology / Q000601:surgery*; D008337:Mandibular Fractures / Q000601:surgery; D059229:Osteotomy, Sagittal Split Ramus / Q000379:methods*; D011897:Random Allocation; D015203:Reproducibility of Results; D012756:Sheep