title: Comparative study of the mechanical resistance of 2 separate plates and 2 overlaid plates used in the fixation of the mandibular condyle: an in vitro study.
abstract: OBJECTIVE
  The objective of this study was to carry out a comparative evaluation of the mechanical resistance of 2 rigid internal fixation techniques for fractures of the mandibular condyle using miniplates.
  
  
  METHODS
  Forty polyurethane resin replicas of human hemimandibles were used. The hemimandibles were sectioned to simulate a high subcondylar fracture and then stabilized with 2 fixing techniques using 2.0-mm system plates and screws. The fixation techniques were 2 separate 4-hole plates with 8 screws, and 2 overlaid 4-hole plates with 4 screws. Each system was submitted to load tests, with the application of the load in mediolateral and anteroposterior directions in an Instron 4411 universal assay machine (Instron, Norwood, MA).
  
  
  RESULTS
  Load values and peak displacement were measured. Means and standard deviations were evaluated by analysis of variance (P < .05) and Tukey tests, in which it was verified that the antero-posterior peak load value was affected by the arrangement of the plates on the models, although no differences were observed between the groups for the mediolateral peak load. The arrangement of the plates did not have any influence on peak displacement. Similarly, the final value of the mediolateral load was not affected by the arrangement of the plates on the model.
  
  
  CONCLUSIONS
  The experimental model with 2 separate plates was statistically superior to the model with 2 overlaid plates only in relation to anteroposterior peak load. Despite showing superiority in mediolateral peak load and peak displacement, there was no statistical difference between the groups for these parameters.
authors.affiliation: MSc Student, Dental School, State University of Sao Paulo (Julio de Mesouita Filho) UNESP-Arasatuba, Campo Mourão, Paraná, Brazil. waltergealh@gmail.com
authors.forename: Walter Cristiano
authors.initials: WC
authors.lastname: Gealh
authors.forename: Julyano Vieira
authors.initials: JV
authors.lastname: Costa
authors.forename: Geovane Miranda
authors.initials: GM
authors.lastname: Ferreira
authors.forename: Liogi
authors.initials: L
authors.lastname: Iwaki Filho
mesh_terms: D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws; D003799:Dental Stress Analysis / Q000295:instrumentation; D004867:Equipment Design; D004868:Equipment Failure; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D006801:Humans; D008335:Mandibular Condyle / Q000293:injuries* / Q000601:surgery; D008337:Mandibular Fractures / Q000601:surgery*; D008422:Materials Testing; D008953:Models, Anatomic; D011140:Polyurethanes / Q000737:chemistry; D013314:Stress, Mechanical
chemical_list: D011140:Polyurethanes