title: Biomechanical evaluation of a new MatrixMandible plating system on cadaver mandibles.
abstract: OBJECTIVE
  Current mandibular plating systems contain a wide range of plates and screws needed for the treatment of mandibular reconstruction and mandibular fractures. The authors' hypothesis was that a single diameter screw could be used in all applications in a plating system. Therefore, the purpose of this study was to test if the 2.0-mm locking screws could replace the 2.4-mm screws to stabilize a 2.5-mm-thick reconstruction plate in the treatment of mandibular discontinuity.
  
  
  METHODS
  Thirty-six fresh human cadaveric mandibles were used: 18 were plated using 2.0-mm locking screws (experimental) and the other 18 were plated using 2.4-mm locking screws (control). Each group was further divided into 3 subgroups based on the site of loading application: the ipsilateral (right) second premolar region, the central incisal region, and the contralateral (left) first molar region. The same ipsilateral (right) mandibular angular discontinuity was created by the same surgeon. The mandible was mounted on a material testing machine. The micromotions between the 2 segments, permanent and elastic displacements, were recorded after incremental ramping loads. The magnitude of screw back-out and the separation between plate and bone were recorded using a laser scanner (resolution, 0.12 mm) before and after the loading applications. The data were processed. Descriptive analyses and a general linear model for repeated measures analysis of variance were performed.
  
  
  RESULTS
  There was no statistically significant difference in permanent displacement (mean, 1.16 and 0.82 mm, respectively) between the 2.0-mm and 2.4-mm screw groups. There also was no statistically significant difference in elastic displacement between the 2 groups (mean, 1.48 and 1.21 mm, respectively). Finally, there were no statistically significant differences in screw back-out or separation between plate and bone between the 2 groups. All means for screw back-out and separation between screw and bone for each group were judged within the error of the laser scanning system (<0.12 mm).
  
  
  CONCLUSIONS
  One may anticipate that the mechanical functions of the 2.0-mm locking screws are not different from those of the 2.4-mm screws when a 2.5-mm-thick reconstruction plate is used to reconstruct mandibular angular discontinuity. However, further biomechanical studies (ie, fatigue of screws) are warranted before a randomized clinical trial can be conducted to definitively prove that the 2.4-mm screws can be replaced by 2.0-mm screws.
authors.affiliation: Chairman, Department of Oral and Maxillofacial Surgery, The Methodist Hospital, Houston, TX; Professor of Clinical Surgery, (Oral and Maxillofacial Surgery), Weill Medical College, Cornell University, New York, NY.
authors.forename: Jaime
authors.initials: J
authors.lastname: Gateno
authors.forename: Christopher
authors.initials: C
authors.lastname: Cookston
authors.forename: Sam Sheng-Pin
authors.initials: SS
authors.lastname: Hsu
authors.forename: Drew N
authors.initials: DN
authors.lastname: Stal
authors.forename: Salim K
authors.initials: SK
authors.lastname: Durrani
authors.forename: Jonathan
authors.initials: J
authors.lastname: Gold
authors.forename: Sabir
authors.initials: S
authors.lastname: Ismaily
authors.forename: Jerry W
authors.initials: JW
authors.lastname: Alexander
authors.forename: Philip C
authors.initials: PC
authors.lastname: Noble
authors.forename: James J
authors.initials: JJ
authors.lastname: Xia
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D001696:Biomechanical Phenomena; D001732:Bite Force; D015519:Bone Density / Q000502:physiology; D001860:Bone Plates; D001863:Bone Screws; D002102:Cadaver; D003198:Computer Simulation; D003724:Dental Arch / Q000601:surgery; D003799:Dental Stress Analysis / Q000295:instrumentation; D004548:Elasticity; D004867:Equipment Design; D004868:Equipment Failure; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D007834:Lasers; D008334:Mandible / Q000601:surgery*; D063175:Mandibular Reconstruction / Q000295:instrumentation*; D008875:Middle Aged; D008953:Models, Anatomic; D008954:Models, Biological; D009068:Movement; D013314:Stress, Mechanical; D014584:User-Computer Interface; D055815:Young Adult