Does plate adaptation affect stability? A biomechanical comparison of locking and nonlocking plates.
OBJECTIVE
The purpose of this investigation was to determine whether the degree of plate adaptation and effects of locking influenced the mechanical behavior of the plate/screw/substrate system for 2.0-mm monocortical superior border plates and 2.4-mm reconstruction plates secured at the inferior border intended to stabilize simulated mandibular angle fractures.


METHODS
A total of 130 polyurethane synthetic mandible replicas (Synbone, Landquart, Switzerland) were used in this investigation. Five controls each, for incisal edge and molar loading, as well as 5 samples each for 2.4-mm locking and nonlocking reconstruction plates and 2.0-mm locking and nonlocking monocortical superior border plates, intimately adapted (0.0-mm offset), 1.0-mm offset and 2.0-mm offset were subjected to loading at the incisal edge and molar region with an Instron 1331 (Instron Corp, Canton, MA) servohydraulic mechanical testing unit. Load/displacement data were recorded, and yield load, yield displacement, and stiffness were determined. Mean and standard deviation values were calculated. Statistically significant differences were determined for the effects of locking and degree of plate adaptation using a 1-way analysis of variance (P <.05). For differences within categories and among groups, a Sheffé multiple-comparison test was performed. First-order polynomial best-fit curves were created for each group to further evaluate and compare the mechanical behavior.


RESULTS
There were no statistically significant differences (P <.05) for yield load, yield displacement, and stiffness within the 2.4 and the 2.0 locking categories for both molar and incisal edge loading. For the 2.4 nonlocking category, there were statistically significant differences for yield load, yield displacement, and stiffness between the 0.0-mm offset group and both the 1.0-mm and 2.0-mm offset groups for both molar and incisal edge loading but not between the 1.0-mm and 2.0-mm groups. For the 2.0 nonlocking category, there were statistically significant differences for yield load, yield displacement, and stiffness between both the 0.0-mm and 1.0-mm offset groups and the 2.0-mm offset group for both molar and incisal edge loading but not between the 0.0-mm and 1.0-mm groups.


CONCLUSIONS
The degree of adaptation (amount of offset) affected the mechanical behavior of the nonlocking systems evaluated. It did not affect the locking systems. Failure occurred as an "all-or-nothing" pattern.
Haug
Richard H
RH
Oral and Maxillofacial Surgery, University of Kentucky, College of Dentistry, Lexington, KY 40536, USA.
Street
Chad C
CC
Goltz
Michele
M
D000704:Analysis of Variance; D001732:Bite Force; D001860:Bone Plates; D001863:Bone Screws; D003799:Dental Stress Analysis; D004867:Equipment Design; D004868:Equipment Failure; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D006801:Humans; D019248:Jaw Fixation Techniques / Q000295:instrumentation*; D008337:Mandibular Fractures / Q000601:surgery*; D008953:Models, Anatomic; D011140:Polyurethanes; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical
D011140:Polyurethanes