Are different screw lengths associated with osteosynthesis quality in the region of the mental foramen?

Abstract

IntroductionThe use of two monocortical malleable 04‐hole miniplates, placed above and below the mental foramen, has been indicated to prevent the adverse effects of tension and torsion forces on fracture healing. To obtain good fixation in the mandible's outer cortex screws, 5–8 mm long have been recommended. However, studies have shown thicknesses in the mental foramen region of up to 3 mm, meaning the length of the screw could be a risk to nerve or tooth root damage. The purpose of this study is to identify the influence of screw length on osteosynthesis quality in the region of the mental foramen.Materials and Methods10 synthetic polyurethane human lower jaw replicas were subjected to a linear loading test to evaluate fixation techniques with 5 and 10 mm of displacement. In the photoelastic analysis, 02 lower jaw models were made of photoelastic resin and subjected to linear loading in the fixation technique with 10 mm of displacement. Two 04‐hole miniplates in the region of the mental foramen either fixed completely with 4 mm screws (group 1) or with 5 mm screws in the tension zone and 8 mm screws in the compression zone (group 2). The variables were registered for peak load and peak displacement, and final load and final displacement. One‐way analysis of variance (ANOVA) was applied, followed by the Tukey test, with a significance of 5% (p = 0.05) for the comparisons between the means.ResultsConsidering 95% confidence intervals, the mechanical test showed no statistical differences in peak load between the fixations groups. In the photoelastic analysis, the fringes were concentrated on the distal segment of the fracture in both groups.ConclusionDue to the lack of statistical difference in the biomechanical and photoelastic tests, considering the methodologic limitation, our study indicates a tendency of advantage toward the treatment of fractures with two 04‐hole plates, fixed with 4 mm screws, to minimize complications like tooth or nerve damage. In vivo studies are needed to verify the convergence of the results of in vitro studies to evaluate the resistance and stability in real masticatory forces.