Plates and Jaw Stress-Strain State in Case of a Lower Jaw Angular Fracture

Abstract

One of the most pressing issues of maxillofacial surgery is the traumatism of the facial bones. At present, titanium plates with screw joints are the commonest for fixing jaw fragments in maxillofacial surgery. The cause of complications in osteosynthesis with titanium is the force generated by the masticatory muscles, transmitted through the plate and jaw fragments, and causing looseness of the screw joints. Moreover, plate fractures are caused by material fatigue due to plate bending occurring under surgery. The purpose of this paper is to compare the plate designs according to the maximum stresses arising under the action of masticatory loads and to check the fixation reliability with the subsequent plate development of a reduced bone-plate contact area. Ansys Workbench software package, namely the Transient Structural module, is used for calculations based on the finite element method to study the stress-strain state of the lower jaw after titanium osteosynthesis. Plates' designs for osteosynthesis metal are developed considering the strength of the masticatory muscles. The maximum stresses in the plates have been determined, which are 481 MPa for a straight plate, 487 MPa for a y-shaped plate, and 301 MPa for a square plate. Following the mentioned, these stresses do not exceed the yield strength of titanium grade ВТ1, the smallest of them occurring in a square-shaped plate. The maximum gap has been also determined, between fragments it is 0.75 mm for a straight plate, 0.15 mm for a y-shaped plate, and 0.13 mm for a square plate. Therefore, the square plate provides the most reliable fixation of jaw fragments.