Is Perpendicular Double Two-Hole Plates Fixation Superior to Single Four-Hole Plate Fixation to Treat Mandibular Symphysis Fracture?—A Finite Element Study

The effectiveness of a single four-hole plate (S4HP), perpendicularly oriented four-hole and two-hole plate (Per4H2HP), and perpendicularly oriented double two-hole plate (PerD2HP) for the fixation of a mandibular fracture was studied. A finite element analysis of the mandibular symphysis fractures treated with S4HP, Per4H2HP, and PerD2HP was performed. All surface nodes were fixed in the mandibular condyle region and occlusal muscle forces were applied. The maximal von Mises stress (MaxVMS) values of the plates, screws and screw holes were investigated. The displacement of the fracture site on the lower border of the mandibular symphysis was recorded. The displacement on the lower border of the fracture sites in the S4HP group was greater than that in the Per4H2HP group and the PerD2HP group. There was no eversion at the fracture site among all groups. Both the S4HP and Per4H2HP groups showed stress concentrations on the screws close to the fracture site. The MaxVMS increased when the number of screw holes on the mandibular anterior lower border decreased. The displacement of the fracture site and eversion with Per4H2HP and PerD2HP were far lower than those with S4HP. PerD2HP is a stable and green fixation technique for mandibular symphysis fractures.