In vitro mechanical test of grid plates for mandibular angle fractures.

This study evaluated, by mechanical testing, the strength of four-hole grid plates used for mandibular angle fracture fixation. Much has been discussed about the treatment of mandibular fractures with straight or curved plates. However, there are few studies about the use of grid plates. The geometry of such plates provides three-dimensional stability, resistance against torque associated with a low profile. Ninety polyurethane hemimandibles were used as substratum. The hemimandibles were divided into nine groups and fixation of the fractures was performed varying the type and position of plate and type of screw. An intact hemimandible group was used as control. It was possible to observe that plates positioned at the tension zone present the highest load values, both for dislocations of 3 and 5 mm. There was no statistical difference when plates with or without an intermediate bar were tested. The locking screws were more efficient than the non-locking screws when the plates were positioned at the neutral zone. Results allowed us to conclude that grid plates installed at the tension zone presented greater mechanical efficiency. If grid plates are positioned at the neutral zone, they should have an intermediate bar and be fixed with locking screws.