The use of miniplates in mandibular fractures. An in vitro study.

To test the stability of miniplate osteosynthesis in the mandible, a three-dimensional in vitro model was developed. Four clinically relevant fracture situations were simulated by osteotomies in polyurethane mandibles. The stability of the osteosyntheses was tested according to a reproducible procedure of unilateral loading under conditions of static equilibrium. The mandible was supported at the condyles in silicon rubber fossae and was held in position by traction on the coronoid processes in combination with preloading in the region of the incisors with a force of 10 N. Six points were tested to register the effects of unilateral loading on bending and torsion at the sites of the osteotomies. The following results were obtained. The preliminary results show that in cases of jaw angle fracture neither bending nor torsional forces are sufficiently controlled by miniplate-fixation in the commonly proposed position. Furthermore, it was confirmed that fracture treatment in the canine region requires two plates instead of one to resist displacement of the fracture fragments during function.