Combination of microplate and miniplate for osteosynthesis of mandibular fractures: an experimental study

Because of the limited space available in the mandible, especially in the mental foramen and apical region, miniature osteosynthesis material is desirable. Recently, metal deposition in the direct neighbourhood of osteosynthesis plates made of titanium or even in peripheral organs have been reported in the literature with increasing frequency. The size and amount of osteosynthesis material used should therefore be kept to a minimum. In an experimental study on 60 models, we examined load-carrying stability and in a second series, torsional strength of two-piece plastic models connected by either a single miniplate, two miniplates, or a titanium microplate plus a miniplate. In our test arrangement, the average loading capacity of the combination miniplate/miniplate was 470N; that of the combination microplate/miniplate was only 267N. The test group with the single miniplate had an average loading capacity of only 225N. Masticatory loads on the plates exceeding 200N occur only 3 months after osteosynthesis. At that time the fracture has largely consolidated. The torsional strength of the microplate/miniplate combination was similar to that of the miniplate/miniplate combination (1000Nmm resulting in a width of the gap measuring 0.8mm and 0.5mm, respectively). The single miniplate was considerably less stable (0.8mm gap width as early as with 300Nmm). According to Champy, rotational forces in the anterior region of the mandible amount to approximately 1000Nmm and need to be withstood by the osteosynthesis material. Our results suggest that treatment of fractures in the interforaminal region with a combination of microplate and miniplate will be stable enough for early mobilization.