[Mechanical study on the stability of multiform mini-plates. I. Double-T-type plate (90, regular, 6-holes) in mandibular body fracture].

: In this present paper, we reported the stability of osteosynthesis using a special type of mini-plate for mandibular fractures as evaluated from a mechanical study with static loading. The materials used in this study were fifteen bars made of acrylic resin, each divided at the center of its length into two parts to simulate a condition of mandibular body fracture. Following the fixation of these materials with mini-plates firmly attached between their cut ends, the bars were secured in a vice at one end and a static load was applied from the vertical direction at the other end. The amount of displacement of the loaded end was investigated with a displacement-measuring device, and the strains on mini-plates and test bars were measured with strain gauges. A comparative study was conducted on three kinds of mini-plates: 1) Group S, fixed with one Champy mini-plate, 2) Group W, fixed with two Champy mini plates, 3) Group T, fixed with one double-T-type mini-plate. The following results were obtained: 1) The amount of displacement was largest in the vertical direction and smallest in the horizontal direction in the three groups. Especially in group T, it was smaller the longitudinal and horizontal axes than in the other two groups. 2) Longitudinal strain of the plate was smallest in group W. However, the strain on the test bar was smallest group S. Especially , in group T, the largest compressive strain was observed at the lower portion of the synthesized ends.(ABSTRACT TRUNCATED AT 250 WORDS)