[Mechanical studies on the dental bridges by the finite element method (3). --Behavior of a posterior bridge model under various loads -- (author's transl)].

Forces and moment transmitted to the abutment teeth were numerically analyzed using a model for a posterior bridge. Three cases were chosen to investigate the influence of loading condition; a vertical (A) and a mesially inclined (B) load at the center of pontic and a vertical load at the abutment (C). The results obtained are as follows: Under the condition (A), as reported previously, both moment and force increase as bridge flexural rigidity is less or bridge span longer. When the load shifts to the abutment tooth, the moment slightly increases as flexural rigidity is greater or bridge span shorter, but horizontal force is scarcely transmitted to the abutment teeth. Maximum moment under the condition (C), however, is not so great as that under the condition (A) and the difference decreases among the moment values calculated from the present model and two theories of general-beam and rigid-beam model. Consequently, special attention should be given to the more flexible pontic which might very possibly cause injury to the abutment teeth under the first two conditions. Even though the resultant force is not very great, its supporting tissues with smaller surface area tend to be subject to higher stress.