[Mechanical studies on the dental bridges by the finite element method (2). --An idealized symmetrical bridge with a vertical load at the center of pontic-- (author's transl)].

The biomechanical behavior of bridge support was studied by the finite element method. An idealized bridge model was constucted by using the previously reported tooth model as the two-sided abutment teeth. Under a vertical load at the center of pontic the stress distributions were shown in the constituent elements. Forces transmitted to the abutment teeth were calculated from these distributions. The results obtained were compared with theoretical models based on the beam theory in engineering. 1) For the finite element model, moment M and horizontal force H are given by (see article) wherein P is load, B is flexural rigidity of pontic, L is bridge span length, and KM and KH are spring constants of the supports with respect to moment and horizontal force, respectively. 2) If it is assumed that a dental bridge is a rigid body, the moment is underestimated and the horizontal force is neglected. 3) According to the fixed-ended-beam model which allows neither movement nor deformation of the supports, the moment is overestimated in many cases. 4) According to the general-beam model which allows the vertical movement and rotation of the supports, the moment is underestimated because of the assumption that no forces are acting in the longitudinal direction of beam.