Application of the finite–element method as an aid in dental appliance design

The objective of this study is to apply the finite–element technique to study abutment movements and stress distributions in the case of mandibular free–end situations. The effect of the following factors were studied: (1) sagittal residual ridge angulations '0, 5 or l0°', (2) occlusal rest positions 'either distal or mesial' and (3) load positions 'either anterior or posterior'. The model was idealized as a system of quadrilateral elements of different thicknesses. A two–dimensional finite–element program, based on the displacement approach, was developed to evaluate the elastic behaviour of the model. It was shown that (1) the direction of abutment movement was mainly influenced by occlusal rest position. Load position and ridge angulation did not alter the results significantly. (2) The magnitude of abutment movement was influenced by ridge angulation, rest and load positions. (3) The stress distribution was influenced by ridge angulation, rest and load positions. The intensity of stresses along the residual ridges was inversely proportional to the angle of the ridge.