When the occlusal force was applied to the bridge on molar region, accompanied with a defect of the supporting tissue of abutment tooth, which ranged from 0 to 2/3 of the root length, possible change in the stress distribution occurring in the residual supporting tissue was analytically examined using two-dimensional finite element method. Furthermore, radicular tooth accompanied with various defects of the supporting tissue was simulated by a two-dimensional and a three-dimensional models and was analyzed using two-dimensional and three-dimensional finite elemnet methods.
The following information was obtained:
1. The stress of the mesial supporting tissue of the most anterior abutment tooth increased most with a larger defect of the supporting tissue of the abutment tooth.
2. Additional abutment tooth was effective for the stress relief of the adjacent abutment tooth.
3. When the defect of the supporting tissue of the most posterior abutment tooth exceeds 2/3of the root, no difference in stress distribution of the supporting tissue was found between intension bridging and free end bridging with extraction.
4. Comparison of the analytical results of the two-dimensional and three-dimensional models revealed the approximation of stress values in the vicinity of root apex and largestress of the three-dimensional model in nearer approach to the dental neck.
