Abstract
Restoration of an edentulous space with a removable partial denture presents various problems of the design of a retainer set on a distal molar, when the molar shifts in angle or position. The two-dimensional finite element technique was used to analyze the design factors of the retainer's arm influencing the periodontium of an abutment tooth, for a direct retainer being set on a tilted molar.
The results obtained are as follows:
1. When only a retentive arm is used, the von Mises stress of the periodontium increases as the shifted position or angle of a retentive tooth increases.
2. When both retentive and reciprocal arms are properly located, von Mises stress is less than what with the retentive arm only. It is suggested that the reciprocation is effective for the stress -relaxation of the periodontium of a abutment tooth.
3. When both retentive and reciprocal arms are properly located and a retentive force is equal to a reciprocal one, the value of von Mises stress is within 0.10 kg/mm2.
4. Effective design factors of a retainer's arm for the stress relaxation of the periodontium are suggested.
