Motion vector analysis of an abutment for a distal-extension removable partial denture: a pilot study.

An investigation was conducted on the effect of various rest-clasp designs on abutment tooth movement when a testing prosthesis was subjected to vertical loading of the bilateral distal-extension base. The results did not reveal statistically significant differences among the rest-clasp designs tested. Variations in rest placement and/or clasp design had an effect on the magnitude and direction of force transmission to, and resultant movement of, the abutment tooth. Less force to the abutment tooth was recorded when a mesial rest was used with the rest-clasp designs as compared to a distal rest. Force transmission to the abutment was found to be greater when the vertical load was applied to the denture base on the same side than when applied to the opposite side of the denture base.