Rest seat designs for inclined posterior abutments: a photoelastic comparison

Forty-five photoelastic stress analyses were conducted with two-dimensional models of one side of a mandibular Kennedy class III removable partial denture. Fifteen separate rest seat configurations were tested for each of three varied inclinations of the distal second molar abutment. The data indicate that: Rest seat placement on an abutment tooth primarily affects stress concentration of that tooth. There is no direct relationship between rest seat design on one abutment and resultant stress on another. Inclined abutments demonstrate greater resultant bending of interradicular bone than vertical abutments, and the greater the inclination, the greater the bending (as the result of tipping force). Mesial rests on inclined molar abutments demonstrate maximum tipping forces. Channel rests on inclined molar abutments demonstrate the least amount of tipping force.