A photoelastic replica system was used to study stresses produced within the periodontium of abutment teeth for a fixed partial denture. Three replicas, each representing a different level of periodontal support, were constructed. Abutment teeth were subjected to occlusal forces and examined in a polariscope before and after prosthesis construction. Stress distributions and concentrations produced in the periodontium of abutment teeth by an occlusal force were favorably altered by the placement of a fixed partial denture. Stress concentrations produced in the periodontium of abutment teeth were notably altered by a moderate (20%) loss of support. Further (40%) loss of periodontium did not result in appreciably additional change. The stress patterns produced in the periodontium of both replicas which simulated loss of periodontium were also favorably altered by the placement of a fixed partial denture.