The purpose of this study was to photoelastically compare the load transfer characteristics of a distal extension RPD with implant assisted support in the posterior of a mandible with an atrophic edentulous ridge. The model included the anterior teeth and the first premolars bilaterally. Threaded implants, 3.75mm diameter 7mm length, were embedded 20mm distal to the first premolars on the posterior edentulous ridges. I-bar partial dentures with mesial rests were fabricated and physiologically adjusted to the models. The implant support conditions tested were healing abutments and 3mm ball attachments. Simulated vertical and lateral occlusal loads were applied at the first molar position and the stress developed in the abutment teeth were monitored photoelastically. Posterior implants with both healing abutment and ball attachments in the posterior of a mandible tended to assist support of a distal extension RPD and produce only low level stresses in the supporting atrophic edentulous ridge.
