Tomofumi Sasaki

Stress Transfer Characteristics of Various Retainer Designs in Unilateral Distal Extension Mandibular Cases Abutment

Previous studies have reported on the effects of I-bar retained prostheses and splinted abutments in bilateral and unilateral distal extension cases with reduced periodontal support. Producing favorable stress redistributions in the abutments and surrounding tissues is difficult. Various retainer designs have been developed to address this issue. The purpose of this study was to investigate the stress redistribution in the abutments and surrounding tissues of three retainers device configurations based on the RPI system, Konus Krone system, and Bracing arm system using quasi three-dimensional photoelastic methods. Three composite photoelastic models were made of a mandible unilaterally edentulous distal to the right second premolars. Individual simulant materials were used for tooth structure, periodontal ligament, and alveolar bone. Three normal periodontal conditions of the right first and second premolar abutment teeth were considered, and three retainers were cast for the teeth. Unilateral partial dentures with various retainer designs, RPI system, Konus Krone system and Bracing arm system were made for the three models. Simulated vertical and lateral occlusal loads were applied to the dentures, and the stresses which developed in the supporting structures were monitored photoelastically. Under comparable loading conditions, stress redistribution patterns in the abutments and surrounding tissues differed between the three systems, and The RPI system configurations showed the most uniform redistributions across loads directed in all five directions, while Konus Crone systems showed strongly stress redistribution for vertically, posteriorly, and buccally directed loads and Bracing arms configurations showed strongly stress redistribution for anteriorly and lingually directed loads. The results of this study demonstrated that the condition of vertical axiss angle, contact position and contact area of between abutments and retainers has considerable influence on favorable stress distribution.