[A photoelastic study of the stress distributions in the surrounding tissues of the abutments of a fixed partial denture with secondary abutments].

The purpose of this study was to evaluate the stress distributions of fixed partial dentures with secondary abutments. In the case where the lower first premolar and the second premolar were missing, four 2-dimensional photoelastic models with the canine and the first molar as primary abutments with secondary abutments were prepared as follows; Model I: primary abutments only. Model II: primary abutments with the lateral incisor as the secondary abutment. Model III: primary abutments with the second molar as the secondary abutment. Model IV: primary abutments with the lateral incisor and the second molar as secondary abutments. Two-dimensional photoelastic stress analysis was used with the stress areas recorded photographically. A vertical load was applied to the pontic in each case. After the stress patterns in surrounding tissues of the abutments were observed and recorded, the conclusions were as follows: 1. In model I, applied force was distributed to the long axis of the abutments. 2. In model II, III, IV, all the secondary abutments showed compressive stresses. No tensile stresses were developed. 3. The mesial aspect of the lateral incisor and the distal aspect of the second molar as the secondary abutment showed no compressive stresses.