Photoelastic stress analysis in resin bonded bridge design

The aim of this investigation was to determine the stress magnitudes and directions in resin bonded bridges. 3D models (2.5 x life size) were prepared from photoelastic materials that represented the ratio of the elastic moduli of enamel and metal. The models were loaded during a stress freezing cycle and sectioned to view in a transmission polariscope. The fringes observed, indicated that the stress magnitudes concentrated at the proximo-lingual line angles to the pontic. The stress trajectories were plotted to show the pattern of stress direction. The stress factors which may contribute to debonding of these designs were analysed. It is suggested that the use of vertical grooves at the proximolingual line angles to the edentulous area in the preparation should reduce the stresses and hence improve the long term prognosis.