Stress analysis of four-unit fixed bridges on abutment teeth with reduced periodontal support.

The variable properties of photoelastic models and the difficulty of fabrication of the model limit experimental designs. The 'material fringe value' is introduced into the definition of the 'stress concentration index' by multiplying the fringe orders. Three levels of periodontal support in three photoelastic models (nine cases) were compared quantitatively by determining the stress concentration induced in periodontium by point loading vertically on a span of the fixed partial denture of four units length. The results indicate that comparison among photoelastic models is possible and useful. The stress concentration effects produced by the second molar were more prominent and determinant than that by the first premolar in the periodontium of the abutments.