Measurement of Stresses in Fixed-bridge Restorations Using a Brittle Coating Technique.

Three principal methods used to study stresses in materials are photoelastic stress analysis, brittle lacquer-coating techniques, and electronic strain gauges. A number of studies have been conducted using models and the photoelastic method' to examine stress patterns in oneand two-surface inlays, complete dentures, teeth and supporting bone, and rests used in partial dentures. Strain gauges4 9-13 have been used in the evaluations of stresses of mastication, but brittle lacquer coatings have not been used to any extent in the measurement of stresses in dental restorations.4 Brittle lacquers have been used in the study of stresses in the human mandible and other bones under static and dynamic loading.14' The brittle lacquer coatings are particularly useful in detecting and measuring strains at the surface of the structure as well as indicating the direction and sequence of the tensile strains. Although the method is not as accurate as strain gauges, it is an excellent means of obtaining an over-all picture of the pattern of the stress distribution." The information obtained using brittle lacquers may be used, therefore, as a basis for more detailed studies with strain gauges. It was the purpose of this investigation to study the general stress patterns in typical fixedbridge restorations using various static loading conditions and a brittle lacquer-coating technique.