Shear and tensile bond testing for resin cement evaluation

Objectives. The aim of this study was to compare the tensile and shear bond strengths of one experimental and four commercially available resin cements following the ISO document TR 110405 for bond measurement. Methods. Tensile and shear bond tests were performed using bovine enamel and dentin as the tooth substrate with each of the resin cements. Resin composite rods were cemented to the prepared tooth surfaces. The bond strengths were obtained 24 h after cementation, and mode of failure was classified after fracture of the bonds, both visually and by SEM observation. Results. Significant differences existed between the two bond test methods for all materials with enamel and three of the five cements when bonded to dentin. The shear test results were always the higher of the two test methods. Mode of fracture varried little for the visual classification, but the morphology from SEM observations showed considerable differences. Significance. Although there are deficiencies in the current test methods, these may be outweighed substrate variables. A test mode should be designed to determine which stresses, tensile or shear, are the greatest for different types of restorations. With this information, the type of test selected could provide appropriate information before clinical trials are commenced.