Evaluation of micro-tensile, shear and tensile tests determining the bond strength of three adhesive systems

Abstract

Objectives. The aim of this study was to determine bond strength between dentin and three adhesive systems, by means of micro-tensile, shear and tensile tests. Methods. Extracted human molars were embedded in acrylic resin and had the dentin exposed on three of their smooth surfaces. On each surface a specimen was prepared to be submitted to either micro-tensile, shear or tensile bond strength testing. For shear and tensile tests, after adhesive application, a cone 3 mm high and diameter of 3 mm in the small surface was built with composite resin. The shear test was performed with a chisel. Tensile testing was made by pulling the resin cone via a metallic clamp. For micro-tensile testing, composite approximately 5 mm high was placed over the entire exposed dentin. Then, using a diamond disk perpendicular to the bonding interface, `sticks' with 0.25 mm 2 rectangular cross-sectional area were obtained and subjected to tensile force. Results. All tests ranked the adhesives in the same order. Mean values obtained by the micro-tensile test were not statistically different. For shear and tensile tests, Single Bond gave higher bond strength than Etch&Prime 3.0 ( p<0.05). Scotchbond Multi-Purpose Plus originated bondings that were statistically similar to both Single Bond and Etch&Prime 3.0. Comparing the three tests, a higher mean ( p<0.05) and a smaller coefficient of variation were found with the micro-tensile test. Significance. The one-bottle adhesive system obtained higher bond strength values than the self-etching adhesive upon shear and tensile strength tests. Depending on the test applied, differences among materials may not be disclosed.