Bond strength of polyacid-modified resins using a new one-step adhesive system

During the last few years a number of one-bottle adhesive systems have been developed. However, no "universal" adhesive system recommended for use wit h different polyacid-modified resins (PMR) is currently available. This stu dy compared the shear bond strengths of four PMR Dyract AP (D), Compoglass F (C), F 2000 (F) and Hytac (H)) to enamel and dentin using (1) the adhesiv e system provided by the manufacturer and (2) a new one-step "universal" ad hesive system (Prompt L-Pop). Seventy enamel and 70 dentin-surfaces were prepared for 10 replications of each bonding combination (C1, C2, D1, D2, F1, F2, H1/2). After the bonding procedure and subsequent storage of the specimens in distilled water at 37 degreesC for 24 hours, shear bond strengths were determined using a Univers al Testing Machine at a cross-head speed of 0.75 mm min(-1) until failure o ccurred. Fracture modes were examined at 25x magnification under a light mi croscope. The median shear bond strength values (MPa) to enamel were 13.2 (C1), 16.5 (C2), 17.7 (D1), 41.2 (D2), 12.7 (F1), 41.2 (F2), 33.9 (H1/2); to dentin, v alues of 3.3 (C1), 3.7 (C2), 7.4 (D1), 12.2 (D2), 11.4 (F1), 8.6 (F2) and 4 .6 (H1/2) were measured. In both enamel and dentin, bond strengths of the t ested PMR were either not significantly different or significantly higher u sing the universal adhesive system compared to the adhesive systems provide d by the manufacturers. Bond strengths to enamel and dentin were not signif icantly different from each other in D and F with their corresponding adhes ive system. In all other groups, bond strengths to enamel were significantl y higher compared to dentin. Failure modes were mostly adhesive in dentin a nd mixed adhesive/ cohesive in enamel. SEM observations revealed similar hy brid layer and tag formation in dentin for the four adhesive systems. On en amel, a clearly visible etch pattern was detected only for the universal ad hesive system. In conclusion, the universal adhesive system achieved equal or higher bond strengths of the tested PMR to enamel. and dentin compared to the adhesive systems provided by the manufacturers.