Influence of smear layer pretreatments on bond strength to dentin.

PURPOSE: To evaluate the tensile bond strength of two self-etching adhesive systems and one one-bottle system applied on dentin surfaces after different smear layer treatments. MATERIALS AND METHODS: The crowns of 36 extracted third molars were transversally sectioned with a diamond saw to expose dentin. Flat dentin surfaces were abraded wet with 600-grit SiC paper and randomly assigned to 12 groups, according to three adhesive systems--Prime & Bond NT (PB), Clearfil Mega Bond (CMB) and Etch & Prime 3.0 (EP)--and four dentin surface treatments: direct application over smear layer (no treatment), sandblasting with 50 microm Al2O3 for 10 s, etching with 36% phosphoric acid for 15 s, or conditioning with 0.5 M EDTA for 2 min. Composite "crowns" (6.0 mm high) were incrementally built on the bonded surfaces and teeth were stored in distilled water at 37 degrees C. Teeth were vertically, serially sectioned in both x and y directions to obtain bonded specimens of approximately 0.8 mm2 cross-sectional area. Each specimen was tested in tension in a universal testing machine at 0.5 mm/min. RESULTS: Overall microtensile bond strength (MPa) was 40.43 +/- 7.63 for PB, 27.03 +/- 8.40 for CMB, and 14.73 +/- 3.91 for EP. Mean bond strength for PB was significantly higher than self-etching systems. No significant differences were observed among smear layer treatments within the same dentin adhesive. CONCLUSION: Bond strength values were significantly different according to the adhesive system used. Different smear layer treatments prior to bonding did not affect tensile bond strength within the same bonding agent.