Effect of collagen removal on shear bond strength of two single-bottle adhesive systems

This study evaluated the effect of collagen removal on the shear bond stren gth for two single-bottle adhesive systems. The ultrastructure of the denti n after treatments and the dentin-resin interface were examined under SEM. The buccal and lingual surfaces of 80 extracted human third molars were gro und to expose dentin. Teeth were randomly assigned to four groups and recei ved the following treatments: Group 1(P&B 2.1), Prime & Bond 2.1 adhesive w as applied according to the manufacturer's directions and Restorative Z100 composite resin was bonded to the dentin surface; Group 2 (P&B 2.1/NaOCl), the same procedures were followed as for Group 1 except that the surfaces w ere treated with 10% sodium hypochlorite (NaOCl) for one minute after acid conditioning; Group 3 (SB), Single Bond (3M) was applied according to the m anufacturer's recommendations; Group 4 (SB/NaOCl), the same procedure was f ollowed for Group 2, using Single Bond. The specimens were stored in humidi ty at 37 degrees C for 24 hours and tested in a shear mode at a crosshead s peed of 0.5 mm/minute. The Kruskal-Wallis test and Multiple Comparisons wer e used for statistical analysis of the data. A one-minute exposure of denti n to 10% NaOCl following acid conditioning resulted in a significant increa se of the dentin shear bond strength for Prime & Bond 2.1. The same treatme nt for Single Bond resulted in a significant reduction in bond strength. Gr oups 1 and 3 were not statistically different from each other. The presence of a collagen layer resulted in the formation of a hybrid layer and simila r values of adhesion for both adhesive systems. The results may suggest tha t collagen removal improves the bond strength for this acetone-based adhesi ve system but several such systems would need to be investigated.