Quantitative contribution of resin infiltration/hybridization to dentin bonding

This study determined, quantitatively, the role of resin infiltration in dentin bonding. Four groups contained 10 molar teeth. Thirty were sectioned in the mid-coronal region and the dentin ground flat with 600 grit silicon carbide paper. Group 1: smear layer intact; Group 2: smear layer removed with a Prophy Jet; Group 3: conditioned with 10% H3PO4 for 20 seconds; Group 4: comprised dentin exposed by a transverse, mid-coronal fracture. Dentin surfaces were treated with All-Bond 2, its companion bonding agent, followed by P50 resin composite, polymerized in 1 mm increments. After storage in water at 37 degrees C for 24 hours, the assemblies were tested to failure in a shear mode at a crosshead speed of 5 mm/minute. Surface and interfacial morphology was characterized using SEM. Values in MPa were: Group 1: 10.24 +/- 2.98; Group 2: 20.37 +/- 4.62; Group 3: 32.68 +/- 7.12; and Group 4: 26.77 +/- 4.85. ANOVA and student t-test showed the means statistically different (P < 0.05). Since resin penetration was only found appreciably in dentin tubules in Group 4 and tubular and intertubular penetration in Group 3, it was concluded that resin infiltration can contribute approximately one third of the shear bond strength of this total etch system.