RESUMEN
Bonding type and curing time may affect shear bond strength of composite to dentin. This study was conducted to evaluate the effect of these factors on composite to dentin bond strength. The buccal dentin of seventy-two intact extracted premolar and molar teeth were etched with phosphoric acid 37% for 5 seconds [S] and washed with water, for 15S and dried for 2-3S. The teeth were randomly assigned to six groups. Group 1: Dentin Bonding [DB] was applied once and not cured; Group 2: DB was applied once and cured for 10S; Group 3: DB was applied once and cured for 20S; Group 4: DB was applied twice and not cured; Group 5: DB was applied twice and each layer cured for 10S; Group 6: DB was applied twice and each layer was cured for 20S. Then composite blocks were placed on bonded surfaces and cured for 40S. The specimens were thermo-cycled and the shear bond strength was measured using Instron testing machine. The data were analyzed with two-way ANOVA and Tukey HSD tests. Mean shear bond strengths of the groups in MPa were as follows: Group 1: 15.57; Group 2: 16.22; Group 3: 16.68; Group 4: 17.39; Group 5: 18.18 and Group 6: 20.02. [P<0.001] Additionally the mean bond strength of groups cured 20S was significantly higher than other groups [P<0.05]. Adequate polymerization time and increased adhesive layer thickness could improve bond strength of composite to dentin