Comparison of enamel and dentin shear bond strengths of current dental bonding adhesives from three bond generations.

OBJECTIVE: Durability is still a major challenge in adhesive dentistry. One of the biggest areas of development has been to simplify the bonding process by using all-in-one adhesives. The aim of this study was to compare the shear bond strength (SBS) to dentin and enamel of nine dental bonding agents (DBAs) from three generations after simulated aging.

METHODS AND MATERIALS: For this study, 108 sound extracted human molars were randomly assigned to nine groups (n=12). The sample teeth were mounted in self-cure acrylic resin sectioned to provide paired enamel and dentin samples. All samples were polished with 240 and 600-grit silicon carbide sandpaper and randomly grouped according to the product and substrates (enamel or dentin). Herculite Ultra resin composite cylinders were bonded on each test surface, stored in 100% humidity at 37°C for 24 hours, and then thermocyled for 1,000 cycles at 5°C and 55°C. SBS testing was performed using an Ultratester at a crosshead speed of 0.5 mm/min. Statistical analysis included two-factor analysis of variance, one-sample Wilcoxon and Kruskal-Wallis tests, and the Scheffe post hoc test at an alpha level of 0.05 using SAS version 9.2.

RESULTS: Significant differences in SBS were observed between the sixth- and seventh-generation DBAs (p=0.002) but not between the sixth- and fourth-generation DBAs. Scheffe post hoc tests for the sixth-generation DBAs showed that some DBAs yielded significantly higher enamel SBS than others, but not as much as dentin SBS. As for the seventh-generation DBAs, similar post hoc tests showed significant variations in SBS between substrates (enamel and dentin) and DBAs tested. Significant main effects were also found for the different substrates for the fourth-generation (F[1,96]=10.532; p=0.003) and seventh-generation (F[1,96]=22.254; p<0.001) DBAs, but not for the sixth-generation DBAs (F[1,96]=1.895, p=0.172). The SBS was higher on dentin than enamel for the fourth- and seventh-generation DBAs.

CONCLUSION: As expected, fourth- and sixth-generation DBAs generally showed stronger SBS values than the seventh-generation all-in-one DBAs. The new sixth-generation DBA OptiBond XTR (Kerr) showed strong SBS values to both substrates and performed well in comparison to the other DBAs tested.