In vitro comparison of dentin bonding systems: Effect of testing method and operator

Objectives: The purpose of this study was to investigate the influence of different in vitro tests on the ranking of four dentin bonding systems (OptiBond FL, Solid bond, OptiBond Solo, Etch 3.0) and to determine operator influence on push-out test results. Method and materials: One-hundred eighty extracted human molars were used in this study. For all bonding systems, bond strengths were determined using the shear, tensile, and push-out tests. In the push-out test, two series of specimens were bonded by two operators. Additionally, margin adaptation in Class V cavities was evaluated using scanning electron microscopy and dye penetration. Results: Both test methods and bonding systems revealed a significant influence on bond strength. Ranking of mean bond strengths was identical in the shear and tensile tests but different in the push-out test. In addition, material ranking in the push-out test was found to be operator dependent. No correlation was observed between bond strength and margin adaptation. A weak correlation was found between the percentage of gap formation and dye penetration in Class V cavities. Conclusion: Comparisons of dentin bonding systems based on the results of different in vitro tests may be misleading. Operator influence on the results of push-out tests require further consideration.