Assessment of Bonding Effectiveness of Adhesive Materials to Tooth Structure using Bond Strength Test Methods: A Review of Literature

Background: The rapid developments in the field of adhesive dental materials have led to improvements in many aspects of clinical dentistry. Adhesive bond strength plays an important role in determining the clinical performance and longevity of dental restorations. Nevertheless, bond strength tests have never been well-standardized, although a number of important recommendations have been made. Objective: The aim of this paper is to critically review the validity of different bond strength testing methods for assessment of bonding effectiveness of adhesive materials to tooth structure and discuss factors that may affect bond strength measurement. Data Collection: Relevant literature published between 1983 and 2018 was collected and reviewed from the PubMed database and Google scholar resources. Review Results: Results of the current bond testing methods should be used to compare materials tested under the same laboratory settings, but they shouldn't be used to make direct inferences on their clinical behaviour. Shear and micro-shear tests, result in non-uniform stress distribution, stress concentration at the substrate area, and predominantly tensile stresses rather than shear stresses. Micro-tensile bond tests provide many advantages over the shear tests, although these methods are technique sensitive and labour intensive. Conclusion: Bond strength testing methods should be well-standardized, but there are many factors that cannot be fully controlled which leads to variation and misinterpretation of the data about the bonding abilities of adhesives. Clinical Significance: New adhesive materials should be subjected to a combination of testing protocols to properly assess their bonding effectiveness.