Battle of the bonds: Practice-based standardized dental adhesive testing of immediate dentin shear bond strength over 25 years

Abstract

Objective: To compare the immediate dentin shear bond strength (SBS) of contemporary dental adhesives using a uniquely large, practice-based dataset collected over 25 years and to identify material- and technique-related factors associated with bonding performance.

Methods: A total of 31,201 standardized macro-SBS tests from 90 adhesive/application-mode combinations were analyzed. Univariable comparisons were performed using the Kruskal‒Wallis and Dunn‒Holm tests. A multivariable linear mixed-effects model was used to assess the independent influence of application mode, universal status, 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) content, packaging, and commercialization year, with adhesive/application mode as a random intercept.

Results: Immediate SBS values covered a broad performance range, from approximately 7 MPa to 20 MPa, reflecting the considerable heterogeneity among contemporary adhesive formulations. Thirteen of the 20 most effective systems were one-bottle universal adhesives. However, the multivariable model revealed no significant independent effect of application mode, universal status, 10-MDP content, or commercialization year after adjusting for product-level clustering (p > 0.05). Single-dose packaging yielded a significantly higher SBS than bottle delivery did (p < 0.01).

Conclusion: Drawing on the largest standardized dataset to date, this study shows that contemporary adhesives cannot be meaningfully ranked by category or advertised attributes and that their immediate SBS performance is instead driven by formulation-specific chemistry and must be assessed on an individual basis.

Clinical significance: Adhesives should be selected on the basis of their demonstrated individual performance rather than on generational classifications. The use of single-dose packaging may help preserve formulation integrity and improve the consistency of bonding outcomes.

Clinical trial registration: Not applicable.

Keywords: Adhesion; Biomaterials; Bond strength; Dental adhesive; Practice-based research.