Physical characterization and bond performance of a non-methacrylate dental adhesive in long-term biochemical and...

The objective of this study was to formulate a biostable methacrylate-free 3-step total-etch adhesive (EA) with the goal of exceeding or achieving the as-prepared values of both an in-house formulated (IH-MA) and commercial (C-MA, Adper Scotchbond™ Multi-Purpose) methacrylate-based adhesives, while maintaining bond stability following long-term simulated thermal or biochemical aging.

9 candidate EAs were screened for their as-prepared physical properties (degree of conversion, surface microhardness, surface water contact angle) and microtensile bond strength (µTBS) and compared to the properties of both the C-MA and IH-MA. Following screening, the candidate EA and C-MA were subjected to either thermocycling (10,000 cycles, 5-50°C) or 1 year of biochemical aging in simulated human salivary esterase (SHSE) media using miniature short-rod specimens and evaluated for changes in interfacial fracture toughness (K_IC), stiffness, and failure mode.

A candidate EA (EA 5) was identified through formulation screening that achieved comparable (p > 0.05) physical and adhesive (µTBS and K_IC) properties to that of the C-MA immediately post-fabrication. While thermal aging had no effect (p > 0.05) on the interfacial mechanics and fracture mode of the EA 5 or C-MA, biochemical aging of the C-MA in SHSE led to a significant decrease (p < 0.05) in K_IC (20 %) and stiffness (33 %) following just 6 months of aging. In contrast, the EA 5 experienced no changes (p > 0.05) in bonding performance following the entire duration (1 year) of biochemical aging.

Biostable dental adhesives may have the potential to improve the clinical service life of restorative materials by delaying interfacial degradation.