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

OBJECTIVES

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.

METHODS

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 (KIC), stiffness, and failure mode.

RESULTS

A candidate EA (EA 5) was identified through formulation screening that achieved comparable (p > 0.05) physical and adhesive (µTBS and KIC) 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 KIC (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.

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