Effect of Surface Moisture on Bur-cut Dentin on Bonding of HEMA-free and HEMA-containing Universal Adhesives with or without Methacrylamide Monomer
Abstract
Purpose: The effect of surface moisture on bur-cut dentin on the microtensile bond strength (μTBS) of universal adhesives with various contents of 2-hydroxyethyl methacrylate (HEMA) and methacrylamide monomers was evaluated. Materials and methods: Flat mid-coronal dentin surfaces of human molars were exposed, and a standardized smear layer was prepared using a fine-grit diamond bur.
The surfaces were either left wet or air dried for 10 s before bonding with Clearfil Universal Bond Quick (UBQ), experimental UBQ without an amide monomer (UBQexp), Scotchbond Universal (SBU), Prime&Bond Universal (PBU), or BeautiBond Universal (BBU). The specimens were built up with resin composite, sectioned into sticks and subjected to the μTBS test after 24 h or 10,000 thermal cycles.
The μTBS data were analyzed using three-way ANOVA followed by pairwise comparisons with Bonferroni's correction (α = 0.05). Results: The level of dentin moisture did not significantly affect μTBS of UBQ and BBU (p > 0.05).
HEMA-containing UBQ, UBQexp, and SBU exhibited higher μTBS to dry dentin, while HEMA-free PBU and BBU showed higher μTBS to wet dentin. Thermocycling significantly decreased the μTBS of UBQexp (p 0.05).
Conclusion: Dry surfaces enabled obtaining optimal bonding for HEMA-containing adhesives to bur-cut dentin, while wet surfaces enabled optimal bonding for HEMA-free adhesives. Methacrylamide monomers could contribute to the improvement of the initial and long-term bonding performance of universal adhesives to bur-cut dentin.