Effect of the Amount of Hydroxyethylmethacrylate in an Experimental Dentin Bonding System on the Degree of Conversion and Microleakage of Class V Composite Restorations

Background: Experimental dentin bonding systems containing nanoclay fillers have shown high microleakage, which may be due to the high concentration of hydroxyethylmethacrylate (HEMA) in their composition. Objectives: This study sought to assess the effect of using different concentrations of HEMA in an experimental dentin bonding system containing PAA-g-nanoclay on the degree of conversion and microleakage of class V composite restorations. Methods: This in vitro experimental study was conducted on 60 class V cavities prepared in the buccal and/or lingual surfaces of sound-extracted premolar teeth. The cavities were restored using an experimental dentin bonding agent containing PAA-g-nanoclay and a light-cure composite in three groups (n = 20) with a HEMA concentration of 15% (group 1), 20% (group 2), and 30% (group 3) in the adhesive. After thermocycling, microleakage was assessed at the occlusal and gingival margins of the restorations using the dye penetration method. The degree of conversion of the dentin bonding agent was calculated using Fourier transform infrared spectroscopy. The data was analyzed using SPSS version 16 and the Kruskal-Wallis, Fisher’s exact, Wilcoxon, and Mann-Whitney tests (α = 0.05). Results: Microleakage at the occlusal and gingivalmargins was not significantly different between the three groups (P > 0.05), but the difference inmicroleakage between the occlusal and gingival margins was significant within each group (P < 0.001). The three groups were not significantly different in terms of degree of conversion (P > 0.05). Conclusions: Based on the results, HEMA concentrations of 15%, 20%, and 30% in our experimental bonding agent had no effect on themicroleakage of class V restorations. They were not significantly different in terms of degree of conversion either.