(2016). Degree of conversion and adhesion of methacrylate-based resin cements with phosphonic or phosphoric acid acrylate to glass fiber posts at different regions of intraradicular dentin. Journal of Adhesion Science and Technology, 30(3):328-337. DOI: https://doi.org/10. 1080/01694243.2015.1105122 Degree of conversion and adhesion of methacrylate-based resin cements with phosphonic or phosphoric acid acrylate to glass fiber posts at different regions of intraradicular dentin Zürich, 2 Abstract: This study evaluated the degree of conversion (DC) and adhesion of methacrylate-based resin cements to glass fiber posts at different regions of intraradicular dentin. Single-rooted teeth (N=24, n=12per group) were cut at the cement-enamel junction (CEJ), endodontically treated and post space (depth= 8 mm) was prepared. Teeth were randomly divided into two groups according to the resin cements: a) Group ML: Methacrylate-based cement with phosphonic acid acrylate (Multilink Automix, Ivoclar Vivadent); b)Group RXU: Methacrylate-based cement with phosphoric acid acrylate (RelyX Unicem 2 Automix, 3M ESPE). Fiber reinforced composite root posts (RelyX Fiber Post, 3M ESPE) were cemented according to the manufacturers' instructions of the resin cements. Root slices of 2 mm thick (n=3 per tooth) were cut below the CEJ 1, 3, 5 mm apically. The DC of each section was analyzed with micro-Raman spectrometer and push-out test was performed in the Universal Testing Machine (0.5 mm/min). After debonding, all specimens were analyzed using optical microscope to categorize the failure modes. While data (MPa)were statistically evaluated using Kruskal Wallis, Mann-Whitney U tests, for DC data 3-way ANOVA and Tukey`s tests were used (α=0.05). Regardless of the resin cement type, the mean push out bond strength results (MPa), were significantly higher for the coronal slices (ML: 9.1±2.7; RXU: 7.3±4.1) than those of the most apical ones (ML: 7±4.9; RXU: 2.89±1.5) (P=0.002). Resin cement type and (P<0.001) root level (P=0.002) significantly affected the DC values, while the interaction terms were not significant (P=0.606).Overall, DC was significantly higher for ML (67±8.2%) than RXU (26±8.8%) (P<0.001). Adhesive failures at the cement-dentin interface were more commonly experienced in RXU than in ML, whereas ML presented more incidences of adhesive failures at the cement-post interface. Considering the push-out bond strength, degree of conversion and failure types, methacrylate-based cement with phosphonic acid acrylate should be preferred to those containing phosphoric acid to adhere glass fiber posts in the root canal.

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