engleski

Degree of Vinyl Conversion in Experimental Bioactive Composites

Objectives: The aim of this study was to asses the effect of resin composition and curing time on degree of vinyl conversion (DVC) attained in experimental composites based on amorphous calcium phosphate (ACP). Bioactivity of ACP composites instigates from their ability to release calcium and phosphate ions in aqueous ambience which may aid in arresting caries development. Methods: Experimental composites used in this study contained 35 mass % of zirconia-modified ACP filler and 65 mass % of either 2, 2-bis[p-(2'-hydroxy-3'-methacryloxypropoxy)phenyl]-propane (bis-GMA)-based or ethoxylated bisphenol A dimethacrylate (EBPADMA)-based resin. ACP powder and resins were thoroughly mixed and pressed under 107 Pa into composite disk specimens (thickness = 0.1 mm, diameter = 1.0 cm). The total of 32 samples (16/each experimental resin) were polymerized using soft start mode of Bluephase (Ivoclar Vivadent, Liechtenstein) LED curing unit for 20 s (8 samples/group) or 40 s (8 samples/group). The DVC was determined by Fourier Transform infrared spectroscopy (Perkin Elmer 2000 spectrometer ; Perkin Elmer, UK), as the % change in the ratio of the integrated peak areas between the aliphatic and aromatic absorption bands. Results: Statistical analysis of the experimental data (t-test) indicated that, when polymerized for 40s, EBPADMA-based composites have higher DVC than bis-GMA-based composites [(76.9 &plusmn ; 2.9) % vs. (74.2 &plusmn ; 1.8) % ; p<0.05]. However, no significant difference was found for the overall samples of each material if the polymerization time was not taken into account (p=0.76). Conclusions: Experimental ACP composites formulated with EPADMA as a base monomer have potential to attain higher degree of vinyl conversion compared to the composites based on Bis-GMA, a constituent of the majority of contemporary composites. This study was supported by grant 065-0352851-0410 of MZOS, Croatia.

composite resin; amorphous calcium phosphate; polymerization

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