Long-term in vitro monomer release analysis of bulk-fill resin composites

The aim of this study was to evaluate the long-term (6 months) release of Bis-GMA, Bis-EMA and UDMA monomers from different resin composites polymerized at different times with different light curing units. In the study, 3 different bulk fill (Filtek Bulk Fill Flow, Tetric EvoCeram Bulk Fill, SonicFill Bulk Fill) and conventional (Filtek Z250) resin composites were used. A total of 80 samples (n=20 per group) of 2 mm in height and 8 mm in diameter for conventional resin composite and 4 mm for bulk fill resin composites were prepared using metal molds, polymerized with halogen (Optilux 501) and LED (Demi Ultra) light curing units for 20 seconds and for 40 seconds (n=5). Immediately after polymerization, the samples were stored in 75% ethanol/water solution at room temperature for monomer release. Monomer release analyzes were performed with LC-MS/MS device in 24 hours, 1 week, 1 month and 6 months periods. Multivariate analysis of variance (Multivariate ANOVA) and repeated measures analysis of variance (Reperated measure ANOVA) were used to evaluate time-dependent monomer release values and variation, Tukey HSD and Tamhane multiple comparison tests were used to determine differences in monomer releases between groups (p<0.05). Type of light curing unit significantly affected the monomer release values (p<0.001). Increasing the polymerization time caused a significant decrease in monomer release values (p<0.001). In terms of total monomer release, UDMA was the monomer with the highest release, while the least release was observed in Bis-EMA monomer. It was determined that the release of UDMA and Bis-GMA monomers in Tetric EvoCeram Bulk Fill resin composite was significantly higher than other resin composites (p<0.001). Type of light curing unit and polymerization time have a significant effect on monomer release values. The chemical structure of resin composites affects the long-term monomer release. Key Words: Monomer release, Light curing unit, Polymerization time, Bulk Fill composite, LC-MS/MS