Effects of modelling liquids on monomer release from composite resins

Objective: There is no clear consensus on the effect of modelling liquids used to facilitate the manipulation of composites, which are frequently preferred in restorative treatments, on the structure of composite resins. The aim of this study was to evaluate the effect of different modelling liquids on the monomer release of composites. Materials and Methods: In this study, 80 samples (n=10) of 2x8 mm were prepared by applying three different modelling liquids (Composite Wetting Resin, Ultradent; Modeling Resin, Bisco; Modeling Liquid, Gc) to two different composite resins (Estelite Sigma Quick, Tokuyama Dental; Harmonize, Kerr Dental). The composite resins were placed in Teflon moulds in 0.5 mm layers and the modelling liquids were prepared by using a brush for a total of 4 layers. The control group was prepared in accordance with the company recommendations of the composites without the use of modelling agent. The samples were polished using a multi-stage disc system (Sof-Lex; 3M™ ESPE™, St. Paul, USA) and stored in 75% ethanol at 37°C until the measurement day. The monomers released from the samples (urethane dimethacrylate (UDMA), bisphenol A-glycidyl methacrylate (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA), 2-Hydroxyethyl methacrylate (HEMA)) were determined using Shimadzu 8045 LC-MS/MS. Samples were kept in 75% ethanol water mixture. Measurements were repeated in the first 24 hours, 7th day and 30 days. Statistical analyses of the data were performed using SPSS v.19 package programme (SPSS Inc, IBM Corp, IL, USA). Repeated measures Analysis of Variance (ANOVA) and post-hoc Tukey HSD tests are planned to be used in the analyses (p˂0.05). Results: Application of modelling liquid significantly reduced BisGMA release for both composite resins (p<0.05). While TEGDMA release was significantly decreased in Sigma groups (p<0.05), no difference was observed in Harmonised groups. Modelling liquid application increased total HEMA and UDMA release (p<0.05). TEGDMA release in Sigma-control group was higher than Harmonise-control group (p<0.05). Conclusion: The organic matrix structure and application procedure of composite resins significantly affect the residual monomer release. The use of modelling liquid showed differences on monomer release according to the content of the liquid.