ISSN 0970-938X www.biomedres.info Biomed Res 2020 Volume 31 Issue 5 148 Elution of residual monomers from dental composite resins. Ezgi Sonkaya 1 , Seyhmus Bakır 2 , Elif Pınar Bakır 3* 1 Department of Restorative Dentistry, Cukurova University, Adana, Turkey 2 Department of Restorative Dentistry, Dicle University, Diyarbakir, Turkey Introduction The use of long-life and biocompatible materials in restorative dentistry is important. The characteristics and biocompatibility of composite resins are determined by the monomers in their contents. The most commonly used monomers to form a polymer matrix are Bis- GMA (bisphenol A diglycidyl methacrylate), UDMA (urethane dimethacrylate), TEGDMA (triethylene glycol dimethacrylate) HEMA (hydroxyethyl metacrylate) and Bis-EMA (bisphenol A diglycidyl methacrylate ethoxylated) [1]. The mechanical properties of the polymer depend on the degree of conversion of the monomers and other components of the composite (e.g. The filler and initiator systems) [2]. The degree of conversion in composite resins is 40%-75%. Therefore, it is difficult to provide complete polymerization in each region of the resin at the same rate [3-5]. As the monomer conversion rate falls, it leads to increase of water absorption of the material, decrease of wear resistance and color stability, inadequate binding and unwanted tissue reactions [6,7]. Abstract The biocompatibility of composite resins decreases with the increase of released monomer since they are cytotoxic on pulp or living tissues. Commercialy used composites should be choosen according to their biocompatibility to not jeopardize the patient’s health. Analyze of the composite biocompatibility and determination of the monomers elution of four different composite resin materials with nano filler content is completed in the study to investigate if there is difference and the most possible healty way of usage. The amount of Bis-GMA, UDMA and TEGDMA released from four different composite resins measured on three different day using the HPLC. Four groups (n=10, diameter: 5 mm, thickness: 2 mm) of each material were prepared. Samples were placed in 75% ethanol-water. On days 1, 15 and 30, 1 mL samples were taken for measurement. A total of 120 samples’ findings were analysed statistically. Bis-GMA and UDMA were released from all the materials used in the study. There were significant differences in the total monomer release of all composite resins in terms of time (P=0.001). Tetric Evoceram is the most residual monomer-releasing composite in experiment groups. The maximum amount of monomer release for all three monomers was on the 15th day. In order to reduce concerns about toxicity, taking measures to protect the pulp for example using cavity liners and bases specially in case of having less than 0.5 mm thickness of dentin. There is a need for these results to be supported by further clinical studies. Keywords: Nanofiller Composite Resin, Residual Monomer, High Performance Liquid Chromato Figurey, Biocompatibility, Cytotoxicity. Accepted on October 16, 2020 The conversion rate of the Bis-GMA monomer with high molecular weight and viscosity is lower than that of other monomers. Reducing the Bis-GMA ratio increases polymerization shrinkage. Some of the dimethacrylates are densely bound to the cross linkage while others are loosely bound. Thus, an unreacted amount of monomers remains between the polymer chains [3]. UDMA monomer with similar weight to Bis-GMA but lower viscosity provides color stability in composite resins and increases adhesion. This monomer, which exhibits less polymerization shrinkage than Bis-GMA, has a high biocompatibility potential [8]. To reduce the viscosity of composite resins, TEGDMA is added as the diluent and the high reactivity, low viscosity and molecular weight of TEGDMA increases the degree of polymer conversion and shrinkage. The lipophilic nature of TEGDMA enables it to easily penetrate the cytoplasm and membrane lipid compartments of mammalian cells [9]. Residual monomers are separated from the mass by Biomedical Research 2020; 31 (5): 148-154