International Journal of Engineering Research & Science (IJOER) ISSN: [2395-6992] [Vol-2, Issue-4 April- 2016] Page | 117 Effects of curing systems and light units on cytotoxicity of dental composites Afife Binnaz Hazar Yoruç 1 , Kadriye Atıcı Kızılbey 2 , Arzu Karaul 3 , Özcan Çakmakcıoğlu 4 1 Yıldız Technical University, Institute of Science, Division of Metallurgical and Materials Engineering, Davutpasa Campus, Esenler 34210, İstanbul, Turkey 2 İstanbul Yeni Yüzyıl University, Division of Biomedical Engineering, Cevizlibağ, Zeytinburnu, 34010, İstanbul, Turkey 3 Yıldız Technical University, Institute of Science, Division of Bioengineering, Davutpaşa Campus, Esenler, 34210, İstanbul, Turkey 4 Dental Clinic, Nişantaşı, İstanbul, Turkey Abstract— The objective of this study was to examine and compare the cytotoxicity behavior of commercial two restorative (light-cured) and three adhesive composites (dual-cured) polymerized by using two different light curing units (LCU). Commercial composites Filtek Z250, Filtek Supreme XT, Rely X Arc, Rely X U100 and Variolink II were polymerized using different light densities of halogen (H) and Light Emitting Diod (LED) curing units. After the polymerization process samples sterilized under UV light for 15 minutes. Dulbecco's Modified Eagle's Minimal Essential Medium (DMEM) containing 200 μL of serum was placed in 96 well cell plates and samples were added in the wells. They were incubated 5% CO 2 incubator for 48 hours at 37°C. Sample surface area/solution volume was adjusted to 2.5 cm 2 /ml. Cytotoxicity of samples was examined by the extraction method and the results were evaluated using the MTS test. The extracts of the samples were collected for 24 hours and incubated in L-929 mouse fibroblast cells (MFCs). The data was analyzed with the SPSS statistics program. Samples polymerized by H light source were generally cytotoxic than the samples polymerized by LED light source. Rely X Arc in dual-cure system is the most biocompatible material and Variolink II-LED combination is the most cytotoxic one. Furthermore, there was no statistically significant difference between the cytotoxicity levels of composites using H and LED light sources (p>0.05).This study showed that the curing treatment used power density LED affects biocompatibility positively and nano-structures increase the biocompatibility. Keywords— Cytotoxicity, dental composites, light curing, dual curing, halogen, LED, light curing units. I. INTRODUCTION Light- and dual-curing composite materials have been used with increasing interest as fillers, luting cements and adhesive resin cements in restorative dentistry for many years [1-5]. Increasing usage of these composite materials has recently provided to improvement of new formulations, simplification of bonding procedures and decreasing of aesthetic concern. Therefore physical properties, clinical performance and polymerization degree of resin composites developed. Halogen (H) and light-emitting diode (LED) light-curing units are the most widely used light sources to achieve the sufficient polymerization degree for restorative composites. Recently, several research teams reported that usage of both composite and light curing unit can influence the cytotoxicity of the material [1-11]. Influence of light curing on the toxic behaviour of composite materials is the interest issue for dental restoration [1-5]. The relation between the type of light curing unit and the degree of polymerization of dental composites is currently being discussed in the literature [1-3]. Recently Siguscha et al. reported on the influence of different light curing units on the cytotoxicity of various dental composites. They proved that the combination of a high power LCU with various composites caused the lowest cell toxicity [4]. Goldberg explained that cytotoxicity mechanisms effected by the short-term release of residue monomers during polymerization and long-term release of soluble substances after polymerization process [12]. Photopolymerization process uses the light energy to initiate photochemical and chemical reactions in organic molecules and this energy converses the monomer units to macromoleculer polymeric structure with cross linking interactions. Improved photopolymerization process decreases amount of the residue monomer [6], increases the optimization of mechanical properties [7, 8], biocompatibility [9] and color stability [10] of light-activated dental composites. Polymerization of the