Materials Science and Engineering B 181 (2014) 33–38 Contents lists available at ScienceDirect Materials Science and Engineering B jou rn al hom ep age: www.elsevier.com/locate/mseb Short communication Effect of resin chemistry on depth of cure and cytotoxicity of dental resin composites V. Susila Anand a,b , Venkatesh Balasubramanian a,∗ a Rehabilitation Bioengineering Group, Department of Engineering Design, Indian Institute of Technology Madras, Chennai 600036, India b Department of Conservative Dentistry and Endodontics, Saveetha Dental College, Saveetha University, Chennai 600077, India a r t i c l e i n f o Article history: Received 29 March 2013 Received in revised form 26 August 2013 Accepted 5 September 2013 Available online 21 September 2013 Keywords: Dental composite Degree of conversion Cytotoxicity FTIR Resin elution a b s t r a c t New dental composite restorative materials are being introduced aiming to overcome the disadvantages of contemporary materials. Hence there is a need to analyze the critical properties of these composites to aid in clinical application. This study aims to comparatively analyze the degree of conversion (DC), resid- ual reactivity (DBC/reactivity) and cytotoxicity of 2 composites based on different resin chemistry. Ceram X and Filtek P90 were used in the study to prepare disc shaped samples of 2 mm thickness and 4 mm diameter. The samples for cytotoxicity were cured for 40 s and those of Fourier Transform Infra-red Spec- troscopy (FTIR) (DBC/reactivity and DC) for 5 s, 10 s, 20 s and 40 s, at an average intensity of 800 mW/cm 2 with Quartz–Tungsten–Halogen (QTH) light. DC was calculated in 60–100 m thick and 6 mm diameter samples. Double bonds concentration/reactivity was measured in approximately 80 m thick sections prepared from the 2 mm thick discs using a hard tissue microtome. The cell viability was scored by Trypan blue exclusion staining technique at 24 h and 48 h. Both composites showed a progressive increase in dou- ble bonds/reactivity as the distance from curing probe increased which was inversely proportional to the curing time. The DC of Filtek P90 was 20% and 96% and that of Ceram X 33% and 50% at 5 s and 40 s, respec- tively. Ceram X showed statistically significantly higher cell viability score at both 24 h and 48 h than Filtek P90. The results were statistically analyzed using non-parametric Kruskal–Wallis, Mann–Whitney U and Wilcoxon Signed Ranks tests. Though DC plays an important role in biocompatibility of dental composites, other factors like elution may play a significant role and hence need further evaluation. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Dental resin composites were developed as an aesthetic and safer alternative to amalgam restorations [1–4]. Besides their advantages, clinical studies show that they indeed have much lower longevity compared to amalgam [5]. The factors contributing to their poor long term performance are polymerization shrinkage, marginal gap formation, secondary caries, low fracture toughness and adverse effects on pulpal health [5–8]. Some of these factors stem from their resin chemistry [9]. Incomplete polymerization of dental resin composites and resin-based bonding agents under clinical conditions result in unreacted resin monomers that may be released from the resin matrix into the aqueous environment of oral cavity [10]. All monomers exhibited a dose dependent cytotoxic effect, and the ranking of the cytotoxicity based on ∗ Corresponding author at: Rehabilitation Bioengineering Group, Department of Engineering Design, IIT Madras, Chennai 600036, India, Tel.: +91 44 2257 4117; fax: +91 44 2257 4732. E-mail addresses: chanakya@iitm.ac.in, chanakya@live.com (V. Balasubramanian). TC50 was GMA > TEGDMA > HEMA. The authors also confirmed a dose-dependent genotoxicity of the resin monomers [10]. Cases of genotoxicity without cytotoxicity can be found at various concen- trations of all resin monomers. Thus it is likely that resin monomers can cause genotoxicity at the concentrations relatively lower than those for apoptotic effects [11]. Hence newer resin chemistries that overcome these potential problems are being explored [12–18]. A review of literature reveals that these newer resins do not ful- fil all the essential requisites for a significantly better resin than conventional resin matrix [8,13–24]. A dendrimer–methacrylate copolymer was found to have increased degree of conversion, but poor mechanical properties [13]. Methacrylated beta Cyclo Dextrin-based composite formulations containing tri ethylene gly- col dimethacrylate, 1,10-decamethylenediol dimethacrylate, or benzyl methacrylate yielded flexural strength and volumetric shrinkage values comparable to those of the Bis-GMA/tri ethyl- ene glycol dimethacrylate formulation [14]. Appropriate ratio of Polyhedral Oligomeric Sil Sequioxane-Methacrylate, Bis-GMA and TEGDMA was found to result in improved mechanical properties [15]. Thiol-ene systems were found to have reduced shrinkage stress, increased polymerization rate, increased functional group conversion, and decreased leachable species while retaining the 0921-5107/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.mseb.2013.09.007