Ulker, Ulker, Zortuk, Bulbul, Tuncdemir, Bilgin INtRoduCtIoN Dental materials contain a great variety of different monomers and additives.1 Because of the complex chemical composition and the incomplete monomer–polymer conversion, several components are leached out from each resin-based restorative material into the oral environment.2,3 This in turn may cause some adverse effects.4 Previous studies have used in vitro cytotoxicity tests to evaluate the biological risks of resin composites used in dentistry.1,5 Cytotoxicity tests have primarily focused on restorative materials such as glass ionomers, dental adhesives and composite resins.6-8 However, fewer studies on prosthodontic materials have been published, and investigations regarding the cytotoxicity of provisional prosthodontic materials are even more limited.5,9 Provisional restorations are used in the interim between tooth preparation and fitting a definitive restoration. The length of time between preparation of teeth and cementation of final restorations can vary from a few days for straightforward cases, to several weeks or even, in the case of complex reconstruction, several months. Provisional restorations are generally essential to cover freshly cut dentine, stabilize the position of the prepared tooth, regain chewing function and phonation, maintain esthetic appearance and evaluate the minimal thickness of the definitive restoration. They can also help stabilize the periodontal condition prior to definitive restoration.10 Provisional materials can be classified by the type of resin. Acrylic polymethyl or polyethyl methacrylates belong to the oldest group of provisional materials. The latest class of materials is formed by bis-acryl composite resins, which are comparable to composite resins used for direct restoration therapy.10 They consist of an organic matrix and inorganic fillers. Bis-acryl composites produce less heat and shrinkage during polymerization than other resins, resulting in a better marginal fit.11 Aesthetically they are reasonable and are more color stable than polymethyl or polyethyl methacrylates.12 Most recently, visible light cured resins have been introduced based on urethane dimethacrylate. These resins have good mechanical properties, being light cured, the operator has some control over the material’s working time and colour is relatively stable but marginal fit can be poor.10,13 Acrylates and mainly methacrylates were found to cause cytotoxic effects.14 Evaluation of the cytotoxicity of dental resin materials showed a relationship between their composition and the degree of cytotoxicity.15 Continuous cell lines, like L929 mouse fibroblasts are being routinely used for the testing of cytotoxic properties of dental materials because of their reproducible growth rates and biological responses.1 The purpose of this in vitro study was to evaluate the effect of current bis-acryl and urethane dimethacrylate based provisional materials on the fibroblast cell viability. MAtERIALS ANd MEtHodS The provisional restoration materials tested in this study are shown in Table 1. Two of the tested materials were bis-acryl based (Tempofit Duomix, Detax, Germany & Protemp 3 Garant, 3M ESPE, Germany) and one was urethane dimethacrylate based (Revotek LC, GC Corporation, Japan) provisional restoration materials. Test specimens were prepared according to the manufacturers’ instructions in standard teflon discs, 5 mm in diameter and 2 mm of height. All specimens were prepared and handled under aseptic conditions to limit the influence of biological contamination on Table 1. Material name, company, lot number and composition. Materials Tempofit Duomix Protemp 3 Garant Revotek LC April 2009 - Vol.3 Company Detax, Ettlingen, Germany 3M ESPE, Seefeld, Germany GC Corporation, Tokyo, Japan Lot # 315185 51200 704091 Composition Mixture of methacrylic resins and silane treated glass with auxiliary matters and pigments Dimethacrylate, Silicic acid, Initiators, Diacrylate, Stabilizers, Synthetic resins, Pigments,Dyes, Strontium glass powder Urethane, Silica powder, Camphorquinone 115 European Journal of Dentistry