1 e-Polymers 2012, no. 047 http://www.e-polymers.org ISSN 1618-7229 Observation of oxygen inhibited layer of organic dental resin by confocal Raman-microscopy Jean Baptiste Robin, 1 Jean Cédric Durand, 1 Loic Derely, 1 Bruno Jacquot, 1 Frédéric Cuisinier, 1 Jean-Jacques Robin 2* 1 Laboratoire Biosanté and Nanomatériaux , EA 4203, UFR d'Odontologie, Université Montpellier 1, 545, Av du Prof J.L. Viala, 34193 Montpellier Cedex 5, France ; fax.(33)4 67 10 74 31; e-mail : frederic.cuisinier@univ-montp1.fr 2 Institut Charles Gerhardt Montpellier, UMR5253, CNRS-UM2-ENSCM-UM1 – Equipe Ingénierie et Architectures Macromoléculaires, Université Montpellier II, cc1702 Place Eugène Bataillon, 34095 Montpellier Cedex 5, France ; fax. (33)4 67 14 40 28; e-mail: Jean-Jacques.Robin@univ-montp2.fr. (Received: 07 February, 2011; published: 08 April, 2012) Abstract: This study investigated degrees of conversion of oxygen inhibited layer (OIL) of organic dental resins for restoration using Confocal-Raman spectroscopy. The aim was to determine which laser is adapted to determine the degrees of conversion of OIL and to measure variations of thickness and degrees of conversion in OIL with respect to monomers proportions. Bis-GMA (bis-phenol A glycidyl dimethacrylate) and TEGDMA (triethylene glycol dimethacrylate) based resins with various ratio of an equimolecular mixture of camphorquinone/EDMAB (ethyl (4-dimethyl amino) benzoate) were studied with different lasers by confocal- Raman spectroscopy. Results show that this technique is adapted for the non destructive measurement of OIL. The Thickness of OIL is not correlated with the proportions of Bis-GMA and TEGDMA in the resin and was close to 3-4μm. Thickness of OIL is very thin without inorganic fillers (3 or 4 μm). Inorganic fillers might be responsible of greater OIL in composite resins. Introduction Organic dental resins are commonly used in dentistry restoration. These materials are polymerized directly into the mouth under a light source. However, some problems remain like the existence of surface non polymerized layer. This phenomenon is due to oxygen which inhibits polymerization. A low polymerization led to poor mechanical properties, undesirable color and dimensional instabilities. In some cases, a low polymerization degree can appear as a useful characteristics and help linking together successive thicknesses of resin [1]. The biocompatibility of the final material can be affected [2] by release of formaldehyde for instance [3]. Typically, commercial dental composites are composed of a mixture of monomers like 2,2-bis [4-(2-hydroxy-3-methacryloxypropoxy) phenyl] propane (Bis-GMA) and triethyleneglycol dimethacrylate (TEGDMA) to adjust viscosity [4]. Initiators added to these dimethacrylate monomers mixtures initiate polymerization under a light source producing radicals. In the peculiar case of camphorquinone initiator, co-catalysts such as amines are needed to perform the polymerization [5-7]. Organic resins are more often filled (>80w.%) with different types of inorganic fillers like silica, borosilicate glasses, and strontium glasses to improve the resistance of the final composite (rigidity, hardness…).