Observation of oxygen inhibited layer of organic dental resin by confocal Raman-microscopy

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.