EFFECT OF PHOTOINITIATOR ON DEGREE OF CONVERSION OF UNFILLED LIGHT-CURED RESIN

In general, the concentrations of photosensitizer and reducing agent i n light-cured dental polymers are fixed by manufacturers for a specifi c product. These concentrations vary from product to product and the e ffect of photoinitiator concentration on the final network structures is not clear. Accordingly, the influence of varying concentrations of camphorquinone (CQ) and amine reducing agent, 2-(N, N-dimethylamino)et hyl methacrylate (DMAEMA), on the degree of conversion (DC) of an unfi lled light-cured resin was investigated. The resin consisted of 50 wt% triethyleneglycol dimethacrylate (TEGDMA) and 50 wt% yloxy-2-ethoxyca rbonylamino)-2,4,4-trimethylhexane (UDMA) activated with varying conce ntrations of CQ (0.25-5 mol.%) and DMAEMA(0.125-5 mol.%). At low CQ co ncentrations, the DC measured by a Fourier Transform Infrared (FTIR) s pectrometer increased rapidly with increasing concentration of DMAEMA and reached a plateau. At CQ concentrations of 0.5 mol.% and above, th e plateau DC values were approximately 75-77%. On the basis of the sys tematic variations of CQ and DMAEMA a contour representing the optimal combination of photoinitiator concentration from the standpoint of DC was established.