Effect of photoinitiator on degree of conversion of unfilled light-cured resin.

In general, the concentrations of photosensitizer and reducing agent in light-cured dental polymers are fixed by manufacturers for a specific product. These concentrations vary from product to product and the effect 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)ethyl methacrylate (DMAEMA), on the degree of conversion (DC) of an unfilled light-cured resin was investigated. The resin consisted of 50 wt% triethyleneglycol dimethacrylate (TEGDMA) and 50 wt% 1,6-bis(methacryloxy-2-ethoxycarbonylamino)-2,4,4-trimeth ylhexane (UDMA) activated with varying concentrations of CQ (0.25-5 mol.%) and DMAEMA (0.125-5 mol.%). At low CQ concentrations, the DC measured by a Fourier Transform Infrared (FTIR) spectrometer increased rapidly with increasing concentration of DMAEMA and reached a plateau. At CQ concentrations of 0.5 mol.% and above, the plateau DC values were approximately 75-77%. On the basis of the systematic variations of CQ and DMAEMA, a contour representing the optimal combination of photoinitiator concentration from the standpoint of DC was established.