Monomer conversion in a light‐cured dental resin containing 1‐phenyl‐1,2‐ propanedione photosensitizer

The efficiency of 1‐phenyl‐1,2‐propanedione (PPD) photosensitizer for the photopolymerization of a dental resin based on 2,2‐bis4‐(2‐hydroxy‐3‐methacryloxyprop‐1‐oxy)phenyl]propane/triethylene glycol dimethacrylate was assessed. Experimental formulations containing PPD or/and camphorquinone (CQ) in combination with dimethylaminoethyl methacrylate (DMAEMA), ethyl‐4‐dimethylaminobenzoate (EDMAB), 4‐(N,N‐dimethylamino)phenethyl alcohol (DMPOH) and N,N‐3,5‐tetramethylaniline (TMA) at different concentrations were studied. The photopolymerization was carried out by means of a commercial light‐emitting diode (LED) curing unit. Near‐infrared spectroscopy was used to follow the consumption of double bonds versus irradiation time. No significant differences in the conversion values among formulations prepared with PPD in combination with DMAEMA, DMPOH and TMA were found. In contrast, the conversion was markedly increased by the presence of EDMAB. At low concentrations of photosensitizer, when used in combination with DMAEMA and EDMAB, PPD resulted in a final conversion equivalent to CQ. However, when DMPOH and TMA were used, PPD was found to be less efficient than CQ. In addition, at high photoinitiator concentration, the effectiveness of PPD was less than that of CQ independently of the co‐initiator used. The replacement of some CQ by an equivalent amount of PPD resulted in similar final monomer conversion as formulations having the same amount of CQ alone. The LED light source employed emitted in the wavelength range 410–490 nm with a peak around 470 nm, whereas the maximum molar absorbance of PPD was in the UV region. However, the small overlap of the spectral distribution of the LED curing lamp and the PPD absorption spectrum was compensated by the large extinction coefficient of PPD. Copyright © 2007 Society of Chemical Industry