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

WALTER SCHROEDER; ARENAS GUSTAVO F.; VALLO CLAUDIA I.

POLYMER INTERNATIONAL

JOHN WILEY & SONS LTD

Año: 2007 vol. 56 p. 1099 - 1105

0959-8103

The efficiency of 1-phenyl-1,2-propanedione (PPD) photosensitizer for the photopolymerizationof a dental resin based on 2,2-bis[4-(2-hydroxy-3-methacryloxyprop-1-oxy)phenyl]propane/triethylene glycoldimethacrylate was assessed. Experimental formulations containing PPD or/and camphorquinone (CQ) incombination with dimethylaminoethyl methacrylate (DMAEMA), ethyl-4-dimethylaminobenzoate (EDMAB),4-(N,N-dimethylamino)phenethyl alcohol (DMPOH) and N,N-3,5-tetramethylaniline (TMA) at differentconcentrations were studied. The photopolymerization was carried out by means of a commercial light-emittingdiode (LED) curing unit. Near-infrared spectroscopy was used to follow the consumption of double bonds versusirradiation time. No significant differences in the conversion values among formulations prepared with PPD incombination with DMAEMA, DMPOH and TMA were found. In contrast, the conversion was markedly increasedby the presence of EDMAB. At low concentrations of photosensitizer, when used in combination with DMAEMAand 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 ofPPD was less than that of CQ independently of the co-initiator used. The replacement of some CQ by an equivalentamount of PPD resulted in similar final monomer conversion as formulations having the same amount of CQalone. The LED light source employed emitted in the wavelength range 410?490nm with a peak around 470 nm,whereas the maximum molar absorbance of PPD was in the UV region. However, the small overlap of the spectraldistribution of the LED curing lamp and the PPD absorption spectrum was compensated by the large extinctioncoefficient of PPD.