Degree of conversion and plasticization of dimethacrylate-based polymeric matrices: influence of light-curing mode.

This study analyzed the correlation between the degree of conversion (DC) and the plasticization (P) of experimental dimethacrylate-based polymeric matrices. Six polymeric matrices produced with Bis-GMA (G), UDMA (U) and TEGDMA (T) dimethacrylate monomers were studied: G, U, GT55, GT73, GU55, GU73 - (55 = 50/50wt% and 73 = 70/30wt%). Photoactivation was induced by camphoroquinone/ethyl N, N-dimethyl-4-aminobenzoate. The matrices were light-cured using two modes: Standard (S) - 850 mW/cm(2) for 20 s, and Gradual (G) - 100 up to 1000 mW/cm(2) for 10 s + 1,000 mW/cm(2) for 10 s. The degree of conversion (%) was obtained by using a FT-IR spectrometer equipped with an attenuated total reflectance crystal (ATR), and plasticization was estimated by the softening effect of ethanol. No correlation was found between the degree of conversion and plasticization (r = 0.32 / P = 82.35 +/- 0.85DC). The means of DC% were: GT55 (66.18 +/- 3.29) > U (59.34 +/- 5.61) > GT73 (54.97 +/- 7.89) > GU55 (50.60 +/-6.26) > GU73 (44.02 +/- 4.85) > G (38.25 +/- 3.35), (P < 0.05). The matrices with TEGDMA showed the highest plasticization. The light-curing mode influenced only G > S plasticization (P < 0.05).