Degree of Conversion of dual-cured resin cements and filler content

Purpose: The purpose of this study was to evaluate the degree of conversion (DC) of 2 resin cements following storage at 37°C immediately after light-curing and at 24h, 48h & 7 days. Methods: Twenty specimens were made in a metallic mold (8 mm diameter x 1 mm thick) from each of 2 cements, Panavia F2.0 (Kuraray) (PV) and RelyX-Unicem Applicap (3M/ESPE) (RU). Each specimen was cured with LED light (LEC 1000, MM Optics) with power density of 500 mW/cm2 for 30s. Immediately after curing, 24h, 48h & 7 days DC was determined. For each time interval 5 specimens were pulverized, pressed with KBr and analyzed with FT-IR (Bomen). Data were analyzed with ANOVA and Tukey's tests at (p<.05). Filler content by weight was determined by thermogravimetric analysis (TG) for the two cements. TG measurements were performed in Netzsch TG 209 under oxygen atmosphere and heating rate of 10 ºC/min from 25 ºC to 700 ºC. Results: Means and standard deviations (±SD) for DC (%) were: RU/Immediate: 62 (±4); RU/24h: 63.8 (±2.9); RU/48h: 66.2 (±2.7); RU/7d: 70.2 (±2.7); PV/Immediate: 40.7 (±1.5); PV/24h: 46.4 (±2.5); PV/48h: 45.4 (± 2.8); PV/7d: 48.5 (±1.9). ANOVA revealed significant differences in DC between the two cements (p<.05). However, no significant differences in DC were detected for specimens tested at 24h and 48h for both cements (p>0.05). Percentages of fillers by weight were 73% for PV and 70 % for RU. Conclusions: RU had significantly higher DC than PV at all test intervals. DC increased significantly after one-week of storage for both cements. Both cements had high inorganic filler content. Acknowledgements: 3M and Kuraray.