Monomer Conversion in Dual-cured Core Buildup Materials

Objectives: To examine the impact of self-curing (SC) and light-curing (LC) mechanisms on the curing efficiency of dual-cured buildup restorative materials (DCB). Methods: The DCB materials tested were: Clearfil DC Core Automix (CD), Cosmecore DC (CM), LuxaCore DC (LX) and Multi Core DC Flow (MC). The SC material Clearfil Core New Bond (CN) and the LC material Clearfil Photo Core (CP) were used as controls. Specimens (empty set=4 mm, d=1 mm, n=4) of DCB materials prepared without light-exposure were tested after 10-, 20-, 30- and 60-minutes of storage in dark and dry conditions (37 degrees C), whereas DCB specimens light-cured immediately after mixing (20 seconds, 850mW/cm(2)) served as a reference. The amount of remaining C=C bonds (%RDB) was measured on the bottom specimen surfaces using ATR-FTIR, spectroscopy. One-way ANOVA and multiple comparison tests were used to evaluate the statistically significant differences (alpha=0.05). Results: Polymerization mode had a strong effect on the polymerization efficacy of the DCB materials (p<0.0001). The control materials (CN, CP) performed better than the DCB materials (p<0.0001), except for LX in the LC mode. LX and MC showed better SC conversion during the initial 20-minute period. After 60 minutes, the %RDB values of CM were still above 60%, whereas in CD and LX, they reached the level of LC specimens. Conclusions: The LC initiation mechanism of the DCB materials that were tested resulted in better C=C conversion when compared to their native SC mechanisms. The SC and LC control materials performed better than the DCB materials, with the exception of LX in the LC mode.