Abstract: Objective To explore the polymerization efficacy of dual-cured fluid composite resin cores under different light irradiation conditions. Methods Three types of dual-cured fluid composite resin cores A( DC CORE ONE ), B（MultiCore Flow）and C（Rebilda DC）were filled into organic glass moulds, and then exposed to LED light-curing devices with two different light irradiation conditions, 1 000 mW∕cm2 continual exposure for 20 s and 3 200 mW∕cm2 continual exposure for 6 s. Each group included 6 specimens, with a total of 36 specimens. Nou’s microhardness of surface was detected at 15 min and 24 h post-curing to determine degrees of polymerization. After post-curing for 24 h, specimens were soaked in 100% ethanol for 24 hours and the percentages of reductions of hardness after soaking were recorded to compare cross-link density. Data were analyzed using paired t test and independent t test. Results After 24 hours’ post-curing，three types of materials all displayed increased hardness compared with that of 15 minutes’ post-curing when exposed to the same light irradiation condition, except for Material A, the difference in hardness of Material B and C were statistically significant ( P < 0.05 ). The hardness of the same materials for the same period, when exposed to light irradiation condition of 3 200 mW∕cm2 × 6 s was higher than 1 000 mW∕cm2 × 20 s, apart from Material B and C after 24 hours’ post-curing , the rest materials for the same period under different light irradiation conditions were statistically significant ( P < 0.05 ). After being soaked for 24 h in ethanol, Material B and C showed higher percentage of hardness reductions when exposed to condition of 1 000 mW∕cm2 × 20 s than that of 3 200 mW∕cm2 × 6 s. In contrast, Material A showed higher percentage of reductions when exposed to light irradiation condition of 3 200 mW∕cm2 × 6 s. Conclusion For dual-cured fluid composite resin cores materials, short-time super-intense light exposures conditions are feasible.

Key words: Flowable resion composites core, Dual cured, Light intensity, Microhardness