Abstract: PURPOSE: To evaluate the polymerization of dual-cured flowable composite core irradiated by super-high intensity light with short time. METHODS: The light-proof silicon rubber cuboid mold with one end open was syringed and filled by dual-cured flowable resin composite core, then the open end of mold was irradiated directly by a light unit at 1000 mW/cm² ×10, ×20 s; or at 3200 mW/cm² × 3, ×6 s. The specimens were stored in the light-proof box. After irradiation for 1 h and 24 h, Knoop microhardness was measured along the vertical surfaces of specimens from 1mm to 10 mm depth at 1 mm interval. The data was analyzed by one-way ANOVA with SPSS 16.0 software package. RESULTS: 3200 mW/cm² ×3 s light irradiation did not initiate light curing of the specimens. The other three light irradiations could make specimens obtaining higher microhardness than that by pure chemical cure; however, the depth of specimens affected by light irradiation was limited. Within the area affected by light, the microhardness of specimens could be improved by increasing the light irradiation time; after irradiation for 24 h, the microhardness of specimens had no difference between 3200 mW/cm² ×6 s and 1000 mW/cm² ×20 s light irradiation. CONCLUSIONS: 3200 mW/cm² light intensity should be used for irradiation at least for 6 s, which could initiate light curing of flowable composite core to sufficient polymerization.

Key words: Light intensity, Irradiation time, Flowable, Composite core, Microhardness