Objective To compare the hardness development of dual-cured self-adhesive and universal resin cement in simulated root canal. Methods The light-proof half-cylinder steel slot with one end open were syringed and filled respectively by self-adhesive A（RelyX Unicem）, B（BisCem） and universal C（DUOLINK） resin cements, then the open end of slot was irradiated directly by a light unit for 20 s. Specimens were stored in a light-proof box for 0.5 h, Knoop microhardness was measured along the vertical surfaces of specimens from 1 mm to 10 mm depth at 1 mm intervals. The same measurements were taken at 24 h and 120 h after irradiation. Data were analyzed by One-way ANOVA. Results Hardness of each group decreased with the increase of simulated canal depth（P
