Objective To evaluate the effects of a bleaching gel and a whitening strip on the microleakage of three different glass-ionomer cements. Methods Forty-five freshly extracted human premolars were used and class Ⅴ cavity was prepared on the buccal and lingual surfaces. The teeth were randomly assigned to A, B and C groups and restored as follows: Conventional strengthen glass-ionomer cement（KetacTM Molar Easymix）, compomer（F2000） and compomer （Dyract AP）. Teeth were kept in distilled water at 37 ℃ for 7 days. Then the specimens were thermocycled for 500 times. Each group was randomly divided into 3 subgroups which were treated for 21 days with one of the following: Whitening strip（14% hydrogen peroxide）, bleaching gel（10% carbamide peroxide）, or distilled water（control）. After bleaching, the teeth were placed in a solution of basic fuchsin dye for 24 hours, then the teeth were sectioned longitudinally to evaluate the dye penetration. The depth of staining along the tooth restoration interface was recorded with a stereomicroscope. Results There were no signicant differences between the two bleaching agents in microleakage of restorations（P>0.05）. The two bleaching agents did not significantly affect the microleakage of compomer（P>0.05）, whereas the microleakage of glass-ionomer cement in the experimental groups was higher than that in the control group （P
