Objective To compare the microleakage of compomer sealant with non - rinse conditioner and resin sealant with phosphoric aci（d 35%）by dye test and scanning electron microscop（e SEM）observation. Methods 16 extracted third permanent molars were divided into 4 groups: Group Ⅰ, non- rinse condition（er NRC）+ Prime & Bond NT+ Dyract seal; Group Ⅱ, phosphoric acid（ 35%）+ Concise sealant; Group Ⅲ, phosphoric acid（ 35%）+ Dyract seal; Group Ⅳ, NRC+Prime & Bond NT+Concise sealant. The teeth were then coated with nail polish, placed in a 50% AgNO3 dye for 18 hours, and sectioned with a diamond saw. SEM observation was performed to evaluate microleakage in the teeth. Results Silver nitrate penetration was found in each group. The percentage of microleakage in group Ⅰ was higher than that in group Ⅱ, and group Ⅳ was higher than that in group Ⅱ（ P
