Abstract: Objective To compare the microleakage and microtensile bond strengths of glass ionomer cement sealant with or without acid etching in primary molars. Methods A total 24 second primary molars in vitro were randomly divided into two groups: the acid etching and the liquid conditioned groups. Both groups were placed in pit and fissure sealant with Ketac Molar Easymix glass ionomer by ART filling finger pressing technique. Then the microleakage and the microtensile strength tests were performed, the microsurface changes of enamel of the samples and the conditions of the section combination and interface of pits and fissures with sealant were observed by scanning electron microscope (SEM). Results The microleakage score in the acid etching group was lower than the liquid conditioned group with significant difference (P<0.05). The microtensile bond strengths of the acid etching and the liquid group were （0.93±0.40）MPa and (0.56±0.22)MPa, respectively, indicating significant difference between the two groups (P<0.05). SEM images showed that enamel surfaces presented topical etching pattern and the enamel and GIC interface revealed the hybridlikely layer in the acid etching sample. The continuous microgap was found between the enamel and GIC interface in the conditioner sample. Conclusion Acid etching produces microporous structure on the surface of enamel, which is conducive to improve GIC sealant penetration and the bonding with enamel structure and reduce microleakage.

Key words: primary teeth, glass ionomer cement, pit and fissure sealant, acid etching , microleakage, microtensile bond strengths