Abstract: Objective　The effects of four surface treatment methods and the depth of root canal on the adhesive strength of glass fiber posts were compared. Methods　25 single-root premolars were randomly divided into five groups after conventional root canal therapy.Surface treatment of 25 popo Fiber piles:group A(untreatedl ),group B（H2O2），groupC（ silanization），group D（HF），group E（sodium ethoxide）.he fiber post was bonded into the isolated root canal and made into thin pieces. According to the depth of root canal, the specimen was divided into three subgroups: upper root, middle root and lower root，and use Microlaunch test to test bonding strength.Observation of the appearance and Morphology of Fiber piles in each Group under scanning Electron Microscopy. Results　The adhesive strength of fiber posts is :group B>group D>group E>group A,and the differences among groups are significant（P<0.05）.There was no significant difference between group C and group A(P>0.05). The bonding strength of fiber pile at different depths of root canal is as follows: upper root> middle root >lower root.Sem observation showed that the surface morphology of the treated groups was higher than that of the control group.Conclusions　H2O2,HF and sodium ethoxide can significantly improve the bonding strength of glass fiber posts;With the increase of root canal depth, the adhesive strength of fiber posts decreases gradually.

Key words: fiber post, surface treatment, bond strength