Abstract: BACKGROUND: H2O2 treatment had been proven to be effective for enhancing the bonding strength of fiber pile-resin, with a time-consuming process.  
OBJECTIVE: To compare the effects of pure H2O2 treatment or combined with ultrasonic cleaning of core piles with different durations on the interfacial bonding strength of fiber post-resin.
METHODS:  Totally 65 glass fiber posts were randomly divided into five groups (n=13 per group): group A: pure silanization treatment; group B: immersed in 30% H2O2 solution for 15 minutes and then received silanization; 30% H2O2 solution immersion with ultrasonic washing for 2 minutes (group C), 5 minutes (group D) or 15 minutes (group E), respectively, then received silanization treatment. The surface roughness and fiber fracture of each specimen were observed by scanning electron microscope. The PP plastic straw was used as the external plastic support, filled with resin bonding material and inserted into the processed fiber post to make the test piece. Three slices with a thickness of 1.5 mm were cut from each fiber post specimen by diamond grinder, which was used to conduct wafer rush-out test, and the fracture of the slices was observed under anatomic microscope.  
RESULTS AND CONCLUSION: (1) Scanning electron microscope: Resin materials on the surface of the group A were evenly distributed, with smooth surface and rare fracture. In group B, surface was rough, and a lot of broken glass fibers were observed; a large number of grooves were left after glass fiber fracture, and the inner part of the groove was relatively smooth. In group C, the surface of the fiber post was rough, with a small amount of broken glass fiber and remaining grooves, and the grooves were rough inside. The surface roughness of fiber post was greater in group D than that of group C, and a large number of broken glass fibers and remaining grooves were observed. The inner roughness of the grooves was relatively rough. The surface roughness of the fiber post in group E was similar to that in group D; and there were a large number of broken glass fibers and remaining grooves, while the interior of the grooves was smooth. (2) Push-out test results showed that the bonding strength of group C was significantly higher than that of groups A, B and E (P < 0.05), and that of group D was significantly higher than that of group E (P < 0.05), and the difference between the other groups was not significant (P > 0.05). (3) The fracture mode of the thin section in groups C and D was significantly different from that in group A (P  <  0.05). (4) The results showed that the fiber posts treated with 30% H2O2 combined with ultrasonic wash for 2 minutes could significantly improve the bonding strength of the fiber post-resin interface.

Key words: materials, oral cavity, fiber post, resin, surface treatment, bonding strength, hydrogen peroxide, ultrasonic vibration