Bond strength of two glass-fibre post systems in root canals

Objectives: To compare the bond strengths, measured by a push-out test, of two glass-fibre post systems: pre-fabricated RelyX™ Fiber Post (PR) and custom made everStick® (CE) post, cemented with a self adhesive composite (SC, RelyX™ Unicem), and a glass-ionomer (GI, AquaCem®) luting cement.

Methods: Forty non carious, single rooted human teeth were decoronated at the cemento-enamel junction. The pulpal tissues were removed and the canals were prepared using the RelyX™ Fiber Post drills (1.3 – 1.6mm). The teeth were divided into 4 equal groups and the canals were filled with the posts and cements as follows: CE+GI; CE+SC; PR+GI; PR+SC Each post cemented root was then sectioned horizontally into three ~2mm thick slices (n=30). The post portion in each slice was subjected to vertical load using a tensile testing machine (JJ Instrument T30K) with a push-out rod of 1mm diameter at a crosshead speed of 1mm min-1 until bond failure occurred between the post and the internal root surface. The shear bond strengths were calculated and the Student's t-test was used to compare the results between groups using a significance level of p≤0.05.

Results: The mean bond strength (±sd) for each group were: CE+GI– 0.61 (±0.68); CE+SC- 1.62 (±1.50); PR+GI – 3.53 (±2.06); and PR+SC – 3.62 (±4.05) MPa. The bond strength of CE was significant lower than that of PR irrespective of cement used. In the CE system, the bond strength was significantly higher with the composite cement. However, the type of cement had no significant influence on the bond strength in the PR system.

Conclusions: The higher bond strength of the pre-fabricated glass-fibre post system may be due to its matching drill size. Glass ionomer cement should not be used with the custom made glass-fibre post system.

We acknowledge our thanks to 3M ESPE and Stick Tech for supplying the materials.