Effect of posts treatment on bond strength to composite cores

Objectives: Aiming effective bond between fiber posts and composite resin cores, this study tested the hypothesis that the surface treatment of glass and carbon fiber posts influences on bond strengths to composite resin cores.

Methods: It was employed glass fiber (Gf) and carbon fiber (Cf) posts (n= 15) associated with 5 surface treatments (t) resulting 10 groups (n=6): t1- cleanness with alcohol 70%; t2- immersion in 10% hydrogen peroxide for 20 min; t3- immersion in 24% hydrogen peroxide for 10 min; t4- immersion in 4% hydrofluoric acid for 1 min; t5- immersion in phosphoric acid 37% for 30s. After the treatments the silane-coupling agent was applied for 1min. The posts had been located in a matrix for incremental insertion of composite resin that was photoactivated for 40s (800mW/cm2). Samples were sectioned perpendicularly to the post in 4 slices of 1,5 mm of thickness resulting in 24 slices for group, which were submitted to push-out test with 0.5 mm/min.

Results: The factorial analysis of bond strength (2x5) showed interaction between the factors. Values in MPa were: Gf: t2-14.37(1.28)a; t4-13.87(2.21)ab ; t3-13.51(3.31)ab; t1-10.79(2.49)bc; t5-9.77(3.76)c; Cf: t5-16.22(3.51)a; t3-13.77(3.42)ab; t2-13.28(2.23)ab; t1-12.68(2.23)bc; t4-9.58(2.26)c. The behavior between posts was different only in the treatment t4 where Gf presented higher bond strength than Cf and in the treatment t5 where Cf presented higher bond strength than Gf.

Conclusion: It can be concluded that should be avoid the use of t5 for Gf and t4 for Cf, and that the influence of the surface treatment is related to the type of post used.