Resin-Bond to Root Dentin: Effect of Prolonged Application Times

Objective: To evaluate the effect of prolonged application times of adhesive system on the bond strength of fiber post luted to root dentine. The hypothesis was that the bond strength is influenced by the application times of the adhesive system. Methods: The canals of ninety single-root bovine roots (16mm in length) were prepared at 12mm using the preparation drill (FGM, Brazil). 14 mm of each root was embedded with acrylic resin and the specimens were allocated into nine groups (n=10), considering the factor “adhesive” (3 levels) and “application times of the adhesive” (3 levels): Gr1-Scotchbond Multipurpose Plus - SBMP(3M ESPE)+40s (control), Gr2-SBMP+90s, Gr3-SBMP+150s, Gr4-One Step-OS (Bisco)+40s (control), Gr5- OS+90s, Gr6- OS+150s, Gr7- Excite DSC- ED (Ivoclar Vivadent)+40s (control), Gr8- ED+90s, Gr9- ED+150s.The adhesive systems were applied according to the manufacture's recommendations. The fiber-posts (White Post DC, FGM) were luted (All-Cem, FGM) and light-cured (40s). After, the cores with composite-resin (Llis, FGM) were made and each set of root/post/core was submitted to the mechanical cycling (Erios, Brazil), during 1,000,000 cycles (84N, 4 Hz, inclination of 45º, water, 37ºC). Each specimen was cut in 4 samples (1.8mm in thickness), which were submitted to the push-out test in a universal testing machine (EMIC) (50Kgf, 1mm/min). The data (MPa) were analyzed using ANOVA (2-way) and Tukey test (5%). Results: The factor “adhesive” (p=0.0081) influenced the bond strength significantly, but the factor “time” (p=0.54) did not influence the bond strength significantly (ANOVA 2-way). When the factor “adhesive” was analyzed, the SBMP-groups (6.0±2.2 MPa)a presented higher bond strength values than the OS (3.7±2.1 MPa)b and similar to ED (4.4±3.4)a,b. Moreover, OS and ED were similar between them (Tukey test). The hypothesis was not accepted. Conclusion: The prolonged application times of the adhesive system does not affect the bond strength of fiber post luted to root dentine.