Effect of Irrigation Solutions on Bond Strength of Fiber Posts

Objectives: To evaluate the effect of endodontic irrigants on the bond strength and resin tag formation of fiber posts cemented with resin cement. Methods: Fifty-two human anterior teeth were stored in 1 % sodium azide. The crowns were sectioned 2 mm incisal from the CEJ. Endodontics was performed using 6.15 % NaOCl during instrumentation and a final flush with 17% EDTA. Root canals were obturated with gutta percha and sealer. Teeth were assigned into four groups for post space rinsing (n=13): Group 1- 6.15% NaOCL; Group 2- 17% EDTA; Group 3- 6.15 % NaOCl + 17% EDTA; Group 4 - 6.15% NaOCl + 0.12% Chlorhexidine. Parallel-sided fiber posts were cemented with self-adhesive resin cement and samples were embedded in a PVC mounting jig for sectioning. Cervical and apical sections, were subjected to a push-out test using an Instron and failure mode was analyzed. One tooth from each group was cut longitudinally for SEM evaluation of the dentin surface. Results: Group 2 had the highest bond strength, (18.63±2.85 MPa cervical; 13.49±3.67 MPa apical) and was significantly higher than other groups. Cervical specimens in Group 3 had the next highest bond strength (11.22±4.55 MPa). Group 1 had the lowest bond strengths, 5.93±2.33 cervical and 5.18±1.53 apical. Cervical specimens of Groups 2 and 3 were significantly different than their apical specimens, however, Groups 1 and 4 were not. Adhesive failure was the main failure mode in all groups. Groups 2 and 3 showed better resin tag formation, while Groups 1 and 4 showed less resin tag formation Conclusions: Irrigation with 6.15% NaOCl reduced the bond strength of cemented fiber posts. Post spaces irrigated by 17% EDTA produced higher bond strength and more distinct resin tag formation.

 Partially funded by Delta Dental Fund of Michigan