The mean tensile bond strengths for the various subgroups are illustrated in Fig. 4. Mean tensile bond strengths ranged from 0.07 MPa (Apexit (AP)) to 1.19 MPa (AH Plus (AH)). AH had the highest bond strength amongst the sealers investigated. The differences in bond strength between the other sealers were not statistically significant.
Removal of the smear layer with EDTA significantly reduced, rather than increased, the adhesion of AH (P < 0.01) and of AP (P < 0.05). The adhesion of Roeko-Seal Automix (RS) and Ketac-Endo (KE) was not influenced by dentine pretreatments significantly. The use of a primer with RS significantly enhanced its adhesion incase of untreated dentine (P < 0.001) (Fig. 5).However, no significant difference was found when the primer was applied to dentine pretreated with EDTA or acids. The bond strength of Grossmanâ€™s sealer (GS), on the other hand, was significantly increased when dentine had been pretreated with phosphoric acid (P < 0.01).
Inspection of fractured surfaces revealed the bond failure to be mainly adhesive to dentine for GS and RS, and mainly adhesive to gutta-percha for KE. The failure appeared to be predominantly cohesive with in the sealer for AP, with some areas debonding in the sealer-dentine interface. For AH, the failure was mainly cohesive within the sealer (Fig. 3A).When the primer was applied, the failure for RS in case of untreated dentine was adhesive to gutta-percha (Fig. 3C), whilst that to pretreated dentine was adhesive to dentine.
Figure 3. Stereomicrographs of debonded surfaces (magnification x25). Left, gutta-percha surface; right, dentine surface.
(A) Cohesive Failure with sealer left on both surfaces; AH, no pretreatment.
(B) Adhesive failure to dentine; AP, EDTA pretreatment.
(C) Adhesive failure to gutta-percha; RP, no pretreatment.
Figure 4. Mean tensile bond strengths (MPa) of root-canal sealers when applied as a thin layer between gutta-percha and dentine pretreated with different solutions.
Figure 5. Mean tensile bond strengths (MPa) of RS when applied as a thin layer between gutta-percha and dentine pretreated with different solutions.