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simultaneously etch and penetrate into demineralized dentin without application of separated etching and bonding
agents. Therefore, the bond strengths did not significantly decrease.
The etch-and-rinse system, Variolink II, had the highest technique sensitivity. After etching and rinsing,
moisture control had to be carefully performed to obtain a good bond strength. The limitation of accessibility and
visibility during the bonding procedure was an obstacle for good adhesion. Moreover, the Variolink II system
requires syntac adhesive application before resin luting. The syntac adhesive has no initiator, and it requires the
initiator for polymerization from the luting resin. Due to light energy limitation, the free radicals, which are the
initiators for polymerization procedure, were too small for both syntac and resin luting. Therefore, the adhesive
might not be adequately cured, resulting in poor bond strength, especially in the apical portion. The self-etch
system had less technique sensitivity compared with the etch-and-rinse system. However, the incompatibility
between uncured acidic monomers and dual cure luting resin might be the reason for lower bond strength of
Panavia F 2.0 (Ikemura K and Endo T 1999).
Analysis of failure modes was presented in Table 2; the most fractured specimens failed at dentin-
cement interfaces. Cohesive failure within the bonding substrate was rare. It indicated that the bond strengths to
root canal dentin were weaker compared with the cohesive strengths of the cement or dentin.
Table 2
. Failure modes
Failure mode (%)
Luting agent
Adhesive
dentin/cement
Adhesive
post/cement
Cohesive
cement
Cohesive
dentin
Cohesive post
Variolink II
27(90.00)
0
3(10.00)
0
0
Panavia F 2.0
27(90.00)
1(3.33)
2(6.67)
0
0
RelyX Unicem
29(96.67)
1(3.33)
0
0
0
Conclusions
Within the limitation of this study, it can be concluded that the bond strengths of fiber post to root canal
dentin using various resin-based luting agents were affected by the type of resin-based luting agent and the region
of post space. The highest push-out bond strength was obtained from the RelyX Unicem luting agent. The regional
differences in bond strength were presented for all groups except RelyX Unicem.
Acknowledgements
The author wishes to thank Mrs. Chanya Chuenarrom for her assistance with the universal testing
machine, and Mr. Pornpot Nuthong and Mrs.Apinya Sukolrat for their assistance with the SEM. Particularly, I am
grateful to Faculty of Graduate Studies, Prince of Songkla University, Thailand, for supporting financial to part of
my research.
