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Parameters affecting degree of conversion of dual-cure resin cements in the root canal: FTIR analysis.

OBJECTIVE
To evaluate the degree of conversion of dual-cured resin cements applied for luting of translucent and opaque fibre posts.


METHODS
Two dual-cured resin cements, RelyX ARC and Nexus 2, were used to cement 2 types of tooth-coloured fibre posts, D.T. Light-Post (translucent) and D.T. White-Post (opaque). The degree of conversion for each resin cement was measured. Post-curing polymerization and chemical curing of the cements were also measured. The degree of conversion was measured at various distances (4, 6 and 8 mm) from the tip of the light-curing unit by Fourier transform infrared spectroscopy. The data were analyzed with analysis of variance and post hoc tests (α = 0.05).


RESULTS
The degree of conversion of the dual-cure cements was significantly higher with the D.T. Light-Posts than with the D.T. White-Posts (p < 0.05). No significant difference was observed in the degree of conversion at different depths for the RelyX ARC resin cement in conjunction with the D.T. Light-Posts (p > 0.05). The overall degree of conversion decreased linearly with increasing distance from the light-curing tip. Monitoring of post-curing polymerization and chemical curing revealed no further increase in degree of conversion after 5 minutes (p > 0.05).


CONCLUSION
The translucent fibre posts (D.T. Light-Posts) allowed a significantly higher degree of conversion with dual-cure resin cements than the opaque fibre posts (D.T. White-Posts) because of the light-transmitting property of their optical fibres.