Effect of indirect-post placement on bonding to root canal dentin

Objectives: To evaluate the effect of placement of indirect composite post into root cavity on the microtensile bond strength of a dual-cure resin core material with or without light-curing. Methods: Twelve extracted human premolars were decoronated at the cementoenamel junction, and post spaces were prepared to a depth of 8mm and a diameter of 1.5mm in the roots.  A one-step dual-cure adhesive (Unfil Self-etching Bond) with chemical curing mode was applied to the root canal dentin in post space according to manufacturer's instruction.  A dual-cure resin core material, Unifil Core (GC, Japan), was filled in post spaces with or without placement of pre-polymerized indirect composite post (diameter 1.0mm), and then light-cured by 10s irradiation from the top of the cavity or chemical-cured by placement in darkness for 30min.  After storage in water at 37^oC for 24h, each specimen was serially sliced perpendicular to the bonded interface into eight beams (0.6mm x 0.6mm, 4coronal & 4apical regions), and then subjected to the microtensile bond strength (µTBS) test. Data were analyzed using a three and two-way ANOVA (p<0.05).  Results: Values are in MPa±S.D. (n=12).  Groups identified by the same superscript letter are not significantly different. (p>0.05)

Conclusion: In all experimental groups, there were no significant differences in the µTBS between the apical and coronal regions. When chemical-curing, the placement of composite post did not affect the µTBS to root canal dentin. On the other hand, when light-curing, the placement of composite post significantly decreased the µTBS.