Methods: Embedded human molars were cut parallel to the occlusal surface, apical to the enamel-dentin junction. For the IDSt group, one-step, one-bottle bonding system (Clearfil S3 Bond, Kuraray) was applied and photopolymerized for 10s, followed by application of a thin layer of low viscosity composite resin (Protect Liner F, Kuraray) and 40s photopolymerization. For the modified IDSt group, a one-step, two-bottle bonding system (ED Primer, Kuraray) was applied followed by application of a thin layer of dual cure resin cement (Panavia F, Kuraray) and 20s photopolymerization. The conventional technique (control) group had no surface treatment. All dentin surfaces were covered with a temporary filling material (Cavit-G, 3M ESPE) and stored in 37°C water for seven days. After removing the temporary material a self-adhesive tape with two 1mm diameter holes was placed on each dentinal surface. Composite cylinders 1.6mmX1mm (HFO, Micerium) were cemented in the areas delineated by the holes using ED Primer and Panavia F. Photopolymerization followed. Each experimental group included ten cylinders (N=10). Specimens were stored in 37°C water for seven days. The micro-shear test was performed using a mechanical testing machine (Tensometer 10 Monsanto). Data was analyzed by one-way ANOVA (P<0.05).
Results: Mean bond strength values and standard deviations were: IDSt: 11.42±5.05MPa; modified IDSt: 9.07±4.76MPa; conventional technique: 6.61±3.30MPa. No statistically significant differences were observed. Inspection of fracture surfaces using an optical microscope at 50X magnification showed that failure mode for all groups was adhesive.
Conclusion: Using the selected bonding and cementing systems, the IDSt and a modified version for cementing composite cylinders provides no advantage in one-week micro-shear bond strength over the conventional technique.