Effect of conditioning time of self-etching primers on dentin bond strength of three adhesive resin cements

Objectives: To evaluate the effect of increasing the dentin conditioning time with self-etching primers of different aggressiveness (pH) on the microtensile bond strength (μTBS) of three resin cements. Materials and methods: Pre-cured composite blocks were cemented with M-Bond, Bistite II DC, or Panavia F to flat occlusal dentin surfaces of human third molars, which were conditioned with M-Bond or Bistite II-primer for 30, 60 or 180 s or with Panavia-primer for 60 or 180 s. Each dentin–composite block assembly (four in each group) was longitudinally sectioned to obtain 1×1 mm microbars and tested for the μTBS. The morphology of the conditioned dentin surface and the hybrid layer was examined with SEM. Results: Extending the primer conditioning time for Bistite II DC from 30 to 60 s significantly increased the μTBS (p<0.001), but did not further increase from 60 s to 180 s. For M-Bond there was only a significant increase from 30 to 180 s (p<0.05). For Panavia F the primer-conditioning time had no influence on the μTBS. SEM observations of conditioned dentin showed that the Bistite II DC and M-Bond self-etching primers with the lowest pH completely dissolved the dentin smear layer and plugs and formed well-defined hybrid layers. This was not found for Panavia F. Significance: Dentin bond strength of resin cements using more aggressive self-etching primers is improved by increasing the conditioning time. To enable resin infiltration of highly filled resin cements, sufficient smear layer dissolution is necessary.