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 (muTBS) 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 1x1 mm microbars and tested for the muTBS. 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 muTBS (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 muTBS. 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.