Effect of pulpal pressure on the microtensile bond strength of luting resin cements to human dentin

Abstract 

Objectives

The objectives of this study were to examine the effect of pulpal pressure on the microtensile bond strength (mTBS) of luting resin cements to human dentin and the permeability of dentin surfaces pre-treated with an adhesive and a self-etching primer.

Methods

Cylindrical composite blocks were luted with resin cements (RelyX ARC, 3M ESPE: ARC; Panavia F, Kuraray Medical Inc.: PF; RelyX Unicem, 3M ESPE: UN) in the absence or presence of simulated pulpal pressure. The application of Adper Single Bond 2 (3M ESPE) and ED primer 2.0 (Kuraray) was performed under 0cm H₂O. After each resin cement was applied, the pulpal pressure group was subjected to 20cm H₂O of hydrostatic pressure for 10min during the initial setting period. Testing for mTBS was performed on 0.9mm×0.9mm sectioned beams after 24h water-storage. Scanning electron microscopy was performed to investigate the fractured surfaces after mTBS testing and additional dentin surfaces that were treated by an etchant, ED primer 2.0 and UN. Fluid permeability was measured on dentin surfaces that were applied with Adper Single Bond 2 and ED primer 2.0.

Results

Application of pulpal pressure reduced mTBS significantly in groups ARC and PF. Porous bonding interfaces due to water permeability through the cured adhesive were observed on fractured surfaces. Dentin surfaces that were applied with the adhesive and the primer were more permeable than smear layer-covered dentin. The mTBS of UN was significantly lower than ARC and PF regardless of the absence/presence of pulpal pressure.

Significance

Fluid permeation during the initial setting period deteriorated the bonding quality of resin cements.

Keywords: Resin cement, Permeability, Pulpal pressure, Microtensile bond strength, SEM, Fractography