Micropermeability of Adhesives Applied to Water or 100% Ethanol-saturated Dentin

Objectives: The aim of this study was to evaluate the micropermeability of 5 experimental resins and 1 commercial adhesive applied on etch-and-rinsed water or 100% ethanol-saturated dentin.  Methods:  Extracted human third molars were ground flat and acid-etched for 15s with 37%PA.  There were two groups: water-wet dentin (n=36) or 100% ethanol-saturated dentin (n=36).  Each group was further divided into 6 sub-groups based on the tested adhesives (n=6/each).  Ethanol-saturation of dentin was achieved by immersion in absolute ethanol for 5 min. Two coats of each experimental primer (50 wt% ethanol/50% resin) were applied followed by a layer of each respective neat resin that was then light-cured. SingleBond-Plus was applied per manufacturers' instructions.  Composite build-ups (5-mm) were constructed with a flowable composite. The pulp chamber of each bonded specimen was then filled with Lucifer-Yellow in water and placed under 20 cm H₂O pressure for 3 hrs to evaluate the micropermeability of the bonded interface.  After longitudinally sectioning the bonded teeth into 0.5 mm thick slabs, two-photon microscopy was performed using a Zeiss Model 510 CLSM  to quantify the intensity of the fluorescence emission of the Lucifer-Yellow taken up by the hybrid layer. The results were analysed by a 2-way ANOVA and Sidak's test. Results: All adhesives applied to water-wet dentin showed high levels of micropermeability. The highest leakage was obtained using the experimental hydrophobic resins with values of intensity emission of 1876±178 vs 530±86 for ethanol-saturated hydrophobic resins (p<0.05). Conclusion: High micropermeability was seen when the adhesives were applied onto water-wet dentin. Ethanol-saturated dentin permitted better infiltration of all resins and significantly reduced the micropermeability of all the adhesives tested in this study (p<0.05).  Supported, in part, by grant R01 DE014911 from the NIDCR to DHP (PI) and by the Dickinson USA fund of King's College London Dental Institute.