TEM morphological characterization of a one-step self-etching system applied clinically to human caries-affected...

To examine morphologically the hybrid layer of one-step self-etching adhesive, Clearfil S3 Bond (S3bond), in caries-affected dentin (CAD) and deep sound dentin (DSD) cavities performed clinically. For a comparative group, the two-step self etching adhesive Clearfil Protect Bond (Pbond) was used in a similar clinical situation.

This study was carried out on carious and sound teeth clinically selected for extraction. In carious teeth, CAD was obtained by way of subjective criteria by removing infected tissue to form a cavity bottom. DSD was obtained at a depth of 4 mm in the dentin cavity of sound teeth. S3bond and Pbond were applied in the CAD and DSD cavities as indicated by the manufacturer, followed by a composite restoration. Teeth were extracted about 20 minutes after the bonding procedure, and processed for TEM analysis.

Expression of S3bond in CAD was morphologically highly variable. When affected tubules were occluded by intratubular mineralized deposits, the interface displayed a dense poly-HEMA hydrogel as water sorption by the hydrophilic S3bond toward the porous affected collagen. Conversely, when tubules appeared empty, voids of various sizes were formed by tubular fluid shift. In DSD, S3bond clearly exhibited voids and water channels as signs of the high permeability of the sub-surface. Although porosities were somewhat retained, Pbond expression showed a hermetic character which was independent of the dentin substrate.