Permeability of dentin to adhesive agents

The permeability of dentin to adhesive agents is of crucial importarice in ohiaining good dentinal bonding. In those systems that remove the smear layer, the opportunity exists for resin to infiltrare both tubules and intertubular dentin. Resin penetration into tubules can effectively seal the tubules and can contribute to bond strength if the resin bonds to the tubule wall. Resin infiltration into intertubular dentin can only occur if the mineral phase ofdetitin is removed by acidic conditioners or chelators. This is more easily accomplished in fractured dentin than in smear layer-covered dentin because oJ the residual collagen debris that remains on the surface following acid etching of smear layers. The channels for resin infiltration are the perifibrillar spaces created around the collagen fibers of dentin following removal of apatite mineral hy acids. The diffusion of adhesive resi)is through these narrow, tortuous, long channels in 1 to 2 minutes offers a number of challenges that require further research.