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Figure 6. Modified SEM illustration of bonding to dentin with conventional (three-step) total-etching adhesives. (A) Acid etching of the dentin. The smear layer has been removed, and both peritubular and intertubular dentin is demineralized. The exposed collagen fibers are highly hydrophilic (blue) and particularly sensitive to dehydration. (B) Priming of the dentin. The water has been replaced by hydrophilic primers (orange) which have impregnated the collagen fibers. Priming with water-based primers is a slow diffusing process. The evaporation of the water solvent will leave the collagen fibers coated and stiffened by the resins. The substrate has changed from hydrophilic to hydrophobic. (C) Application of the adhesive resin. The hydrophobic resin (red) diffuses into the dentinal tubules and impregnates the entire depth of the demineralized dentin before being polymerized.
