Dentin bonding: overview of the substrate with respect to adhesive material

The current challenge in adhesive dentistry is to develop dentin bonding systems that will reproducibly achieve high bond strengths similar to those obtained between resins and acid-etched enamel. Some of the limitations of dentin as a bonding substrate are that it changes its structure as it is prepared deeper, it is difficult to dry, and its smear layer is weak. Further, it is difficult to avoid contaminating proximal boxes with blood. Such contamination lowers dentin bond strengths to very low values. Decontamination of such dentin must be done prior to resin placement. The forces of polymerization contraction depend, in part, on the shape of cavities and how they are filled. Bulk filling of class I cavities can lead to conditions in which the forces of polymerization contraction exceed dentin bond strength with some materials and locations. The future development of resin systems that do not shrink on polymerization would eliminate many current problems in adhesive dentistry.