Dentin-predentin complex and its permeability: pathology and treatment overview.

This review paper focuses attention on tissue changes which may take place in dentin and on localized alterations in tissue formation in the predentin area. A number of reaction patterns has been described in dentin affecting both the inorganic and organic components. Dentinal tubules may become partly or completely obturated by growth of the peritubular dentin. Precipitation of mineral salts within the tubules, which may be a reprecipitation of minerals from adjacent demineralized dentin, represents a fundamentally different mode of obturation of dentinal tubules. Initially, demineralization selectively affects the peritubular dentin. If dentin is exposed to the oral environment, the surface layer may become hypermineralized. The surface layer of dentin, exposed by grinding, becomes covered by a smear layer. Displacement of the contents of the tubules or of the odontoblasts is a characteristic change in the organic components. Odontoblast destruction or degeneration will lead to a lack of, or reduced, predentin formation. Changes in the protein components which lead to alterations in dentin permeability have also been reported. The structure of the interface between dentin and localized formations of irregular secondary dentin varies considerably. If there is no tubular communication between primary and secondary dentin, the interface will act as an impermeable barrier. Changes in dentin, including irregular secondary dentin formation, affect the permeability of the tissue. Such changes are clinically important for the outcome of all types of restorative work performed on vital teeth.