Dentin extracellular matrix and dentinogenesis.

The formation of dentin involves secretion of matrix proteins by odontoblasts, prior to the deposition of apatite crystals. These matrix proteins probably play a role in transformation of predentin to dentin. The physical and chemical properties of dentin collagen, similar to those of bone, are especially adapted for binding matrix proteins and as a grid for mineral deposition. Phosphophoryns, polyanionic, and dentin-specific proteins are secreted at the mineralization front and are involved in some way in the mineralization process of circumpulpal dentin. Dentin sialoprotein is specifically made by odontoblasts and pulp cells and may be in the family of bone proteins known to promote cell attachment. Several proteins originally isolated from bone are also found in dentin and are expressed by odontoblasts. Although the mechanisms of dentinogenesis have not been elucidated, detailed studies of dentin matrix proteins should give valuable insights into this process.