[Frontiers in Bioscience E3, 711-735, January 1, 2011]

Dentin: Structure, Composition and Mineralization

Michel Goldberg1, Askok B. Kulkarni2, Marian Young3, Adele Boskey4

1UMR-S 747, INSERM, Universite Paris Descartes, 75006 Paris, France, 2Functional Genomic Section, Laboratory of Cell and Developmental Biology, NIDCR/ NIH Department of Health and Human Services Bethesda, MD, Maryland, 3Craniofacial and Skeletal Diseases Branch, NIDCR/NIH , Bethesda, MD, Maryland, 4Starr Chair in Mineralized Tissue Research, Hospital for Special Surgery and Weill Medical College of Cornell University, USA.

TABLE OF CONTENTS

1. Abstract
2. Introduction
3. Dentin: Structure and ultrastructure - the three-compartments model
3.1.Peripheral outer layers
3.2. Circumpulpal dentin
4. Odontoblasts: Implication in the synthesis, secretion and mineralization of dentin ECM
4.1.Odontoblasts and dentin formation
4.1.1.From the pre-odontoblasts to pre-secretory polarizing odontoblasts
4.1.2.Odontoblasts differentiate and become functional
4.1.3.The functional odontoblasts: Synthesis and secretion of extracellular matrix components
4.1.3.1. Collagen
4.1.3.2.Phosphorylated proteins
4.1.3.3. Glycosaminoglycans and proteoglycans
4.2. Intercellular pathway: Phospholipids and albumin as lipid carrier, calcium transfer
5. Global composition of the extracellular matrix
5.1. Mechanisms of dentin mineralization: How ECM molecules contribute to the formation of a mineral phase
5.2. ECM molecules implicated in dentinogenesis
5.2.1. Genes coding for dentin ECM
5.2.2. Type I Collagen
5.2.3. Non-collagenous molecules
5.2.3.1. SIBLINGs
5.2.3.1.1.DSPP and daughter molecules after cleavage
5.2.3.1.1.1. DSP
5.2.3.1.1.2. DGP
5.2.3.1.1.3. DPP
5.2.3.1.2. DMP-1
5.2.3.1.3. BSP
5.2.3.2.Other dentin ECM proteins
5.2.3.2.1.Phosphorylated ECM molecules
5.2.3.2.1.1.Osteopontin OPN
5.2.3.2.1.2. MEPE/OF45 (osteoregulin)
5.2.3.2.2. Non-phosphorylated ECM molecules
5.2.3.2.2.1. Osteocalcin OC
5.2.3.2.2.2. SPARC
5.2.3.2.2.3. Ca++-binding proteins and enzymes
5.2.4.Proteoglycans (PGs)
5.2.4.1. Small Leucine-rich proteoglycans (SLRPS)
5.2.4.2. Large aggregation chondroitin/keratan sulphate family members in dentin: versican
5.2.5. Phospholipids and proteolipids
6.Conclusions
7. Acknowledgements
8. References

1. ABSTRACT

We review firstly the specificities of the different types of dentin present in mammalian teeth. The outer layers include the mantle dentin, the Tomes' granular and the hyaline Hopewell-Smith's layers. Circumpulpal dentin forming the bulk of the tooth, comprises intertubular and peritubular dentin. In addition to physiological primary and secondary dentin formation, reactionary dentin is produced in response to pathological events. Secondly, we evaluate the role of odontoblasts in dentin formation, their implication in the synthesis and secretion of type I collagen fibrils and non-collagenous molecules. Thirdly, we study the composition and functions of dentin extracellular matrix (ECM) molecules implicated in dentinogenesis. As structural proteins they are mineralization promoters or inhibitors. They are also signaling molecules. Three different forms of dentinogenesis are identified: i) matrix vesicles are implicated in early dentin formation, ii) collagen and some proteoglycans are involved in the formation of predentin, further transformed into intertubular dentin, iii) the distal secretion of some non-collagenous ECM molecules and some serum proteins contribute to the formation of peritubular