Odontoblasts

The major non-collagenous components of the dentin matrix are highly-phosphorylated proteins, phosphoryns, with many phosphoserine and aspartate residues (Butler et al., 1992). Dentin contains fewer proteoglycans than predentin. The proteoglycans from predentin are degraded upon mineralization, while small proteoglycans and phosphoryns are excreted by odontoblasts and incorporated into dentin (Goldberg et al., 1987 Linde, 1989). 

Alliot Licht B, Bluteau G, Magne D, Lopex Cazaux S, Lieubeau B, Daculsi G and Guichenx J (2005). Dexamethasone stimulates differentiation of odontoblast-like cells in human dental pulp cultmes. Gell Tissue Sep 321(3) 391 400. 

The effect of fluoride on odontoblast seems to follow similar pathways however, fluoride does not seem to show any effect on the proliferation of ameloblast cells. In addition to direct biological effects, fluoride ions may also exhibit indirect effects related to the decrease in Calcium concentration they can involve, and the change in the surface properties of biological apatites. 

M. Inoue, R.Z. LeGeros, M. Inoue, H. Tsujigiwa, H. Nagatsuka, T. Yamamoto, N. Nagai, In vitro response of osteoblast-like and odontoblast-like cells to unsubstituted and substituted apatites, J. Biomed. Mater. Res. 70A (2004) 585-593. 

The odontoblasts secrete an extracellular matrix that is rich in collagen I and which also contains all of the other major bone proteins as well as a dentin sialoprotein and poorly characterized phosphate carriers, the phosphophoryns. 

Linde, A. Glycosaminoglycans of the odontoblast-predentine layer in dentinogenically active porcine teeth. Calc. Tiss. Res. 12, 281-294 (1973). 

Mineralization takes place in intimate association with the collagen framework, as well as in matrix vesicles that bud off the odontoblast processes. The very first dentin to mineralize (mantle dentin) contains a relatively large proportion of matrix vesicle derived mineral [31], whereas in the bulk of the dentin, most of the mineral is associated with collagen. The collagen fibril structure is therefore the key to understanding dentin structure and mineralization. Its main features are schematically depicted in Fig. 1.7d. We assume below that the basic characteristics of dentin collagen mineralization are the same as those for bone. 

Odontoblasts more or less columnar cells on the outer surface of the pulp of a tooth specialized cells that contribute to many aspects of tooth structure and function. They give rise to the dentine matrix that underlies the enamel of a tooth Otoliths earstones, are small calcareous structures found in the head of all bony fishes (other than sharks, rays, and lampreys)... 

Dentine is the first calcified tissue to be deposited during tooth embryogenesis by the odontoblasts lining the inner pulp chamber. Odontoblasts lay down the dentinal organic matrix, and the dentine formation proceeds inwards. The mineralization begins when an organic layer of about 10-20 pm thick was deposited, and only cells process encased in the dentinal tubules are present in dentine. 

Several theories have been advanced to explain the mechanism of dentinal hypersensitivity innervation of the dentinal tubules, permitting transmission of impulses to the pulp, or the presence of lymph fluid in the dentinal tubules. In the latter case, exposure of dentin results in increased colloidal pressure on the tubules (thereby increasing pressure on the odontoblastic cells). Also proposed is a hydrodynamic... 

Irving, J.T., 1958a. Sudanophil inclusions in ameloblasts, odontoblasts and cells of the oral epithelium. Nature, 181 569—570. 

Intramembranous ossification is responsible for most of the mineralization of the skull, including the maxilla and mandible. It begins with the differentiation and activation of osteoblasts from fibroblast-related precursors within a region of connective tissue that demarcates where the bone will develop. The osteoblasts secrete a nonmineralized protein-rich (osteoid) matrix and, as they move away, the matrix mineralizes (Fig. 9.3a). The periosteum remains uncalcified and contains latent and undifferentiated osteoblasts for bone remodeling. Odontoblasts (Ob) and cementoblasts secrete an osteoid-like matrix similar to that of intramembraneous ossification. 

Teeth develop from tooth buds, an aggregation of cells derived from the ectoderm of the first branchial arch and ectomesenchyme of the neural crest. The tooth bud is divided into enamel organ (EO), dental papilla (DP), and dental follicle. An enamel organ has four layers outer and inner enamel epithelium, stratum intermedium (SI), and stellate reticulum (SR). The inner enamel epithelium induces the development of odontoblasts from the opposing mesenchymal cells of the dental papilla. As dentin forms, the inner enamel epithelium becomes converted to ameloblasts (Fig. 9.9). 

A portion of the dental papilla (DP) shows odontoblasts (Ob) adjacent to early dentine (D). E enamel, DF dental follicle outside the outer epithelium, AB alveolar bone. Scale bar = 70 pm (From Fig. 1 in Cerri PS, de Faria FP, Villa RG, et al. (2004) Light microscopy and computer three-dimensional reconstruction of the blood capillaries of the enamel organ of rat molar tooth germs. Journal of Anatomy 204 191-195. 

Osteoblasts, odontoblasts, and cementoblasts need vitamin C to make collagen, vitamin D for uptake of calcium into the body (Chap. 10), and vitamins A and K to synthesize and secrete the active form of osteocalcin. Vitamins C and D are the most important during childhood and adolescence to make adequate amounts of type I collagen and supply a net increase in calcium to the body. Ameloblasts, like other cells of ectodermal origin, require vitamin A to differentiate and secrete their proteins, but none of the other vitamins. Calcification of enamel appears independent of the increase in blood calcium level mediated by vitamin D. 

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