Tooth odontoblasts

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. 

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. 

Radioactive Strontium. Osteonecrosis was reported for 2-day-old rats that were injected intraperitoneally with 2 mCi 90Sr/kg of body weight (Hopkins and Casarett 1972). In weanling rabbits, injection of 600 pCi 90Sr/kg resulted in increasing cell death of differentiating odontoblasts and pulp cells of immature teeth and disordered tooth structure (Rushton 1963). Mature teeth in the same animal, or teeth in adults injected at the age of 3 years or older, were not affected as severely. 

The typical injury of scurvy consists of an incapacity of the mesenchymal cells—such as fibroblasts, osteoblasts, or odontoblasts—to produce their normal fundamental substance. In other words, the cell can proliferate, but it cannot form collagen, osteoid, or dentin. This basic alteration is responsible for increased fragility of the capillaries, retarded wound healing, abnormal bone growth, and eventually abnormal tooth growth [78]. 

FIGURE 61.2 Stages of tooth development A schematic frontal view of an embryo head at embryonic day (E)l 1.5 is shown with a dashed box to indicate the site where the lower (mandibular) molars will form. Below, the stages of tooth development are laid out from the first signs of thickening at El 1.5 to eruption of the tooth at around 5 weeks after birth. The tooth germ is formed from the oral epithelium and neural-crest-derived mesenchyme. At the bell st e of development, the ameloblasts and odontoblasts form in adjacent layers at the site of interaction between the epithelium and mesenchyme. These layers produce the enamel and dentin of the fully formed tooth. (Reproduced from Tucker, A. and Sharpe, P. Nat. Rev. Genet. 5 499-508,2004. With permission.)... 

Tooth development—Vitamin A is essential for normal tooth development. Like other epithelia, the enamel-forming cells are affected by lack of vitamin A instead of an even protective layer of enamel, fissures and pits will be present and the teeth will tend to decay. Also, when there is a shortage of vitamin A, the odontoblasts which form dentine become atrophied. 

Sound teeth and bones— Vitamin C is required for the normal development of odontoblasts, a layer of cells that forms dentin in teeth. It follows that a deficiency of vitamin C may cause defects in tooth dentin, especially during the critical period of tooth formation. 

In a fully healthy tooth, pulp fibroblast cells differentiate into odontoblasts, and these cells contribute to the development of the tooth. Low concentrations of bonding agent monomers have been shown to affect this development. A variety of processes can be affected at levels well below toxic concentration, including expression of collagen 1, osteonectin, and dental sialo-protein. This, in turn, affects the formation of mineral structures within the tooth (Buoillaguet et al. 2000). 

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