| Odontoblast |
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The Biological Tissue formed by odontoblasts is a type of Hard Tissue . Mature odontoblasts, which are located around the pulp chamber as a single cell layer, result from the differentiation of mesenchymal cells of the dental papilla during tooth development (Couve 1986, Ten Cate 1994c). Fully differentiated odontoblasts have withdrawn from the cell-cycle and are, thus, postmitotic cells in nature. Functionally active odontoblasts are polarized, having long cell bodies, which contain a well-developed granular endoplasmic reticulum, many mitochondria, a Golgi apparatus, a nucleus and several secretory vesicles (Linde & Goldberg 1993, Torneck 1994). At the distal end of the cell body, close to the predentin, odontoblasts are attached to each other by intercellular junctions, which enable communication between the cells (Ushiyama 1989, Bishop & Yoshida 1992). Peripheral to the intercellular junctions odontoblast cell processes arise and insert into dentinal tubules, crossing through the predentin zone to the mineralized dentin (Linde & Goldberg 1993). The cell processes lack major organelles involved in protein synthesis, but contain an abundance of longitudinally arranged microfilaments and microtubules. In addition, numerous vesicles reflecting both endo- and exocytosis traffic exist in the processes (Torneck 1994). The main task of the odontoblasts is to synthesize and secrete collagens and several non-collagenous proteins of which the dentin organic matrix is formed. In addition, odontoblasts secrete signalling molecules, mainly of TGF-β superfamily (Cassidy et al. 1997), which are significant for cellular functionality (Bessho et al. 1991). Odontoblasts control dentin matrix mineralization at least by determining the nature of the extracellular matrix and by controlling the influx of mineral ions (Ten Cate 1985). After completion of primary dentin formation, odontoblasts transit into a resting state and their cell body structure transforms to a smaller and flattened type, with cellular structures changing their conformation or even disappearing (Couve 1986, Ten Cate 1994c). However, odontoblasts remain functional and still secrete and synthesize physiological secondary dentin, but at much slower rate. It is suggested that upon various stimuli, resting odontoblasts are capable of up-regulating their secretory activity and responding by synthesizing tertiary dentin (Ten Cate 1994c). EXTERNAL LINKS |
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