Odontogenic Tumours - OdontogenicTumours Odontogenic...

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Odontogenic Tumours Odontogenic tumours are generally considered rare in all species. However, precise epidemiological data are not available for the dog and cat. One of the main reasons for this is the continuing confusion regarding the true nature of some of these lesions. In many surveys the so-called epulides , which are localized swellings on the gingival margin and which constitute a variety of pathological entities, are either grouped together or excluded. Recent findings indicate that many epulides are odontogenic tumours. Another reason is the fact that many clinicians do not routinely submit epulides for histopathological examination, thereby introducing bias in the studies based on archival material. An accurate assessment of the nature of the condition is a prerequisite for therapeutic decision-making. It is therefore important to understand the biology of odontogenic tumours. CLASSIFICATIONS Odontogenic tumours have traditionally been classified based on the presence or absence of the phenomenon of induction . To understand the classification based on induction, it is important to consider the reciprocal interactions of epithelial and mesenchymal tissues during odontogenesis. The epithelial dental lamina invaginates to form the enamel organ. The inner enamel organ epithelium consists of the pre-ameloblasts. The mesenchymal odontoblast precursors migrate to the basement membrane and eventually make contact with the pre-ameloblasts. The pre-ameloblasts then induce the odontoblasts to form the dentin. In turn, the odontoblasts influence the ameloblasts and these cells start secreting the enamel matrix. The mesenchymal stroma enclosed in the developing dental follicle is induced to take on the characteristics of dental pulp. As tooth formation is completed, the odontogenic epithelium disappears leaving behind the epithelial rests of Malassez in the periodontal ligament. These clusters of epithelial cells retain their odontogenic potential, which may subsequently be expressed in neoplasia. The ameloblastoma is an example of a non-inductive tumour. In this tumour-type, the neoplastic cells of ameloblast origin do not induce the surrounding mesenchymal cells.
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Odontogenic Tumours - OdontogenicTumours Odontogenic...

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