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Dentin is classified into three types: primary, secondary, and tertiary. [24] [25] Secondary dentin is a layer of dentin formed after the tooth's root has fully formed. Tertiary dentin develops as a result of a stimulus, such as a carious attack or wear. [26]
Genetic changes in animal models can increase tertiary dentin production. [6] This suggests certain species may have evolved to produce tertiary dentin in response to dietary changes. For example, gorillas may have evolved high rates of tertiary dentin as protection against severe wear, since they consume a lot of tough vegetation. [1]
Reactionary dentin is formed by odontoblasts when the injury does not damage the odontoblast layer. Reparative dentin is formed by replacement odontoblasts when the injury is so severe that it damages a part of the primary odontoblast layer. Thus a type of tertiary dentin forms in reaction to stimuli, such as attrition or dental caries.
Dentin formation, known as dentinogenesis, is the first identifiable feature in the crown stage of tooth development. The formation of dentin must always occur before the formation of enamel. The different stages of dentin formation result in different types of dentin: mantle dentin, primary dentin, secondary dentin, and tertiary dentin. [31]
An animal's dentition for either deciduous or permanent teeth can thus be expressed as a dental formula, written in the form of a fraction, which can be written as I.C.P.M I.C.P.M, or I.C.P.M / I.C.P.M. [10] [11] For example, the following formulae show the deciduous and usual permanent dentition of all catarrhine primates, including humans:
Odontoblasts also secrete tertiary dentin when irritated. Tertiary dentin secreted by odontoblasts is often due to chemical attack, either by chemicals diffusing through the dentin and insulting the odontoblasts, or by diffusion of toxic bacterial metabolites down the dentinal tubules in the instance of a carious attack with dental decay. This ...
The overall pulp cavity may become smaller by the addition of secondary or tertiary dentin and cause pulp recession. The lack of sensitivity associated with older teeth is due to receded pulp horns, pulp fibrosis, the addition of dentin, or all these changes. Restorative treatment can be performed without local anaesthesia on older dentitions. [2]
The labial half is made of enamel and resembles a crown, while the lingual half is made of dentin and resembles a root. The mineral distribution in rodent enamel is different from that of monkeys, dogs, pigs, and humans. [12] In horse teeth, enamel and dentin layers are intertwined, which increases the strength and decreases the wear rate of ...