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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]
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]
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.
As more tertiary dentin is produced, the size of the pulp decreases. This type of dentin has been subdivided according to the presence or absence of the original odontoblasts. [85] If the odontoblasts survive long enough to react to the dental caries, then the dentin produced is called "reactionary" dentin. If the odontoblasts are killed, the ...
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]
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]
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 ...
They also have the secondary palate that other primitive therapsids lacked, except the therocephalians, who were the closest relatives of cynodonts. (However, the secondary palate of cynodonts primarily comprises the maxillae and palatines as in mammals, whereas the secondary palate of the therocephalians primarily comprises the maxillae and ...