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Secondary dentin is formed after root formation is finished and occurs at a much slower rate. It is not formed at a uniform rate along the tooth, but instead forms faster along sections closer to the crown of a tooth. This development continues throughout life and accounts for the smaller areas of pulp found in older individuals.
Secondary dentin (adventitious dentin) is formed after root formation is complete, normally after the tooth has erupted and is functional. It grows much more slowly than primary dentin but maintains its incremental aspect of growth. It has a similar structure to primary dentin, although its deposition is not always even around the pulp chamber.
The odontoblasts secrete dentin throughout life, unlike enamel, which is considered secondary dentin once root formation is complete, which may be an attempt to compensate for natural wear of the enamel. This is because of the retention of the odontoblasts within the tooth, along the outer pulpal wall. [2]
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]
There are three types of dentin, primary, secondary and tertiary. [19] Secondary dentin is a layer of dentin produced after root formation and continues to form with age. Tertiary dentin is created in response to stimulus, such as cavities and tooth wear. [20]
These materials protect the pulp from noxious agents (heat, cold, bacteria) and stimulate the cell-rich zone of the pulp to lay down a bridge of reparative dentin. Dentin formation usually starts within 30 days of the pulp capping (there can be a delay in onset of dentin formation if the odontoblasts of the pulp are injured during cavity ...
Amelogenesis is the formation of enamel on teeth and begins when the crown is forming during the advanced bell stage of tooth development after dentinogenesis forms a first layer of dentin. Dentin must be present for enamel to be formed. Ameloblasts must also be present for dentinogenesis to continue.
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]