Tertiary dentin is dentin formed as a reaction to external factors such as caries
. It is of two types, either reactionary or reparative. Tertiary dentin, according to dentists in Collierville, is only formed by an odontoblast directly affected by stimulus, therefore architecture and structure depends on the intensity and duration of the stimulus, which is if the stimulus is a lesion, there would be extensive destruction of dentin and damage to the pulp, due to the differentiation of bacterial metabolites and toxins.