There are two major reasons for hypersensitivity of teeth.

First, as one becomes of middle or of elderly age, one's alveolar bone level that embraces the root of the teeth recesses. In this process the exposure of the root of the teeth makes him or her hypersensitive to outer cold stimulation.

This hypersensitivity is one of the symptoms of periodontal diseases in which the destruction of the alveolar bone progresses rapidly. When there is no bleeding in the gums or any dental calculus seen in the naked eyes, there can be some wedge-shaped grooves caused by inappropriate brushing in the exposed root of teeth, which are also the cause of hypersensitivity for anyone regardless of age.

Second, decayed teeth can be one reason. As tooth decay progresses, walls to the pulp in the middle of the tooth are getting thinner. That process makes the tooth more sensitive to both hot and cold stimulants. Moreover, in the case of tooth decay, food intake alone can cause hypersensitivity or pain