Tooth sensitivity is caused by the movement of fluid within tiny tubes located in the dentin, which is the layer of tissue beneath the hard enamel that contains the inner pulp of the tooth. This can irritate the tooth's nerve. When the hard enamel is worn down or gums have receded, these tiny tube surfaces can become exposed.
Pain can result from eating or drinking hot or cold foods and beverages, touching your teeth, or exposing them to cold air. Taking a spoonful of ice cream, for example, can be a painful experience for people with sensitive teeth.