Tooth sensitivity is caused by the stimulation of cells within tiny tubes located in the dentin (the layer of tissue found beneath the hard enamel that contains the inner pulp). When the hard enamel is worn down or gums have receded-causing the tiny tube surfaces to be exposed-pain can be caused by eating or drinking food and beverages that are hot or cold; touching your teeth; or exposing them to cold air. Hot and cold temperature changes cause your teeth to expand and contract.
Over time, your teeth can develop microscopic cracks that allow these sensations to seep through to the nerves. Exposed areas of the tooth can cause pain and even affect or change your eating, drinking and breathing habits. Taking a spoonful of ice cream, for example, can be a painful experience for people with sensitive teeth.