If your dentist has ruled out cavities and fractured teeth which can cause sensitive teeth. Then additional reasons for sensitive teeth can be, worn tooth enamel, a cracked tooth or an exposed tooth root may be the cause.
A layer of enamel, the strongest substance in the body, protects the crowns of healthy teeth. A layer called cementum protects the tooth root under the gum line. Underneath the enamel and the cementum is dentin, a part of the tooth that is less dense than enamel or cementum.
The dentin contains microscopic tubules (small hollow tubes or canals). When the dentin loses its protective covering, the tubules allow heat and cold or acidic or sticky foods to stimulate the nerves and cells inside the tooth. This causes hypersensitivity and occasional discomfort. Fortunately, the irritation does not cause permanent damage to the pulp. Dentin may be exposed when gums recede. The result can be hypersensitivity near the gum line.
Proper oral hygiene is the key to preventing gums from receding and causing sensitive-tooth pain. If you brush your teeth incorrectly or even over-brush, gum problems can result. Ask your dentist if you have any questions about your daily oral hygiene routine.