The dentine layer that is exposed due to tooth decay has very small ducts. At the same time, these channels, which contain a liquid that feeds our gears, cause the fluid to move through stimuli such as cold-hot and lead to the delivery of the fluid to the nerve. In this case, ache causes pain.

When the caries reach the pulp with nerves and veins, the blood pressure in the pulp chamber increases for protection from the bacteria. This pressure causes severe pain in the nerves jammed.