Why do your teeth hurt when you eat ice cream? A tooth has three layers. The outside layer, enamel, is very hard and has no nerves. Under it is dentin, which has many tiny tubes.

If enamel wears away or your gums move down, the dentin is not covered. Then cold can reach the nerves. In 2021, scientists found cells inside teeth with a sensor for cold.

A spoonful of ice cream can make a tooth hurt sharply. Why does cold do this? A tooth has three layers. Hard enamel covers the outside. Dentin is in the middle, and the pulp, which contains nerves, is at the center.

Dentin has countless tiny tubes filled with fluid. When enamel wears away or gums pull back, the dentin becomes exposed. According to the most widely accepted theory, cold makes the fluid in the tubes move slightly, and this movement stimulates the nerves.

In 2021, an international team discovered that odontoblasts, cells along the inner edge of the dentin, have a cold sensor called TRPC5. Mice without this sensor showed much less pain behavior after a tooth injury.

Bite into ice cream and a tooth may answer with a sudden, sharp pain. This is dentin hypersensitivity, and it usually starts when dentin becomes exposed. A tooth has three layers. Enamel, the hardest tissue in the body, has no nerves.

Beneath it lies dentin, pierced by countless microscopic tubules, and at the center is the pulp, with its nerves and blood vessels. Aggressive brushing, tooth grinding, acidic drinks and gum disease can uncover dentin near the root. A 2012 dental review called the hydrodynamic theory the most widely accepted explanation.

Cold and other stimuli make the fluid inside the tubules shift slightly, and that movement excites nerve endings. How the nerves themselves respond was poorly understood. In 2021, an international team found that odontoblasts, the cells lining the boundary between dentin and pulp, carry TRPC5, a channel that responds to cold.

Mice without TRPC5 showed far less pain behavior after a tooth injury. Eugenol, the main component of the clove oil long used in dentistry, blocked TRPC5, though whether it eases pain in patients has not been tested. The channel was also found in human odontoblasts. The two theories are not mutually exclusive, and both could be at work.