Do you experience discomfort or intense pain when you eat something cold, hot, sweet or salty?

If you do, you might have sensitive teeth - which means the nerves in your teeth are being exposed (more than usual) to what you consume.

On the outer layer of your teeth, there is Enamel, which protects the crowns of your teeth (located just above the gum line). Underneath the gum line, there is what's called Cementum, which protects your actual tooth root. Beneath the Enamel and Cementum is Dentin. Dentin is made up of hollow, microscopic tubules. Below the Dentin is the nerve itself.

When Enamel and Cementum begin to degrade, Dentin is more exposed, leaving little to no protection for the nerve since these tubules are porous. In this state, if you drink something cold or hot, or eat something sweet or salty, you will feel it more since your nerves aren't as protected.