Why do teeth become sensitive after whitening?

This is a question I talk about a lot in my office. In order to answer this question you must first understand a little about the anatomy of a tooth.

A tooth has three basic layers: The hard enamel layer, a softer middle layer called dentin, and an inner layer comprised of nerves and blood vessels. The middle layer has channels called “tubules” that communicate with the nerves in the teeth by moving fluid back and forth inside them. This is how a tooth senses pain.

When you whiten your teeth the bleach gets absorbed through the enamel into the dentin layer. What you’re really trying to whiten is this middle layer of the tooth which is naturally yellow. When you do this, the tooth becomes dehydrated, thus moving the fluid in the tubules away from the nerves and creating a signal of pain to the nerves.

After about 24 hours, the teeth rehydrate fully and the nerves stop being stimulated. Of course, everyone has a different threshold at which the nerves are stimulated and so you may or may not feel pain after whitening, but if you do now you know why!