To get right to the point, tooth pain happens when the nerves in your teeth become irritated. Normally, our teeth are covered in a protective layer of enamel. On the inside, there is a layer of material called dentin and then the pulp at the core of the tooth which is filled with connective tissue, blood vessels and the nerve of the tooth. If enamel becomes too thin or there’s a breach exposing the dentin, the nerve is no longer protected. Tooth sensitivity is most commonly caused by any number of practices or conditions that erode or damage tooth enamel.