That sharp zing when you sip something cold can catch you off guard. Understanding tooth sensitivity causes  helps explain why it happens and what you can do to find relief. Worn Enamel and Exposed Dentin Tooth enamel protects the inner layers of your teeth. When enamel wears down, the dentin underneath becomes exposed. Dentin contains tiny channels that lead directly to the nerve. As a result, cold air, hot drinks, or sweet foods can trigger discomfort. Gum Recession When gu