Drinking water toothache is caused by the following reasons: First, tooth decay, decay will make the tooth defective to form a cavity, resulting in the exposure and opening of dentin tubules, after drinking cooler and hotter water, there will be a transient pain. Second, the tooth has pulpitis. Patients with pulpitis will experience severe and persistent pain when drinking cold water. Pulpitis is mostly caused by decay or trauma, and teeth with pulpitis are very sensitive to external hot and cold stimuli, which can easily cause persistent and severe pain, so drinking water will cause toothache. Third, suffering from periodontitis, periodontitis patients with multiple teeth in the mouth, there are different degrees of alveolar bone resorption and root exposure, when the root is exposed in the mouth, when drinking water will cause irritating pain. Fourth, if there is a deep wedge-shaped defect in the neck of the tooth, it will also cause toothache when drinking water.