Teeth that hurt when touching hot water may be caused by dentin sensitivity, cavities reaching dentin, purulent pulpitis, and so on. 1. Dentin sensitivity: If there are lesions in the hard tissues of the teeth, such as enamel peeling or severe wear and tear resulting in exposed dentin, or cracks on the surface of the teeth, defects in the neck of the teeth, and the neck of the teeth is exposed due to gum recession caused by periodontal disease, the patient may feel pain when he/she encounters hot water. 2. Cavities reach dentin: after exposing the dentin, there are dentin tubules inside the dentin, and there are nerve endings inside the tubules. When stimulated by hot water, pain may occur. 3. Septic pulpitis: when patients with septic pulpitis encounter hot water stimulation, they will obviously feel increased pain, increased pain at night, and even spontaneous and paroxysmal severe pain. When encountering cold stimuli, the pain can be relieved in the early stage, but not in the late stage. It is recommended that patients whose teeth hurt when they touch hot water should go to a regular dental hospital in time to clarify the cause of the disease under the guidance of the doctor and actively take effective treatment.