Sometimes the tooth hurts and sometimes it doesn’t, i.e. paroxysmal toothache, which may be caused by dental caries, nerve injury, acute pulpitis and so on. 1. Dental caries: a disease in which the hard tissues of the dentin under the influence of many factors, mainly bacteria, undergo chronic progressive destruction. Common causes include poor oral environment, poor diet and so on. Due to the lesions on the teeth, when the lesion area is serious, it can stimulate the gums, which leads to the phenomenon of paroxysmal toothache. 2. Nerve damage: caused by trauma, infection, metabolic disorders and other causes of nerve damage. When the nerve pain involves the teeth, paroxysmal toothache can occur. Such as trigeminal neuralgia. 3. Pulpitis: it is the inflammation of the pulp tissue, mainly caused by bacterial infection, chemical stimulation, physical factors, etc. Patients can have spontaneous pain, night pain, temperature stimulation pain, etc. It is recommended that patients whose teeth sometimes hurt and sometimes don’t hurt should go to the hospital in time and follow the doctor’s instructions for treatment to avoid delaying their condition.