Toothache may be caused by dentin hypersensitivity, caries, pulpitis, apical periodontitis and other diseases, as follows. 1. Dentin hypersensitivity: Dentin is exposed because of wedge-shaped defects, wear and tear, gum recession, etc., and pain will occur when it is stimulated by hot, cold, sweet and sour or mechanical stimulation. 2. Caries: When caries develops to the deep dentin layer, food or cold water into the cavity will cause tooth pain. 3. Pulpitis: acute pulpitis can be manifested as spontaneous pain, paroxysmal pain, night pain, chronic pulpitis can be manifested as spontaneous dull pain, hot and cold stimulation can cause or aggravate pain symptoms. 4. Periapical periodontitis: symptoms of occlusal pain, teeth have a history of hot and cold stimulation pain. There may be other reasons for the toothache, it is recommended to go to the hospital in time, clear cause for targeted treatment.