Toothache when eating hard things may be caused by periapical periodontitis, fracture of the tooth, occult fracture of the tooth and so on. 1. Apical periodontitis: It may be due to the infected material in the root canal seeping out from the apical foramen, resulting in inflammatory reaction of the periapical tissues. Generally, there will be pain when eating hard objects, a clear location of the painful area, and swollen gums, etc. Root canal therapy can be used to remove the infected material completely, and the root canal can be tightly filled in order to avoid re-infection. 2. Fractured tooth: it may be caused by external impact, chewing hard objects, etc. Usually, there will be symptoms such as loosening of the tooth, tenderness of the mucous membrane at the root of the tooth, chewing pain, etc., which can be treated by orthodontic traction surgery and root canal therapy. 3. Hidradenitis suppurativa: it may be caused by underdevelopment of teeth, malformation, caries, etc. When the symptom is more serious, sharp pain will usually appear when eating hard things, which can be treated by full crown restoration treatment, comprehensive oral restoration technology, etc. When eating hard things on the toothache, it is recommended that patients go to the hospital in a timely manner, to clarify the cause of the disease, standardized treatment under the guidance of the doctor.