The causes of toothache when patients eat hot food include dental caries and pulpitis, periodontitis, hidden fracture on the tooth surface or other defects, etc., as follows: First, dental caries and pulpitis: if there are deep and large cavities on the tooth surface, when eating cool and hot food, the hot and cold stimulation will cause congestion of the tooth pulp and cause transient pain. If the caries has developed into pulpitis, the external hot and cold stimulation will cause relatively intense and continuous pain. Secondly, periodontitis: for patients with periodontitis, there will be different degrees of root exposure and gum atrophy, causing dentin hypersensitivity, and when eating cool or hot stimulating food, it will cause tooth soreness and softness, or even soreness. Third, the tooth surface appears hidden crack or other defects: hidden crack when the fissure reaches the dentin, external hot and cold stimulation will cause the reaction of the pulp, causing a transient pain.