The reasons for the pain at the bite of the tooth may be the following: 1, the tooth has periapical inflammation, due to the caries above the tooth induced pulpitis, pulpitis and inflammation spread to the root tip, causing periapical inflammation, due to the inflammatory exudate in the periapical area, and even has appeared granuloma and cyst, when the tooth bites the food, there will be the tooth apical area of swelling and discomfort. 2, suffering from periodontitis, periodontitis The patient will have resorption of the alveolar bone, gum atrophy and exposure of the tooth root, as the length of the root in the alveolar bone becomes shorter and shorter, the tooth will gradually loosen and cannot withstand a lot of occlusal stress, once bitten food teeth will appear pain. 3, the tooth surface appears hidden fracture, after the appearance of hidden fracture, when this tooth bite hard objects will cause severe pain. 4, the tooth surface appears occlusal The high point is usually seen when the tooth has been filled with caries or restored with porcelain or all-porcelain crown, because the tooth is not properly adjusted and ground, so that the tip of the tooth has early contact, resulting in occlusal trauma, which will also cause pain after the tooth bites food.