The main causes of toothache are as follows: 1. Pulpitis or periapical inflammation caused by caries, which is a very common dental disease, due to the infection of the pulp nerve, which will cause pain, especially when eating hot, cold, irritating food, will cause continuous, intense pain, if the infection has reached the tip of the root to cause periapical inflammation, when the teeth bite harder food, will cause the apical area of the swelling pain. 2. If the infection has spread to the root tip and caused periapical inflammation, when the tooth bites hard food, it will cause swelling and pain in the apical area. 2, suffering from periodontitis, periodontitis patients will have exposed tooth roots, when the root is exposed in the mouth, it will easily lead to dentin hypersensitivity, causing tooth soreness and pain, in addition, the root is also easy to appear root surface caries, leading to pulp inflammation. 3, hidden fracture on the tooth surface, when the hidden fracture reaches the deep layer of dentin, it will cause severe pain when biting food. The tooth will have severe pain when biting food.