The causes of pain in the groove teeth are: 1, in chewing hard objects jaw surface occurs hidden cracks or caused by the tip of the tooth, the marginal ridge of the fracture, cold and hot stimuli can be transmitted to the pulp, causing pain.2, the molar teeth mainly bear the function of grinding food, due to the wear and tear of the heavier caused by the exposure of the dentin, chewing pressure and external stimuli will cause soreness.3, the existence of deeper caries in the molar teeth, the embedded food debris will be extruded into the pulp cavity, resulting in pain, the pulp exposure in the cavity, causing pain in the attack of endodontic inflammation. The pulp inside the cavity will be exposed, causing intolerable pain during the attack of pulpitis.4. When suffering from periodontitis, the periodontal atrophy at the root bifurcation of the molar tooth will be exposed, and the bacteria will be infected with the pulp retrogressively along the root divergence and inter-root lateral branch root canal, resulting in pain.