The pain when touching the tooth may be caused by periapical or pulpitis, tooth fracture, or periodontitis, as follows: First, suffering from periapical or pulpitis: usually there are deep and large cavities on the tooth surface of such teeth, and the pulp nerve is infected without timely treatment, or even has developed into periapical lesions. When in the acute inflammation period of pulpitis or periapical inflammation, it will lead to very intense pain, and when touching the tooth or applying biting stress, it can lead to unbearable pain. Secondly, tooth fracture: If you bite hard objects or suffer from trauma, which leads to tooth crown fracture or joint fracture of crown and root, root fracture, the tooth will also appear to be painful when touched. Third, suffering from periodontitis: usually occurs in the case of severe periodontitis, the patient’s roots are mostly exposed in the mouth, the alveolar bone resorption is very obvious, the teeth have been accompanied by different degrees of loosening state, there is no way to withstand the bite pressure, a touch of the teeth will appear obvious pain.