Once a tooth has a tissue defect (such as cavity, wedge-shaped defect, etc.), it can never be repaired by itself without artificial filling treatment, and no new tissue will be grown in the defect. For superficial cavities or defects, the patient usually has no obvious conscious symptoms, so the cavity can be cleaned and filled directly. For medium depth cavity, the patient may have temperature stimulation symptoms, such as slight pain or discomfort when encountering cold, hot, sour, sweet and other stimulation, then the cavity can be cleaned and soothed for observation, and the filling treatment can be carried out after a week or two weeks; if the symptoms are not very obvious, it can also be considered to fill the cavity directly after cushioning the pulp. For deeper cavities, the patient will have obvious or even severe temperature stimulation pain, and the pain will disappear immediately after the stimulation disappears, in this case, the cavity should be cleaned and pulp-protecting material should be used to protect the tooth nerve for one week or two weeks, and then carry out filling treatment when the affected tooth is painless. In some deep cavities, although no nerve is exposed and there is no stimulation, but the tooth will have spontaneous pain or night pain, in this case, it is not possible to clean the cavity and carry out filling treatment, but to carry out the “nerve killing” treatment. In contrast to the filling treatment mentioned above, the “nerve killing” treatment is a destructive treatment, i.e. the tooth has to be caved. Therefore, it is recommended that once you find a cavity in the tooth, it is best to do the treatment in a timely manner, so as not to delay a small disease into a big disease, simple into trouble, of course, small expenses also become a big expense. Finally, it is necessary to remind that there are some cavities are very hidden and hard to find by yourself, so it is better to check your teeth in hospital regularly.