Gradually thinning teeth, gap is likely to be periodontitis or oral occupation and other diseases. 1. Periodontitis: The most important feature of periodontitis is the resorption of alveolar bone, which leads to insufficient support around the teeth. With the aggravation of the disease, the teeth will be shifted, resulting in gaps, and in severe cases, accompanied by loosening. Often occurs in the whole mouth, it is recommended to carry out periodontal sequence treatment, and those with obvious loosening will need to be extracted. 2 . Oral occupation: some jawbone tumors and other early symptoms are not obvious, gradually increase in size and spread to the teeth, which will lead to the loosening of the teeth involved in the gap. Here, the gap is more limited, mostly the teeth affected by the tumor, which needs surgical treatment. It is recommended to check the oral cavity regularly every 6~12 months, maintain oral hygiene, and consult the doctor in time if there is any discomfort.