Adults with tooth decay may be caused by autoimmunity, tooth alignment, sweet food, bacterial infection, etc. It is recommended to go to the hospital for timely examination and treatment. 1. Adults with poor oral hygiene, poor general condition, especially those who have undergone radiotherapy, have poor immunity in the oral cavity and are prone to tooth decay. 2. Dysplasia and plaque can be easily retained and difficult to clean when eating, which can easily cause tooth decay. 3. Eating sweets, especially if you eat sweets frequently and in large quantities, it is easy to make plaque fermentation and promote the occurrence of tooth decay. Not brushing your teeth carefully. 4. Bacterial infections due to disorders of the oral flora, gastrointestinal diseases that induce bacterial infections in the mouth, etc. are prone to tooth decay.