The answer to the question of whether secondary caries needs to be refilled is yes. Once the tooth has been treated with filling, and the secondary caries is formed, i.e., there is bacteria between the filling and the tooth, and after the secondary caries is formed, it is necessary to clean the bacteria and the bacteria-infected tooth tissue, and after the cleaning, then refill the cavity with new material to prevent the secondary caries from further deepening, aggravating, and affecting the nerve in the tooth. The secondary caries must be refilled to prevent the development of secondary caries. It is recommended that patients should go to the hospital for dental examination regularly, including the patients who already have cavities and fillings in their lives, and brush their teeth more carefully to prevent the occurrence of secondary caries.