Whether to extract or fill a tooth that is half decayed or rotten is determined by whether there is still space left in the tooth itself and the condition of the tooth. 1. After confirming the diagnosis of a half decayed or lost tooth through dental radiographs, the doctor will need to determine whether the tooth can be repaired based on the vitality of the nerve, the condition of the pulp, and the oral environment. For caries that can be repaired, synthetic resin material is the most common choice of filling material, which can effectively fill the tooth cavity and remove the decayed area, thus avoiding a series of diseases such as toothache and gum inflammation. 2. At the same time, dental fillings can be operated repeatedly, and the original structure of the tooth can be preserved to the greatest extent. However, for caries that has lost its basic occlusal function and dental health, extraction is the most effective operation to quickly remove the lesion and avoid infection or necrosis of the neighboring teeth, and then choose implant or prosthetic restoration after extraction. The earlier the caries is detected and treated, the greater the possibility of retaining teeth, so caries must be treated in time to avoid missing the best treatment period.