The decayed milk tooth is already rotten and empty, if the inflammation has reached below the root apex it may affect the permanent tooth, you need to take a picture to confirm. Most of the decayed tissues of milk teeth will cause pulpitis and then develop into periapical inflammation. Inflammation spreads in the periapical tissues, which can affect the permanent tooth germ and cause the integrity of the permanent tooth germ to be lost, resulting in abnormal enamel development or abnormal morphology of the permanent teeth. It is necessary to go to the hospital as soon as possible for treatment. In addition, for milk tooth decay, most of the caries has led to can not be retained, need to be extracted as soon as possible, to avoid the inflammation affects the permanent tooth germ, after extraction, also need to make a gap retainer, to avoid future tooth malocclusion.