For the treatment of the secondary caries, it is necessary to perform the filling treatment by the dentist. The filling treatment is the same as the first filling, the decayed tooth tissue is removed and then the artificial material is filled in. The treatment principle of secondary caries is also the same, but generally the material filled before is mostly removed, or even the material is completely removed, after the removal, the tooth in the cavity is exposed, and then the infected tooth tissue, including some soft tooth tissue, then the soft tooth tissue is removed. After the removal, the infected tooth tissues that are darker in color should be removed as well. However, after these are removed, there may still be some brownish tissues left, but after examining the tissues by instruments, the tissues are hard, so there is no need to remove the brownish tissues too much, because these are healthy tissues, but they are stained. Once the bad tissue is removed, the artificial material is filled in.