If the tooth is rotten to the flesh, the following treatment can be carried out respectively: 1.If the deep caries occurred on the buccal and lingual surface, located in the subgingival 2mm, the gingival line can be placed first to make the gum recede, then apply the low-speed ball drill to remove the decaying matter and use the glass ion cementum or composite resin to fill. 2.If the caries hole is deeper than 2mm below the gingiva, the soft tissue can be removed under local anesthesia to fully expose the caries hole and then carry out filling. 3.If the x-ray If the X ray shows that the pulp chamber bottom of the molar is perforated and the root is stable, MTA can be applied to repair the perforation and make pile crown restoration after completing root canal treatment. 4.If the root of the molar is separated and obviously loose, it should be extracted and then choose implant or fixed denture restoration.