Last time, it was mentioned that the tear trough can be corrected by burying the threads, the little ones will ask, what kind of threads are buried, and how can they have such a miraculous effect? The thread used to correct the tear trough, its chemical material is polypropylene dioxycyclohexanone (PPDO). This is an aliphatic polyester ether material with good biodegradability and biocompatibility, and its unique ether ester structure gives the wire high strength and good flexibility, is an ideal biomedical material. It is widely used in surgical sutures, orthopedic fixation materials, tissue repair materials, cell scaffolds and drug carriers. After PPDO thread is placed into the body, the final metabolites are water and carbon dioxide, which can be completely absorbed by the body. Structurally, the PPDO threads used for filling tear trough depressions are smooth or spiral threads.