PDO or polydioxanone is a well-known thread used in PDO thread lift procedure. These threads have gained immense popularity in the realm of cosmetic treatments as an alternative to the surgical facelift. The PDO thread lift treatment is used for lifting and tightening loose and sagging facial and body skin.
What is PDO?
PDO is a monofilament polymer that was first introduced in the 1980s. It is a polydioxanone polymer which is used for manufacturing PDO threads. These threads are known for their tensile strength as compared to the sutures derived from lactide and glycolide. At 2 weeks time, it retains nearly 74% of its tensile strength while at 4 weeks time, it still retains 58%. The complete absorption of these threads takes place in 180 days. This property makes PDO threads a good option as absorbable sutures when a prolonged tensile strength for wound healing is required. It also has minimal reactivity to tissues.
PDO threads are now being used for cosmetic purposes to lift and tighten the facial and body skin. The ongoing research and development on refining the structure of PDO threads for cosmetic uses have ensured that the practitioners are able to deliver best, long lasting and most effective results.
Biochemistry and process of degradation of PDO threads
Polydioxanone is a unique monofilament suture that holds inherent characteristics of the flexibility of its polymer which allows the fabrication of this suture into a monofilament fibre. Its chemical formula is a linear polymer that forms during the process of catalytic polymerization of a heterocyclic compound called p-dioxanone.
The hydrolysis of the PDO polymer begins due to the process of disintegration which forms 2-hydroxy-ethoxy- acetic acid (C4H804) monomers. These then broke down into water and carbon dioxide and are absorbed into the skin.
The stages of PDO disintegration
The process of PDO thread disintegration comprise of two stages:
The duration of the first stage is from 3-12 weeks. The strength, weight and shape of the thread during this period is not visibly lost. There are no visible signs of cracks or any damage on the filament surface though it loses 9% of its weight. This implies that during the first 3 months the polymer hydrolysis occurs only on the surface of the filament ( the polydioxanone structure is dense and the water molecules cannot penetrate through it). Therefore the changes in filament strength are not pronounced.
In the second stage, the PDO threads begin to show signs of disintegration. The peripheral circular cracks appear on the thread surface which allows the penetration of water molecules inside the structure of filament. Due to the little loss of thread weight, the strength of thread is lost to some extent (during 60 days, thread loses 90% of the strength while losing only 1.5% of the mass).
Then the smallest PDO thread fragments are produced which diffuse into filament surface. After that, they diffuse into the surrounding tissues. This process of disintegration cause massive loss of filament mass and finally the thread destruction. Simultaneously, there occurs an increase in the level of local pH (because the acidic hydrolysis products accumulate) which triggers autocatalytic effects resulting in acceleration of PDO degradation.
The ultrastructure of PDO Thread comprises of the knot crystal structure and amorphous regions. The strength of the filaments is determined by this ultrastructure. Due to this structure, the process of hydrolysis is slow. This is the reason that PDO thread remains intact inside the tissues for 4-6 months.
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