Polydioxanone (PDO) Smoothing threads are a simple and relatively painless way to soften fine lines and wrinkles gently, tight, lift, and even plump different regions of the face. The threads are placed in a specific fashion, under the skin, and over the next 4-6 months, your body will produce more natural collagen to lift, plump, support, and smooth the skin. Smoothing threads can be used in the face, lips, neck, chest, and other areas of the body.