Both PDO and Silhouette Soft threads are composed of 100% biocompatible, natural materials and FDA approved PDO thread lifts get their name from the polydioxanone material that they are made of. typically dissolve in the body within six months. Silhouette Soft, on the other hand, utilises threads composed of poly-l-lactic acid, or PLLA. PLLA threads demonstrate greater longevity than PDO threads and typically last up to twelve months before dissolving. Both have effects that will last up to 2 years. The choice of use for either one depends on the areas that are wanting to be treated. Both are good options. However, the result is more dependent on the positioning of the threads correctly and a proper assessment at the beginning.