Thanks for your question. The Silhouette sutures are made primarily of PLLA (Poly-L-lactic acid. Once placed they stimulate a build-up of collagen over time, creating volume at the site of injection, while the PLLA microparticles are metabolized to carbon dioxide and water and expelled through the respiratory system. You are now approximately 4 months out from this procedure so the sutures are still having that effect. Should you decide to do an additional collagen induction procedure such as Ultherapy it is possible that the heat from that procedure would cause the suture to break down more quickly. That isn't necessarily something you would notice, since the Ultherapy procedure would be producing collagen at the same time and resulting in a lift on its own. So, as far as "safety" I don't expect there would be a concern but we cannot be sure what effect or how much effect there would be in terms of the 'life' of the Silhouette sutures, because that has not been specifically studied. Best, Lisa Vuich, MD