Silicone was one of the very first fillers which is permanent, but we prefer not to have anything permanent because if there is some complication, if you don't like the way it looks, so it's going to stick with you for the rest of your life. So technically the old permanent fillers are not really favored.
Temporary Fillers vs. Silicone Injections: Here's the Best Option
Synthetic fillers typically last up to two years before the patient needs to go back in for another injection. Permanent fillers may seem like a better option, but Dr. Sid Danesh has some words of warning.