The chin implants I used in my San Francisco Bay Area practice are comprised of rubberized solid silicone. The implants are flexible enough to allow insertion into a carefully created pocket along the front of the jaw bone but are firm enough that they feel like the underlying bone after placement. The implants are placed underneath the skin, fat and muscle of the chin. They should not be palpable if placed properly. The procedure can be performed under local anesthesia (with or without light sedation) or general anesthesia, depending on patient preference.
As for the look of the implants, I utilize computer imaging during the consultation. This allows the patient to communicate to me how large they would like the chin to be. I then use these photos as a guide during the surgery to determine which size chin implant would most appropriate. The keys to yielding a natural look include proper sizing of the implant and placement in a symmetric fashion.
Best,
Dr. Mehta