Silicone Jewelry
While it is not uncommon for jewelry to be partially silicone in construction (spikey silicone "ball covers" for tongue barbells for example), it is less common but not unheard of for the jewelry to be made entirely of silicone. "Solid silicone" body jewelry was first introduced to the market by Kaos Softwear.
By constructing jewelry out of silicone problems such as gum recession can be minimized by using an all-silicone labret stud (manufactured with a longer post and then cut down by the piercer as needed; also creating an excellent retainer if the silicone is cast in flesh-tone), as well as increasing biocompatibility. Stretching may also be slightly easier using soft silicone jewelry (which can "auto-stretch", although this comes with its own problems), and silicone's excellent mobility has applications in surface piercing as well. That said, for a large majority of people the pressures exerted from silicone for stretching often do more harm than good — many people have had their ears injured by pushing silicone jewelry harder than their body could handle.
It is important to note that improperly designed or cured silicone jewelry can be too "tacky" for some people to handle also, the softer silicone is, the stickier it is as well, which means it can adhere to the thin skin on the inside of a piercing. If this happens, the skin can tear off when the jewelry is shifted or removed, resulting in a badly damaged piercing.
In addition, because silicone is soft and conforms to the shape of the piercing, it can form an occlusive dressing over the tissue it's in contact with. Dead skin, lymph, blood, and so on can build up behind this dressing and form an abscess if care is not taken to keep the tissue healthy. This also means that the skin under silicone jewelry can't "breathe", and will not usually ever be as healthy as it would be with wood jewelry, for example.
It is very important to take good care of and pay attention to your piercings when wearing silicone jewelry. While silicone comes with many benefits, it should also be treated appropriately and purchased from a reputable vendor. It should be noted that because of these issues, the official stance of Kaos Softwear is that while silicone is excellent for healed piercings, it is not recommended for stretching or for problem piercings.