new position. The chin can be lengthened 2 to 3 mm on average. The mentalis muscles controls the elevation functions of the lower lip and chin, so extra caution should be taken to carefully attach the mentalis muscle back after the surgery. Potential risks and side effects The usual complications are relatively minor and include swelling, hematoma (blood pooling), weakness or numbness of the lower lip, which usually does not last long. Other, less common risks include infection, bony changes and displacement of the implant. Surgeon experience can help reduce risks of complications. Chewing should be kept at a minimum immediately after this procedure, and patients are recommended to eat only soft food and drink for a time after the surgery. Types of implants Silicone - Silicone chin Implants are one of the most commonly used implants for chin augmentation. They are soft, smooth, flexible and come in different shapes and sizes. They do not incorporate (stick) to the surrounding tissues, so the pocket must be made precisely. They usually stay in place, but may move, buckle and cause bone resorption where they contact the mandible in some cases. Since they are smooth, they can also be removed easily. Polyethylene - Polyethylene chin implants, brand name Medpor, are hard, porous, slightly flexible and come in various shapes and sizes. They do incorporate, as the surrounding tissues can grow into the pores of the material. This fixes the polyethylene chin implants in place, and provides a blood supply to help prevent infection. It also makes these implants much more difficult to remove. Polytetrafluoroethylene - Polytetrafluoroethylene, brand name Gore-Tex, is used in plastic surgery and other operations is known by an abbreviation of its chemical name, ePTFE (expanded polytetrafluoroethylene) or Gore S.A.M. (subcutaneous augmentation material). Because ePTFE is flexible and soft but very strong, it is inserted during operations in trimmed sheets and carved blocks and held to the bone by titanium screws. But because the material is porous, the force that really holds the implant in place is soft tissue and bone growing through and into the implant. The above artificial materials are used in medicine because they are biocompatible and have a low incidence of causing problems inside the human body. They are abundant, FDA cleared and can be used "off-the-shelf", without a donor site injury to the recipient. Acellular dermal matrix - ADMs are another chin augmentation implant material.