There have been a wide variety of materials used for facial implants over the past fifty years. But as today there are really only three basic biomaterials that have proven consistently effective and easily manufactured with a relatively low incidence of complications in human facial implantation use. These biomaterials are silicone, polyethylene (Medpor) and polytetrafluoroethylene. (PTFE) None of them are perfect and each have their own distinct advantages and disadvantages. By far silicone is the most widely used facial implant material around the world followed by Medpor at a very distant second.
The least well known facial biomaterial is that of PTFE even though it has been used in the face for over thirty years in various forms, most commonly for soft tissue augmentation. PTFE implants are made of carbon and fluorine molecular chains (CF2-CF2) that create a synthetic polymer that is completely inert and non-resorbable. (there is no known enzyme capable of cleaving the carbon-fluorine bond) It simply can degrade or breakdown under any circumstances.
The original PTFE was known as Teflon® and was made from a paste into many forms including strands, sheets and tubes. But innovations in its manufacture led to its most current form known as expanded polytetrafluoethylene or ePTFE. This is made through a manufacturing process where PTFE is extruded through a dye which creates a microporous framework of PTFE nodules interconnected with PTFE fibrils. This makes a woven form of the material and creates a mesh-like surface structure. It is the expanded fibrils of the materials that allows this microfibrillar surface texture to be achieved. Such a surface structure allows for some tissue ingrowth and attachment into it. In addition it has the chemical property of having a highly electronegative surface due to the fluorine molecules. The exact biologic benefit to this material property is unclear although bacteria may be less like to stick to it. At the implant level, ePTFE has the handling properties of being soft and flexible but yet very strong.
What is most relevant about ePTFE is that host cells around the implant site can adhere directly to the material. This is done through a substrate formed by extracellular proteins and proteoglycans onto which fibroblasts lay down collagen into the interstices of the microfibrillar surface of the implant.
The ePTFE polymer has pore sizes ranging of 10 to 30 microns. It is well known that implants with pore sizes greater than 1 micron can harbor bacteria. Since macrophages can not enter a pore size smaller than about 50 microns, it is not an infection proof material. (but no materials are)The ideal infection-proof implant would have no pores (i.e., silicone) to prevent bacterial invasion or pores greater than 50 ?m to allow tissue ingrowth and cellular antimicrobial activity. That being said, there is no clinical evidence that infections rate are higher with ePTFE implants than those of either silicone or Medpor.
ePTFE facial implants are available in two forms. Certain styles of performed silicone facial implants have been coated with a thin layer of ePTFE, known as Composite Facial Implants. This has the advantage of using known and popular silicone implant styles but giving them the added bonus of a coating that can allow for some actual tissue adhesion. They are available in basic designs for the cheek, chin and nose.
The second form are ePTFE facial implants come in sheets and blocks. These allow the surgeon to cut and carve their own implant designs at the time of surgery. This material is very easily carved with a scalpel somewhat similar (although easier) than a bar of soap. A #10 scalpel blade works quite well.
Solid and coated ePTFE facial implants offer the patient another well known biomaterial that develops a soft tissue reaction to the material somewhere between that of silicone (which has none) and that of Medpor. (which develops a significant soft tissue ingrowth) But unlike Medpor it is very easily shaped during surgery and subsequently removed if needed.
Dr. Barry Eppley
Indianapolis, Indiana