Alloplastic Chin Implants
Chin implants are composed of synthetic (alloplastic) materials such as silicone and porous polyethylene - materials that provide a stable, long-lasting and natural-looking enhancement to the receding chin.
Chin implants augment areas of deficiency and increase the projection of the chin. Anatomically tapering into the mandibular bone to which they are attached, their function is to enhance facial contours and provide structural support to the overlying soft tissues.
Biological implants made of bone and cartilage have been in use throughout the last century while synthetic implants have been used since the 1940’s. However, today’s gold standard for chin augmentation is the use of synthetic alloplastic materials, which provide the firmness and tensile strength of bone. These implants are biologically inert and well-tolerated (biocompatible), and are designed to permit tissue in-growth and secure integration.
Biological implants
Although well-tolerated, biological material (bone graft) has a tendency to undergo resorption after implantation and therefore does not provide the same predictable contouring usually associated with alloplastic materials.
The biological component successfully used today for implanting is fat cells (fat grafting). This can be used to restore and volumise the soft tissues of the face. Fat grafting may be used to further enhance the definition achieved with chin implants.
Alloplastic implants
One of the first medical-grade synthetic materials for implants was solid polyethylene, a component still widely used today. Modern polyethylene implants are porous, light and strong (high density), and are primarily used for craniofacial reconstructive purposes and often require fixation.
For aesthetic contouring, silicone rubber provides an advantageous combination of firmness, form-stability and flexibility, allowing the implants to gently wrap around the lower edge of the mandible. Silicone implants come in an extensive number of pre-formed shapes.
Both polyethylene and silicone implants can easily be refined during positioning, if required.
Chin implant composition
● Silicone implants
Silicone (silastic rubber) exists in varying degrees of flexibility and firmness, and is the most frequently used implant. Solid silicone does not allow tissue in-growth, and thus the implants can easily be removed. Modern anatomical silicone implants incorporate a permeable grid pattern to enhance tissue interaction and allow the implants to closely conform to underlying bone structure.
● Polytetrafluoroethylene (Gore-Tex) implants
Known by its chemical name ePTFE, Gore-Tex is able to provide softness, flexibility and strength. It is inserted in thin sheets or as customised implants. Because ePTFE is micro-porous, soft tissues adhere to the implant and enhance its stability.
● Composite implants
Silicone implants coated with ePTFE.
● Porous polyethylene (Medpor) implants
Porous high-density polyethylene (PHDPE) is a material commonly used in facial skeletal reconstruction and aesthetic chin augmentation. It is a strong, inflexible material that is customised to the mandibular bone. The material is macro-porous and provides for tissue in-growth (fibro-vascular integration).
Other alloplastic materials exist (Polyester and Acrylics), but those described are the most commonly used.
