Find Out More About Fillers

By: Zoe D. Draelos, MD, and Peter T. Pugliese, MD

Many new technologies have been developed to rejuvenate the aging face. One of the most successful techniques is the use of fillers to replace lost bone, subcutaneous fat and collagen on the face. While the esthetician will not inject fillers in an unsupervised setting, it is worthwhile to understand the theory and technology behind this medical anti-aging strategy.

The variety of fillers

There are a variety of substances that can be used as fillers to take up the space created by the lost bone and fat. The first fillers that were introduced were made of cow collagen. The collagen came from a special herd and was treated for facial injection. It was possible to be allergic to the bovine collagen, so skin testing was required. This product has been removed from the market, as have other collagen materials derived from pigs.

The next filler to be introduced into the marketplace was hyaluronic acid. Hyaluronic acid is naturally found in the dermis and is responsible for maintaining skin water balance. The first hyaluronic acid fillers introduced were made from a cock's comb. These fillers of animal origin have also been removed in favor of bacterially made hyaluronic acid that is identical to human hyaluronic acid. The bacterially made hyaluronic acid does not require skin testing as it is not possible for humans to be allergic to human hyaluronic acid. Hyaluronic acid products are available as thin gels to inject around the eyes, thicker gels for injection in the folds around the mouth, and very thick gels to put on top of the bone to replace the lost fat pads of the upper cheeks. Hyaluronic acid is the most popular filler used today.

There are two other widely used filler substances: poly-L-lactic acid hydrogel and calcium hydroxylapatite. Poly-L-lactic acid is used in absorbable sutures. It is a sugar that is broken down by the body in time. It is packaged as a freeze-dried powder in a sterile vial that must be reconstituted with sterile water before use. The poly-L-lactic acid filler creates an inflammatory response, resulting in new collagen formation, and is slowly degraded. It is not as easy to inject as the hyaluronic acid, but may last up to one year or longer. It is also more rigid than hyaluronic acid, more expensive per tube and less forgiving. Calcium hydroxylapatite, used in concentrations of 30%, is a form of synthetic bone suspended in an aqueous gel composed of water, glycerin and sodium carboxymethylcellulose. Once injected, the aqueous gel is absorbed, leaving behind tiny 25–45 micrometer diameter microspheres. The bioceramic microspheres form a framework on which fibroblasts can grow to make new collagen. The new fibrous collagen grows around the particles and in time they dissolve into calcium and phosphorus ions. It is a more rigid filler and can be seen on dental films after injection into the face lasting around six months. Both of these fillers are effectively used in special case conditions, but hyaluronic acid remains more popular. Many new fillers are poised to enter the market within the next few years. Filler technology is only in its infancy, making this an important area for the esthetician to watch.