Synthetic polymer-based wrinkle fillers

One approach to developing nontoxic synthetic polymers is to use natural nontoxic monomers. (Monomers are repeating chemical units comprising a polymer.) Should such a polymer degrade into monomers inside the tissue, no or little toxicity would result because its monomers are nontoxic substances found naturally in the body. One reasonably successful implementation of such approach is poly-L-lactic acid (sold under the brand of Sculptra), a slow-biodegradable polymer made up of L-lactic acid. L-lactic acid is a nontoxic, natural by-product of anaerobic metabolism of glucose. If you ever had sore muscles after excessive workout, you have survived a lactic acid overload. The amount of L-lactic acid released by poly-L-lactic acid filler is far less than that and is considered quite safe. While poly-L-lactic acid does gradually degrade inside the human body, it does so much slower that more common biodegradable fillers, such as collagen or hyaluronic acid. The average durability of Sculptra is 2 years, as opposed to 3-6 month for collagen. Sculptra is used mainly for deep wrinkles or to fill out facial contours (e.g. cheeks, jaw line) affected by loss of fat due to disease or natural aging. Sculptra has been developed as a less invasive and more consistent (in terms of results and durability) alternative to fat grafting.

Sculptra is generally well tolerated and requires no allergy test. The most common side effects of Sculptra include tenderness, redness, bruising, or swelling upon injection. These side effects are usually temporary, and if present tend to decrease over the next 3 to 15 days. Other side effects may include small bumps under the skin in the treated area which may appear over time. These bumps are not always visible, and often are only detected by pressing on the skin. Notably, the results of Sculptra injections are not obvious immediately after treatment and tend to fully develop over the next 6-8 weeks. The reason is that the filling effect of poly-L-lactic acid is more due to the reactive synthesis of new collagen rather than the injected polymer itself.

Polyacrylamide and Polyalkylimide gel

Polyacrylamide (Aquamid) and polyalkylimide (Bio-Alcamid) are synthetic polymers that can hold large amounts of water, forming a gel with mechanical properties resembling some human tissues. Such gel is injectable and non-biodegradable. The results are permanent, although the manufacturers claim the fillers can be removed by aspiration in case of overtreatment or other problems. These gels are typically used to treat relatively large defects, such as deep lines, folds and furrow, pitted scars and fat loss due to aging or disease. They are not used for fine lines or small wrinkles. Even though the monomers that make up polyacrylamide or polyalkylimide are toxic, the polymers themselves are chemically inert. The manufacturers and many experts believe that they degrade in the body so slowly that the risk of toxicity is very low. So far, there seems to be no evidence to the contrary. Both of these polymers, but especially polyalkylimide are believed to integrate into the skin matrix (they get encapsulated by the body's own collagen) and, as a result, rarely migrate away from the treatment site. Polyacrylamide and polyalkylimide may be something to consider for those who wish permanent results and have relatively large defects to correct but would like a "back-out" option. As mentioned, these polymers can be removed or adjusted via aspiration. However, it is unclear whether a complete removal can be easily accomplished.

Polymethylmethacrylate

Polymethylmethacrylate (PMMA) is a synthetic polymer with a long history of use in medical implants. It has been used in bone cement, dentures, pacemaker covers and so forth. It is considered nonbiodegradable, relatively nontoxic and chemically inert. As a dermal filler, it is being used under the brand of ArteFill (a.k.a. ArteColl), which, in essense, is PMMA microspheres (microscopic particles of spherical shape about 30-40 microns in diameter) suspended in bovine collagen solution. The role of collagen solution is to provide a smoother suspension and possibly aid in skin matrix integration. After the injection of ArteFill, the bovine collagen is degraded over about 2-3 month. At the same time, PMMA gets encased in the patient's own collagen produced in response to foreign material and bovine collagen. This results in good integration of the filler and produces highly durable results with low risk of filler migration. There have been reports of cases when the injections area became hardened or bumpy, possibly due to excessive formation of the scar tissue. Whether this was primarily to the reaction of PMMA or bovine collagen remains unclear. ArteFill requires prior allergy test due to bovine collagen component.

Other synthetic polymeric wrinkle fillers

Many other fillers based on synthetic polymers have recently come or are about to come to the market. Covering every possible brand is beyond the scope of this article. However, it is worth keeping in mind that most of these synthetic newcomers have little or no long-term data, even when approved by the FDA. Before opting for a cutting-edge, newly branded filler, it is prudent to look at better established ones first.

Polyacrylamide gel (Aquamid)
Polyalkylimide gel (Bio-Alcamid)
Poly-L-lactic-acid (Sculptra/NewFill)
Polymethylmethacrylate (ArteFill/ArteColl)