The dermal filler market continues to see increasing growth due to longer-lasting effects of the newer fillers as compared to the original collagen, bovine-derived materials. Much of the research has focused on the hyaluronic acid (HA) class of compounds, and these compounds, taken in total, rank fifth among the most common noninvasive cosmetic procedures, according to 2006 statistics from the American Society of Plastic Surgeons.

Dermal fillers utilizing HA have become popular due to their natural properties as HA is a material found commonly in the human body. HA for dermal fillers has been derived via two sources: they are either animal based or derived via bacterial fermentation. Animal-derived HA products have not produced the consistent, long-lasting results clinicians were hoping for; therefore technology and research have focused on bacterial fermentation of these products. At the time of this writing, there are four HA products currently available in the U.S. market: Restylane, Perlane, Juvéderm Ultra, and Juvéderm Ultra Plus. There are differences among these products, including the concentration of HA included and the amount of cross-linking of HA for each of the products. In summary, Restylane and Juvéderm Ultra do not have as much cross-linking as Perlane and Juvéderm Ultra Plus, which gives these two latter products greater longevity when injected into the skin by skilled physicians and injectors. It is beyond the scope of this chapter to review each of the currently available dermal fillers.

Skin tightening devices have become some of the most popular cosmetic procedures patients are currently asking cosmetic dermatologists to perform in their offices. These devices have been developed to augment many of the other noninvasive cosmetic procedures we are performing on a regular basis in our office settings. They have introduced new terms into our laser vocabulary, which now has to be expanded into the new field of energy-based systems. These energy-based systems utilize terms such as monopolar, unipolar, bipolar radiofrequency (RF), and tripolar. The RF devices that have been developed for skin tightening, as well as several other devices that rely on the absorption spectrum of water in the infrared range of light, allow sufficient deep dermal heating to produce the desired effects. All the skin tightening devices on the market work via the same basic premise: deep dermal heating, which causes collagen denaturation, followed by collagen repair and ultimate deposition of new collagen and, ultimately, skin tightening. The major skin-tightening devices available on the market at the time of this writing are shown in Table 54.1.

RF energy produces a thermal effect when its high-frequency electrical current moves through the skin. The amount of heat generated in the tissue of the skin can be described by the mathematical formula known as Joule's law: H = j2/σ, where j is the density of the electrical current and σ is the specific electrical conductivity. The tissue impedance, or resistance, is inversely proportional to the electrical conductivity.