Ablative resurfacing was first introduced in the mid 1990s. Technological advancements with carbon dioxide (CO2) lasers had emerged to minimize their thermal impact on tissue and, subsequently, possible clinical uses were explored. Two types of CO2 lasers were developed. The first utilized ultrashort pulse durations to minimize heat deposition in the tissue. The other utilized the laser beam in a continuous wave (CW) mode, in conjunction with a scanning device, to shorten the laser dwell time and, thereby, minimize thermal damage (Lask et al. 1995). These lasers were first used for the treatment of rhytides and acne scars; however, investigators soon discovered that superficial sun damage changes, including lentigines, as well as actinic keratoses, fine lines, and other superficial imperfections also improved. Additionally, the deposition of heat was noted to cause a tissue-tightening effect, which softened deeper wrinkles (Fitzpatrick et al. 2000). The CO2 laser proved to be very effective; however, as the technology expanded into the dermato-logic and plastic surgeon's armamentarium, it was found to have significant side effects, especially in inexperienced hands. Many patients experienced erythema that lasted for weeks to months as well as temporary hyperpigmenta-tion, acne, and contact sensitivity to topical products. Yeast, bacterial, and viral infections were a potential problem. Prolonged hypopig-mentation and scarring, although infrequent, were also of great concern.
In an effort to decrease the risk/side effect profile, the use of erbium lasers was explored (Zachary 2000) These short-pulsed lasers, with stronger water absorption at 2.94 ^m were less injurious to deeper tissues; they ablated tissue but left little residual thermal damage. Unfortunately it became apparent that this laser, although good for smoothing out the surface, did not lead to the same tightening effect as was noted with the CO2 lasers. The next level of advancement entailed increasing the pulse width of the erbium lasers to include some deposition of heat, which would allow tightening (Pozner and Goldberg 2000). In addition, lasers were developed that combined both erbium and CO2 lasers to allow heat deposition by the CO2 component as well as pure ablation by the erbium component. The potential benefit was great; however, side effects continued to be present (Tanzi and Alster 2003). A recent paper showed that utilizing a topical anesthetic, which hydrated the skin, minimized side effects even with pure CO2 lasers. In this study, a decreased incidence of prolonged erythema, pigmentary changes, and scarring were noted (Kilmer 2003).
Despite these advances, the significant amount of downtime associated with ablative resurfacing has led to the development of nonablative lasers to improve solar damage, including rhytides, telangiectases, and pigmentation. Nonablative technology evolved beginning with the use of early-pulsed dye lasers (Zelickson 1999) It had been noted that using the pulsed dye laser for the treatment of port wine stains that had been scarred from previous argon laser treatment improved not only the port wine stain, but the scars as well. In addition, patients with facial telangiectases or poikiloderma of Civatte commented on their improved appearance.
These early studies showed that the pulsed dye laser not only improved rhytides but also caused histological changes in the dermis consistent with improvement of sun-damaged collagen. Similarly, the Q-switched Nd:YAG laser used in combination with a topical carbon suspension for laser hair removal was noted to diminish fine lines, most likely due to a photomechanical effect. Lasers with an affinity for water absorption were then investigated for their effects on wrinkle improvement. These lasers, which include the 1320-nm and 1450-nm systems, deliver heat into the dermis to trigger a wound-healing response. In these cases, epidermal damage was avoided by a concomitant cooling mechanism. Laser-induced histological changes showed increased fibroblast activity and new collagen deposition. These changes were similar to those seen with both the pulse dye and Q-switched Nd:YAG lasers. Over time, there has been an ever-increasing surge in patients demanding a "no downtime" wrinkle treatment and, consequently, the field of nonablative facial rejuvenation has expanded tremendously. Because ablative and nonablative lasers and their indications, benefits, risks, and treatment techniques vary so greatly they are separated in the discussion below. Ablative laser resurfacing will be discussed first, followed by the various nonablative technologies.
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