INTRODUCTION
Nonsurgical skin rejuvenation continues to be a major, evolving field in dermatology, especially as more patients seek aesthetic improvement for a variety of skin conditions including: photo-damage, wrinkles, acne scars, surgical scars, striae, and lentigines. In recent years, many devices have been developed for cutaneous laser resurfacing including fully ablative carbon dioxide (CO2) lasers, nonablative lasers, fractional ablative lasers, and fractional nonablative lasers. Each treatment modality has its own risks and benefits. It is important for physicians to understand the safety profiles and potential complications associated with different laser devices.Laser skin resurfacing was introduced in the 1990s with the CO2 laser.1-3 The CO2 laser emits light at 10,600nm, and water is the target chromophore. A variety of CO2 lasers have been utilized for cutaneous resurfacing ranging from high energy, pulsed and continuous wave lasers. These lasers provide excellent results for facial wrinkles, photo-damaged skin, and acne scars; however, there are several major disadvantages associated with the use of these laser devices including the inability to use these lasers on non-facial skin, the need for general anesthesia, 2-3 week post-operative recovery period, and significant risk of dyschromia and scarring. Additionally, commonly reported side-effects included prolonged post-treatment erythema, which persists for approximately 6-8 weeks, transient hyperpigmentation, and permanent hypopigmentation.In an attempt to avoid the surgical morbidity associated with traditional CO2 ablative resurfacing, nonablative lasers and otherdevices were developed. Nonablative lasers heat the dermis causing protein denaturation and thereby stimulating collagen synthesis and tissue remodeling.4 Nonablative devices target the dermis and leave the epidermis intact unlike traditional CO2 lasers that target both the epidermis and dermis. Many devices have been developed for nonablative dermal remodeling, including1320nm, 1450nm, and 1540nm lasers; intense pulsed light; pulsed dye laser; radio- frequency devices; and ultrasound devices. Nonablative laser resurfacing is better tolerated than traditional CO2 laser resurfacing as it leaves the epidermis intact, however, the final aesthetic results are not nearly as impressive.As a result of the significant surgical morbidity associated with traditional, fully ablative CO2 laser resurfacing and the suboptimaloutcomes achieved with nonablative resurfacing devices, the concept of fractionated laser surgery was developed. Fractional photothermolysis (FP) was introduced by Manstein
