The fundamental concept of modern-day laser- and light-based therapies relies on the principles of selective photothermolysis. As we learn more about skin and light interactions, it has become evident that additional factors can influence the safety and efficacy of the delivery of photons to desired targets. This is particularly evident in the treatment of darker skin types. Selective photothermolysis can be further enhanced with a novel approach: fractional photothermolysis. Fractional photothermolysis enhances the safety of traditional ablative resurfacing and can be accomplished with nonablative and ablative modalities. The following two chapters will discuss true nonablative fractional resurfacing (TNFSR) with the Lux 1,540-nm laser and the 1,550-nm Fraxel laser.

TNFSR

Fractional photothermolysis is rapidly gaining momentum as a safe and effective modality for facial and nonfacial resurfacing. Fractional resurfacing can be performed by nonablative and ablative methods. There is much confusion about true versus pseudofractional resurfacing, with the latter merely tweaking existing ablative devices with modifications. True nonablative fractional resurfacing has three criteria: (1) creation of microthermal zones of damage, (2) preservation of the majority of the stratum corneum with rapid reepithelialization, and (3) a resurfacing with epidermal extrusion. If all three of these criteria are not met, the device is merely a traditional ablative or nonablative device with modifications, and the risk of bulk heating is still significant, thereby also promoting greater risks of scarring and pigmentary anomalies. The first commercially launched TNFSR device was the 1,550-nm erbium-doped Fraxel laser (Reliant Technologies).