In vivo experimental evaluation of non-ablative skin remodeling using a 1.54μm laser with surface cooling.

Selective dermal remodeling using diode or 1.32 mu m Nd:YAG lasers has been recently proposed for skin rejuvenation. This new technique consists in inducing collagen tightening and/or neocollagen synthesis without significant damage of the overlying epidermis. Such an approach requires i) a cooling system in order to target dermal collagen with relatively good protection of the epidermal layer, ii) a specific wavelength for confining the thermal damage into the upper dermis (100 to 400 mu m). Based on previous studies, demonstrating a better water absorption and a reduced melanin absorption at 1.54 mu m compared to the 1.32 mu m, this experimental study aimed to evaluate a new laser (co-doped Yb-Er:phosphate glass material, Aramis, Quantel-France) emitting at 1.54 mu m. This laser was used in combination with the Dermacool system (Dermacool, Mableton, USA) in order to achieve epidermis cooling before, during and after irradiation. Male hairless rats were used for the study. Pulse train irradiation (1.1J, 3Hz, 30 pulses) and different cooling temperatures (+5 degrees C, 0 degrees C, -5 degrees C) were screened with clinical examination and histological evaluation at i, 3, and 7 days after laser irradiation. The clinical effects showed that pulse train irradiation produced reproducible epidermal preservation and confinement of the thermal damage into the dermis. The different cooling temperatures did not provide detectable differences in terms of size and depth of thermal damage. New collagen synthesis was confirmed by a marked fibroblastic proliferation, detected in the lower dermis at D3 and clearly seen in the upper dermis at D7. This new laser appears to be a promising new tool for the treatment of skin laxity, solar elastosis, facial rhytids and mild reduction of wrinkles.