Synergistic Sequential Emission of Fractional 10.600 and 1540 nm Lasers for Skin Resurfacing: An Ex Vivo Histological Evaluation

Background: Fractional ablative and non-ablative lasers are useful treatments for skin rejuvenation. A procedure that provides the sequential application of fractional ablative followed by non-ablative laser treatment may reduce patients' downtime and deliver better cosmetic results than with either laser alone. Objective: The purpose of the current study was to demonstrate the ameliorative and therapeutic effects in skin remodeling of the synergistic use of the two laser wavelengths (fractional ablative CO and non-ablative 1540 nm) with three different types of pulse shapes, S-Pulse (SP), D-Pulse (DP) and H-Pulse (HP), through which the CO laser can emit, performing an ex vivo histological evaluation. Methods: In this prospective study, ex vivo sheep inner thigh skin was chosen due to its similarity to human skin tissue, and a histological evaluation was performed. Three irradiation conditions, using all of the three CO pulse shapes (alone or averaged), were investigated: (1) 10.600 nm alone, the sequential irradiation of the two wavelengths in the same perfectly controlled energy pulses (DOT) for the entire scan area; ((2) 10.600 nm followed immediately by 1540 nm; and (3) 1540 nm followed immediately by 10.600 nm). Results: When comparing ablative to sequential irradiations, the synergy of the two wavelengths did not alter the typical ablative pulse shape of the 10.600 nm laser alone. With the same CO pulse shape, the lesion depth did not vary with the synergy of the two wavelengths, while thermal lesion width increased compared to CO alone. The ablation rate was achieved, while the total thermal lesion coverage in the scanning area of CO - 1540 lasers was greater than when using CO alone and then the other sequential irradiation. Conclusions: This study provides important preclinical data for new and early uses of the novel 10.600/1540 nm dual-wavelength non-ablative fractional laser. The synergy of the two wavelengths enhanced all the benefits already available when using CO laser systems both in terms of tone strengthening, thanks to a greater shrinking effect, and in terms of stimulation and collagen remodeling thanks to a greater volumetric thermal effect.