Clinical and histological evaluation of a dual sequential application of fractional 10,600 nm and 1570 nm lasers, compared to single applications in a porcine model

The sequential application of fractional ablative/10,600 nm/CO₂ followed by 1570 nm non-ablative laser treatment might produce better results than applying either laser treatment alone. However, histological data regarding the safety of this combination is lacking. This study aimed to assess and compare clinical effects, histological tissue damage, and wound healing after monochromatic and sequential fractional laser treatments. In this prospective porcine model study, three adult female pigs were each irradiated using three different wavelengths: (a) monochromatic fractional ablative CO₂ laser; (b) monochromatic fractional non-ablative 1570 nm laser; (c) sequential fractional 10,600 nm/CO₂ followed by 1570 nm laser treatment. There were six power levels in the monochromatic 1570 nm laser, five in the 10,600 nm/CO₂, and five in the sequential treatment. The immediate skin reaction (ISR), crusting and adverse effects, was evaluated across different time points throughout the healing process. Wound biopsies were taken at immediately after (0) and at 3, 7, and 14 days after irradiation. Depth and width of craters, and width of coagulation zone were measured and compared. Similar ISR and crusting score values were obtained following the monochromatic and sequential irradiation in a similar dose–response manner. During 14 days of follow-up, the skin looked intact and non-infected with no signs of necrosis. The mean depth and width of craters were comparable only at the maximal energy level (240 mJ) of CO₂ laser, with the coagulation size greater after the sequential treatment. In histology, a similar wound healing was evident. On day 3, crusts were observed above all lesions as was epithelial regeneration. The sequential irradiation with 10,600 nm/CO₂ and 1570 nm lasers did not pose any additional risk compared to the risk of each laser alone.