Low-level red laser improves healing of second-degree burn when applied during proliferative phase.

Abstract

The aim of this study was to investigate the effects of low-level red laser on tissue repair in rats submitted to second-degree burn, evaluating if the timing of laser treatment influences the healing process. The animals had their backs shaved and divided as follows: control group (n = 12)-rats burned and not irradiated, early laser group (n = 12)-rats burned and irradiated from day 1 after injury for five consecutive days, and late laser group (n = 14)-rats burned and irradiated from day 4 after injury for five consecutive days. Laser irradiation was according to a clinical protocol (20J/cm(2), 100mW, continuous wave emission mode, 660nm) as recommended by the laser device manufacturer. Half of the animals were sacrificed 10days after burn, and the other animals were sacrificed 21days after burn. The late laser group accelerated wound contraction 10 and 21days after burn. The late laser group accelerated reepithelialization 18days after burn. The late laser group increases the granulation tissue 10 and 21days after burn. Both irradiated groups increased type III collagen expression and TGF-β 21days after burn. Both irradiated groups increased macrophage and myofibroblast numbers 10days after burn and decreased 21days after. Low-level red laser exposure contributes to the process of tissue repair of second-degree burns, but the intervention during proliferative phase is crucial in the final outcome of the repair process.