Effects of Nd:YAG laser on wound healing processes: Clinical and immunohistochemical findings in rat skin

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Abstract
Background and Objective: The clinical effects of the Nd:YAG laser in the rat skin as well as alterations of the extracellular matrix during healing were presented in this study. Study Design/Material and Methods: This study evaluated the clinical effects of the Nd:YAG laser used with different energy parameters (low energy: 1.75 W and 20 pps / high energy: 3.0 W and 30 pps) in a duration 20–40 s in rat skin. Control incisions were performed with a scalpel blade. Rat skin incisions were examined over a period of 28 days by clinical photographs as well as by using immunohistochemical techniques in order to find the distribution and the amount of the extracellular matrix fibrillar components, i.e., collagen types I and III. Results: Low energy laser treatment caused a rapid wound healing without scar tissue formation (compared to the high energy laser group) and clinical signs of scar tissue formation (compared to control incisions with the conventional scalpel). During the study period, the laser-induced lesions healed through reparative synthesis of the matrix proteins, which led to filling of the tissue defects. The regenerative processes were similar in the low-energy laser group and in the control incisions. In the high-energy lased tissues, we observed a delayed replacement of the defects by newly formed extracellular matrix proteins. Conclusions: This study showed a slower wound healing in the high-energy lased tissues. A similar healing in the low-energy lased tissues and in the incisions with the conventional scalpel was observed. The differences in the distribution of matrix proteins during healing and the coagulation of the tissues, which were exposed to low-energy laser treatment, might be the explanation for the minimal scarring, contraction, and pigmentation of the lased tissues as compared to conventional incisions.