Effects of 1047-nm Neodymium Laser Radiation on Skin Wound Healing MARTHA SIMÕES RIBEIRO, Ph.D., DANIELA DE FÁTIMA TEIXEIRA DA SILVA, B.Sc., EDISON PUIG MALDONADO, Ph.D., WAGNER DE ROSSI, Ph.D., and DENISE MARIA ZEZELL, Ph.D. ABSTRACT Previous research in our laboratory has shown that the polarization component of the electrical field plays an important role on the healing process of inflammatory lesions created in the end of the spinal column of Lewis rats, using a He-Ne laser at l = 632.8 nm. It is well known that polarization is lost in a turbid medium, such as living tissue. However, the Nd:YLF wavelength (l = 1,047 nm) allows more polarization preservation than l = 632.8 nm, and the Nd:YLF laser beam has been used in clinical trials as a biostimulating agent. In this work, we investigated the influence of a low-intensity, linearly polarized Nd:YLF laser beam on skin wound healing, considering two orthogonal directions of polarization. We have considered a preferential axis as the animals’ spinal column, and we aligned the linear laser polarization first parallel, then perpendicular to this direction. Burns of about 6 mm in diameter were created with liquid N 2 on the back of the animals, and the lesions were irradiated on days 3, 7, 10, and 14 postwounding, D = 1.0 J/cm 2 . Lesions 1 and 2 were illuminated using Nd:YLF pulsed laser radiation. Lesion 1 was irradiated with linear polarization parallel with the rat spinal column. Lesion 2 was irradiated using the same protocol, but the light polarization was aligned with the per- pendicular relative orientation. Control lesions were not irradiated. We have taken photographs from the wound areas on the 3rd, 7th, 10th, 14th, and 17th postoperative day for a biometrical analysis. The results have shown that lesion 1 healed faster than the control lesions (p < 0,05), which presented a smaller degree of healing after 14 days postwounding. 37 INTRODUCTION L ow-intensity laser therapy (LILT) has been used in many experiments since the 1960s to examine the influence of laser radiation on the healing process of wounds. Lasers used in wound healing have been shown to speed up the healing pro- cess in leg ulcers and burns wounds. Lasers used in this capac- ity have been demonstrated to improve skin healing capabilities. 5 However, despite a large number of studies pub- lished in the literature, results are frequently conflicting, and very few have presented scientific explanation. 1–4 In some studies, an increase in the wound healing rate of closure after LILT in vivo 6–11 has been observed while others found no change. 12–15 In those experiments, however, polarization ef- fects were not considered. Nicola and collaborators 16 have sug- gested that coherence and polarization of laser light might play an important role in the process of wound repair, but the effect of the polarization components was not considered in that in- vestigation. According to Maxwell’s equations for the optical properties of surfaces, the efficiency of energy deposition in a microroughness interface depends on the electrical field polar- ization component. 17 Considering a linearly polarized beam, this efficiency will depend on the roughness parameters for p-polarized light and will not depend on such parameters for s-polarized light. Previous research in our laboratory has shown that the polar- ization component of the electrical field plays an important role in the healing process of inflammatory lesions created in the end of the spinal column of Lewis rats, using a He-Ne laser at l = 632.8 nm. 18 It is well known that polarization is lost in a turbid medium, such as living tissue. However, the neodymium laser wavelength (l = 1.047mm) allows more polarization preservation than l = 632.8 nm, 19 and indeed this laser has been used in clinical trials as a biostimulating agent. 20 In this Center for Lasers and Applications, Instituto de Pesquisas Energéticas e Nucleares, CNEN/SP, São Paulo, Brazil. Journal of Clinical Laser Medicine & Surgery Volume 20, Number 1, 2002 © Mary Ann Liebert, Inc. Pp. 37–40