title: Effects of low-intensity polarized visible laser radiation on skin burns: a light microscopy study.
abstract: OBJECTIVE
  This study was carried out to investigate the influence of low-intensity polarized visible laser radiation on the acceleration of skin wound healing.
  
  
  BACKGROUND
  Low-level laser therapy (LLLT) at adequate wavelength, intensity, and dose can accelerate tissue repair. However, there is still unclear information about light characteristics, such as coherence and polarization. Some studies indicate that linearly polarized light can survive through long propagation distance in biological tissue.
  
  
  METHODS
  Three burns about 6 mm in diameter were created on the back of rats with liquid N(2). Lesion "L(//)" was irradiated by He-Ne laser (lambda = 632.8 nm), D= 1.0 J/cm(2), with linear polarization parallel to the spinal column of the rat. Lesion "L(inverted v)" was irradiated using the same laser and dose, but the light polarization was aligned perpendicularly to the relative orientation. Lesion "C" was not irradiated in order to be considered as control. The animals were sacrificed at day 3-17 after lesion creation. Samples were collected and prepared for histological analysis.
  
  
  RESULTS
  Histological analysis showed that the healing of irradiated wounds was faster than that of non-irradiated wounds. Moreover, it was observed that skin wound repair is dependent on polarization orientation with respect to a referential axis as the animal's spinal column. Consequently, "L(//)" was completely healed after 17 days, whereas "L (perpendicular) " showed a moderate degree of healing after the same period.
  
  
  CONCLUSIONS
  These results indicate that the relative direction of the laser polarization plays an important role in the wound healing process when highly coherent He-Ne laser is used.
authors.affiliation: Center for Lasers and Applications, IPEN-CNEN/SP, Cidade Universitária, São Paulo, Brazil. mribeiro@ipen.br
authors.forename: Martha Simões
authors.initials: MS
authors.lastname: Ribeiro
authors.forename: Daniela De Fátima Teixeira
authors.initials: Dde F
authors.lastname: Da Silva
authors.forename: Carlos Eugênio Nabuco
authors.initials: CE
authors.lastname: De Araújo
authors.forename: Sérgio Ferreira
authors.initials: SF
authors.lastname: De Oliveira
authors.forename: Cleusa Maria Raspantini
authors.initials: CM
authors.lastname: Pelegrini
authors.forename: Telma Maria Tenório
authors.initials: TM
authors.lastname: Zorn
authors.forename: Denise Maria
authors.initials: DM
authors.lastname: Zezell
mesh_terms: D000818:Animals; D002056:Burns / Q000473:pathology / Q000532:radiotherapy*; D028022:Low-Level Light Therapy; D008297:Male; D051381:Rats; D011917:Rats, Inbred Lew; D012867:Skin / Q000293:injuries / Q000473:pathology / Q000528:radiation effects*; D014945:Wound Healing / Q000528:radiation effects*