title: Effect of GaAlAs laser irradiation on the epiphyseal cartilage of rats.
abstract: OBJECTIVE
  To study the effect of an 830-nm gallium-aluminum-arsenic (GaAlAs) diode laser at two different energy densities (5 and 15 J/cm(2)) on the epiphyseal cartilage of rats by evaluating bone length and the number of chondrocytes and thickness of each zone of the epiphyseal cartilage.
  
  
  BACKGROUND
  Few studies have been conducted on the effects of low-level laser therapy on the epiphyseal cartilage at different irradiation doses.
  
  
  METHODS
  A total of 30 male Wistar rats with 23 days of age and weighing 90 g on average were randomly divided into 3 groups: control group (CG, no stimulation), G5 group (energy density, 5 J/cm(2)), and G15 group (energy density, 15 J/cm(2)). Laser treatment sessions were administered every other day for a total of 10 sessions. The animals were killed 24 h after the last treatment session. Histological slides of the epiphyseal cartilage were stained with hematoxylin-eosin (HE), photographed with a Zeiss photomicroscope, and subjected to histometric and histological analyses. Statistical analysis was performed using one-way analysis of variance followed by Tukey's post hoc test. All statistical tests were performed at a significance level of 0.05.
  
  
  RESULTS
  Histological analysis and x-ray radiographs revealed an increase in thickness of the epiphyseal cartilage and in the number of chondrocytes in the G5 and G15 groups.
  
  
  CONCLUSIONS
  The 830-nm GaAlAs diode laser, within the parameters used in this study, induced changes in the thickness of the epiphyseal cartilage and increased the number of chondrocytes, but this was not sufficient to induce changes in bone length.
authors.affiliation: Department of Physiotherapy, University of São Paulo, São Paulo, Brazil. marcressoni@yahoo.com.br
authors.forename: Marcela Dalla Costa
authors.initials: MD
authors.lastname: Cressoni
authors.forename: Helena Hanna Khalil Dib
authors.initials: HH
authors.lastname: Giusti
authors.forename: Antonio Carlos
authors.initials: AC
authors.lastname: Pião
authors.forename: Rodrigo Leal
authors.initials: RL
authors.lastname: de Paiva Carvalho
authors.forename: Carlos Alberto
authors.initials: CA
authors.lastname: Anaruma
authors.forename: Raquel Aparecida
authors.initials: RA
authors.lastname: Casarotto
mesh_terms: D000818:Animals; D019902:Chondrocytes / Q000473:pathology; D006132:Growth Plate / Q000473:pathology* / Q000528:radiation effects*; D054023:Lasers, Semiconductor; D008297:Male; D051381:Rats; D017208:Rats, Wistar