Effect of laser therapy on bone tissue submitted to radiotherapy: experimental study in rats.
OBJECTIVE
The aim of this study was to investigate the effect of laser therapy (lambda = 780 nm) on bone tissue submitted to ionizing radiation.


BACKGROUND
The biostimulation effect of laser in normal bone tissue has already been demonstrated successfully; however its effect on bone tissue submitted to radiotherapy has not yet been studied.


METHODS
Twenty-two Wistar rats were randomly divided into four groups: group I, control (n = 4), submitted only to radiotherapy; group II, laser starting 1 day prior to radiotherapy (n = 6); group III, laser started immediately after radiotherapy (n = 6); group IV, laser 4 weeks after radiotherapy (n = 6). The source of ionizing radiation used was Cobalt 60, which was applied in a single dose of 3000 cGy on the femur. The laser groups received seven applications with a 48-h interval in four points per session of DE = 4 J/cm(2), P = 40 mW, t = 100 sec, and beam diameter of 0.04 cm(2). All animals were killed 6 weeks after radiotherapy.


RESULTS
Clinical examination revealed cutaneous erosions on experimental groups (II, III, and IV) starting at the 6th week after radiotherapy. The radiographic findings showed higher bone density in groups II and IV (p < 0.05) compared to the control group. The results further showed an increase of bone marrow cells, and number of osteocytes and Haversian canals in experimental groups II and IV (p < 0.05). It was also found an increase of osteoblastic activity, in groups II, III, and IV (p < 0.05).


CONCLUSIONS
Laser therapy on bone tissue in rats presented a positive biostimulative effect, especially when applied before or 4 weeks after radiotherapy. However, the use of laser in the parameters above should be used with caution due to epithelial erosions.
Da Cunha
Samantha Seara
SS
Federal University of Bahia, Salvador, Bahia, Brazil. samanthadacunha@hotmail.com
Sarmento
Viviane
V
Ramalho
Luciana Maria Pedreira
LM
De Almeida
Darcy
D
Veeck
Elaine Bauer
EB
Da Costa
Nilza Pereira
NP
Mattos
Alessandra
A
Marques
Aparecida Maria
AM
Gerbi
Marleny
M
Freitas
André Carlos
AC
D000818:Animals; D001835:Body Weight / Q000528:radiation effects; D001854:Bone Marrow Cells / Q000528:radiation effects; D001842:Bone and Bones / Q000473:pathology / Q000528:radiation effects*; D002452:Cell Count; D006253:Haversian System / Q000528:radiation effects; D028022:Low-Level Light Therapy; D008297:Male; D010011:Osteocytes / Q000528:radiation effects; D051381:Rats; D017208:Rats, Wistar