The effect of equal daily dose achieved by different power densities of low-level laser therapy at 635 and 670 nm on wound tensile strength in rats: a short report.
OBJECTIVE
The aim of our study was to compare the effects of different power densities of LLLT at 635 and 670 nm achieving a daily dose of 5 J/cm(2) on wound tensile strength (TS) in rats.


BACKGROUND
Optimal parameters of low-level laser therapy (LLLT) are still unknown.


METHODS
Under general anesthesia, one full-thickness skin incision was performed on the back of each rat (n = 40) and immediately closed using an intradermal running suture. Rats were separated into five groups depending on treatment parameters: (1) sham irradiated control group (SIC); (2) 635 nm laser-treated group at 4 mW/cm(2) (L-635/4); (3) 635 nm laser-treated group at 15 mW/cm(2) (L-635/15); (4) 670 nm laser-treated group at 4 mW/cm(2) (L-670/4); and (5) 670 nm laser-treated group at 15 mW/cm(2) (L-670/15). The total daily dose was 5 J/cm(2). Seven days after surgery each wound was removed for wound TS measurement.


RESULTS
The lowest wound TS results were measured in the SIC rats (10.5 +/- 2.8 g/mm(2)). Higher wound TS results were measured in group L-670/15 (11.5 +/- 2.5 g/mm(2)) and group L-635/4 (11.7 +/- 4.3 g/mm(2)) rats, while significantly higher results were found in group L-670/4 (15.8 +/- 4.4 g/mm(2)) and group L-635/15 (15.9 +/- 4.8 g/mm(2)). The differences were significant between certain groups (p < 0.01: SIC vs. L-635/15, SIC vs. L-670/4; p < 0.05: L-635/4 vs. L-635/15, L-635/4 vs. L-670/4, L-635/15 vs. L-670/15, L-670/4 vs. L-670/15).


CONCLUSIONS
Both red lasers significantly increased wound TS at selected parameters. Whereas the 635 nm laser significantly improved wound healing by using the higher power density, the 670 nm laser improved healing using a lower power density.
Vasilenko
Tomás
T
Department of Medical Biophysics, Pavol Jozef Safárik University, Kosice, Slovak Republic.
Slezák
Martin
M
Kovác
Ivan
I
Bottková
Zuzana
Z
Jakubco
Ján
J
Kostelníková
Martina
M
Tomori
Zoltán
Z
Gál
Peter
P
D000818:Animals; D028022:Low-Level Light Therapy; D008297:Male; D011829:Radiation Dosage; D051381:Rats; D017207:Rats, Sprague-Dawley; D012867:Skin / Q000293:injuries; D013718:Tensile Strength / Q000528:radiation effects*; D014945:Wound Healing / Q000528:radiation effects; D014947:Wounds and Injuries / Q000503:physiopathology*