The aim of this study was to conduct a histological assessment of the effect of
photodynamic therapy (
PDT) on the repairing of third-degree-
burn wounds made on the backs of rats with a heated scalpel. Ninety-six rats were divided into groups: G1, control (n = 24), cold scalpel; G2, burned, heated scalpel (n = 24); G3,
low-level laser therapy (
LLLT) (n = 24), on
burns; and G4,
photodynamic therapy (
PDT) (n = 24), toluidine-O blue (100 microg/ml) and
LLLT treatment on
burns. The
laser (685 nm) was applied in continuous mode, 50 mW, 4.5 J/cm(2), contact mode at nine points (9 s/point). Eight animals in each group were killed at 3 days, 7 days or 14 days after surgery, and tissue specimens containing the whole wounded area were removed and processed for histological analysis; the results were statistically analyzed with Kruskal-Wallis and Dunn's tests (P < 0.05). The results demonstrated significant differences between G2 and G3, and between G2 and G4, at both 3 days and 7 days, with regard to acute
inflammation scores; G1 and G2 showed significant differences when compared with G4 at 3 days, with regard to neo-angiogenesis scores; G1 and G2 were statistically different from G3 and G4 at both 3 days and 7 days, with regard to re-epithelization scores; G2 showed statistically significant differences when compared with G3 and G4 with regard to
collagen fiber scores at 7 days.
LLLT and
PDT acted as a biostimulating coadjuvant agent, balancing the undesirable effect of the
burn on the wound healing process, acting mainly in the early healing stages, hastening
inflammation and increasing
collagen deposition.