Influence of different energy densities of laser phototherapy on oral wound healing

Abstract

The aim of the present prospective study was to evaluate the impact of laser phototherapy (LPT) on the healing of oral ulcers. Different power densities were used on oral wounds in Wistar rats (n=72) randomly divided into three groups: control (0 J/cm2), 4 J/cm2 laser, and 20 J/cm2 laser. Ulcers (3 mm in diameter) were made on the dorsum of the tongue with a punch. Irradiation with an indium-gallium-aluminum-phosphide laser (660 nm; output power: 40 mW; spot size: 0.04 cm2) was performed once a day in close contact with the ulcer for 14 consecutive days. A statistically significant acceleration in healing time was found with wounds treated with 4 J/cm2 LPT. Moreover, striking differences were found in the ulcer area, healing percentage, degree of reepithelialization, and collagen deposition. The most significant changes occurred after 5 days of irradiation. Based on the conditions employed in the present study, LPT is capable of accelerating the oral mucosa wound-healing process. Moreover, faster and more organized reepithelialization and tissue healing of the oral mucosa were achieved with an energy density of 4 J/cm2 in comparison to 20 J/cm2.

Figures

Fig. 1

(a) Clinical aspect of oral ulcers in different groups on day 5, smaller ulcer area in 4  J/cm2 group; (b and c) Clinical evaluation of mean and standard error of area (in mm2); and (d) Clinical evaluation of percentage of wound healing (%).

Fig. 2

(a) Photomicrographs of experimental groups on day 5, reepithelialization covering entire wound and more chronic inflammatory infiltrate in the 4  J/cm2 group [hematoxylin-eosin; magnification: ×100 (a, c, and e) and ×200 (b, d, and f)]; (b and c) Histopathological evaluation of degree of reepitelialization (mean and standard error); and (d) Histopathological evaluation of degree of inflammation (mean and standard error).

Fig. 3

Photomicrographs of Picrosirius red staining in experimental groups on days 5, 10, and 14 and in normal mucosa (original magnification ×100). On day 5, all groups displayed poorly organized thin collagen fibers (characterized by green birefringence) (a, b, and c). On day 10, no difference was observed between all groups. Collagen fibers were begun to rearrange into bundles among the new muscle fibers (d, e, and f). On day 14, the groups treated with laser (h and i) exhibited an organization pattern similar to the normal oral mucosa (j) with a predominance of reddish fibers organized parallel to the epithelium. Control group revealed a more immature collagen (g).