Morphological Effect of Diode Laser Irradiation of Periapical Lesion in Rat

The aim of this study was to evaluate the morphological effects of diode laser irradiation in the experimentally produced periapical lesion in rat. Fourteen adult male Sprague-Dawley rats weighing approximately 200 gm each were used. Pulp was extirpated from the mesial root of the maxillary first molar using 06 to 25 mm conventional reamers and files. After extirpation, the root canal was exposed to oral flora for 4 weeks to allow periapical periodontitis to develop. After the development of periapical periodontitis, the lesions were irradiated using a diode laser at 5 W for 5 seconds. The root canal was then sealed with cavity filling material for another 4-week period. After 4 weeks, the experimental rats were sacrificed by cervical dislocation. The maxillary first molar was then collected along with the surrounding tissue, which was processed in the laboratory. Hematoxylin and eosin and immunohistochemical staining were used to observe the morphological effects. Proliferating cell nuclear antigen (PCNA), STRO-1 and CD44 were used as the primary antibodies for the immunohistochemical study. A reduction in inflammatory cells, which were mainly composed of lymphocytes, was observed in the periapical lesions after irradiation. The number of PCNA-positive cells increased to approximately twice that observed in the nonirradiated control group. These PCNA-positive cells included STRO-1 and CD44-positive cells, indicating enhancement of wound healing and reduction in inflammatory cells. The present results showed that diode laser irradiation enhanced proliferation of PCNA-positive cells, which included STRO-1 and CD44-positive cells. This increase in these types of cell may improve wound healing in periapical lesions.