Purpose: The stimulating effect of low-power laser (LPL) irradiation on wound healing has been noticed in several in vitro studies. The aim of this study was to investigate the influence of the LPL irradiation in vivo on bone healing of jaw defects created after surgical treatment of chronic periapical lesions. Materials and Methods: This prospective clinical study encompassed 40 patients with radiographically and clinically diagnosed chronic periapical lesions or radicular cysts that were surgically removed. They were divided into two groups: (1) The study group comprised 20 patients who received daily LPL irradiation of the operative field (bone defect) for 7 postoperative days (energy output 4 J/cm2, with constant power density of 50 mW, wavelength 637 nm); (2) The control group comprised 20 patients who did not receive postoperative LPL irradiation of postsurgical bone defects. Healing of bone defects was evaluated by densitometry, investigating optical density in precisely defined areas of the panoramic radiographs made immediately after the operation, and 3 and 6 months thereafter. Comparison of identical anatomical details on different radiographs was made by the use of PVC foil, with inscribed vertical and horizontal lines at equal distances. Results: Differences in values of relative optical density were statistically significant between the examined groups of patients in every period of investigation, as well as between the values registered within each group during the period of investigation. In the study group of patients who were irradiated with the LPL, the process of bone defect healing was noticeably accelerated in all periods of investigation, the mean optical density being 1.56 after 6 months in the study group in comparison to 1.28 in controls, which was statistically significant. Comparing the investigated groups of patients, significantly faster bone regeneration at the periphery of defects (greater optical density) was noticed in the study group than in the control, in all the periods of investigation (2.06 at the beginning, 1.81. after 3 months, and 1.56 after 6 months in the study group, in comparison to 1.74, 1.50 and 1.32, respectively, in the control). Conclusion: LPL irradiation of periapical bone defects with GaAlAs laser, using daily intraoral irradiation with energy output of 4 J/cm2, significantly influences healing of periapical bone defects in vivo. Bone regeneration was faster at the periphery of the defects, which agrees with the fact that bone regeneration proceeds from periphery to central areas of the defect.
Keywords: low-power laser, GaAlAs laser, periapical surgery, bone healing, clinical study