Bone Neoformation Induced by Low-Level Laser and Methylene Blue Suggests Early Ossification in Rats

Introduction: Bone healing depends on inflammation control and tissue repair time. Low-level laser therapy (LLLT) has been investigated to accelerate this process. Methylene blue (MB), together with LLLT, has been investigated for its antioxidant and anti-inflammatory potential; however, the effects of photosensitizers (photodynamic therapy, PDT) are controversial. This study aimed to verify whether the combination of MB and LLLT changes the course of the consolidation of experimental bone defects. Methods: Sixteen Wistar rats underwent femoral bone defects. In the control group (n=4), LLLT simulations were performed without MB. The MB group (n=4) received MB and simulation of LLLT. The LLLT group (n=4) was exposed to LLLT. The PDT+LLLT group (n=4) received MB and LLLT. At the end of 7 or 14 days, the animals were euthanized, and samples were collected. Results: PDT and LLLT induced osteogenic formation with cellularity (after seven days) and union of bony edges (14 days). On the seventh day, LLLT combined with PDT induced an increase (P<0.05) of 484% in the area of bone neoformation compared to the control. On the fourteenth day, LLLT combined with PDT or alone increased (P<0.05) the area of bone neoformation by 214% and 240% respectively, compared to the control group. The PDT/LLLT combination was associated with increased radiopacity (P<0.038). Conclusion: The combined use of MB with LLLT initiated during the transoperative phase may stimulate the bone repair process in rats.