Effects of Low Reactive Level Laser Therapy on the Progress of Bone Healing

Abstract

Purpose: Low reactive level laser therapy（LLLT）is known to promote bone defect healing. This study was designed to investigate the effects of LLLT on bone defect healing using an experimental rat model.
Material and Methods: Eight-week-old male Sprague Dawley rats were used in this study. Bone defects reaching into the bone marrow located 10mm from the femur articular surface on either side were created using a low-speed round bur（ø1.6 mm）under sterile saline. After hemostatic wound closure was attained, one side was irradiated with He-Ne laser（Soft Laser 632, wavelength: 632.8nm）and the other was left unirradiated（laser group and control group, respectively）. The laser irradiation was performed transcutaneously to the bone defects for 5minutes（output power: 25mW, distance: 25mm）every 24hours for 4days immediately after the operation（5times in all）. The rats were sacrificed after either 7 or 14days, and the resected femurs were subjected to radiological evaluation for bone volume（BV）, bone surface area（BS）, bone density（BD）, trabecular number（Tb.N）, trabecular thickness（Tb.Th）, trabecular separation（Tb.Sp）and trabecular spacing（Tb.Spac）. All experiments were approved by the Animal Experimental Committee at the School of Dentistry, Aichi Gakuin University（AGUD 266）.
Results: Micro-CT examination demonstrated that both Tb.Sp and Tb.Spac in the laser group were lower than those in the control group at 7 days but were higher at 14days. The laser group exhibited more BV, BD, Tb.N and Tb.Th at 7days but less at 14days. The progress of bone healing was observed at the early stage in the laser group.
Conclusion: This particular study revealed the positive LLLT effects of He-Ne laser in promoting bone healing of experimental bone defects in a rat model.