High-intensity Nd: YAG laser accelerates bone regeneration in calvarial defect models

High-power pulsed lasers have been recently regarded to be anabolic to bone, but in vivo evidence is still lacking. This study aimed to investigate the capacity of bone repair using a high-power, Q-switched, pulsed, neodymium-doped yttrium aluminium garnet (Nd:YAG) laser, using bilateral calvarial defect models having non-critical sized, 5mm (rat) or 8mm (rabbit) diameter. One of the bilateral defects, which were all filled with collagen sponge or left empty, was irradiated with a Nd:YAG laser once every 2days for 2weeks at a constant total fluence rate (344J/cm²), output power (0.75W), pulse repetition rate (15 pps) and wavelength (1064nm) and examined for the laser effect. The same experimental scheme was designed using a rabbit calvarial defect model implanted with sponge, which was explored for the dose effect of output power at 0.75 and 3W with the same quantities of the other parameters. New bone formation was evaluated by micro-computed tomography-based analysis and histological observation at 4weeks after surgery. Laser irradiation significantly increased new bone formation by approximately 45%, not only in the sponge-filled defects of rats but also when the defects were left empty, compared to the non-irradiated group. Consistently, both doses of output power (0.75 and 3W) enhanced new bone formation, but there was no significant difference between the two doses. This study is one of the first to demonstrate the beneficial effect of Nd:YAG lasers on the regeneration of bone defects which were left empty or filled with collagen sponge, suggesting its great potential in postoperative treatment targeting local bone healing.