Peri-implant osseointegration after low-level laser therapy: micro-computed tomography and resonance frequency analysis in an animal model

The purpose of the present study is to evaluate the effects of low-level laser therapy on the osseointegration process by comparing resonance frequency analysis measurements performed at implant placement and after 30 days and micro-computed tomography images in irradiated vs nonirradiated rabbits. Fourteen male New Zealand rabbits were randomly divided into two groups of seven animals each, one control group (nonirradiated animals) and one experimental group that received low-level laser therapy (Thera LaseA (R), aluminum-gallium-arsenide laser diode, 10 J per spot, two spots per session, seven sessions, 830 nm, 50 mW, CW, 0.0028 cm(2)). The mandibular left incisor was surgically extracted in all animals, and one osseointegrated implant was placed immediately afterward (3.25o Au 11.5 mm; NanoTite, BIOMET 3i). Resonance frequency analysis was performed with the OsstellA (R) device at implant placement and at 30 days (immediately before euthanasia). Micro-computed tomography analyses were then conducted using a high-resolution scanner (SkyScan 1172 X-ray Micro-CT) to evaluate the amount of newly formed bone around the implants. Irradiated animals showed significantly higher implant stability quotients at 30 days (64.286 A +/- 1.596; 95 % confidence interval (CI) 60.808-67.764) than controls (56.357 A +/- 1.596; 95 %CI 52.879-59.835) (P = .000). The percentage of newly formed bone around the implants was also significantly higher in irradiated animals (75.523 A +/- 8.510; 95 %CI 61.893-89.155) than in controls (55.012 A +/- 19.840; 95 %CI 41.380-68.643) (P = .027). Laser therapy, based on the irradiation protocol used in this study, was able to provide greater implant stability and increase the volume of peri-implant newly formed bone, indicating that laser irradiation effected an improvement in the osseointegration process.