抄録
It is clear that sufficient osseointegration markedly influences the prognosis of implant therapy. One problem that is yet to be resolved is the development of a therapy to promote rapid and reliable implant osseointegration. However, there have been few reports investigating the cell biological mechanisms of implant osseointegration. Recently, several experiments demonstrated that carbon dioxide (CO2) laser irradiation as well as mechanical force could stimulate bone regeneration. Given that laser irradiation can induce bone formation, it has been postulated that CO2 laser irradiation may be applicable to implant therapy in order to promote rapid and reliable osseointegration. This study examined the effects of CO2 laser irradiation on implant osseointegration. Sprague-Dawley rats underwent titanium implant insertion at the proximal tibiae and then 24 hours after the implant placement, and CO2 laser irradiation (0.5 W, 60 sec, 30 J) was performed at region of the left tibiae where the implants were inserted (laser group), while implants inserted in the right tibiae did not receive laser irradiation and served as the control group. Two weeks after the surgery, removal torque values of the laser group were significantly higher than those of the control group, but the values in both groups were equivalent 1 and 4 weeks after surgery. Sections of tibiae obtained 2 weeks after surgery showed that large amounts of bone tissue had formed around the implants in the bone marrow region in the laser group, whereas small amounts of bone tissue could be seen in sections from the control group. Interestingly, osteocytes in the bone tissue formed around the implants in the laser group showed a remarkably decreased immunohistochemical reaction for sclerostin as compared with osteocytes in the control group. Mineral appositional rate on bone histomorphometric examination using calcein labeling demonstrated much higher values in bone tissues formed around the implants in the laser group than those in the control group 2 weeks after surgery. These results indicate that bone formation around the implants was stimulated and maturation was accelerated by CO2 laser irradiation. In conclusion, these findings suggest that CO2 laser irradiation could be useful for implant therapy.
