Investigation of the effects of low level laser therapy in boneregeneration at rabbit cranial defects

The aim of this study is to determine the levels of bone filling and bone formation with histological, histopathologic and microCT examinations at the 4th and 8th weeks of rabbit cranial defects of different application protocols of low density (diode) laser. In addition, histological and immunohistochemical evaluations at the end of the second week are aimed to determine the mechanism of the diode laser. In this study 26 New Zealand White Rabbits were used between 2,5-3,5 kg. Firstly, 8 mm diameter defects were prepared by surgical procedure performed under anesthesia in rabbit calvarias. The rabbits received a total of five laser treatments for 10 days, including postoperative day. The laser doses tested were 4 joules, 6 joules and 8 joules. At the end of the second week, 5 rabbits were sacrificed for histological, immunohistochemical and microCT analyzes. At the 4th and 8th weeks, 20 rabbits were sacrificed for microCT, histopathologic and immunohistochemical analysis. The total number of rabbits was 26. Findings of micro CT evaluation revealed , more bone fill found in test treated groups compared to non-treated group (p<0.0001). The most effective group among laser groups was the 6 joules low intensity laser application group. Histopathological examination revealed more bone islands in the defect wall compared to the control defects. Osteoblastic activity was detected around the bone islands. BMP-2 levels were higher in 4 joule group by immunohistochemical evaluation on sacrificed animals at 2nd weeks. However, this difference is not statistically significant. In osteocalcin staining, osteocalcin expression was significantly higher in 4 joule groups. In the light of these findings, low-intensity laser application positively affects new bone formation in rabbit cranial defects. The high efficacy of doses of 4 j/cm2 and 6 j/cm2 is thought to be promising in applications. Stimulation with diode laser during the early phases of clinical applications such as periodontal regeneration, crest augmentation procedures, and dental implant surgery can be useful to modify and enhance wound healing and regeneration.