Dose-dependent effect of radiation on titanium implants: a quantitative study in rabbits.

OBJECTIVES: The aim of the study was to investigate the dose-dependent effect of radiation on dental implant stability and osseointegration using a series of quantitative analyses. MATERIAL AND METHODS: Six rabbits were randomly assigned to 15 and 30 Gy radiation groups. Each rabbit received radiation at the tibial and femoral metaphyseal region of left hind leg. The right leg was used as control. Implant surgery was performed on tibial and femoral metaphyses after 1 week. Totally 24 implants were inserted. The animals were killed at postoperative week four. Implant stability was measured using resonance frequency analysis. Ratio of bone volume to total volume (BV/TV), rate of bone growth, and bone-to-implant contact (BIC) were assessed using micro-computed tomography (micro-CT), fluorochrome labeling analysis, and histomorphometric analysis, respectively. RESULTS: After 4 weeks of healing, all implants were integrated (n = 6). Implant stability was significantly compromised by 15 Gy (P = 0.010) and 30 Gy (P = 0.025) of radiation. Radiation decreased BV/TV, and the significant effect was detected at the dose of 15 Gy (P = 0.008) and 30 Gy (P < 0.001). Bone growth in osseointegration was impaired by radiation. In 15 Gy group, the radiation side showed significant lower rate of bone growth than the control side at week 3 (P = 0.001), while the undistinguishable signals on 30 Gy radiation side suggested the low rate of new bone formation at each time point. Histomorphological BIC had no significant difference between 15 Gy control side and 15 Gy radiation side. 30 Gy radiation side showed a significantly lower BIC than 30 Gy control side (P < 0.001) as well as 15 Gy radiation side (P < 0.001). CONCLUSIONS: Implant stability and osseointegration were compromised by radiation. Radiation compromised osseointegration in a dose-dependent manner.