Methods: A titanium implant (φ 1.2 mm) was inserted at the proximal metaphysis of tibiae in 10 Wistar-rats (20 weeks). Rats were randomly divided into two groups; loaded (test-group) and unloaded (control-group). Intermittent mechanical loading (Acceleration 100g, 4 Hz, 5 min/day) to the exposed upper portion of the implant by means of a custom-made loading devise was initiated at the same day of the installation for test-group. 18F- formed NaF was applied to rats as RI-tracer. The rats intravenously-injected with 18F- (1mCi/rat) were scanned by a high-resolution PET scanner (resolution: 0.7mm, MIP-100, Sumitomo) at 1, 3, 7, 14, 21, 28, 35, 42, 49 days after implantation. Spherical region of interest (ROI) was defined around the implants. Accumulation counts of 18F- at the ROI were examined. Data were analyzed statistically with two-way ANOVA followed by Dunnett’s test with the significance level set at 0.05.
Results: The accumulation value initially increased until 7 days and then gradually decreased to the initial level. The time after the implantation did have a significant effect in both test and control-groups (ANOVA). Significant differences were found between 1day and 7days after implantation (Dunnett’s test). However, no significant difference in accumulation value between the groups was found at any time point. The immediate loading condition employed in this experiments showed little effect on the peri-implants bone metabolism activated during wound healing process after the implantation.
Conclusions: These results are consistent with our previous report examined peri-implant bone metabolism, evaluated in 2D analysis using bone-scintigraphy. High resolution PET with 18F- isotope can be available to evaluate peri-implant bone metabolism 3-dimensionally.