Evaluation of peri-implant bone metabolism under immediate loading using high-resolution Na¹⁸F-PET

This study aimed to examine the influence of immediate loading on the dynamic changes of bone metabolism around dental implants using a high-resolution semiconductor sodium ¹⁸F-fluoride (Na¹⁸F)-PET.

Tibiae of 12 adult male rats were divided into 4 groups: immediate loading (IL), no loading (NL), bone defect (BD), and control (CTR). For the IL group, a 4.0-N load was applied continuously by two closed-coil springs attached between two implants in tibia. Each rat received an intravenous injection of Na¹⁸F and was scanned by high-resolution Na¹⁸F-PET at day 1 and then at weeks 1, 2, 3, 4, 5, 6, and 8 after surgery. Bone metabolism around the implant was evaluated by standardized uptake value (SUV), which indicates the outcome of Na¹⁸F accumulation. CT scanning was also performed, and PET and CT images were superposed to determine the anatomical orientation in PET images.

Bone metabolism peaked at 7 days after surgery and then gradually decreased in all three test groups (IL, NL, and BD). SUVs of all three test groups were significantly higher than the baseline at 1, 2, 3, and 4 weeks after surgery, with SUVs in the IL group returning to baseline levels earlier than those in the NL and BD groups.

Fluorine integrates preferentially with the initial low-calcified bone; thus, our results suggest that immediate loading promotes the calcification of the bone tissue in the early stage on peri-implant bone formation.

Na¹⁸F-PET allows for an estimate of bone metabolism change around the implant.