Methods: Implants with two different surfaces, machined (M implant) or sandblasted/acid-etched (S implant), were placed into the distal femur of rabbits. Their surface morphology was investigated with scanning electron microscope. At 1, 2, 4, 6, 8, and 12 weeks postsurgery, they were sacrificed and subjected to histological and histomorphometric analysis. The indexes for histomorphometric analysis were bone-to-implant contact (BIC), percent of bone area at a distance of 0.5 mm (BT05) and 1 mm (BT10) from the implant surface. The RFA was performed on each implant both at the time of implant placement and animal sacrifice. ISQ at the animal sacrifice and the variation of ISQ (ÄISQ) at the time of implant placement and animal sacrifice were longitudinally and transversally compared at different time points. Additionally, the correlations between the RFA values and the histomorphometric data were assessed.
Results: The observation with scanning electron microscope confirmed that the roughness of the M and S implants had different roughness. The important finding of this study was thatÄISQ increased with the BIC through healing phase (P < 0.001). The ISQ at the sacrifice correlated with BIC (P < 0.001) and BT05 (P < 0.001). ÄISQ also correlated with BIC (P < 0.001) and BT05 (P < 0.028). RFA could distinguish between the M and S implants at 6 (P = 0.033) and 8 weeks (P = 0.004) postoperation.
Conclusion: RFA may be reliable biomechanical technique that can monitor the osseointegration formation.