Measurement of mini-implant stability using resonance frequency analysis

Objective: To investigate whether resonance frequency analysis (RFA) is suitable to measure orthodontic mini-implant stability. Implant size significantly affects the level of resonance frequency. Regarding the operating mode of RFA, it has to be proven whether the resonance frequency of mini-implants in bone fits the range of frequency emitted by the Osstell ISO device. Material and Methods: For this purpose the SmartPegs in the Osstell ISO device were modified to fit with the inner screw thread of orthodontic mini-implants, and 110 mini-implants were inserted into porcine pelvic bone. RFA was performed parallel and perpendicular to the run of superficial bone fibers. A suitability test, Periotest, was also performed in the same directions. Compacta thickness was measured using cone-beam computed tomography. Correlation tests and linear regression analysis were carried out between the three methods. Results: The RFA showed a mean Implant Stability Quotient value of 36.36 +/- 2.67, and the Periotest mean value was -2.10 +/- 1.17. The differences between the two directions of measurement were statistically significant (P > .001) for RFA and the Periotest. There was a high correlation between RFA and the Periotest (r = -0.90) and between RFA and compacta thickness (r = 0.71). The comparison between the Periotest and compacta thickness showed a correlation coefficient of r = -0.64. Conclusion: The present results suggest that RFA is feasible as a measurement method for orthodontic mini-implant stability. As a consequence, it could be used for clinical evaluation of current stability and allow stability-related loading of mini-implants to reduce the failure rate. (Angle Orthod. 2013;83:230-238.)