RESONANCE FREQUENCY MEASUREMENTS OF IMPLANT STABILITY IN-VIVO - A CROSS-SECTIONAL AND LONGITUDINAL-STUDY OF RESONANCE FREQUENCY MEASUREMENTS ON IMPLANTS IN THE EDENTULOUS AND PARTIALLY DENTATE MAXILLA

The aim of this investigation was to evaluate the use of resonance fre quency measurements in the clinical measurement of implant stability. Resonance frequency measurements are undertaken by measuring the respo nse of a small transducer attached to an implant fixture or abutment. Two groups of patients were selected for study. Group A comprised 9 pa tients who had a total of 56 implants placed. Resonance frequency meas urements were made at fixture installation and repeated 8 months later at abutment connection. The resonance frequency of the implant/transd ucer system increased for 50 out of the 56 implants from a mean value of 7473 Hz +/- 127 Hz (P<0.05) to a mean of 7915 Hz +/- 112 Hz (P<0.05 ). Two implants had failed to integrate and the resonance frequency of these had fallen. Group B comprised 9 patients who had been provided with fixed prostheses and had a total of 52 implants placed. They were examined 5 years after fixture placement and the prostheses removed. All implants were judged clinically to be osseointegrated. The level o f the marginal bone around each implant was calculated by measuring th e number of exposed threads on intraoral periapical radiographs and ad ded to the length of each abutment to give a value termed the effectiv e implant length (EIL). Measurements indicated a correlation (R = -0.7 8, P<0.01) between EIL and resonance frequency. The results support th e hypothesis that the resonance frequency of an implant/ transducer sy stem is related to the height of the implant not surrounded by bone an d the stability of the implant/tissue interface as determined by the a bsence of clinical mobility.