A Comprehensive Study on Implant Stability Quotient (ISQ) in View of Resonance Frequency and Spectrum Analysis.

PURPOSE: This experimental study investigated how well implant stability quotient (ISQ) represents resonance frequency. Benchtop experiments on standardized samples, mimicking a premolar section of a mandible, were conducted to correlate an ISQ value and a resonance frequency to synthetic bone density and an incremental insertion torque. A frequency spectrum analysis was performed to check the validity of the resonance frequency analysis (RFA).

MATERIALS AND METHODS: Branemark Mk III implants with dimensions ∅4 Å~ 11.5 mm were placed in Sawbones test models of five different densities (40, 30, 40/20, 20, 15 PCF). An incremental insertion torque was recorded during implant placement. To perform stability measurements, the test models were clamped partially in a vise (unclamped volume 10 Å~ 20 Å~ 34 mm). A MultiPeg was attached onto the implants, and a Penguin RFA measured ISQ. Simultaneously, motion of the MultiPeg was monitored via a laser Doppler vibrometer and processed by a spectrum analyzer to obtain the resonance frequency. Tightness of the clamp was adjusted to vary the resonance frequency. A statistical analysis produced a linear correlation coefficient 𝑅 among the measured ISQ, resonance frequency, and incremental insertion torque.

RESULTS: The resonance frequency had high correlation to the incremental insertion torque (𝑅 = 0.978), confirming the validity of using RFA for this study. Measured ISQ data were scattered and had low correlation to the resonance frequency (𝑅 = 0.214) as well as the incremental insertion torque (𝑅 = -0.386). The spectrum analysis revealed simultaneous presence of multiple resonance frequencies.

CONCLUSIONS: For the designed benchtop tests, resonance frequency does indicate implant stability in view of Sawbones density and incremental insertion torque. ISQ measurements, however, do not correlate well to the resonance frequency, and may not reflect the stability when multiple resonance frequencies are present simultaneously.