RESONANCE FREQUENCY ANALYSIS FOR IMPLANT STABILITY MEASUREMENTS. A review

The resonance frequency analysis (RFA) technique for implant stability measurements was developed by Meredith and coworkers more than 20 years ago. RFA makes use of a transducer (peg), which is attached to the implant and excited over a range of frequencies by electro-magnetic waves to measure the resonance frequency (RF) of the transducer. The underlying RF measurements in Hz are translated to Implant Stability Quotients (ISQ) units from 1 (lowest stability) to 100 ISQ units (highest stability). A new generation of RFA technology has been developed consisting of a small pen-like battery-driven instrument (Penguin) used together with reusable transducers (MulTiPegTM). These are made from biocompatible titanium and can be autoclaved and used numerous times. The instrument can be packed in a sterile pouch and kept on the surgical tray and used by the surgeon without jeopardizing sterility. RFA measures implant stability in bending as a function of interface stiffness and correlates with implant displacement, i.e. micro-mobility, under lateral loading. The ISQ value is determined by the local bone density and is influenced by implant placement technique, implant design, healing time and exposed implant height above the alveolar crest. It seems like implants with low and/or falling ISQ values pose an increased risk for failure compared with implants with high and/or increasing values. The RFA technique can be used at any stage during treatment as one additional parameter to support decision-making during implant treatment and follow-up. For instance, authors have proposed that certain levels of stability should be achieved/reached in order to commence immediate and early loading.