Implant Stability Quotient
An Implant Stability Quotient (ISQ) measurement unit was obtained by an advanced non-invasive technique based on resonance frequency analysis, RFA (Penguin RFA, Göteborg, Sweden), commonly used to monitor implant stability. Briefly, a disposable MulTipeg™ (metal transducer with a magnet top) was attached to the implant and magnetically stimulated to vibrate at a micro scale by a handheld probe put closer by 2–4 mm towards the MulTipeg™ top. Then the resonance frequency, i.e., the frequency with the strongest vibration, is measured in a few seconds. Readings were performed from the buccal-lingual and mesial-distal directions. This way, the stiffness of the implant–bone interface was measured and expressed as an ISQ dimensionless value within a scale from 1 to 100, in which the higher the ISQ, the lower the micromotion and the more stable the implant is. Degree of stability can be classified as low for an ISQ < 60, high for an ISQ > 70, and as medium for values in between. ISQ is an objective standard measure reflecting the degree of stability.