ISQ (Implant Stability Quotient)
Also known as: RFA, resonance frequency analysis, implant stability, Osstell
A measurement of how stable an implant is in bone.
ISQ (Implant Stability Quotient) is a numerical measurement of implant stability, measured using Resonance Frequency Analysis (RFA). A small magnetic peg is screwed into the implant and a probe is held nearby — the natural resonance frequency of the implant-bone system is measured and converted to an ISQ value from 1 to 100.
What the numbers mean
- ISQ 70–85: High stability — typically suitable for immediate loading
- ISQ 60–70: Adequate stability — conventional loading protocol (heal before restoring)
- ISQ below 55: Low stability — implant may need more time before loading, or further assessment
When is it used?
ISQ measurement is used at implant placement to assess primary stability and guide loading decisions. It can also be taken at the restoration appointment to confirm osseointegration before the final crown is placed. Some clinicians monitor ISQ throughout healing — a dip then recovery in the values is characteristic of the bone remodelling process.
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