How it works

The technique behind and the ISQ scale


The technique behind the Penguin Instruments is called Resonance Frequence Analysis (RFA) and the measurement unit is named Implant Stability Quotient (ISQ).

The peg is excited by magnetic pulses and vibrates due to the stiffness in the contact area between the bone and the implant surface.

Once attached to an implant, magnetic pulses cause the MulTipeg™ to vibrate. The instrument measures the frequency of the vibration and translates it to an ISQ scale value between 1 and 99. The higher the ISQ value, the better the stability. RFA measures implant stability as a function of interface stiffness, which correlates with implant displacement, i.e. micro-mobility.

The local bone density determines the ISQ value, and is influenced by factors such as the implant placement technique, implant design and healing time. Implants with low and/or dropping ISQ values seem to pose an increased risk for failure compared with implants with high and/or increasing values.





The ISQ-scale and clinical guidelines

Values above ISQ 70 indicate a very stable implant with low micro-mobility. This value is typically recommended for one-stage and immediate loading. A second measurement is recommended before the final restoration to verify osseointegration.


Values in the range of 75 ISQ means the implant is already so stable that osseointegration cannot add stability in a significant way. The proof of osseointegration is the lack of a drop in ISQ.

If the implant has a low initial ISQ, osseointegration will add stability over time.

The osseointegration development and ISQ

Click link below to access article in Implant Dentistry Today No 14, 2020


The ISQ value correlates also to implant micro mobility, as shown in the articles below:

  • Trisi P, Carlesi T, Colagiovanni M, Perfetti G, J Osteol Biomat 2010; 1:141-151 | ID:-354 |
  • Pagliani L (L) ; Sennerby L (L) ; Petersson A (A) ; Verrocchi D (D) ; Volpe S (S) ; et al., J Oral Rehabil ; 2013-Mar ; 40(3):221-7

In addition, the importance of a primary and secondary ISQ measurement to detect an increase of stability and hence sufficient osseointegration, is shown in the following selection of articles;

  • Barewal RM, Oates TW, Meredith N, Cochran DL., Int J Oral Maxillofac Implants 2003: 18: 641–651
  • Glauser R, Lundgren AK, Gottlow J, Sennerby L, Portmann M, Ruhstaller P, Hämmerle CH., Clin Implant Dent Relat Res 2003: 5: 47–56.
  • Bogaerde LV, Pedretti G, Sennerby L, Meredith N., Clin Implant Dent Relat Res. 2010;12 (Suppl 1):e83-94.

Primary and secondary measurements are equally important in order to detect a decrease in stability, to identify potential implant failures which has been demonstrated in several articles, e.g.;

  • Glauser R, Sennerby L, Meredith N, Re´e A, Lundgren A, Gottlow J, Hämmerle CH., Oral implants Res 2004: 15: 428–434
  • Turkyilmaz I, McGlumphy EA.,BMC Oral Health. 2008;8:32.
  • Östman PO, Hellman M, Sennerby L., Int J Oral Maxillofac Implants. 2008;23:315-22.
  • Vanden Bogaerde L, Rangert B, Wendelhag I., Clin Implant Dent Relat Res 2005: 7(suppl. 1): 121– 130.

Additional scientific publications

More than 2600 articles on the subject have been published in peer-reviewed papers since 1999*.

*The articles are both in-vitro and in-vivo studies using RFA on dental implants. A part of the articles are using other means of measuring RFA than Penguin Instruments. 

Click here to retrieve the latest summary of selected publications.

The people behind



Prof Sennerby is a leading authority within clinical implant dentistry. He has had more than 250 articles published and has lectured extensively across the world. Lars has been a pioneer in the clinical development of RFA since 1996, and has used the technique since then.



Anders started the company Osstell in 1999, together with the inventors of RFA, Prof Neil Meredith and Prof Peter Cawley. Anders developed the RFA technique from its’ early prototypes to a commercial product in 2001 and was later responsible for the development of the contactless technique for measuring. Anders has been in the dental implant industry since 1993.