With increasing stiffness of the bone-implant interface, the vibration frequency of the sensor increases. While RFA is expressed in hertz, implant stability quotient (ISQ) is the scale used to quantify RFA values (range 1–100).

Even though RFA has been reported to be a reliable, reproducible, and objective method to measure the stiffness of bone-implant-complex, it has also been reported that RFA data from immediately placed implants could be misleading in increasing in terms of predicting primary stability. Therefore, this value needs to be supported by another means of quantifying anchorage, especially for immediate loading protocols. The reverse torque test or torque out (TO) could be used in vitro/ex vivo, as it gives information on the ability of the abutment or the whole implant to withstand a given torque value. As this test means to unscrew the implant, this method is inappropriate for clinical use.

Patient-dependent factors affecting implant stability include bone quality and quantity. Greater stability was achieved in more dense bone; here, failure rates accumulated in the upper jaw. Age, gender, smoking status, and periodontal status also affect the DIS. Implant-related factors affecting DIS vary from implant macro-geometry to surface characteristics. The surgical technique also influences DIS, and higher insertion torques as well as under-dimensioned drilling protocols are thought to increase the percentage of initial bone-implant contact by a better fit of the implant into the bone which in turn reduces the amount of micromotion after implant insertion.

Dental implant failure is related to numerous factors such as the quality and quantity of the bone-implant interface, the type of loading, implant geometry and surface characteristics, restoration prosthesis type, and the surgeons’ experience. Even though previous studies showed higher stability values for implants inserted in under-dimensioned cavities, in the last few years research has been directed to over-dimensioned protocols (ODP).