Clinical Monitoring with Resonance Frequancy Analysis (RFA) of Astra Implants

Clinical monitoring with resonance frequency analysis (RFA) of Astra Implants Introduction: A quantitative diagnostic technique capable of assessing implant stability, bone formation and the clinical performance of all implants is supposed to optimise the results and make them more predictable. This study is set up to investigate the healing process of Astra Tech Implants. Materials and methods: 20 patients (at the average age of 50,5 years, 11 women, 9 men) were provided with 47 self-tapping Astra Tech Implants according to the two-stage surgical protocol of Astra Tech Dental Implant System, with lengths of 9 to 15 mm (24 in the mandible and 23 in the maxilla). We used both Astra Tech ST Implants (24) of 4,5 to 5,0 mm in diameter and Astra Tech Uni Implants (23) of 3,5 to 4,0 mm in diameter. The surgical placement was performed under local anesthesia with Ultracain DS following the manufacturer's instructions. Resonance frequency analysis (RFA) according to Meredith et al (1996) was used for implant primary stability measurements. This technique makes use of a small L shaped autoclavable transducer (Type F5, F6 and F7 5mm; Osstell transducer, *Integration Diagnostics Ltd, Sävedalen, Sweden) attached to the Astra Tech Implants. The beam of the transducer extends over a range of frequencies (from 5 to 15 kHz) and the resonance frequency of the beam is measured and presented on the connected instrument* as an ISQ value (Implant Stability Quotient, which is directly related to the resonance frequency). The prosthetic overdentures of the patients were hollow grinded at the implantation area. After a healing period of 90 days the implants were exposed and the secondary stability (ISQ) was determined again with RFA. All fixtures were immediately provided with a fixed prosthetic supply. Results: All 47 Astra Tech Implants showed a high initial primary stability with an average ISQ of 67,35. The fixtures placed in the mandible (24) reached a significantly greater primary stability with an average ISQ of 69,46 than fixtures in the maxilla (23) of 65,25. During the healing period of 90 days all Astra Tech Implants have gained secondary stability. The 24 fixtures inserted in the mandible have gained significantly more stability (ISQ 73,06) than the implants in the maxilla (ISQ 67,08). Until now no implant has failed. Conclusion: Loading Astra Tech Implants after 90 days is a predictable treatment in the mandible as well as in the maxilla. In order to accelerate this procedure we started to expose Astra Tech Implants with a significantly high primary stability (ISQ higher than 65,00) after 56 days. When secondary stability had been increased after 56 days, we started immediately with the prosthetic supply (direct loading). A loss of stability indicated a progressive loading connecting the implant with a healing abutment for additional 56 days. Keywords: clinical monitoring, resonance frequancy analysis (RFA), astra implants