Assessing the implant/bone interface by using natural frequency analysis

Objective. A number of techniques have been proposed for detecting the stab ility of dental implants. However, the clinical applicability of those meth ods is still limited. The purpose of this study was to evaluate a new innov ative, noninvasive, minimum-contact method for the stability assessment of dental implants. Study design. Natural frequency is a physical property of a structure, whic h is strongly related to its boundary conditions. In this study, a modal te sting technique was carried out to measure the natural frequency of dental implants. The implants were fixed by a metal clamp stand and were excited t o vibrate by an impulse hammer. A noncontact piezoelectric microphone then acoustically acquired the vibration responses of the implants. Natural freq uencies of the tested implants were recorded under various clamping forces and clamping levels. Results. Natural frequencies of the tested implants were concentrated from 8 to 19 kHz under different boundary conditions. On the other hand, the nat ural frequency values decreased when boundary levels and boundary force wer e reduced: Linear relationships (P <.005) were found between response frequ encies and the degree of implant stability. Conclusions. Our results show that the boundary status of an implant can be monitored by detecting its natural frequency. A noncontact transducer used in this study can also serve as a useful tool for future clinical investig ations.