COMPARISON BETWEEN ACOUSTIC AND MECHANICAL TAPPING METHODS FOR ASSESSING THE INTERFACIAL STATES OF BONE IMPLANTS

Acoustic and mechanical tapping methods for in vivo assessment of the interfaces of bone implants are experimentally compared using implant models made of metal and glass. The former (AcT method) is based on the measurement of the frequency and amplitude of the vibration of a sample induced by a tapping needle. The latter (MeT method) is based on the measurement of the time during which a tapping rod is contacted with a sample. The vibration of a sample induced in the MeT test is different from that induced in the AcT test; the former is larger in the maximum amplitude and lower in the main frequency than the latter, although both are of damped type. A discrimination between hard and soft interfaces by each test depends on load directions to some extent, reflecting a mechanical difference of the interface and/or the surrounding bone. The MeT test appears to be more sensitive than the AcT test for implant models surrounded by a thin compact bone. For implant models surrounded by a thick compact bone, however, the former is less sensitive.