QUANTITATIVE-DETERMINATION OF THE STABILITY OF THE IMPLANT-TISSUE INTERFACE USING RESONANCE FREQUENCY-ANALYSIS

Bone anchored implants are now being used in dentistry for supporting intraoral and craniofacial prostheses. Although high success rates hav e been reported, a small number of implants may fail during the early healing phase or later in function. Currently available clinical metho ds to determine implant stability and osseointegration are relatively crude and may entail percussing a fixture with a blunt instrument. Rad iographs are of value, but a standardised technique is necessary to en sure repeatability. This investigation was designed to study the appli cation of a non-invasive test method using resonance frequency analysi s to make quantitative measurements of the stability of the implant ti ssue interface in-vitro and in-vivo. The resonance frequency of a smal l transducer was measured when attached to implants embedded at differ ent heights in an aluminium block. A strong correlation (r = 0.94, p < 0.01) was observed between the observed frequency and the height of i mplant fixture exposed. The change in stiffness observed in the bone s urrounding an implant during healing was modelled by embedding implant s in self-curing polymethylmethacrylate and measuring the resonance fr equency at periods during polymerisation. A significant increase in re sonance frequency was observed related to the increase in stiffness. R esonance frequency measurements were also made on implants in-vivo and the results correlated well with the in-vitro findings.