Modal analysis for implant stability assessment: Sensitivity of this methodology for different implant designs

To investigate the influence of implant design on the change in the natural frequency of bone-implant system during osseointegration through a modal 3D finite element analysis. Six implants were considered. Two different models have been considered, differing in the free length of the mandibular branch. Modal analyses were carried out for each model. With reference to the ‘long branch’ model, the first three modes of vibration are whole bone vibration with minimum displacement of the implant relative to bone, with the exception of the initial condition where the implant is not osseointegrated. By contrast, implant displacements become relevant in the ‘short branch’ model, unless osseointegration level is beyond 20%. The difference between resonance frequency at whole bone maturation and resonance frequency at 1% bone maturation remained lower than 6.5% for all modes, with the exception of the third mode of vibration in the ‘D’ implant where this difference reached 9.7%. With reference to the ‘short branch’, considering the first mode of vibration, 61–68% of the frequency increase was achieved at10% osseointegration;72–79% was achieved at20%; 89–93% was achieved at 50% osseointegration. The pattern of the natural frequency versus the osseointegration level is similar among different modes of vibration.