Finite-Element Analysis via Microcomputed Tomography of Implant-supporting tissues

Accurate imaging and modeling of biomechanical forces of osseointegrated oral implants is important in the better understanding of mechanical influences on loading. Orthopaedic spatial structures can be clarified under micro-computed tomography (MCT), however, due to the bulging and scattering effects of titanium under MCT examination, only limited information is available.

Objective: To verify the influence of implant removal on supporting bone using finite element (FE) modeling.

Methods: 1x2 mm cylindrical SLActive titanium oral implants were utilized. To investigate the limitations of MCT, implants were placed into homogenous phantom blocks, and MCT performed in 90kV with copper filters. The influence of implant removal was evaluated using FE models. Different rigidities of supporting bone ranging from 1,000 – 100,000 Mpa, different levels of bone-implant contact (BIC) ranging from 30-100% and 2 different loading situations were evaluated. The simulations assessed were: 5° vertical and oblique load with a rate of 0.05 mm/sec until complete implant displacement through the block. The BIC was modeled using the cohesive concept, and 5 μm interfacial zone was assumed to have similar mechanical properties with surrounding tissues. The simulation procedures were analyzed by ABAQUS software and the strain distribution recorded with the permanent damage of tissue set as 3%.

Results: A range of 120-150 μm higher-intensity zone expanding from the implant border was noted under MCT. Under FE evaluation, no significant difference of strain distribution was found among different rigidities, and the strain elevated with decreasing BIC level and angulations of load. The highest strain occurred in 30% BIC model with oblique load, while the strain level remained within the plastic range.

Conclusion: The implant removal procedure did not damage, but provided spatial conformation of implant-supporting structures. The translation of this information on MCT images should functionally model osteogenesis and osseointegration of peri-implant tissues. Supported by the AO Foundation.