Finite element modeling of dynamic loading on osseointegration to different bone density

Primary stability, micromotion of the implant fixture, is mostly evaluated by static loading in finite element analysis. However, masticatory offers dynamic occlusal loading and may lead to stress accumulation. This finite element analysis evaluated the effect of dynamic loading on primary stability and stress level under different loading frequency. This study was to assess the magnitudes of micromotion and stress within the three-dimensional mandibular bone structure. Implant model, a cylinder neck, was rebuilt from the manufacturer. The contact condition between implant and bone was non-osseointegration. Static loadings with forces of 100 N in an axial direction, 17 N in a lingual direction, and 25 N in mesio-distal direction were applied on the top of implants. The force components of dynamic loadings were the same as static loadings but cyclically applied with varying chewing frequency (0.5, 1 and 1.67 Hz) to simulate the average masticatory speed. Elastic modulus of cancellous bone was changed to express the different quality of bone. The results reveal that the stiffer the cancellous bone, the less micromotion was observed. The highest compressive stress regions under static and dynamic loading were around the step platform and the interface of cortical and cancellous bone. Micromotion induced by dynamic loading was three times higher than those by static loading. Masticatory in a higher frequency causes larger stress accumulation than that in a lower frequency. Masticatory in slow frequency may induce osseointegration and prevent bone loss.