Implant-Bone Interface Biomechanics Distribution in Immediate-Loading Implants of Different Sizes

Objectives: The purpose of this study was to evaluate the effect of the diameter and length on the stress and strain distribution of crestal bone around implants under immediate loading.

Methods: By an ad hoc automatic mesh generator, high quality finite element models of complete range mandible was constructed from CT, with 3 ITI implants of various sizes embedded in anterior zone. The implant diameter ranged from 3.3 to 4.8 mm, and length from 6 to 14 mm, resulting in 7 designs. Each of them included variant sizes implants which was 3.3×10 mm, 4.1×10mm, 4.8×10 mm, 4.1×6 mm, 4.1×8 mm, 4.1×12 mm and 4.1×14 mm respectively. The implant–bone interface was simulated by non-linear frictional contact algorithm. For each design, vertical and oblique loadings of 150 N were applied respectively to each implant, and stresses and strains in the surrounding cortical bone were evaluated.

Results: Results of the analyses demonstrated that: the oblique loading would induce significant higher interfacial stresses and strains than the vertical loading. While, under both loadings, the maximal values were recorded in the 3.3(diameter)×10(length)mm implant configuration, whose mean and peak values were both higher than that of others with significant statistical differences (P<0.05). The second maximal one is 4.1×6mm configuration. And the minimal stresses were recorded in 4.8×10mm configuration, whose strains were also near to lowest.

Conclusions: It was concluded that increasing diameter had a more significant effect than length to relieve the crestal stress and strain concentration. To gain sufficient stability from the cortical plates of alveolar bone for immediate loading, the diameter of implant should be 4.1mm at least, better 4.8mm when there is sufficient bone, and length of 10mm is enough.