A dynamic finite element analysis of stress distribution in bone tissue surrounding solely or splinted implant-borne fixed partial denture / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To study the distribution patterns of stresses induced in bone tissue surrounding solely and splinted implants under dynamic loads.</p><p><b>METHODS</b>Three dimensional finite-element models were created of two 765 sections of the mandible with solely or splinted implants embedded in. Vertical and oblique dynamic loads were applied in a circle of mastication (0.875 s). The stress distribution was analyzed to study the biomechanical behavior of bone tissue surrounding solely or splinted implants.</p><p><b>RESULTS</b>As loading on the solely implant 5, the maximum von Mises value in the surrounding bone tissue under oblique loads at 0.300 s was 4.2 times as much as that under vertical loads at 0.150 s. Meanwhile, as coincidently loading on the splinted implants, the maximum von Mises value at 0.300 s was 1.2 times as much as that at 0.150 s. As loading on the solely implant 5, the maximum stress value was 48.393 MPa at 0.300 s. As separately loading on the splinted implant 5, the maximum stress value of the whole model was 9.541 MPa in the same loading course, and the maximum stress was located at the distal cervical of the indirectly loaded implant 7. When loading on the pontic, the stress in bone tissue surrounding implant 7 was more than that of implant 5.</p><p><b>CONCLUSIONS</b>Stress in the bone-interface of the splinted implants is evenly distributed at the cervical level, which may also reduce disadvantages from oblique loads.</p>

Three-dimensional finite element analysis of the stress in abutment periodontal ligament of cantilever fixed bridge under dynamic loads / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To analyze the stress distribution in the abutment periodontal ligament of posterior cantilever bridge under transient dynamic loads using a three-dimensional finite element(FE) model.</p><p><b>METHODS</b>A cantilever bridge using 5, 6 as abutments to restore missing 7 was designed, and its FE model was established and loaded with dynamic loads. The loads were set as 250 N occlusal forces loaded at different positions on the cantilever, and in different directions to simulate the masticatory cycle. FE analysis was conducted on the ANSYS to analyze stress distributions in abutment periodontal ligament under dynamic loads. Stress-time curves were traced to understand the biomechanical behavior of abutment periodontal ligament.</p><p><b>RESULTS</b>With loading and unloading time accumulated, the stress value in the abutment periodontal ligament increased gradually. Loads in lateral direction induced peak value stress in a masticatory cycle. There was little residual stress in the end of unloading phase. The maximum stress concentrated in abutment periodontal ligament adjacent to the missing tooth. Without restoration abutment periodontal ligament was mainly under compressive stress. However, when 7 was restored with a cantilever bridge, tensile stress was shown in the mesial cervical area of 5, Three masticatory cycles were simulated, and stress values in abutment periodontal ligaments increased with the number of masticatory cycles. But the differences of the stress between different masticatory cycles were not significant.</p><p><b>CONCLUSIONS</b>In the mastication movement, lateral loads induce maximum stress in abutment periodontal ligament. Cantilever fixed bridge design is more demanding for the periodontal condition of the abutment adjacent to the missing tooth than for the other abutment. When loaded with continuous masticatory force, the stress concentration does not increase significantly. Therefore, cantilever bridge is one of the feasible choices to restore missing lower second molar.</p>

Three-dimensional stress analysis of periodontal ligament of mandible incisors fixed bridge abutments under dynamic loads by finite element method / 华西口腔医学杂志

<p><b>OBJECTIVE</b>Three-dimensional finite method was used to analyze stress and strain distributions of periodontal ligament of abutments under dynamic loads.</p><p><b>METHODS</b>Finite element analysis was performed on the model under dynamic loads with vertical and oblique directions. The stress and strain distributions and stress-time curves were analyzed to study the biomechanical behavior of periodontal ligament of abutments.</p><p><b>RESULTS</b>The stress and strain distributions of periodontal ligament under dynamic load were same with the static load. But the maximum stress and strain decreased apparently. The rate of change was between 60%-75%. The periodontal ligament had time-dependent mechanical behaviors. Some level of residual stress in periodontal ligament was left after one mastication period. The stress-free time under oblique load was shorter than that of vertical load.</p><p><b>CONCLUSION</b>The maximum stress and strain decrease apparently under dynamic loads. The periodontal ligament has time-dependent mechanical behaviors during one mastication. There is some level of residual stress left after one mastication period. The level of residual stress is related to the magnitude and the direction of loads. The direction of applied loads is one important factor that affected the stress distribution and accumulation and release of abutment periodontal ligament.</p>