Biomechanical Effects Of Vertical Alveolar Bone Resorption And Apical Surgery On Tooth:A 3-dimensional Finite Element Analysis

ObjectivesThis study aimed to investigate the biomechanical effects of vertical alveolar bone resorption and apical surgery on teeth via 3-dimensional(3D)finite element analysis.It is expected that the results of this study provide a theoretical basis for the prognostic assessment of apical surgery and the improvement of long-term retention rate of the affected teeth,as well as for accurate assessment of the capacity of periodontal support.Methods1.A 3D finite element model of the mandibular second premolar and periodontal tissue was developed as basic model.An adult left mandibular second premolar was scanned by Micro-CT,and a 3D finite element model was established by Mimics 21.0,Geomagic Studio 12,SolidWorks 2020,and ANSYS Workbench 18.1.After axial and oblique loading were simulated,output the von Mises stress and tooth maximum displacement ΔRmax)to verified the mechanical validity of the model.2.To investigate the biomechanical effects of vertical alveolar bone resorption and apical surgery on teeth,3D finite element models of mandibular second premolar with different degrees of vertical alveolar bone resorption on the medial side and before/after apical surgery were constructed.After loading,the distribution and trend of peak value of von Mises stress in alveolar bone were analyzed,as well as the trend of tooth displacement.The maximum displacement of the basic model under maximum occlusal force(ΔRmax ultimate)was taken as a reference to test the load tolerance threshold of each model.Finally,the remaining periodontal bone support area of each model was measured,and its’ correlation with biomechanical parameters was analyzed.Results1.A 3D finite element model of mandibular second premolar and periodontal tissues with good geometric similarity and mechanical validity was successfully established.Based on this model,12 experimental models were established to simulate teeth before/after apical surgery with 6 different degrees of vertical alveolar bone resorption.2.The increase in the peak value of von Mises stress caused by the vertical alveolar bone resorption was up to 16.8%,while the increase caused by apical surgery was 6.9%to 9.8%.The trends of the peak value before/after apical surgery were similar.Vertical alveolar bone resorption changed the von Mises stress distribution in periodontal tissue,which in turn affected the trend of peak value.3.The increase of △Rmax caused by vertical alveolar bone resorption was up to 46.4%,while the increase of △Rmax directly caused by apical surgery was 11.9%-13.9%.The trends of △Rmax before/after apical surgery were similar.4.After apical surgery and the occurrence of vertical alveolar bone resorption on the mesial side,the remaining periodontal bone support area of tooth with mild to moderate periodontitis was still grater than 50%.The load tolerance thresholds of models decayed by 26.6%to 35.1%under the influence of apical surgery and vertical alveolar bone resorption,whereas all load tolerance thresholds were higher than occlusion force of the mandibular second premolar under physiological conditions.5.Compared to the amount of alveolar bone resorption,the peak value of von Mises stress did not show a more significant correlation with the remaining periodontal bone support area,whereas the load tolerance threshold showed a higher correlation with the remaining periodontal bone support area.Conclusion1.The modeling method of mandibular second premolar and periodontal tissue in this study is reliable,which provide a reference for other biomechanical research using finite element analysis method in the future.2.With the aggravation of vertical alveolar bone resorption,the peak value of von Mises stress and the △Rmax exhibited a linear increase.3.The apical surgery did not significantly affect the trends of biomechanical parameters with aggravation of vertical alveolar bone resorption.4.In teeth with mild to moderate periodontitis and vertical alveolar bone resorption,apical surgery did not pose a serious threat to the stability of the affected teeth,and the teeth could still bear the normal occlusal load after apical surgery.5.The remaining periodontal bone support can better reflect the biomechanical conditions of teeth,whereas,simultaneous analysis of multiple factors is still required to achieve an accurate assessment of the capacity of periodontal support.