| Purpose:To investigate the effect of occlusal gap on stress distribution,stress peak value and displacement at implant-bone interface under I-Ⅳ bone conditions by finite element analysis,and to provide some reference for occlusal adjustment of implant restorations.Method:Equal proportion upper right first molar Straumann 4.8 x 8 mm BL RC implants and their related component models were constructed by Solidworks2022,and then the tooth model was scanned by an optical scanner.and then Mimics,Geomagic,and Solidworks software was used,according to the bone quality proposed by Zarb and Lekholm Classification,Norton and Trisi bone density classification method,to establish the upper and lower jaw bone model of I-Ⅳ bone quality.The model was assembled with 0 μm,20 μm,40 μm,60 μm,80 μm,and 100 μm as the occlusal gap of the restoration.but an additional set of homogeneous models without density ratio setting was constructed as a comparison.After the above models were imported into Hypermesh for meshing,the material assignment,boundary constraints and parameter setting of finite element analysis were performed,and finally 250 N was used as the loading force to simulate the maxillary and mandibular stress conditions,and the stress distribution,peak stress and displacement of the implant-bone interface in each group of models were analyzed and compared.Results:(1)Under the same loading condition,the stress distribution of the implant was uniform with the occlusal contact point.When the occlusal gap reached 80 μm and100 μm,the stress interruption phenomenon appeared in the implant crowns under osteoid I and II,III and Ⅳ,respectively.(2)The displacement of the implant-bone interface was mainly concentrated in the cortical bone region around the implant and transmitted down the long axis of the implant to the cancellous bone region at the bottom.With the changes of Ⅰ-Ⅳ jaw bone,the displacement and Von Mises stress in cortical bone region increased in all groups,and were greater than those in cancellous bone region.The Von Mises stress in the cancellous bone region was similar to that in the cortical bone region except that it showed a downward trend from Class II bone.However,when the occlusal gap increased,the stress and displacement peak value in the cortical bone and the cancellous bone region showed a decreasing trend.(3)The interfacial stress of implant-bone tissue was between 20 MPa and 60 MPa when the occlusal space was 0 μm-40 μm for II-Ⅳ osteoid and 60 μm for Ⅳ osteoid,and the stress of other groups was less than 20 MPa.(4)The Von Mises stress was mainly concentrated in the neck of the implant,and the peak value of von Mises stress in II-Ⅳ osteoid with occlusal gap of 20 μm was higher than that in I osteoid with occlusal gap of 0 μm and 144.10 MPa.(5)In the homogeneous model with different elastic moduli,the distribution of stress and displacement is more uniform than that in the heterogeneous model.Conclusion:From the perspective of biomechanics,it is proved that the alveolar bone should be taken into account in the occlusal adjustment of implant denture,and the occlusal gap should increase with the decrease of jaw bone density in clinical work.An occlusal gap of 20 μm-40 μm between a single dental implant and a natural tooth in the opposite jaw is a relatively suitable solution for occlusal adjustment under different bone conditions.However,due to the particularity of finite element analysis method,it needs to be further studied in combination with clinical practice. |
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