Study And Application Of Stress Distribution In Mandible With Non Orthotopic Implants

Dental implant,also known as dental implant,is a kind of dental implant based on the substructure implanted in bone tissue to support and retain the upper part of the dental prosthesis.Dental implant has become the first choice for more and more patients with missing teeth because it can achieve similar results with the function,structure and aesthetic effect of natural teeth.At present,the implantation of implants in dental surgery is determined by the doctor’s experience and is usually perpendicular to the dentin-maxillofacial surface.Due to the obvious difference in masticatory habits of individual bone geometry,implant operation failure frequently occurs.Anatomists have found that when teeth are chewed,there is not only a vertical bite,but also an oblique bite and a meso-distal bite.Due to the unreasonable implantation Angle and position of implants in clinical practice,the phenomenon of implant falling off or breaking occurs frequently due to excessive force,resulting in dental implant failure.In more severe cases,it may lead to resorption or necrosis of the bone tissue of the mandible.Therefore,the selection of appropriate implant location and implant tilt Angle is very important for the long-term success of implants.The internal environment of human oral cavity is extremely complex,and the jaw is irregular shape.In this thesis,finite element analysis was used to study the stress distribution of bone tissue around a single inclined implant and four denture jaw implants under load.To provide some guidance for clinical implant repair.The contents of this thesis are as follows:(1)The mandible of an adult male was scanned by CT,and the complete mandible was modeled by Mimics,a reverse 3D modeling software.Due to the high roughness of the Mimics derived model,a flat and smooth 3D model of the mandible was obtained by surface treatment using Geomagic software.A complete mandible containing cortical and cancellous bone.Meshing,material attribute setting and constraint setting of mandible model were carried out in workbench to provide analysis model basis for finite element analysis.(2)To verify the accuracy of the model,set and simplify the boundary conditions of the finite element model according to the principle of mandibular movement;Mandible model and implant model were prepared by 3D printing.The experimental data and finite element simulation data were compared to verify the accuracy of the model.The results showed that when the mesh was divided into cortical bone 1.5,cancellous bone 1.2,implant 1 and abutment 0.5,the finite element analysis results were most similar to the experimental results.(3)The vertical load and bite force with direction and size were loaded on the mandibular oral model of a single inclined implant.Statics analysis of implants with different inclined angles was carried out by Workbench to obtain the stress concentration point and optimal implant Angle of the inclined implant.The possible factors leading to implant failure in clinic were analyzed.The analysis results show that the experimental model has two equivalent stress lows,one is the planting Angle of about 15°,which may be related to the material attribute setting and mandible morphology,and has uncertainty.The other is that when the planting Angle is 45°,the Angle can decompose the force well,so the equivalent stress is small.Therefore,in the case of a single implant,the most economical and rapid implantation Angle is about 15°.(4)The vertical load was applied to the edentulous whole jaw prosthesis to analyze the load distribution and maximum stress of the cantilever length on the whole jaw prosthesis with different tilt angles.The optimal stress corresponding to the length of the cantilever beam is obtained,which provides some guidance to the clinic.The experimental results show that the equivalent stress increases with the increase of the cantilever beam.At 15°,the equivalent stress increases slowly with the increase of the cantilever beam.At 45°,the equivalent stress increases rapidly with the increase of the length of the cantilever beam.Therefore,the length of the cantilever beam should be minimized during the whole jaw implant.Excessive tilt Angle may lead to implant failure.In the presence of cantilever beam,the optimal implantation Angle of jaw model in this experiment was about 15°.(5)Under the combined action of the cantilever beam and the planting Angle,the length of the cantilever beam can be reduced by changing the Angle of the implant,but excessive tilt Angle will lead to implant failure.When the first molar was loaded with100 N load,the length of the cantilever beam and the equivalent stress of the distal implant decreased with the increase of the implantation Angle.But when planting at 45°,although the length of cantilever beam decreases,the equivalent stress increases sharply.Therefore,the stress concentration can be reduced by increasing the implantation Angle to reduce the length of the cantilever beam,but the Angle should not be too large.