Study On The Stress Distribution Of The Porous Surface Ti2448 Implant In The Jaw

Objective: Implants with appropriate elastic modulus are beneficial to reduce implant failure caused by stress concentration.Compared with traditional implants,the new material Ti2448 is closer to the elastic modulus of human jaw,but there is still a large gap between the two.Based on Ti2448,a new metal material with low elastic modulus,this project aims to further reduce the elastic modulus of the implant by constructing a ball-rod like porous structure on its surface.The influence of porous structure on the stress distribution of the implant and implant-bone interface under different loading conditions is analyzed biomechanically.To provide parameter basis and theoretical reference for mechanical optimization design and clinical application of Ti2448 implant.Methods: 1.Experimental grouping.NX1911 software was applied to construct Ti2448 implant models with a diameter of 4mm and a length of 12 mm.Solid implant were used as the control group(M0),and porous surface implants were used as the experimental groups(M1-9).The pore sizes of the surface porous structure of the implant were set in three gradients: 300μm,400μm and 500μm.The surface porous layers of the implant to the inner solid layers(thickness ratios)were set with three gradients--3:5,4:4 and 5:3.The aperture sizes and thickness ratios were pairwise combined.The experimental groups were divided into nine groups: M1(300,3:5),M2(300,4:4),M3(300,5:3),M4(400,3:5),M5(400,4:4),M6(400,5:3),M7(500,3:5),M8(500,4:4),M9(500,5:3).2.Model building.NX1911 software was used to build the models of jaw,central bolt and abutment,respectively,and they were assembled together with the implant model,i.e.,implant-jaw model,in a total of 10 groups.3.Mechanical loading.The 100 N static force perpendicular(axial)to the long axis of the implant was applied to the implant-jaw model,and the 100 N static force of 45° oblique from the lingual to the buccal to the long axis of the implants were applied to the abutments in the way of surface loading.4.Stress analysis.The stress distribution characteristics of the implants and the implant-bone interfaces were observed by using ANSYS Workbench19.2.Results:1.Under the two loading conditions,the stress concentration mainly occurred in the contact area between the implants neck and the surrounding cortical bone;With the increase of the pore size,the stress distribution area at the upper end of the porous implant group decreased,and the stress distribution area at the root end increased.The stress distribution area in root tip and bone tissue of M1a-M9 a groups was significantly larger than that of M0 solid implants.2.The stress value peaks of each group under oblique 100 N static force loading is significantly higher than that of the same group under axial 100 N static force loading;The stress value peaks of porous implants were all higher than the solid implant.With the increase of porous layer thickness,the stress peak values of 300μm and 400μm pore size group changed little,and the Von Mises stress peak value of 500μm pore size group changed greatly.3.M3 has a higher porosity in M1,M2,M3 and M4 groups.The peak values of Von Mises stress of M1 b,M2b,M3 b and M4 b implants were all less than 900 MPa and within the yield strength of Ti2448.The peak values of Von Mises stress of M5 b,M6b,M7 b,M8b and M9 b implants were all greater than 900 MPa,which exceeded the yield strength of Ti2448,and the implants might be permanently deformed or cracked.The peak values of Von Mises stress at the implant-bone interface in M1 b,M2b,M3 b and M4 b groups were in the range of 60～120MPa,and pathological stress might occur in the bone cortex under the long-term oblique force.The peak values of Von Mises stress at the implant-bone interface in M5 b,M6b,M7 b,M8b and M9 b groups were all greater than 120 MPa,and bone fracture may occur at the stress concentration of bone cortex.Conclusions:The introduction of porous structure is beneficial to the stress conduction to the surrounding bone tissue and reduces the stress shielding effect.Within the range of experimental parameters,the porous structure parameters of M3(300,5:3)group are more reasonable.The stress distribution of implant-bone interface still needs to be evaluated by optimizing the experimental model,and interactive verification of mechanical experiments is also needed.