Preparation Of Porous Structure Implants By Selective Laser Melting And Analysis Of Their Properties

With the development of science and technology,dental implants as a means of repairing missing teeth have become more and more popular.Currently,most of the implants used in the market are made of titanium and titanium alloys,and their elastic modulus is much higher than that of human bone tissue,in the use of the process will have a“Stress shield”phenomenon,long-term use is easy to cause implant failure.Because of the unique internal connecting structure of porous structure,the elastic modulus of porous structure can be reduced effectively.It is difficult to manufacture porous structure by traditional methods,in this paper,selective laser melting technique was used to prepare porous structure implants.The porous structure specimens with different printing parameters were prepared by selected laser melting technique,and the optimal printing parameters were obtained by orthogonal analysis of the densities of the specimens and the influence of each factor on the densities of the specimens using software analysis.Porous structure samples with different porosity were prepared,and the effect of porosity on elastic modulus was investigated.The porous structure implants printed under the optimum parameters were calculated by finite element method,the stress distribution on the surface of the implant under different service conditions was observed and analyzed.The fatigue simulation and fatigue test were carried out to confirm whether the life of the implant could meet the practical use demand.In the selective laser melting process,the main factors affecting the density are scanning speed,laser power and scanning distance.The top and bottom surface quality of the printed specimens with porous structure is good,and there are no voids,cracks and other defects.The quality of the formed holes is good,and the edges are neat while the side surface roughness is high,the quality of forming hole is bad,the hole is elliptical,and there are spheroidized particles in the hole.The microhardness of the specimens with porous structure is about 400HV.Under uniaxial quasi-static compressive loading,the specimen of porous structure exhibits three stress-strain response stages:linear elastic stage,plastic yield stage and densification stage.With the increase of porosity,the elastic modulus of porous samples decreased,the porosity increased from 15%to 30%,and the elastic modulus decreased from 100 GPa to 70 GPa.The pore diameter and thread of the printed porous implant can meet the expected requirements,and its surface quality is good.The results of finite element simulation show that the equivalent stress on the surface of the implant is uniform and decreases from top to bottom and the maximum equivalent stress is concentrated at the junction of the body and the abutment and the first two threads.The maximum equivalent stress is 44.6 MPa under oblique load of 118.2 N and 141.23MPa under vertical load of 600 N.The fatigue simulation shows that the equivalent stress concentration location of the implant is similar to the static load,the maximum equivalent stress is 68.95 MPa,the life of the implant is more than 1.7×10~9 times,the deformation degree of the implant is less than 1%,and no plastic deformation occurs,observation of the surface of the implant,no cracks,holes and other defects,both indicate that the designed porous implant can meet the service life requirements.