Study On The Stability Of Implant Based On Frictional Contact

The stability of dental implant is one of the important indicator to evaluate the success rate of implant.The key to the development of this kind of instrument is to improve the long-term stability of implant.At present,the main problems of implant stability are as follows:(1)The implant-connection screw interface and abutmentconnection screw interface preload is insufficient,resulting in connecting screws loose and implant can not exercise the normal function,and thus promoting the connection screw break;(2)Implant-abutment interface micro-gap was too large,resulting in excessive micro-movement and micro-leakage occurred,causing tissue inflammation,bone resorption.In this paper,the stability of implant system was analyzed by finite element method under the condition of friction contact of each mechanical connection surface.First,the worst conditions of implant fatigue loading were determined according to the dynamic fatigue test standard(BS EN ISO 14801:2016),and a three-dimensional solid model with different axial angles(including straight abutment implant system and angled abutment implant system)was established.The effects of axial implantation angle on the implant system were studied.Then,on the basis of the above content,the influence of different friction coefficient on the connecting screw was analyzed for the same tightening torque and the same preload.In addition,the micro-gap and the micromotion of the implant system were simulated,and the influence of the friction coefficient on the micro-gap was studied.Finally,the torque test platform was designed according to the "YY 0315-2016:titanium and titanium alloy dental implants".The tightening torque and loosening torque of connecting screws with different friction coefficient were measured and the stability of the implants was evaluated.The main conclusions of this paper:(1)The general(straight abutment)implant system analysis showed that when the keyway of the implant is below the base and the anti rotation structure of the abutment is above,it was the most dangerous situation.The analysis of the angled abutment implant system showed that the position of the keyway structure of the implant system had no significant effect on the maximum equivalent stress value of the system.(2)Under the same tightening torque,it was found that the friction coefficient of the connecting screw appears a small stress value between 0.4 and 0.5(especially around 0.45);Under the same preload,it was found that with the increase of friction coefficient,the maximum stress value of the connecting screw decreased,and the contact friction stress increased,which indicated that the friction stress reduced the stress of the connecting screw.(3)The study found that static load and dynamic load of the maximum micro-gap value is not much difference,but the dynamic load was significantly smaller than the static load.In addition,the increase with the coefficient of friction reduced the preload,resulting in increased micro-gap,but not a linear change.(4)The screw torque test of the connecting screw indicated that the ratio of the loosening torque/tightening torque of the common connecting screw was higher than that of the connecting screw after surface nitriding treatment.It is possible that the nitriding treatment reduced the friction coefficient of the surface of the connecting screw,resulting in a decrease in the proportion of loosening torque/tightening torque,so that the stability of the implant system to reduce.