The Model And Experimental Study Of Mechanical Properties Of Periodontal Membrane

As a biomaterial,periodontal ligament has very complex mechanical properties.In previous studies,the viscoelastic mechanical properties of periodontal ligament have always been the focus of research.In this paper,the periodontal ligament of mandibular incisors in miniature pigs was taken as the research object,and the viscoelastic mechanical properties of periodontal ligament were explored from the macroscopic phenomenological point of view through this modeling and experimental research.Study on viscoelastic constitutive model of periodontal ligament.According to the construction principle of viscoelastic model,a new generalized Kelvin(E+2K)viscoelastic model and a generalized Kelvin(N+2K)viscoelastic model are constructed by connecting a spring element and a damping element in series with two Kelvin chains,respectively.At the same time,the formula of creep function of the newly constructed constitutive model is deduced.Experimental study on cyclic stress shear creep of periodontal ligament.The creep response of periodontal ligament under cyclic loading was investigated.The results show that the increase of stress amplitude will lead to the increase of creep value,and the increase of cyclic frequency will lead to the decrease of creep value.The data of the two viscoelastic models are fitted.By analyzing the fitting results of the models and the prediction effect of creep curves,it is shown that the N+2K model is more suitable for the creep behavior of periodontal ligament under the condition of low stress amplitude(0.01MPa),and the E+2K model is more suitable for describing the creep behavior under the condition of high stress amplitude(0.02MPa).Experimental study on constant stress shear creep of periodontal ligament.The creep response of periodontal ligament under constant stress loading was investigated.The experimental results show that the creep strain value increases with the increase of constant stress.Two viscoelastic models are fitted to the experimental data of constant stress.The results show that E+2K model can effectively describe the deceleration creep and steady-state creep stages under the experimental conditions of constant stress creep,while N+2K model is not suitable for describing the deceleration creep stage,and is more suitable for describing the steady-state creep stage than E+2K model.Research on nonlinear model based on E+2K model.In view of the shortcomings that the existing E+2K model and N+2K model can not describe the accelerated creep stage,two viscoelastic constitutive models which can describe the whole creep process are constructed.The feasibility of two new nonlinear viscoelastic models to describe the whole process of periodontal ligament creep is explored from the perspective of theoretical analysis.In this study,the viscoelastic mechanical properties of periodontal ligament were studied by combining viscoelastic constitutive model with shear creep experiment.The construction method of viscoelastic model is innovated,and the application effects of two constitutive models in different experiments are analyzed.Secondly,through the shear creep experiments under cyclic stress and constant stress,the viscoelastic mechanical behavior of periodontal ligament under different experiments was explored.Finally,based on E+2K model,two new nonlinear viscoelastic models are constructed,and the feasibility of describing the whole process of periodontal ligament creep is explored theoretically,which further enriches the research on viscoelastic models of periodontal ligament.