| Objectives In this study,the maxillary first premolar was selected as the research object.Using the finite element method,Under the condition of different thickness and type of bottom material and different repair methods,Stress distribution of each part of the model under physiological force is analyzed.The influence of stress distribution on prosthesis,cushion and tooth tissue was analyzed.Methods Experiment 1:After using spiral CT scanning images,after processing Mimics,Geomagic Studio image processing software and CATIAV5R20 graphics software,the finite element software ANSYS Workbench 15 is introduced to complete the establishment of the three-dimensional finite element model of the first premolar of the upper jaw of class II cavities.Experiment 2:The experimental group used chemical solidified glass ionomer as backing material,the bottom layer thickness was 0.5mm,1.0mm and 1.5mm respectively,and the control group did not bottom.The effect of thickness of base on the stress of vital pulp after filling was compared.Experiment3:Setting the bottom thickness of 0.5mm,the experimental group was light cured glass ionomer,flow resin group,chemical solidified glass ionomer group and control group did not bottom.The influence of elastic modulus of bottom cushion material on stress distribution of vital pulp after filling was analyzed.Experiment 4:The RCT 3D model is built.The bottom material was chemically cured glass ion.The experimental group was divided into four groups according to the thickness of the base:0.5mm group,1.0mm group,1.5mm group and 2mm group,and the control group was not the bottom group.The influence of bottom thickness on the stress distribution of the model is analyzed.Experiment 5:The finite element model of the maxillary first premolar was established after RCT,and the bottom thickness of the experimental group was 0.5mm,which was divided into the light cured glass ion group,the flow resin group,the chemically cured glass ion group and the control group without the bottom.The influence of elastic modulus of bottom on the stress distribution of RCT teeth was analyzed.Experiment 6:The finite element model of the maxillary first premolar was established after RCT,and the bottom thickness of the experimental group was 0.5mm,which was divided into the light cured glass ion group,the flow resin group,the chemically cured glass ion group and the control group without the bottom.The influence of elastic modulus of bottom on the stress distribution of RCT teeth was analyzed.Results Experiment 1:a three-dimensional finite element model was successfully e stablished.Experiment 2:when the bottom thickness is 0.5mm,the maximum tens ile/compressive stress of filling body,cushion bottom and dental tissue is the s mallest:28.00MPa/-30.98 MPa,6.53MPa/-39.31 MPa,94.38MPa/-207.33 MPa,28.83MPa/-86.34 MPa,When the bottom thickness increases from 1.0mm to 1.5mm,the stress v alue increases obviously.1.5mm bottom,the maximum pressure at the bottom laye r of the maximum compressive stress of super dentin stress 11.4MPa.Experiment 3:The experimental data show that the stress size of the tooth and filling body is:l ight cured glass ion>flow resin>chemically cured glass ion,and the tensile/compressive stress of the chemically cured glass ions with the largest modulus of elasticity is the smallest.Enamel:94.38MPa/-207.26 MPa,dentin:28.83MPa/-86.34 MPa,fillingbody:28.00MPa/-30.98 MPa.The stress size of the bottom layer is the light cu red glassion<liquid resin<chemically cured glass ion,and the minimum tensile/c ompressive stress of the light cured glass ion with the smallest modulus of elastic ity:2.59Mpa/-27.59 Mpa.Experiment 4:when the thickness of the bottom of the cus hion is 2.0mm,the maximum tensile stress/maximum compressive stress of the fill ing body,bottom layer,enamel and dentin is the largest:228.51Mpa/-475.13 Mpa,126.00Mpa/-220.14 Mpa,31.71Mpa/-81.44 Mpa,5.21×10-3Mpa/3.05×10-2Mpa.The bottom material has no obvious effect on the rest of the model.Experiment 6:different di rection force,inlay should direct filling capacity of water is less than the average model.The stress distribution in the bottom of the cave II and the neck of the t eeth changed,and the stress of the bottom surface of the type II cavities repaired by the inlay was 16.96 MPa,and the resin was filled with the resin directly to re pair the 28.83 MPa.The tongue was loaded at 45 degrees:the stress of inlay repair was 18.37 MPa,and resin was directly filled to repair stress 26.52 MPa.After RC T,there were two ways to repair the affected teeth.The stress in each part of th e experimental group was slightly smaller than that of the non repaired tooth mod el,but the difference was smaller,but much bigger than the normal tooth.Conclusions 1It is suggested that the 0.5mm-1.0mm should be selected from the angle of protecting the tooth tissue when the pulp is filled at the bottom of the vital pulp.The elastic modulus of the bottom material is approximately or more than that of the dentin elastic modulus,and the filling effect and stress distribution are reasonable.2The material and thickness of the bottom material had no effect on the stress distribution of RCT model.From the angle of stress,the RCT teeth were not bottom.3For the II type of the living pulp premolar,the resin inlay is a better choice than the resin direct filling.For the root canal treatment,the effect of the inlay and direct filling is not good. |
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