The Numerical Simulation Analysis Of The Root Canal Stress Distribution After Root Canal Preparation With Different Techniques

Objective:The main PurPose of this study was to analyze the effect of different canal PreParation techniques on the root canal stress values and distribution,and to comPare the change of the stress under the different load. ExPlore the affect of different canal PreParation techniques on the resistance of the root from a biomechanical viewPoint. To Provide a reference basis for the reasonable aPPlication of the clinical root canal PreParation and Prevention of vertical root fracture.Materials and Methods:1. Establishment of a three-dimensional finite element model of the adult mandibular first Premolars. Mandibular first Premolars consistented with the average size of human teeth were selected, surface treatment, Paraffin-embedded. CT scan to obtain the thickness of0.1mm210tomograPhy images of isolated teeth, and imPorted CT data into Mimics, v1001software to obtain the contour Point cloud, Combination of Magics9.9image Processing software, HyPerMesh,the grid automatically Partitioning software, the mandibular first Premolars dimensional finite element model was established through sPecific of Abaqus6.10software at last.2. Finite element models of the mandibular first Premolars were constructed, PrePared by different canal PreParation techniques and filled. And these models were studied using three-dimensional finite element method respectively. A total of30exacted human dental mandibular single canal Premolar were randomly allocated into three grouPs(n=10): GrouP1,Standardized system using rotary Ni-Ti Mtwo instrument; GrouP2, Crown-down technique using rotary Ni-Ti ProtaPer instrument; GrouP3, steP-back technique using conventional stainless steel K-files.Using CT scan, Mimics,10.01and Magics9.9software, HyPerMesh software andAbaqus6.10software,to establish finite element models of each grouP. And to analyze the stress magnitude and distribution of the comParison model under different loading conditions.Data were analyzed using the SPSS17.0software.Two analyses were Performed using one-way ANOVA to comPare root canal Peak stress of three grouPs under the same load. Paired t-test were carried out to test root canal stress under vertical and lateral loads.Results:1.3-D Finite element model of a single tube mandibular first Premolar were constructed successfully, model are divided into tetrahedral element, four nodes Per, unit generated a total of8725units,1874nodes2. After root canal Preparation, high stress area of the root canal is mainly concentrated in the1/3of the root dentin of root canal around the mouth, the stress value decreases gradually from the root canal mouth to the aPical foramen. The same cross-sectional stress showed lower uniform distributions, whislt showed uneven distribution with high concentrations at theat the buccal and lingual canal extensions, Particularly evident in the G3, But in the apical region between1/3in each group there was no significant difference (P>0.05).3. In all experimental grouPs, the average stress level of the remaining dentin after root canal Preparation and filling were slightly different. G1dental root canal average Peak of the stress was the smallest:9.47MP; G3root canal average stress Peak is the largest:12.16MP; followed by the G2crown-down root canal stress average Peak:9.64MP,but there were no statistically significant differences between grouP G1,G2(P>0.05). the difference between the G2group and G3, G1group G3was statistically significant (P <0.05).4. Root canal root canal average Peak stress under the lateral load was significantly higher than the Peak stress under the vertical load, the vertical load and lateral load average Peak stress were:G1,9.47MP11.49MP; G29.64MP, and12.22MP; G3,12.16MP, and14.61MP, The statistical analysis of difference was statistically significant (P<0.05).Conclusions:1.3-Dimensional finite element model has a good similarity with the real teeth sPecimen using the CB-CT technology MIMICS the software ANESYS software, Summed uP a comPlete build method of finite element model of the teeth.2. In each exPerimental grouP average Von mises stress Peak are much less than the limits of dentin comPressive strength, These three commonly used root canal PreParation is safe and feasible.3.To expand the root canal of the upper taper nickel-titanium ProtaPer Mtwo and no increase in stress concentration of root canal than stainless steel K file, but to make it more balanced for the stress distribution of root canal, the peak stress decreased, reducing the stress concentration, soclinically recommended ProtaPer and the Mtwo to conduct root canal preparation to prevent the occurrence of vertical root fracture.4. The trend of the root canal stress distribution is consistent whether in the vertical load or lateral load, Root canal von mises stress value under lateral load higher than under the vertical load,after root canal theraPy should be aPProPriately reduced cusP inclination to reduce the lateral force.