Finite Element Analysis Of Cast Pure Titanium Post And Core For Restoration Of Mandibular Premolar Defects And Case Report

How to preserve the residual roots and crowns after the root canal treatment to the maximum extent,and how to ensure the strength of the restored roots and to avoid the occurrence of root fracture,is the current research hotspot of post core restoration.According to many experimental reports and clinical retrospective analysis,it is found that the premolars are the teeth with higher frequency in post core restoration,and the risk of fracture of premolar is relatively high.At present,when a large area of teeth defect to subgingival,the new pure titanium cast post is widely used in clinic.With the development of oral biomechanics,a new interdisciplinary subject,we can conduct researches more in-depth and more accurately on related issues.Objective: In this paper,the diameter and length of cast pure titanium post and core system were divided into several groups,and the stress distribution of different length and diameter of cast pure titanium post and core system was analyzed by three-dimensional finite element method.The effect of different length and diameter of cast pure titanium post on the stress distribution of root is explored,in order to theoretically design the optimal combination of length and diameter for the clinical application of cast pure titanium post and core,in order to improve the success rate of post and core restoration and reduce the occurrence of root fracture.Method: A mandible premolar was selected,whose appearance was in accordance with the standard.After the preparation of the experimental specimen,it was scanned by CBCT.The solid model of the first mandibular premolar was established by using the interactive medical image control system and the automatic reverse engineering software of Geomagic.Several groups of cast pure titanium piles with different length and diameter were designed by ABAQUS finite element analysis software,and each part of the model was meshed,attribute was assigned,loading mode and boundary conditions were set,then mechanical analysis was carried out.In this study,the general force of the occlusal state was simulated: a static load of 150 N,45 degrees to the long axis of the teeth,was applied on the functional cusp.Finally,the stress distribution of several groups of cast pure titanium post and core with different length and diameter was calculated,and the von Mises stress nephogram and von Mises maximum stress value were obtained.The optimized combination of length and diameter was selected through comparative analysis.Result: 1.The three-dimensional finite element model of the first mandibular premolar is successfully established.2.The root stress distribution and von Mises value(equivalent stress value)of each group are obtained in ABAQUS software.3.In this experiment,when the first mandibular premolar is designed with cast pure titanium post and core,the maximum stress peak value of von Mises is the smallest when the length of post is 14 mm and the diameter of post is 3 mm.4.The stress nephogram of the root shows that the stress mainly concentrated in the neck 1 / 3,the middle 1 / 3 and the buccolingual 1 / 3 of the surface of root.5.When the pile diameter is constant,the length of the pile is within the set range.With the decrease of the length of the pile,the peak value of von Mises stress of the root decreases first,and then tends to be stable.6.When the length of the pile is constant,the diameter of the pile is in the set range.With the decrease of the diameter of the pile,the peak value of the von Mises stress of the root shows the trend of first decreasing and then increasing.7.The optimal parameters of cast pure titanium post and core for mandibular first premolar restoration: 12 mm ? length ? 14 mm,and 2.4mm ? diameter ? 3.0mm.At this time,the maximum root stress value is relatively small,that is,the length is 69.3%-80.9% of the root length,and the diameter is 30.0%-37.5% of the root buccolingual diameter.Conclusion:1.When the mandibular first premolar is repaired with cast pure titanium post and core,the length of the post should be extended as long as possible on the premise of ensuring the apical sealing;when the diameter of the post is equal to 3 / 8 of the buccal and lingual diameter of the root,it is more conducive to the stress distribution of the root.2.When the root canal treatment,post canal preparation and tooth preparation of the first mandibular premolar are carried out clinically,the buccal and lingual tooth tissue of the tooth neck should be preserved as much as possible,so as to reduce the risk of root fracture.