Using Three-dimensional Finite Element Analysis To Analyze The Stress Distribution In Root Canals With Different Curvature Prepared By Different Kind Of Instruments

Objective:The purpose of this experiment is to explore the stress distribution in root canals while using various different instruments to prepare them. It could provide direct and effective evidence for dental clinics to choose right instruments in different situations. Methods:(1) Select adult mandibular central incisors which are defect-free, invisible wear, no obvious root canal curvature. Access the three-dimensional dynamic pictures with Micro-CT scanning technology, then input scanned images to Mimics10.01software to get geometry reconstruction, save the images in STL geometry file format, import them into Geomagic Studio10software, after finishing and surface curving, then save the images in IGES format.(2) Use Pro/Engineer Wildfire4software to establish three-dimensional finite element model of teeth in different root canal curvature angles (20°,40°) and the bending radius (2mm,5mm).(3)Use Pro/Engineer Wildfire4and Workbench software to build finite element model of mandibular central incisors with different curvatures, prepared by35#K files0.02, ProTaper0.09, Profile0.06(4)Use ANSYS software to Analyze the stress distribution in different models’loading conditions. Results:(1) Combined Micro-CT technology with three-dimensional model software Mimics10.01and Geomagic Studio10software, the three dimensional models were constructed successfully and well simulated to the morphological characteristics of real tooth specimen in surface and internal structure.(2) Use Pro/Engineer Wildfire4software to built different bending angle and bending radius of four curved root canals respectively:20°2mm,20°5mm,60°2mm,60°5mm.(3) Use Pro/Engineer Wildfire4software to simulate three different instruments in root canal preparation and filling the four curved root canals:20°2mm K file0,02Protaper,20°2mm,20°2mm Protaper0.09Protaper Profile0.06,20°5mm K file0,02Protaper,20°5mm,20°5mm Profile0.06Protaper0.09Pro taper,60°2mm K file0,02Protaper,60°2mm,60°2mm Protaper0.09Protaper Profile0.0660°5mm K file0,02Protaper,60°5mm,60°5mm Profile,0.06ProTaper,0.09Protaper.(4) Teeth models were meshed by ANSYS12.0software:K file No.35prepared and filling teeth have30536units, the root canal system has4254units, a total of34790nodes tetrahedron elements;31140Profile0.0625units for filling teeth and4950units for root canal systems, total of37090nodes tetrahedron elements.31520ProTaperF3units for filling teeth and5158units for root canal system, total of36678nodes tetrahedron elements.(5) For entire tooth, the stress in coronal1/3of root canal is maximum, followed by the apical1/3,the middle1/3is minimum. In part, after root canal preparation and filling, the maximum stress reached16.53Mpa at orifice which prepared by Protaper, and the minimum stress is12.72Mpa in apical1/3which prepared by K file. The stress value is directly proportional to bending angle, but inverse proportional to bending radius. Conclusion:Three kinds of root canal instruments didn’t have obvious difference in preparation of middle-curved root canals, but in preparation of severe-curved root canals, Protaper is better than Profile and K file.