| Objective To use the 3D-printed resin tooth model to establish the instrument separation model,select the Chinese Deyue re-treatment working tip,the French Saiteli ET25 working tip,and the Japanese group TFRK-12 working tip.The standard micro-ultrasound method was used for the removal of broken instruments,and the working efficiency of the three ultrasonic working tips and the changes of tooth resistance after the broken instruments were compared.experimental basis.Methods 1 Extract the 3D model of the apical 1/3 severely curved isolated tooth using CBCT,conduct 3D modeling with Mimics Medical 20.0 and Geomagic Studio 13.0 software,and use Poly Jet printing technology for 3D printing to mass-produce the target isolated tooth1 : 1 resin tooth model.2 Establish a fracture model of 2mm Pro Taper F1 with 1/3 apical separation on 45 resin teeth printed uniformly.A microscope with the same operation on the broken instrument model using the working tips of A(French Saiteli ET25 ultrasound working tip),B(China Deyue retreatment ultrasound working tip),and C(TFRK-12 ultrasound working tip of Japan group)in sequence The operation time was recorded accurately.CBCT scans were performed on the remaining 30 resin tooth models after the removal of the broken tool,and analyzed by Mimics Medical 20.0 modeling software.Crosssection of the root canal section for comparison.Five samples were randomly selected from groups A,B,and C.After root canal preparation,CBCT scanning was performed again,and the measurement data were used to calculate and compare the root canal deviation rate.3Among the 5 samples prepared in groups A,B,and C,one sample was randomly selected and named after the group,and imported into Mimics Medical 20.0 and Geomagic Studio13.0 software for 3D modeling,and the model was imported into ANSYS Workbench 18.1finite element analysis software.For the vertical direction,a fixed force of 500 N was evenly applied to the root coronal section,and a three-dimensional finite element force analysis was carried out.Results 1 Using CBCT for imaging 3D data acquisition,Poly Jet 3D printing technology successfully produced a 3D resin tooth model of the target isolated tooth.2 Time: The working time of group C was lower than that of group AB,and the difference was statistically significant(P<0.05).Comparing group B and A,the working hours of group B were different from those of group A,and the results were not statistically significant(P>0.05).3 Cross-sectional area: The cross-sectional area of broken mechanical crown,middle and root in group C was larger than that in group AB,and the difference was statistically significant(P<0.05).The cross-sectional area of the middle and root of the fractured instrument in group B was larger than that in group A,and the difference was statistically significant(P<0.05).4 Root canal deviation rate: at the distance of 1 mm from the apical foramen,there was no significant difference in the root canal deviation of the three groups of ABC;at 3 mm from the apical foramen,the root canal deviation of the TFRK-12 ultrasonic working tip group It was significantly higher than the other two groups,and the difference was statistically significant;at 5 mm from the apical foramen,the root canal offset of the TFRK-12 ultrasound working tip group was significantly higher than that of the ET25 ultrasound working tip group,and the difference was statistically significant.5 Threedimensional finite element: when a fixed force of 500 N is applied in the vertical direction,the maximum force point of the ET25 working tip model appears at the root tip,with a maximum value of 73.848N;For the inner tooth at the tube bend,the maximum value is79.282N;for the TFRK-12 working tip model,the maximum stress point appears at the root apex,and the maximum value is 216.58 N.Conclusions 1 The accuracy of CBCT data collection fully meets the needs of 3D printing.The resin tooth samples produced by the Poly Jet printing method have high consistency with the isolated tooth shape,high simulation and high precision.2 TFRK-12 ultrasonic working tip has high working efficiency and can shorten the operation time of the operator.It is suitable for the teeth with more remaining tooth tissue and the separation instrument is located in the middle and upper part of the root canal.It is suitable for cases that are sensitive to operation time.3 Deyue re-treatment ultrasonic working tip special treatment,suitable for the separation of instruments with small diameter or easy to break,the degree of separation of the instrument is low,and there is a bypass space.When the separation instrument is in the apex 1/3 should be used with care.4 ET25 ultrasonic working tip is suitable for various types of foreign body removal in root canal,and the prognosis is better than the other two groups.Figure18;Table3;Reference 89... |
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