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Biomechanics Analysis of Preparation of Curved Root Canals with Different Endodontic Instruments

Author: GuanQing
Tutor: NiLongXing；GuYongChun
School: Fourth Military Medical University
Course: Clinical Stomatology
Keywords: Root canal treatment Epoxy resin Photoelastic stress analysis Three - dimensional finite element
CLC: R781.05
Type: Master's thesis
Year: 2011
Downloads: 79
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Abstract

Root canal treatment (root canal therapy, RCT) is the clinical treatment of endodontic and periapical disease the most effective way. The root canal preparation is one of the key steps of the root canal treatment, including root canal cleaning and root canal shaping. Through the preparation of the root canal, you can form an ideal root canal morphology (continuous tapered), which is conducive to a thorough root canal flushing and tight root canal filling. However, when using the traditional stainless steel instruments in preparation of curved root canals, could easily lead to a root canal straightened apical opened, elbow and stepped formation, root canal offset adverse morphological, thereby reducing the success rate of root canal treatment. Endodontic instruments in curved root canals restoring force is considered to be the root cause of the produce adverse morphology of the root canal. In addition to the the endodontic instruments blade geometry, mechanical properties of metallic materials, the bending angle and bending radius of the root canal key factors that affect fracture of root canal preparation effects and instruments. At home and abroad although reported, detailed mechanical mechanism, however, has not been elucidated. The purpose of this study photoelastic method and finite element method to analyze the stress distribution of the blade root canal wall and endodontic instruments in curved root canal preparation to explore the bad form of root canal preparation and instrument separation mechanism of mechanical, clinical curved root canals preparation to provide experimental basis. This topic is divided into two parts. The first part of the bend photoelastic analysis experiments prepare the root canal wall by the force of an epoxy resin root canal curved root canal preparation of photoelastic model templates resin artificial root canal (Densply, Switzerland) with silicone rubber reproduction size 10mm × 10mm × 30mm rectangular parallelepiped female die. Bend made of 20 # / .02 the side presser (Densply, Switzerland) central angle of 60 °, the bending radius of 5 mm arcuate bend, and then fixed to the female mold of silicone rubber, and then maleic anhydride , epoxy resin, dibutyl phthalate, dimethylphenoxy after mixed at a proportion of 30:100:5:0.05 poured into the female mold of silicone rubber, cured in a secondary curing process. Finally, removing side pressure needle and consistent shape epoxy curved canal model 20. Experiment two canal preparation, root canal wall by the force of the photoelastic 20 curved root canals photoelastic resin model were randomized equally divided into 2 groups, respectively (SS group) with stainless steel K-files K-files and nickel-titanium (NiTi group) step-back technique for root canal preparation (preliminary order: 15 # → 20 # -> 15 #> 25 # -> 20 #> 30 # Of → 25 → 35 # → 30 # Of → 40 #). No. filing preparation is completed the file remains in the root canal, then the model is placed in 409 - Ⅱ polarized shells instrument moire photo shoot photoelastic EOS 350D digital camera (Canon, Japan). Photoelastic digital image import image analysis software Image Pro plus 6.0 (Media Cybernetics, USA), measuring stress area (area of ??stress, AS). The results showed that: 15 #, 20 # file prepared either SS group or NiTi group, have not resulted in significant stress areas; 25 # file the SS group AS mean is significantly greater than the NiTi group (P lt; 0.05). 2 group compared with the 25 # AS SS group mean the NiTi group of 35 # AS mean more close to (P gt; 0.05); # 40 SS 30 # AS NiTi group AS mean equal (P gt; 0.05). In addition, SS AS lateral wall of root canal curvature significantly larger than the root canal wall (P lt; 0.05), the NiTi group, AS bending of the root canal, lateral wall of the difference was not statistically significant ( P gt; 0.05). The second part of the bend endodontic instruments in root canal preparation of three-dimensional finite element stress analysis of experimental thirteen kinds of root canal file and four curved root canals of three-dimensional finite element model based on stainless steel K file, H file and Protaper geometric design parameters, The use of CAD / CAM software Pro / Engineer 5.0 (PTC) to establish 25 # K filing 25 # H rasps and the Protaper system F1 filing cutting edge three-dimensional finite element model. The curved canals modeling geometrical parameters: bending radius of 2 mm and 5 mm, the bending angle (Pruett measuring method) taken at 30 ° and 45 °, forming a total of four combinations of parameters. The experimental two pipe filing bending and torsional load finite element stress analysis of metal material properties of the finite element model of three root canal file assignment, the definition of load size constraint position (from the apical 5mm) and the direction of rotation (cis threaded and the inverse thread). Run Pro / MECHANICA finite element analysis software stress analysis of curved root canals root canal file. The experimental results show that the K file and H file group torsional load, the stress was no significant difference in size in cis thread and inverse thread. In bending and torsion loads, K filing is located at 45 ° / 2mm curved root canals in stress concentration area cutting edges sharp; H filed in the stress concentration zone 30 ° / 5mm and 45 ° / 2mm curved root canals at two cutting edge the groove in the maximum stress zone is located in the tip of the cutting edge 30 ° / 5mm and 45 ° / 2mm curved root canals; Protaper F1 filing maximum stress zone at the cutting edge of the trench 45 ° / 5mm curved root canals within 30 ° / 2mm, 30 ° / 5mm and 45 ° / 2mm curved root canals maximum stress area at the tip of the cutting edge. In summary, the photoelastic analysis and finite element analysis method can effectively analyze and predict poor root canal morphology, and instrument separation occurred parts can be more accurate and intuitive interaction analysis of root canal wall and devices, analytical results, curved root canal preparation, the proper selection and use of the instrument guiding significance.

Biomechanics Analysis of Preparation of Curved Root Canals with Different Endodontic Instruments

Abstract

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