• Restorative Dentistry and Endodontics
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• v.40 no.2
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• pp.123-127
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• 2015

Objectives: Glide path preparation is recommended to reduce torsional failure of nickel-titanium (NiTi) rotary instruments and to prevent root canal transportation. This study evaluated whether the repetitive insertions of G-files to the working length maintain the apical size as well as provide sufficient lumen as a glide path for subsequent instrumentation. Materials and Methods: The G-file system (Micro-Mega) composed of G1 and G2 files for glide path preparation was used with the J-shaped, simulated resin canals. After inserting a G1 file twice, a G2 file was inserted to the working length 1, 4, 7, or 10 times for four each experimental group, respectively (n = 10). Then the canals were cleaned by copious irrigation, and lubricated with a separating gel medium. Canal replicas were made using silicone impression material, and the diameter of the replicas was measured at working length (D0) and 1 mm level (D1) under a scanning electron microscope. Data was analysed by one-way ANOVA and post-hoc tests (p = 0.05). Results: The diameter at D0 level did not show any significant difference between the 1, 2, 4, and 10 times of repetitive pecking insertions of G2 files at working length. However, 10 times of pecking motion with G2 file resulted in significantly larger canal diameter at D1 (p < 0.05). Conclusions: Under the limitations of this study, the repetitive insertion of a G2 file up to 10 times at working length created an adequate lumen for subsequent apical shaping with other rotary files bigger than International Organization for Standardization (ISO) size 20, without apical transportation at D0 level.

• Restorative Dentistry and Endodontics
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• v.32 no.2
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• pp.87-94
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• 2007

This study was done to evaluate transportation of the apical foramen after 0.5 mm overinstrumentation by ProFile, ProTaper and $K^3$ in simulated resin root canal. Sixty simulated resin root canal with a curvature of J and S-shape were divided into two groups. Each group consisted of three subgroups with 10 blocks according to the instruments used: $ProFile^{(R)},\;ProTaper^{TM},\;and\;K^{3TM}$. Simulated resin root canal was prepared by ProFile, ProTaper and $K^3$ with 300 rpm by the crown-down preparation technique. Pre- and post-instrumentation apical foramen images were overlapped and recorded with Image-analyzing microscope 100X (Camcope, Sometech Inc, Korea). The amounts of difference in width and dimension on overlapped images were measured after reference points were determined by Image Analysis program ($Image-Pro^{(R)}$ Express, Media Cybernetic, USA). Data were analyzed using Kruskal-Wallis and Mann-Whitney U-test. The results suggest that ProFile showed significantly less canal transportation and maintained original apical foramen shape better than $K^3$ and ProTaper.

• Korea Science and Art Forum
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• v.16
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• pp.157-169
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• 2014

Lake Biwa Canal was a dream project that reminds us the passion and innovation of Kyoto Citizens more than water supply. It is a modernization project combining engineering knowledge and scientific technology, which started transportation by ship through big-scale civil construction as well as supplying electricity as the first waterpower plant in Japan, and it overcame the physiographic limit through adopting unique method of waterway transportation. Lake Biwa Canal, which has tangible and intangible culture heritage value as the traditional space of Kyoto, the Old Capital of 1200 years, conceives a cultural meaning that is connected through various mutual relation as well as scientific technologic factor. Lake Biwa Canal is not only the function for supplying water to gardens and temples of Kyoto region, but it is also a cultural fruit that is formed by complex causal relationship of various contents such as geographical and environmental background, the phases of the times, local development policy, political circumstances and religions. This study is aimed at interpreting the value of Lake Biwa Canal multilaterally by the convergence of cultural and technological aspects through the view of the world which the age tried to pursue, focusing on the construction of Lake Biwa Canal which was accomplished in the process of promoting the modernization of Kyoto.

• Restorative Dentistry and Endodontics
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• v.36 no.1
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• pp.59-65
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• 2011

Objectives: The purpose of this study is to compare the apical transportation and working length change in curved root canals created in resin blocks, using 3 geometrically different types of Ni-Ti files, K3, NRT, and Profile. Materials and Methods: The curvature of 30 resin blocks was measured by Schneider technique and each groups of Ni-Ti files were allocated with 10 resin blocks at random. The canals were shaped with Ni-Ti files by Crown-down technique. It was analyzed by Double radiograph superimposition method (Backman CA 1992), and for the accuracy and consistency, specially designed jig, digital X-ray, and CAD/CAM software for measurement of apical transportation were used. The amount of apical transportation was measured at 0, 1, 3, 5 mm from 'apical foramen - 0.5 mm' area, and the alteration of the working length before and after canal shaping was also measured. For statistics, Kruskal-Wallis One Way Analysis was used. Results: There was no significant difference between the groups in the amount of working length change and apical transportation at 0, 1, and 3 mm area (p = 0.027), however, the amount of apical transportation at 5 mm area showed significant difference between K3 and Profile system (p = 0.924). Conclusions: As a result of this study, the 3 geometrically different Ni-Ti files showed no significant difference in apical transportation and working length change and maintained the original root canal shape.

• Restorative Dentistry and Endodontics
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• v.23 no.1
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• pp.391-400
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• 1998

The aim of this study was to determine the shaping ability of stainless-steel K file (S-S K file), nickel-titanium K file (Ni-Ti K file) and engine driven nickel-titanium file (Quantec file) in resin simulated root canal. Computed tomography was used to evaluate the change of the root canal morphology. Thirty nine resin simulated root canal were divided into four groups (A:12, B:12, C:12, D:3). Resin simulated canals were scanned by computed tomography before instrumentation (1st C-T scan). Canals were instrumented using step back preparation technique with S-S K file in group A and Ni-Ti K file in group B. Group C was prepared with engine driven Ni-Ti file. Group D was uninstrumented to compare the 1st C-T scan images with 2nd C-T scan images of root canal. Instrumented canals were again scanned using computed tomography (2nd C-T scan), and reformated images of the uninstrumented canals were compared with images of the instrumented canals. In the sections of 2mm and 6mm from the apex, Quantec file caused significantly less canal transportation than S-S K file and Ni-Ti K file (p<0.05). Quantec file produced more centered than S-S K file and Ni-Ti K file in the sections of 2mm and 4mm from the apex (p<0.05). There was no significant difference in the removed volume of canals among the each groups (p>0.05). However the removed canal volume from the apex to 5mm were significantly higher than them from 5mm to 1mm (p<0.05) in each groups. Under the conditions of this study, preparation with Quantec file was more effective and produce more appropriate canal shapes than S-S K file and Ni-Ti K file.

• Restorative Dentistry and Endodontics
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• v.36 no.3
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• pp.231-237
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• 2011

Objectives: The purpose of this study was to determine the optimal master apical file size with minimal transportation and optimal efficiency in removing infected dentin. We evaluated the transportation of the canal center and the change in untouched areas after sequential preparation with a #25 to #40 file using 3 different instruments: stainless steel K-type (SS K-file) hand file, ProFile and LightSpeed using microcomputed tomography (MCT). Materials and Methods: Thirty extracted human mandibular molars with separated orifices and apical foramens on mesial canals were used. Teeth were randomly divided into three groups: SS K-file, Profile, LightSpeed and the root canals were instrumented using corresponding instruments from #20 to #40. All teeth were scanned with MCT before and after instrumentation. Cross section images were used to evaluate canal transportation and untouched area at 1-, 2-, 3-, and 5- mm level from the apex. Data were statistically analyzed according to 'repeated nested design' and Mann-Whitney test (p = 0.05). Results: In SS K-file group, canal transportation was significantly increased over #30 instrument. In the ProFile group, canal transportation was significantly increased after preparation with the #40 instrument at the 1- and 2- mm levels. LightSpeed group showed better centering ability than ProFile group after preparation with the #40 instrument at the 1 and 2 mm levels. Conclusions: SS K-file, Profile, and LightSpeed showed differences in the degree of apical transportation depending on the size of the master apical file.

• Restorative Dentistry and Endodontics
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• v.43 no.2
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• pp.15.1-15.7
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• 2018

Objectives: The present study aimed to evaluate the shaping ability of 2 thermally treated nickel-titanium reciprocating systems in simulated curved canals. Materials and Methods: Forty simulated canals were prepared to apical size 25 using Reciproc Blue R25 (VDW) and WaveOne Gold Primary (Dentsply Sirona) instruments. Standard pre- and post-preparation images were taken and superimposed. The removal of resin material was measured at 5 standard points: the canal orifice, halfway between the canal orifice and the beginning of the curve, the beginning of the curve, the apex of the curve, and the end-point of the simulated canal. The data were analysed using the independent sample t-test with a 5% significance threshold. Results: The canals in which Reciproc Blue R25 was used showed a significantly greater widening than those in which WaveOne Gold was used at 4 of the 5 measurement points (p < 0.05). The Reciproc Blue R25 instrument removed significantly more resin from the inner aspect of the curve at 2 of the 5 points and similar amounts at the remaining 3 points. At the 2 apical points, there was no significant difference between the Reciproc Blue R25 and WaveOne Gold Primary instruments. Conclusion: Both instruments respected the original canal anatomy; however, WaveOne Gold resulted in a more conservative shape with less transportation.

• Geomechanics and Engineering
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• v.17 no.2
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• pp.133-143
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• 2019

An optimal hydraulic section is critical for irrigated water conservancy in seasonal frozen ground due to a large proportion of water leakage, as investigated by in-situ surveys. This is highly correlated with the frost heave of underlain soils in cold season. This paper firstly derived a practical model for frost heave of clayey soils, with temperature dependent thermal indexes incorporating phase change effect. A model test carried out on clay was used to verify the rationality of the model. A novel approach for optimizing the cross-section of irrigation canals in cold regions was suggested with live updated geometry characterized by three unique geometric constraints including slope of canal, ratio of practical flow section to the optimal and lining thickness. Allowable frost heave deformation and tensile stress in canal lining are utilized as standard in computation iterating with geometry updating while the construction cost per unit length is regarded as the eventual target in optimization. A typical section along the Jinghui irrigation canal was selected to be optimized with the above requirements satisfied. Results prove that the optimized hydraulic section exhibits smaller frost heave deformation, lower tensile stress and lower construction cost.

• Journal of Dental Rehabilitation and Applied Science
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• v.22 no.2
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• pp.173-180
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• 2006

Objectives The aim of this study is to compare the quality of root canal preparation completed using MFile-$System^{(R)}$ instrument ( Komet, Gebr.Brsaseler, Germany) and conventional stainless steel file in the canals of Maxillary molar teeth that had a canal curvature between $25^{\circ}$ or more Materials & Methods Buccal canals of 24 first and second maxillary molar teeth, extracted for periodontal and prosthetic reasons were used. Tissue fragments and calcified debris were removed from teeth by scaling and the teeth were stored in 10% formalin solution for 24 hour. Then, teeth were stored in saline until used. To be included the roots had to have completed formed apices and angle of curvature ranging between $25^{\circ}$ or more according to the criteria described by Schneider(1971). Palatal and Second mesiobuccal canals were not included. Teeth were embedded into transparent acrylic. The teeth were randomly divided into two experimental groups. All teeth were scanned by Dental CT (PSR9000N, Asahi, Japan) to determine the root canal shape before instrumentation. Image slices were prepared from the apical end point to the pulp chamber. The first two sections were 2 mm from the apical end of root and 2 mm below the orifice. Further section was recorded, dividing the distance between the sections of apical and coronal levels into two equal lengths. 12 teeth were instrumented using stainless steel fileand another 12 teeth were instrumented using MFile-$System^{(R)}$. Following the completion of the instrumentation, the teeth were again scanned and compared with the cross sectional images taken prior to canal preparation. Amount of transportation and centering ability was assessed. Student's t-test was used for statistical analysis. Result Less transportation occurred with MFile-$System^{(R)}$ rotary instrumentation than stainless steel instrument. MFile-$System^{(R)}$ had better centering ability than stainless steel instrument. Conclusion MFile-$System^{(R)}$ rotary instrumentation transported canals less and had good centering ability.

• Restorative Dentistry and Endodontics
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• v.22 no.1
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• pp.244-253
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• 1997

During preparation of narrow curved canals, procedural accidents such as, ledge, zipping, and transportation are frequently encountered and may lead to failure of endodontic therapy. To reduce these procedural errors and efficiently manage curved canals, various modifications in instrumentation technique and the design and flexibility of instruments have been advocated. This study compared the maintenance of the original canal curvature, cross sectional canal shape, and preparation time during instrumentation with stainless steel hand (K-Flexo) file, and nickel-titanium rotary files (Profile and Lightspeed). Thirty resin blocks with simulated curved canals of 20~25 degrees were used and divided into three groups of 10 each. In group 1, canals were instrumented using a quarter turn/pull technique with K-Flexofiles. Group 2 canals were prepared with rotary NiTi Profiles. Group 3 was prepared with rotary NiTi Lightspeed instrument. Before and after instrumentation, all canals were scanned using stereo microcope, FlexCam camera, and Photoshop 3.0 computer program. The results were as follows : 1. All groups showed some loss of canal curvature after instrumentation. Average loss of canal curvature was 8.6 degrees for K-Flexofile, 7.7 degrees for Profile, and 5.8 degrees for Lightspeed. Lightspeed exhibited significantly less curvature loss than K-Flexofile (p<0.05). 2. At the apical 1-mm level, Profile produced significantly rounder canals than Lightspeed (p<0.05). At the 3-mm level, Profile and Lightspeed exhibited significantly rounder canals than K-Flexofile (p<0.05). 3. Preparation with Lightspeed was significantly faster than Profile and K-Flexofile, and Profile was faster than K-Flexofile (p<0.05). 4. There was no significant difference in incidence of zipping between the hand K-Flexofile and rotary NiTi (Profile and Lightspeed) instruments. Most of apical canals were slightly widened near the apical foramen. As a results of this study, rotary NiTi instruments are superior to the K-Flexofile in regard to the maintenance of original canal curvature, cross-sectional shape and preparation time. But more investigations and studies should be needed to evaluate the ideal canal instrumentation.