The purpose of this study was to evaluate the consistency of two electronic apex locators in vitro model.

Materials consisted of fifty two extracted premolars and two electronic apex locators; Root ZX (J. Morita, Osaka, Japan) and E-Magic Finder Deluxe (S-Denti, Cheonan, Korea). After access preparation, the teeth were embedded in a saline-mixed alginate model. Canal lengths of each tooth were measured at "0.5" and "Apex" mark of the apex locators, respectively so that each tooth had two measurements from 0.5 and Apex points. The file was fixed at final measurement using a glass ionomer cement. The apical 4 mm from the apex was exposed to measure the distance from the file tip to the major apical foramen of each tooth. Average distances and standard deviations were used to evaluate the consistency.

Results showed that all measurements of both Root ZX and E-Magic Finder located the major foramen the range of ± 0.5 mm level. Both apex locators showed better consistency at Apex mark than at 0.5 mark. The average distance of file tip-major foramen was - 0.18 mm at 0.5 mark and - 0.07 mm at Apex mark in Root ZX, - 0.25 mm at 0.5 mark and - 0.02 mm at Apex mark in E-Magic Finder. Standard deviation was 0.21 at 0.5 mark and 0.12 at Apex mark in Root ZX, 0.12 at 0.5 mark and 0.09 at Apex mark in E-Magic Finder.

Citations

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• Variations in the morphology of apical constriction affecting electronic readings: An in vitro investigation using 3D‐printed tooth models
  Juhee Nam, Lucila Piasecki, Doun Kwak, Jung Hwa Hong, Il‐Young Jung, Sung‐Ho Park, Sin‐Yeon Cho
  Australian Endodontic Journal.2023; 49(S1): 245.     CrossRef
• In vivo evaluation of accuracy and consistency of two electronic apex locators
  Chien-Yun Pi, Euiseong Kim, Il-Young Jung, Seung-Jong Lee
  Journal of Korean Academy of Conservative Dentistry.2010; 35(6): 453.     CrossRef

This in vitro study examined the effect of surface defects on cutting blades on the extent of the cyclic fatigue fracture of HEROShaper Ni-Ti rotary files using fractographic analysis of the fractured surfaces. A total of 45 HEROShaper (MicroMega) Ni-Ti rotary files with a #30/.04 taper were divided into three groups of 15 each. Group 1 contained new HEROShapers without any surface defects. Group 2 contained HEROShapers with manufacturing defects such as metal rollover and machining marks. Group 3 contained HEROShapers that had been clinically used for the canal preparation of 4-6 molars. A fatigue-testing device was designed to allow cyclic tension and compressive stress on the tip of the instrument whilst maintaining similar conditions to those experienced in a clinic. The level of fatigue fracture time was measured using a computer connected the system. Statistical analysis was performed using a Tukey's test. Scanning electron microscopy (SEM) was used for fractographic analysis of the fractured surfaces. The fatigue fracture time between groups 1 and 2, and between groups 1 and 3 was significantly different (p < 0.05) but there was no significant difference between groups 2 and 3 (p > 0.05). A low magnification SEM views show brittle fracture as the main initial failure mode. At higher magnification, the brittle fracture region showed clusters of fatigue striations and a large number of secondary cracks. These fractures typically led to a central region of catastrophic ductile failure. Qualitatively, the ductile fracture region was characterized by the formation of microvoids and dimpling. The fractured surfaces of the HEROShapers in groups 2 and 3 were always associated with pre-existing surface defects. Typically, the fractured surface in the brittle fracture region showed evidence of cleavage (transgranular) facets across the grains, as well as intergranular facets along the grain boundaries. These results show that surface defects on cutting blades of Ni-Ti rotary files might be the preferred sites for the origin of fatigue fracture under experimental conditions. Furthermore, this work demonstrates the utility of fractography in evaluating the failure of Ni-Ti rotary files.

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• The Effect of Canal Curvature and Different Manufacturing Processes of Five Different NiTi Rotary Files on Cyclic Fatigue Resistance
  Panupat Phumpatrakom, Awiruth Klaisiri, Sukitti Techapatiphandee, Thippawan Saekow, Panuroot Aguilar
  European Journal of General Dentistry.2024;[Epub]     CrossRef
• Effect of internal stress on cyclic fatigue failure in .06 taper ProFile
  Hye-Rim Jung, Jin-Woo Kim, Kyung-Mo Cho, Se-Hee Park
  Restorative Dentistry & Endodontics.2012; 37(2): 79.     CrossRef
• Effect of internal stress on cyclic fatigue failure in K3
  Jun-Young Kim, Jin-Woo Kim, Kyung-Mo Cho, Se-Hee Park
  Restorative Dentistry & Endodontics.2012; 37(2): 74.     CrossRef
• Stress distribution for NiTi files of triangular based and rectangular based cross-sections using 3-dimensional finite element analysis
  Hyun-Ju Kim, Chan-Joo Lee, Byung-Min Kim, Jeong-Kil Park, Bock Hur, Hyeon-Cheol Kim
  Journal of Korean Academy of Conservative Dentistry.2009; 34(1): 1.     CrossRef
• Comparative analysis of various corrosive environmental conditions for NiTi rotary files
  Ji-Wan Yum, Jeong-Kil Park, Bock Hur, Hyeon-Cheol Kim
  Journal of Korean Academy of Conservative Dentistry.2008; 33(4): 377.     CrossRef

The purpose of this study was to examine the viability of PDL cells in rat molars by using in vivo MTT assay, which was used to compare fast cryopreservation group by liquid nitrogen (-196℃) with 4℃ cold preservation group.

A total of 74 Sprague-Dawley white female rats of 4 week-old with a body weight of 100 grams were used. The maxillary left and right, first and second molars were extracted as atraumatically as possible under ketamine anesthesia.

Ten teeth of each group were divided as six experimental groups depending upon the preservation. Cryopreservation groups were Group 1 (5% DMSO 6% HES in F medium), Group 2 (10% DMSO in F medium), Group 3 (5% DMSO 6% HES in Viaspan®), Group 4 (10% DMSO in Viaspan®) which were cryopreserved for 1 week and cold preservation groups were Group 5 (F medium), Group 6 (Viaspan®) at 4℃ for 1 week. Immediate extraction group was used as a control. After preservation and thawing, the in vivo MTT assay was processed. Two way ANOVA and Duncan's Multiple Range Test was performed at the 95% level of confidence. Another 2 teeth of each group were treated as the same manner and frozen sections 10 µm thick for microscopic observation.

The value of optical density obtained after in vivo MTT analysis was divided by the value of eosin staining for tissue volume standardization. Group 1, 2 had significantly higher optical density than Group 3 and 4 which had the lowest OD value. Group 6 had higher OD value than in Group 5 (P < 0.05). Histological findings of periodontal ligament cell, after being stained with MTT solution were consistent with the in vivo MTT assay results.

In this study, the groups which were frozen with DMSO as a cryoprotectant and the groups with F medium showed the best results.

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• Evaluation of the Viability of Rat Periodontal Ligament Cells after Storing at 0℃/2 MPa Condition up to One Week: In Vivo MTT Method
  Sun Mi Jang, Sin-Yeon Cho, Eui-Seong Kim, Il-Young Jung, Seung Jong Lee
  Journal of Korean Dental Science.2016; 9(1): 1.     CrossRef
• Comparative study on survival rate of human gingival fibroblasts stored in different storage media
  Hee Su Lee, You Sun Lim
  Journal of Korean society of Dental Hygiene.2012; 12(4): 733.     CrossRef
• The evaluation of periodontal ligament cells of rat teeth after low-temperature preservation under high pressure
  Jin-Ho Chung, Jin Kim, Seong-Ho Choi, Eui-Seong Kim, Jiyong Park, Seung-Jong Lee
  Journal of Korean Academy of Conservative Dentistry.2010; 35(4): 285.     CrossRef
• Comparison of viability of oral epithelial cells stored by different freezing methods
  Do-Young Baek, Seung-Jong Lee, Han-Sung Jung, EuiSeong Kim
  Journal of Korean Academy of Conservative Dentistry.2009; 34(6): 491.     CrossRef
• The efficacy of programmed cryo-preservation under pressure in rat periodontal ligament cells
  Young-Eun Lee, Eui-Seong Kim, Jin Kim, Seung-Hoon Han, Seung-Jong Lee
  Journal of Korean Academy of Conservative Dentistry.2009; 34(4): 356.     CrossRef

The purpose of this in vitro study was to evaluate the effect of surface defects and cross-sectional configuration of NiTi rotary files on the fatigue life under cyclic loading. Three NiTi rotary files (K3™, ProFile®, and HERO 642®) with #30/.04 taper were evaluated. Each rotary file was divided into 2 subgroups: control (no surface defects) and experimental group (artificial surface defects). A total of six groups of each 10 were tested. The NiTi rotary files were rotated at 300rpm using the apparatus which simulated curved canal (40 degree of curvature) until they fracture. The number of cycles to fracture was calculated and the fractured surfaces were observed with a scanning electron microscope. The data were analyzed statistically. The results showed that experimental groups with surface defects had lower number of cycles to fracture than control group but there was only a statistical significance between control and experimental group in the K3™ (p<0.05). There was no strong correlation between the cross-sectional configuration area and fracture resistance under experimental conditions. Several of fractured files demonstrated characteristic patterns of brittle fracture consistent with the propagation of pre-existing cracks.

This data indicate that surface defects of NiTi rotary files may significantly decrease fatigue life and it may be one possible factor for early fracture of NiTi rotary files in clinical practice.

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• Torsional behavior and microstructure characterization of additively manufactured NiTi shape memory alloy tubes
  Keyvan Safaei, Mohammadreza Nematollahi, Parisa Bayati, Hediyeh Dabbaghi, Othmane Benafan, Mohammad Elahinia
  Engineering Structures.2021; 226: 111383.     CrossRef
• Effect of internal stress on cyclic fatigue failure in K3
  Jun-Young Kim, Jin-Woo Kim, Kyung-Mo Cho, Se-Hee Park
  Restorative Dentistry & Endodontics.2012; 37(2): 74.     CrossRef
• An evaluation of rotational stability in endodontic electronic motors
  Se-Hee Park, Hyun-Woo Seo, Chan-Ui Hong
  Journal of Korean Academy of Conservative Dentistry.2010; 35(4): 246.     CrossRef
• Effect of cross-sectional area of 6 nickel-titanium rotary instruments on the fatigue fracture under cyclic flexural stress: A fractographic analysis
  Soo-Youn Hwang, So-Ram Oh, Yoon Lee, Sang-Min Lim, Kee-Yeon Kum
  Journal of Korean Academy of Conservative Dentistry.2009; 34(5): 424.     CrossRef
• The Effect of Surface Defects on the Cyclic Fatigue Fracture of HEROShaper Ni-Ti rotary files in a Dynamic Model: A Fractographic Analysis
  Jung-Kyu Lee, Eui-Sung Kim, Myoung-Whai Kang, Kee-Yeon Kum
  Journal of Korean Academy of Conservative Dentistry.2007; 32(2): 130.     CrossRef
• Comparative study on morphology of cross-section and cyclic fatigue test with different rotary NiTi files and handling methods
  Jae-Gwan Kim, Kee-Yeon Kum, Eui-Seong Kim
  Journal of Korean Academy of Conservative Dentistry.2006; 31(2): 96.     CrossRef