• Restorative Dentistry and Endodontics
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• v.17 no.1
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• pp.235-243
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• 1992

The purpose of this study was to evaluate the accuracy of an electronic apex locator, the Neosono - M, in determining the location of the cementodentinal junction. A total of 26 teeth with 46 canals were evaluated. The apex locator was used to locate the file and the teeth extracted. The specimen were prepared with highspeed burs and sandpaper discs to a thickness of $250{\sim}300{\mu}m$. Distances were measured from the cementodentinal junction with the use of polarizing microscope. Measurements made by the apex locator were also compared with those by the X - ray. The results were as follows. 1. The apex locator and X - ray were to measure a mean value of 0.17, 0.45mm coronal to the CDJ respectively. There was no significant difference between the accuracy of the apex locator and that of X - ray. 2. There was no significant difference between the accuracy of apex locator in vital and in nonvital teeth, and between in narrow and in wide canals. 3. The files in nonvital and narrow group were apical to the CDJ significantly than those of vital and narrow, vital and wide, and non vital and wide groups.

• Restorative Dentistry and Endodontics
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• v.23 no.2
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• pp.676-681
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• 1998

The purpose of this study is to explain theoretically the mechanism of the frequency-dependent apex locator which can detect the apex of the root in moist canals with blood or other conductible canal irrigants. The frequency-dependent apex locator is based on measuring the ratio of the two impedances of the two alternating currents with different frequencies. We analyzed the changes of the ratio between the two impedances by using differential calculus. Our analysis shows that : 1. When the file is in the moist canal, the ratio between the two impedances is almost constant. 2. As the file approaches the apex of the root, the ratio decreases sharply. By this mechanism, the frequency-dependent apex locator can detect the apex of the-root quite accurately in moist canals.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.647-648
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• 2006

The length of root canal has to be measured to cure root canal. Several apex locators were developed to measure the length of root canal. And they were verified by X-ray or micrometer method. But these methods do not consider the non-linear bends of pulp and have ${\pm}0.5mm$ error which is large to measure the length of root canal. The purpose of this study is the research of new method to measure the length of root canal and verifying the apex locator using Micro-CT. The length of root canal of 6 teeth were measured with the apex locator. When the apex locator reads 0.5, 0.6, 0.7, 0.5, 0.9, 1.0mm, the teeth with the file fixed were photographed. The average lengths of root canal of 6 teeth measured by Micro-CT were 0.488, 0.589, 0.680, 0.775, 0.897, 0.992mm.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.8 s.197
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• pp.116-121
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• 2007

The length of root canal has to be measured for endodontic treatment. Several electronic apex locators were developed to measure the length of root canal by other researchers. And their accuracies were verified by X-ray or micrometer method. But these methods did not consider the non-linear bends of pulp and had ${\pm}0.5mm$ error which was large enough to measure the length of root canal. The purpose of this study is the introduction of a new method to measure the length of root canal and the verification of the accuracy of an electronic apex locator using a Micro-CT. The length of root canal of 6 teeth were measured with the electronic apex locator. When the electronic apex locator reads 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0 mm length of the file which was inserted in the hole of the tooth to measure the length of root canal. The average (${\pm}$Standard deviation) length of root canal of 6 teeth measured by the Micro-CT was $0.49{\pm}0.03,\;0.59{\pm}0.04,\;0.68{\pm}0.03,\;0.78{\pm}0.03,\;0.90{\pm}0.04\;and\;1.01{\pm}0.03mm$, respectively. The maximum error of the electronic apex locator was 0.06 mm.

• Restorative Dentistry and Endodontics
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• v.41 no.1
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• pp.6-11
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• 2016

Objectives: The purpose of this in vitro study was to evaluate the accuracy of working length (WL) determination of four electronic apex locators (EALs), namely, Root ZX (RZX), Elements diagnostic unit and apex locator (ELE), SybronEndo Mini Apex locator (MINI) and Propex pixi (PIXI) using Stainless steel (SS) and nickel-titanium (NiTi) hand files. The null hypothesis was that there was no difference between canal length determination by SS and NiTi files of 4 EALs. Materials and Methods: Sixty extracted, single rooted human teeth were decoronated and the canal orifice flared. The actual length (AL) was assessed visually, and the teeth were embedded in an alginate model. The electronic length (EL) measurements were recorded with all four EALs using SS and NiTi files at '0.5' reading on display. The differences between the AL and EL were compared. Results: The results obtained with each EAL with SS and NiTi files were compared with AL. A paired sample t test showed that there was a statistical significant difference between EAL readings with SS and NiTi files for RZX and MINI (p < 0.05). The accuracy of RZX, ELE, MINI and PIXI within ${\pm}0.5 mm$ of AL with SS/NiTi files were 93.3%/70%, 90%/91.7%, 95%/68.3%, and 83.3%/83.3%, respectively. Conclusions: The results of this study indicate that Root ZX was statistically more accurate with NiTi files compared to SS files, while MINI was statistically more accurate with SS files compared to NiTi files. ELE and PIXI were not affected by the alloy type of the file used to determine WL.

• Restorative Dentistry and Endodontics
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• v.23 no.1
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• pp.339-345
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• 1998

The purpose of this study was to evaluate the in vitro accuracy of Root ZX(Morita Co., Japan) which is the ratio type electronic apex locator. The 86 extracted human palatal roots of maxillary molar with fully formed apices were used. File lengths with the file tip just visible at the foramen were compared to those measured with Root ZX. For length measuring with Root ZX, saline test model with which the apical 1/3 of each root was submerged into normal saline were designed. The root canal lengths were determined with Root ZX and the radiographs were taken with a file in the canal. The distances from file tips of Root ZX lengths to apecies in radiographs also were measured with Profile projector PJ311(Mitutoyo Co., Japan). The results were as follows : 1. The root canal length determined with electronic apex locator was $0.78{\pm}0.53mm$ shorter than the length with visual measurement. 2. The file tip of Root ZX lengths was located at $0.85{\pm}0.49mm$ away from the apex in radiograph. 3. The accuracy of the Root ZX was 79.1% within 0.5mm of visual working length and 96.5% within 1.0mm.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.399-402
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• 1997

It is important to find a accurate root canal length or successful endodontic therapy. By X-ray method takes a long time and difficult in a curved canal. After developed electronic apex locator has allowed to measure the root canal length with easy, in a short time also in a curved canal. But most electronic apex locators have the disadvantage which is too short reading or sometimes the measurement itself becomes impossible if there are electrolytes in the canal. To overcome this drawback, impedance ratio method has been developed. In this study, we have developed frequency dependent electronic apex locator to minimize the interference of electrolytes. And based on that also some error in clinic use, we added the other method. Difference of two signals which are used in calculation of impedance ratio was can be represent the status of root canal fluid. As a result, using impedance ratio method and auto-calibration by voltage difference method can reduce the measurement error.

• Journal of Korean Dental Science
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• v.13 no.2
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• pp.52-58
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• 2020

Purpose: Using two types of electronic apex locators, this study aimed to investigate the differences in accuracy according to the evaluator and equipment. Materials and Methods: Artificial teeth of the lower first premolars and two mandibular acrylic models (A and B) were used in this study. In the artificial teeth, the pulp chamber was opened and the access cavity was prepared. Using calibrated digital Vernier calipers, the distance from the top of the cavity and the root apex was measured to assess the actual distance between two artificial teeth. The evaluation was conducted by 20 dentists, and each evaluator repeated measurements for each electronic apex locator five times. The difference between the actual distance from the top of the cavity to the root apex and the distance measured using electronic measuring equipment was compared. For statistical analysis, the Friedman test the Mann-Whitney U-test were conducted and the differences between groups were analyzed (α=0.05). Result: As for the accuracy of measurement according to the two types of electronic apex locators, the value of the measurement error was 0.4753 mm in Dentaport ZX and 0.3321 mm in E-Cube Plus. Moreover, electronic apex locators Dentaport ZX and E-Cube Plus showed statistically significant differences (P<0.05). As for the difference in the accuracy of the two types of electronic apex locators according to the evaluator, the resulting values differed depending on the evaluator and showed a statistically significant difference (P<0.001). Conclusion: Electronic apex locator E-Cube Plus showed higher accuracy than did Dentaport ZX. Nevertheless, both types of electronic apex locators showed 100% accuracy in finding the region within root apex ±0.5 mm zone. Furthermore, according to the evaluator, the two electronic apex locators showed different resulting values.

• The Journal of the Korean dental association
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• v.55 no.1
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• pp.42-52
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• 2017

The purpose of this study is to evaluate the preferred method of root canal length determination and the apical limit for canal instrumentation among endodontic teachers of dental school. A questionnaire on the preferred method of root canal length determination and the apical limit for canal instrumentation was designed and distributed to endodontic teachers of various dental schools. The response rate was 90%. The most preferred method of root canal length determination was Electronic apex locator (EAL)(89%). The most favoured apical limit for canal instrumentation was 0.5 to 1.0 mm short of the radiographic apex(78%). The most preferred method of using EAL was that the working length is taken at 'APEX' mark and then distracted 0.5mm from that length.(41%). When there is no agreement between radiographic measurement and EAL measurement, 74% of respondents chose the length of EAL measurement. The majority of endodontic teachers from Korean dental schools preferred EAL to radiograph method in determining root canal length.

• Restorative Dentistry and Endodontics
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• v.22 no.2
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• pp.809-819
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• 1997

The purpose of this study was to develop an accurate frequency-dependent type apex locator. To compensate the impedence differences of different canal contents, voltage differences were pre-measured and stored for saline, HOsb1/$2O_2$ and NaOCl. The circuit was adjusted to recognize the different voltages of each solution, thereby the machine could automatically compensate the voltage differences. In the process of this study, the following informations were observed. 1. Most stable apical reading was obtained at 500Hz and 10kHz. 2. There were no differences in accuracy among three different frequency types, sign wave, triangular wave and rectangular wave(p>0.05). 3. Before the compensation of voltage differences, saline, H2O2 and NaOCl showed different readings at the apex even with the frequency-type (p<0.05). 4. After compensating the voltage difference, the accuracy was enhanced from + 0.42 to +0.32 in H2O2(p<0.05), from -0.34 to -0.12 in NaOCl(p<0.05).