• Restorative Dentistry and Endodontics
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• v.21 no.1
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• pp.289-299
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• 1996

It is necessary to measure the length of a root canal in order to attain a satisfactory prognosis after root canal therapy. There are several methods for determining root canal length, such as tactile sensation by the dental practitioner, the utilization of x-ray film, and electronic root canal measurement. Among these, the electrical measurement methods, in which the impedence between the oral mucous membrane and periodontal membrane is determined, have advantages of simplicity and accuracy. During root canal treatment, the root canal contains a solution of high electrical conductivity such as pus, blood, sodium hypochlorite and so on. Recently a new electronic root canal measurement device of frequency-dependent type has been developed, which is capable of measuring the length of root canal under moist conditions. Endex and Root ZX, which are frequency-dependent type, were evaluated for accuracy of measuring root canal length in vivo by stereomicroscope. The result were as follows ; 1. 82.5% of Endex and 87.5% of Root ZX measured in the range of ${\pm}0.5$ mm from the apical foramen and both showed 57.5 % in the range of 0.1 mm to 0.5 mm. 2. Endex showed significantly higher accuracy in vital teeth than nonvital teeth(p<0.05). But in case of Root ZX, there was no significant difference between vital and nonvital teeth. 3. As a result of this study, there was no significant difference in accuracy between Endex and Root ZX, and both devices showed file passes the apical foramen in more than half of the cases, and it is thought that this must be considered clinically.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.28 no.2
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• pp.471-489
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• 1998

For the successful endodontic treatment, root canal should be cleaned thoroughly by accurate mechanical and chemical canal preparation and sealed completely with canal filling material without damaging the periapical tissues. The accuracy of the root canal length measurement is a prerequisite for the success of the endodontic treatment, and the root canal length is often determined by the standard periapical radiographs and digital tactile sense. In this study, the accuracy and the clinical usefulness of Digora/sup (R)/, an intraoral digital imaging processor and the conventional standard radiographs were compared by measuring the length from the top of the file to the root apex. 30 single rooted premolars were invested in a uniformly sized blocks and No.25 K-file was inserted into and fixed in each canal. Each block was placed in equal distance and position to satisfy the principle of the bisecting angle and paralleling techniques and Digora/sup (R)/ system's image and standard periapical radiographs were taken. Each radiograph was examined by 3 different observers by measuring the length from top of the file to the root apex and each data was compared and analyzed. The results were as follows; 1. In the bisecting angle technique, the average difference between the Digora/sup (R)/ system and standard periapical radiograph was 0.002 mm and the standard deviation was 0.341 mm which showed no statistically significant difference between the two systems(p>0.05). Also, in the paralleling technique, the average difference between these two system was 0.007 mm and the standard deviation was 0.323 mm which showed no statistically significant difference between the two systems(p>0.05). 2. In Digora/sup (R)/ system, the average difference between the bisecting angle and paralleling technique was -0.336 mm and the standard deviation was 0.472 mm which showed a statistically significant difference between the two techniques(p<0.05). Also, in the standard periapical radiographs, the average difference between the bisecting angle and paralleling technique was 0.328 mm and the standard deviation was 0.517 mm which showed a statistically significant difference between these two techniques(p<0.05). 3. In Digora/sup (R)/ system and the standard periapical radiographs. there was a statistically significant difference between the measurement using the bisecting angle technique and the actual length(p<0.05), But there was no statistically significant difference between the measurement using the paralleling technique and the actuallength(p>0.05). In conclusion. the determination of the root canal length by using the Digora/sup (R)/ system can give us as good an image as the standard periapical radiograph and using the paralleling technique instead of the bisecting angle technique can give a measurement closer to the actual canal length. thereby contributing to a successful result. Also. considering the advantages of the digital imaging processor such as decreasing the amount of exposure to the patient. immediate use of the image. magnification of image size. control of the contrast and brightness and the ability of storing the image can give us good reason to replace the standard periapical radiographs.

• Restorative Dentistry and Endodontics
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• v.30 no.6
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• pp.477-485
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• 2005

The aim of this study was to compare the length between the mesio-buccal and mesio-lingual canal of the mandibular molars before and after early coronal flaring at the different measuring time using several electronic apex locators. Fifty mandibular molars with complete apical formation and patent foramens were selected. After establishing the initial working length of the buccal and lingual canal of the mesial root using a surgical microscope (Carl Zeiss Co Germany) at 25X with #15 K-fle tip just visible at the foramen, radiographs were taken for the working length. After measuring the length of mesio-buccal and mesio-lingual canal (control group), the electronic lengths were measured at different times using several electronic apex locators (experimental groups; I-Root ZX, II-Bingo, III-Propex, IV-Diagnostic). After early coronal flaring using the $K^3$ file, the additional electronic lengths were measured using the same manner The results were as follows: One canal has a correct working length for the mesial root of the mandibular molar, it can be used effectively for measuring the electronic working length of another canal when the files are superimposed or encountered at the apex. In addition, the accuracy of the electronic apex locators was increased as the measurement was accomplished after the early coronal flaring of the root canal and the measuring time was repeated.

• Restorative Dentistry and Endodontics
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• v.25 no.3
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• pp.474-482
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• 2000

Currently frequency-dependent type electronic apex locators have been widely used to determine the working length in endodontic treatment. But, accuracy of electronic apex locators is controversial. The purpose of this study was to evaluate the accuracy of Root-ZX(Morita Co., Japan) at different kinds of conditions of root canals compared with the radiographic working length. The 40 extracted human anterior teeth with fully formed apices and without any caries were used. The radiographs were taken for working length with the 0.5mm short of #15 K-file tip just visible at the foramen under the surgical microscope(Carl Zeiss Co. Germany) at 25X. Then the electronic working lengths were determined with Root-ZX at the different kinds of conditions of root canals according to the presence of electrolyte and Crown-down pressureless technique. The results were as follows ; 1. There was no significant statistical difference in working length between radiograph and Root-ZX. 2. There was no significant statistical difference in electronic working length between the canal with electrolyte and without electrolyte. 3. There was no significant statistical difference in electronic working length between the canal without any instrumentation and after Crown-dow pressureless technique. 4. Of the total 40 root canals, 85% in Group I, 92.5% in Group II, 95% in Group III and 95% in Group IV using Root-ZX showed coincidence within 0.5mm accuracy compaing with the radiographic working length. The results showed that the Root-ZX can be use effectively for measuring the working length of root canal after instrumentation with Crown-down pressureless technique regardless of the presence of electrolyte in root canal.

• Restorative Dentistry and Endodontics
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• v.7 no.1
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• pp.25-31
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• 1981

One of the most important factors for successful endodontic therapy is an accurate length determination of physiological root apex. Some methods suggested for the measurement of root canal length, include digital-tactile sense and roentgenographic technique with measuring wire, scale and grid. But these methods do not derermine an accurate working length to physiological root apex. Recently electronic measuring devices are used to locate the physiological root apex in root canal length determination and these devices are accepted as an effective apparatus. The 89 patients (116 teeth, 144 canals) among the out-patients of Yonsei University Dental Infirmary, who had had an endodontic treatment in the Department of Operative Dentistry, were measured by the Root-Canal Meter$^{(R)}$ as an electronic device, and radiographs to determine the distribution and location of physiological root apex, then the following results were made: (1) Range of ${\pm}$1mm from the radiographic root apex were present in 88.88% (128 canals) of the subjects. (2) Physiological root apex and radiographic root apex were coincided in 31.94% (46 canals) of the subjects. (3) The actual length of the physiological root apex of the teeth were as follow; A : in the maxillary central incisor : 0.46mm B : in the maxillary lateral incisor : 0.44mm C : in the maxillary canine : 0.44mm D : in the maxillary 1st premolar : a) Buccal : 0.59mm b) Lingual : 0.34mm E : in the maxillary 2nd premolar : 0.54mm F : in the maxillary 1st molar : a) Mesio-buccal : 0.50mm b) Disto-buccal : 0.42mm c) Lingual : 0.56mm G : in the mandibular central incisor : 0.62mm H : in the mandibular lateral incisor : 0.45mm in the mandibular canine : 0.54mm J : in the mandibular 1st premolar : 0.47mm K : in the mandibular 2nd premolar : 0.34mm L : in the mandibular 1st molar : a) Mesio-buccal : 0.54mm b) Mesio-lingual : 0.31mm c) Distal : 0.37mm.

• Restorative Dentistry and Endodontics
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• v.10 no.1
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• pp.169-175
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• 1984

This study was undertaken to obtain the average canal length of upper & lower anterior teeth which was important in canal length measuring procedure of endodontic treatment. It was based upon 827 out-patients who had endodontic treatment on their upper & lower anterior teeth at the Department of Operative Dentistry, Dental Infirmary, Yonsei Medical Center from February, 1978 to June, 1984. The 1249 teeth of these patients were devided into sex and age groups. The root canal length of these teeth were measured. The following results were obtained; 1. The mean root canal length of upper & lower anterior teeth were as follows; Upper central incisors : 21.8mm Upper lateral incisors : 21.0mm Upper canines : 24.1mm Lower central incisors : 18.6mm Lower lateral incisors : 19.9mm Lower canines : 22.6mm 2. There was no significant difference in root canal length between sex. (P > 0.05) 3. There was no significant difference in root canal length between age groups. (p > 0.05) 4. The distribution of upper central incisors showed the highest distribution followed by upper lateral incisors and lower central incisors between 10 to 40 year old age groups, and there was no signigicant difference in the rest of the age groups. There was no significant difference in sex distribution, which was 49.5% for males and 50.4% for females. The number of the upper anterior teeth was 74.3% of all the specimens and the lower anterior 25.7%, and 40.6% of all the specimens were upper central incisors.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.28 no.2
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• pp.435-459
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• 1998

In order to achieve a successful endodontic treatment, root canals must be obturated three-dimensionally without causing any damage to apical tissues. Accurate length determination of the root canal is critical in this case. For this reason, I've used the conventional periapical radiography, Digora/sup (R)/(digital imaging system) and Root ZX/sup (R)/(the frequency dependent type apex locator) to measure the length of the canal and compare it with the true length obtained by cutting the tooth in half and measuring the length between the occlusal surface and the apical foramen. From the information obtained by these measurements, I was able to evaluate the accuracy and clinical usefulness of each systems. whether the thickness of files used in endodontic therapy has any effect on the measuring systems was also evaluated in an effort to simplify the treatment planning phase of endodontic treatment. 29 canals of 29 sound premolars were measured with #15, #20, #25 files by 3 different dentists each using the periapical radiography. Digora/sup (R)/ and Root ZX/sup (R)/. The measurements were then compared with the true length. The results were as follows: 1. In comparing mean discrepancies between measurements obtained by using periapical radiography(mean error: -0.449±0.444 mm), Digora/sup (R)/(mean error: -0.417±0.415 mm) and Root ZX/sup (R)/(mean error: 0.123±0.458 mm) with true length. periapical radiography and Digora/sup (R)/ system had statistically significant differences(p<0.05) in most cases while Root ZX/sup (R)/ showed none(p>0.05). 2. By subtracting values obtained by using periapical radiography, Digora/sup (R)/ and Root ZX/sup (R)/ from the true length and making a distribution table of their absolute values. the following analysis was possible. In the case of periapical film. 140 out of 261<53.6％) were clinically acceptable satisfying the margin of error of less than 0.5 mm. 151 out of 261 (53,6％) were acceptable in the Digora/sup (R)/ system while Root ZX/sup (R)/ had 197 out of 261(75.5％) within the limits of 0.5mm margin of error. 3. In determining whether the thickness of files has any effect on measuring methoths, no statistically significant differences were found(p>0.05). 4. In comparing data obtained from these methods in order to evaluate the difference among measuring methods, there was no statistically significant difference between periapical radiography and Digora/sup (R)/ system(p>0.05), but there was statistically significant difference between Root ZX/sup (R)/ and periapical radiography(p<0.05). Also there was statistically significant difference between Root ZX/sup (R)/ and Digora/sup (R)/ system(p<0.05). In conclusion, Root ZX/sup (R)/ was more accurate when compared with the Digora/sup (R)/ system and periapical radiography and seems to be more effective clinically in determining root canal length. But Root ZX/sup (R)/ has its limits in determining root morphology and number of roots and its accuracy becomes questionable when apical foramen is open due to unknown reasons. Therefore the combined use of Root ZX/sup (R)/ and the periapical radiography are mandatory. Digora/sup (R)/ system seems to be more effective when periapical radiographs are needed in a short period of time because of its short processing time and less exposure.

• Restorative Dentistry and Endodontics
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• v.29 no.6
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• pp.541-547
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• 2004

The aim of this study was to compare the initial apical file (IAF) length between the mesio-buccanl and mesio-lingual canals of the mandibular molar before and after early coronal flaring. Fifty mandibular molars with complete apical formation and patent foramens were selected. After establishing the initial working length of the buccal and lingual canal of the mesial root using the Root-ZX, radiographs were taken for the working length with a 0.5 mm short of #15 K-file tip just visible at the foramen under a surgical microscope (OPMI 1-FC, Carl Zeiss Co. Germany) at 25X. After early coronal flaring using the $K^3$ file, additional radiographs were taken using the same procedure. The root canal morphology and the difference in working length between the buccal and lingual canals were evaluated. These results show that the difference in the length between the mesio-buccal and mesio-lingual canals of the mandibular molar was $\leq$ 0.5 mm. If one canal has a correct working length for the mesial root of the mandibular molar, it can be used effectively for measuring the working length of another canal when the files are superimposed or loosening. In addition, the measured the working length after early coronal flaring is much more reasonable because the difference in the length between the mesio-buccal and mesio-lingual canals can be reduced.

• 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.05
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• pp.316-317
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• 1997

For successful endodontic therapy, complete and accurate biochemical and chemical preparations will allow accurate root canal. Hence the accurate determination of root length is very important for the highest rates of success in endodontic therapy. Among the apex locators, frequency dependent type has higher accuracy and more advantages than others. In this paper, we proposed better frequencies for the method of measuring root canal length by the ratio of two different impedances. It was found that 500Hz and 10kHz is better selection than other frequencies used in the commercial products.