|Year : 2015 | Volume
| Issue : 4 | Page : 288-291
|Comparison of third generation versus fourth generation electronic apex locators in detecting apical constriction: An in vivo study
Devarsanahalli Venkataramanaswamy Swapna1, Akash Krishna2, Anand C Patil3, Krishna Rashmi1, Veena Suresh Pai1, Mandagere Aswathanarayana Ranjini1
1 Department of Conservative Dentistry and Endodontics, Dayanandasagar College of Dental Sciences, Bengaluru, Karnataka, India
2 Department of Endodontics and Cosmetic Dentistry, NMC Specialty Hospital LLC, Abu Dhabi, United Arab Emirates
3 Department of Conservative Dentistry and Endodontics, KLE VK Institute of Dental Sciences, Belgaum, Karnataka, India
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|Date of Submission||26-Mar-2015|
|Date of Decision||07-May-2015|
|Date of Acceptance||02-Jun-2015|
|Date of Web Publication||1-Jul-2015|
| Abstract|| |
Aim: The aim of this in vivo study was to compare the accuracy of Root ZX and Raypex 5 in detecting minor diameter in human permanent single-rooted teeth.
Materials and Methods: Thirty-one patients with completely formed single-rooted permanent teeth indicated for extraction were selected for the study. Crown was flattened for stable reference point and access cavity prepared. Working length was determined with both apex locators. A 15 K file adjusted to that reading was placed in the root canal and stabilized with cement. The tooth was then extracted atraumatically. Following extraction apical 4 mm of root was shaved. The position of the minor diameter in relation to the anatomic apex was recorded for each tooth under stereomicroscope at ×10. The efficiency of two electronic apex locators to determine the minor diameter was statistically analyzed using paired sample t-test.
Results: The minor diameter was located within the limits of ±0.5 mm in 96.6% of the samples with the Root ZX and 93.2% of the samples with Raypex 5. The paired sample t-test showed no significant difference.
Conclusion: On analyzing the results of our study it can be concluded that Raypex 5 was as effective as Root ZX in determining the minor diameter.
Keywords: Minor diameter; Raypex 5; Root ZX
|How to cite this article:|
Swapna DV, Krishna A, Patil AC, Rashmi K, Pai VS, Ranjini MA. Comparison of third generation versus fourth generation electronic apex locators in detecting apical constriction: An in vivo study. J Conserv Dent 2015;18:288-91
|How to cite this URL:|
Swapna DV, Krishna A, Patil AC, Rashmi K, Pai VS, Ranjini MA. Comparison of third generation versus fourth generation electronic apex locators in detecting apical constriction: An in vivo study. J Conserv Dent [serial online] 2015 [cited 2021 May 16];18:288-91. Available from: https://www.jcd.org.in/text.asp?2015/18/4/288/159726
| Introduction|| |
The exact location of the physiological root apex is a prerequisite for the successful endodontic therapy. It is imperative to completely clean and shape the canal in order to prevent irritation to the periapical tissues.  Failure to determine the proper working length can result in short working length with tissue being left in the canal or a long working length, with possible sequelae of damage to the periradicular tissues. This can result in patient discomfort, reinfection and/or extrusion of irrigating solution beyond the confines of the canal. ,
Traditionally, the point of termination of endodontic instrumentation and obturation has been determined by digital tactile sense, apical periodontal sensitivity, paper point measurement, and radiographic technique. 
However, among all these methods, none of them was singly able to accurately determine the apical constriction. To date, radiographs are the most commonly used technique, but they are subjected to distortion, magnification, lack of three-dimensional representation, increased radiation exposure to the patient, interpretation variability among the different clinicians and is time-consuming. 
Apart from the above mentioned, radiograph has inherent drawbacks when the apical portion of the canal is obscured by anatomic structures, such as impacted teeth, tori, zygomatic arch, excessive bone density, overlapping roots, or shallow palatal vault. Electronic apex locator (EAL) currently are being used to determine the working length and is an important adjunct to radiographs which has overcome its drawbacks. 
Since the introduction of first electronic apex locater by Sunada, it has undergone lot of improvements. This has led to a greater precision, fewer procedural errors, less discomfort to the patient and faster case completion.  Although many generations of EAL's are available for use in clinical practice, Root ZX has become the benchmark to which other apex locators are compared. Root ZX has been exhaustively tested for accuracy in vivo and in vitro. Root ZX has shown 90-100% accuracy in determining the minor apical foramen. 
As there are not enough clinical studies reported in the literature regarding the accuracy of Raypex 5 in determining the location of minor diameter, there arises a need to compare the efficacy of newer EAL's to the older ones.
The purpose of this study was to evaluate in vivo accuracy of Raypex 5 and compare it with Root ZX in detecting the minor apical foramen.
| Materials and Methods|| |
Thirty-one patients with completely formed single-rooted permanent teeth indicated for extraction due to orthodontic, prosthodontic and periodontal reasons were selected for the study. Before initiation of treatment, informed consent was obtained from each patient.
Two percent 1:80,000 lignocaine (Lignox, Warren) anesthetic was administered; the tooth was isolated under rubber dam (Hygenic Corp., Coltene Whaledent). The occlusal surface was flattened using number 201 flat end tapered fissure diamond point (Shofu, Kyoto, Japan) in a high-speed handpiece and water spray. This was to allow for easy access to pulp chamber and to create a flat reference point for working length. Endodontic access was prepared with Endo Access Bur (dentsply.co.uk) pulp extirpated using barbed broach (Dentsply Maillifer). Root canal orifice was flared using Orifice Shapers 1 and 2 (Dentsply Tulsa Dental, USA). 2.6% Sodium hypochlorite solution (Venson's India) was used for irrigation. Fifteen size K-file (Kendo, Europe) was used to obtain the working length of each tooth from both the apex locators-Root ZX (J. Morita Corporation, Tokyo, Japan) and Raypex 5 (VDM, Munich, Germany). The file was withdrawn from the canal each time, and WL recorded using digital caliper.
The working length reading from the apex locator that was used last was taken and 15 K file adjusted to that reading was placed in the canal and cemented with Type-II GIC (FUJI II, GC Corporation, Japan). The estimated working length was reconfirmed by adapting the electrode to the cemented file, to make sure that GIC placement did not disturb the recording. The handle of the instrument was sheared off using orthodontic wire cutter. The tooth was then extracted as atraumatically as possible with the cemented file in the root canal. The extracted tooth was then placed in 5.25% of sodium hypochlorite for 15 min, to remove organic debris. The samples were then placed in 0.2% thymol saline solution till examined.
The same procedure was repeated for all the teeth, but the sequence of use of Raypex 5 and Root ZX were alternated to avoid bias. The working length determination was done with both the apex locators, following manufactures instructions. The position of the minor diameter in relation to the anatomic apex and presence of resorption was recorded for each tooth under stereomicroscope at ×10.
The apical 4 mm of root was shaved using a 12 fluted bur, size ET6 with 1.4 mm diameter (E.T. Carbide, USA) along the long axis of the tooth in a plane that was determined to show the best representation of the minor diameter in relation to the file. Shaving with bur was performed under an operating microscope (Alltion, Germany) at ×12.5 such that the file could be seen through a thin layer of dentin. This last layer was then removed using a number 15 Bard Parker blade.
A double-blind examination was performed with regard to the use of two EALs. Two investigators, blinded at which EALs was used, recorded the distance from the end of the file to minor diameter (narrowest part of canal as given by Kuttler's) under stereomicroscope (Labomed) at ×10 (negative value indicates short or coronal to minor diameter) [Table 1]. The data were statistically analyzed using paired sample t-test to know the statistical significance of the two EALs.
|Table 1: Two investigators, blinded at which electronic apex locator was used, recorded the distance from the end of the file to minor diameter under stereomicroscope (labomed) at ×10 magnification. (negative value indicates short [or coronal] to minor diameter)|
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During the histomorphometric analysis in one of the teeth included in the study was found to have apical defect (fracture) and hence was excluded and another case was taken to compensate the sample size of 30.
The minor diameter was determined in all the teeth. [Figure 1] and [Figure 2] showed the distances of the file tips for the EALs in relation to the minor diameter. The mean distance between the instrument tip and the minor diameter was +0.00 ± 0.21 mm for the Root ZX and +0.05 ± 0.23 mm for the Raypex 5 [Table 2].
|Table 2: Distances from the tip of file relative to the minor diameter (mm) a paired sample t-test: There was no statistically significant difference between the accuracy of the two electronic apex locators in locating the minor diameter (P < 0.362271)|
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The minor diameter was coinciding with the tip of the instrument in 10 cases when Root ZX was used and in 12 cases when Raypex was used. In 96.6% of cases tested with Root ZX the minor diameter was within the limit of ±0.5 mm. In 93.2% of cases, minor diameter was within a limit of ±0.5 mm with Raypex 5 [Table 3].
|Table 3: Distance-instrument to minor diameter. Distances of the instruments tip for Root ZX and Raypex 5 in relation to the minor diameter|
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An exact agreement between the results of the two EALs was not found in any of the cases. The paired sample t-test showed that there was no significant difference between the results of Root ZX and Raypex 5 in determining the minor diameter (P < 0.362271) [Table 2].
| Discussion|| |
In clinical practice, the apical constriction is the narrowest and more consistent anatomical feature in the root canal system.  Thus, preferred apical end point for instrumentation and obturation in endodontic therapy. Posttreatment discomfort is greater when this area is violated by instrumentation or filling materials and the healing process may be compromised. Kuttler in 1955 gave the most comprehensive anatomic microscopic study of the root tip. Minor foramen is often thought to coincide with the apical constriction and regarded as being at or near the cemento-dentinal junction (CDJ) (Kuttler 1958). The minor diameter represents the transition between the pulpal and the periodontal tissue, located in the range of 0.5-1.0 mm from the external foramen or major diameter on the root surface.  Kuttler concluded that the average distance between the minor and major diameters was 0.524-0.659 mm.  Modern apex locators help to determine the apical end point of root canal instrumentation. Hence, they are recommended to complement conventional radiographic working length determination techniques. 
Although many generations of EALs are available for use in clinical practice, since the introduction of Root ZX, it has become a benchmark to which other apex locators are compared.  Root ZX uses two different frequencies (8 KHz and 400 Hz) simultaneously to measure the impedances in the canal. The device then determines a quotient value by dividing the 8 KHz impedance value by 400 Hz impedance value. The minor diameter is located when a quotient equals 0.67. Root ZX can be used in canals filled with all types of fluids because the quotient (0.67) is always the same. ,,
Raypex 5 is a newly introduced apex locator that uses two separate frequencies (400 Hz and 800 Hz). It is claimed that the combination of using only one frequency at a time and basing the measurements on the root mean square values of the signal frequency increases the measurement accuracy and the reliability of the device. ,
Numerous studies have reported the accuracy of EALs in determining minor diameter. These studies differ in establishing the reference point from which measurement accuracy was determined, some authors measured from the minor diameter while others measured from the major diameter or apical foramen. ,,,,,
Root canals terminate at the CDJ. ,, The location of CDJ in the root canal varies considerably. It generally is not in the same area as the apical constriction and estimates place it approximately 1 mm from the apical foramen. Lacking such demarcations, an error to tolerance of 1.0 m is deemed clinically acceptable. In previous studies testing the accuracy of frequency-dependent EALs, the major foramen at a tolerance of ±0.5 mm or ±1.0 mm was used as a reference. , The accuracy of Root ZX in locating the apical constriction in our study was as high as 96.6% and Raypex 5 was 93.2%. This precise comparison of the accuracy of different EALs in determination of the working length is possible as the same teeth were evaluated clinically with both the EALs and examined histologically after extraction. 
Our results coincided with the results of a study where Root ZX and Raypex 5 were used to compare and to determine the minor diameter and concluded that statistically no difference existed between Root ZX and Raypex 5. 
In none of the teeth tested, the tip of the file had not gone beyond the major foramen while using both the Root ZX and Raypex 5 as apex locators. In another study, the file had gone beyond the major foramen.  During working length determination, the file should only be advanced until the display indicates the apex. This is to avoid the files passing through the major foramen and overestimating the working length. ,
In the present study, both the Root ZX and Raypex 5 showed the accuracy of the results to the extent of 96.6% and 93.2% accurate in detecting the minor diameter to the strictest acceptable range of 0.5 mm. Hence, from these results, it can be concluded that Raypex 5 is as effective as Root ZX in determining the minor diameter.
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Conflicts of interest
There are no conflicts of interest.
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Dr. Devarsanahalli Venkataramanaswamy Swapna
Department of Conservative Dentistry and Endodontics, Dayanandasagar College of Dental Sciences, Bengaluru - 560 078, Karnataka
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3]
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