Abstract
Context:
Accurate working length determination is essential for successful root canal therapy. This study compares the accuracy of two electronic apex locators—e-Magic Finder (EMF)-100 and WOODPEX I—with digital radiovisiography (RVG; Suni Ray) in determining root canal working length.
Aims:
To evaluate and compare the accuracy of EMF-100 and WOODPEX I apex locators with RVG in determining the working length of root canals.
Settings and Design:
This was an in vivo, comparative observational study conducted in a clinical dental setting. The study included 30 patients (aged ≥15 years) requiring endodontic therapy on 45 mature permanent teeth. The aim was to evaluate and compare the accuracy of two electronic apex locators—EMF-100 and WOODPEX I—with digital radiovisiography (Suni Ray) in determining working length.
Subjects and Methods:
A total of 45 teeth from 30 patients (aged ≥15 years) requiring endodontic treatment were included. After obtaining consent and recording medical history, preoperative RVG images were taken using the paralleling technique. Working length was measured using three methods: EMF-100 apex locator (Group I), WOODPEX I (Group II), and RVG (Group III).
Statistical Analysis Used:
Paired t-test and Chi-square test.
Results:
Both apex locators demonstrated clinically acceptable accuracy. EMF-100 showed slightly better agreement with RVG than WOODPEX I.
Conclusion:
Both EMF-100 and WOODPEX I are effective for working length determination, with EMF-100 exhibiting slightly higher accuracy.
Keywords: Apex locator, apical constriction, radiovisiography, working length
INTRODUCTION
The successful outcome of root canal treatment depends on the determination of accurate working length (WL). Working length is defined in the Endodontic Glossary as “the distance from the coronal reference point to the point at which the canal preparation and obturation should terminate.”[1]
Anatomically, the apical constriction (AC) indicates the apical limit for the termination of endodontic treatment,[2] as it often coincides with the narrowest diameter of the root canal and also helps in WL determination. Locating the AC and the cementodentinal junction (CDJ) in a clinical setting, however, is critical. The location of the CDJ varies in relation to the apical foramen. It is widely accepted as being 0.50–0.75 mm coronal to the apical foramen.[3]
Modern electronic apex locators (EALs) determine distance from the end of the apex by comparing impedances, which are measured by using different current frequencies.[4] The difference in impedance is calculated to determine the position of the file in the canal.[2] The impedance is small at the AC and has a higher value at the major foramen.
The e-Magic Finder (EMF-100) and WOODPEX I are fifth-generation EALs that use advanced T-Surge circuitry and multiple frequencies for accurate measurement without requiring calibration.
This clinical study aims to compare their accuracy with radiovisiography (RVG) in determining root canal WL.
SUBJECTS AND METHODS
This study included 45 mature-apex teeth from 30 patients (≥15 years) requiring endodontic therapy for irreversible pulpitis or necrosis. After obtaining informed consent and recording comprehensive histories, preoperative digital periapical radiographs were taken. Included teeth had adequate structure for rubber dam isolation, patent canals, and fully developed apices; teeth with resorption, obliteration, perforation, calcification, and patients who were pregnant or had pacemakers were excluded from the study. The sample was divided into three groups, and WL was measured under rubber dam isolation using the EMF-100 apex locator in Group I, Woodpecker Apex Locator (WOODPEX I) in Group II, and RVG (SuniRay RVG) in Group III.
Group I: Determination of WL by EMF-100 apex locator
After local anesthesia and rubber dam isolation, a coronal reference point was established post caries and restoration removal. Access was prepared with sterile burs, and orifices enlarged using Gates Glidden drills no. 1 and 2. Canals were irrigated with 2.5% sodium hypochlorite, apical patency maintained with K-files (sizes 15–30), and left moist. WL was determined using the EMF apex locator (set at 0.5 EMR). A K-file was advanced until the device indicated apex location; the silicone stop was set at the reference point, and the length was recorded. This was repeated for all Group I teeth.
Group II: Determination of WL by Woodpecker apex locator (WOODPEX I)
After measurement with the EMF, WL was determined using the Woodpecker apex locator (WOODPEX I) per manufacturer’s instructions. Set at 0.5 EMR, a K-file connected to the electrode was advanced apically with the lip clip placed contralaterally. The device signaled apex location with a beep and “APEX” LED; at 0.5 mm, a green LED and rapid tone were triggered. The distance from file tip to silicone stop was measured and recorded as the WOODPEX I WL (Group II). This was repeated for all teeth.
Group III: Determination of WL by RVG
A snug-fitting K-file was used, with the sensor protected by disposable sleeves to prevent contamination. A diagnostic radiovisiograph was taken using the paralleling technique at a 4-inch object–source distance. The distance between the file tip and radiographic apex was measured, then adjusted by a 0.5 mm safety margin to the AC. Three endodontists independently calibrated each image to determine WL from the reference point to the file tip. Measurements from EMF-100 (Group I), WOODPEX I (Group II), and RVG (Group III) were recorded for all teeth.
RESULTS
The statistical analysis was done to analyze the accuracy of the apex locator with RVG. Statistical analysis was done using descriptive and univariate summary statistics using the paired sample t-test and Chi-square test. The software used in the analysis was SPSS 22.00 and Graph Pad Prism 5.0, and P < 0.05 is considered as level of significance.
The mean WL and standard deviation of the two apex locators when compared with average radiovisiographic WL revealed a significant difference. The P value was set at 0.05. The P value for this was 0.028, which is significant.
DISCUSSION
Accurate WL determination is one of the vital procedures for successful endodontic therapy. The various methods for the determination of WL are tactile, radiographic, apex locators, etc., but none of these are accurate.[5] The capacitance of a root canal increases significantly at the AC, and the quotient of the impedances reduces rapidly as the AC is reached.[6] In this study, the RVG method was performed with a source-to-object distance standardized at 4 inches for both maxillary and mandibular teeth. Radiographic magnification increases as the object–sensor distance increases, because it is physically impossible to place either the sensor directly against the tooth being imaged in a parallel technique. Digital image calibration was performed before each tooth length determination using the on-screen calibration tool to measure the image of an endodontic file of a known length. It was done because it has been shown that calibrated digital measurements are more accurate than uncalibrated measurements. In this study, irrespective of age, we have considered the AC located at 0.5 mm from the apical foramen while determining the WL for standardization. The range value was chosen based on previous in vivo studies that used the same range method.[7] The mean difference between the two apex locators was determined in comparison with RVG. The results of this study indicate that EMF-100 is better when compared to WOODPEX I. The mean difference shown by EMF-100 is 0.0978 mm and by WOODPEX I is 0.2089 mm, which is very significant [Figure 1].[8] This result is in agreement with an earlier study by Sung et al. that assessed the accuracy of measurements in pre-enlarged canals with small instruments, to compare the accuracies in enlarged canals with small-sized instruments and instruments that match the actual canal diameter using Root ZX, Bingo 1020, Smarpex, and EMF. The file size made no difference in the accuracy of electronic measurement in an enlarged canal with the same device. The EMF was the most accurate device among the four apex locators used in this study. This study showed 96% and 87% acceptable radiographic measurements for EMF-100 and WOODPEX I, respectively [Figure 2]. A variable range of 0.1 mm up to 2 mm distance from the radiographic apex has been considered as acceptable values by several authors.[9] In this study results from both the EALs were acceptable in the range of 87%–96%. Similar results were found in other studies,[10] which stated that the correct use of EAL may help to reduce the risk of instrumentation beyond the apical foramen and also reduce the repeated radiation exposure by radiographs. Within the limitations of this in vivo study, the WL determined using two fifth-generation apex locators and RVG revealed more acceptable results, even though there was a significant difference between the two electronic apex locators. Further studies are needed to achieve 100% clinical accuracy.
Figure 1.
Mean difference between EALs & RVG
Figure 2.
Acceptable and non acceptable measurements in percentage
CONCLUSION
Within the limitations of this in vivo study, the following conclusions were drawn:
By determining mean differences, the EMF-100 apex locator performed better than the WOODPEX I apex locator when compared with RVG.
Both the apex locators produced good results while considering the acceptable and nonacceptable measurements in comparison with radiographic measurements. However, EMF-100 performed slightly better than the WOODPEX I apex locator.
Key messages
Both EMF-100 and WOODPEX I electronic apex locators are reliable tools for determining root canal working length, but EMF-100 demonstrates slightly higher accuracy when compared to digital radiovisiography, making it a preferable choice for clinical use.
Conflicts of interest
There are no conflicts of interest.
Funding Statement
Nil.
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