Journal of Indian Society of Pedodontics and Preventive Dentistry
Journal of Indian Society of Pedodontics and Preventive Dentistry
                                                   Official journal of the Indian Society of Pedodontics and Preventive Dentistry                           
Year : 2015  |  Volume : 33  |  Issue : 3  |  Page : 208--212

Comparative evaluation of adequacy of final working length after using Raypex5 or radiography: An in vivo study

Deepika Singh1, Shashi Prabha Tyagi2, Swati Gupta3, Ankita Jain4,  
1 Department of Conservative Dentistry and Endodontics, Teerthanker Mahaveer Dental College and Research Centre, Moradabad, Uttar Pradesh, India
2 Department of Conservative Dentistry and Endodontics, Kothiwal Dental College and Research Centre, Moradabad, Uttar Pradesh, India
3 Department of Conservative Dentistry and Endodontics, Idea Dental College, Gwalior, Madhya Pradesh, India
4 Department of Public Health Dentistry, Teerthanker Mahaveer Dental College and Research Centre, Moradabad, Uttar Pradesh, India

Correspondence Address:
Dr. Ankita Jain
Department of Public Health Dentistry, Teerthanker Mahaveer Dental College and Research Centre, Moradabad - 244 102, Uttar Pradesh


Aim: The aim of this clinical study was to compare the effect of working length (WL) determination using electronic apex locator (EAL) or WL radiograph on the length adequacy of final WL. Materials and Methods: A total of 153 patients with 153 teeth with single canal were randomized into two groups; in Group 1, the WL was determined by WL radiograph; whereas in Group 2, it was determined by the Raypex5 EAL (VDW, Munich, Germany). Length adequacy was assessed in each group for master cone and categorized into short, acceptable, and over cases. Statistical Analysis Used: The data were statistically analyzed using the Pearson chi-square test at a significance level of P < 0.05. Results: There was no statistically significant difference between the groups in the rates of acceptable (Group 1 = 83.1% and Group 2 = 92.1%) and short cases (Group 1 = 3.9% and Group 2 = 5.2%). Over cases in master cone radiography were significantly more in Group 1 (13.1%) than Group 2 (2.6%) (P = 0.017). Conclusion: The results of our study have shown that under clinical condition, success of Raypex5 was comparable to the radiographic WL determination technique in terms of acceptable and short cases. However, there were significantly lesser over cases in EAL group, showing that EALs can avoid the overestimation of WL.

How to cite this article:
Singh D, Tyagi SP, Gupta S, Jain A. Comparative evaluation of adequacy of final working length after using Raypex5 or radiography: An in vivo study.J Indian Soc Pedod Prev Dent 2015;33:208-212

How to cite this URL:
Singh D, Tyagi SP, Gupta S, Jain A. Comparative evaluation of adequacy of final working length after using Raypex5 or radiography: An in vivo study. J Indian Soc Pedod Prev Dent [serial online] 2015 [cited 2022 Jan 18 ];33:208-212
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Accurate determination of root canal length is critical for successful endodontic treatment. The debridement, shaping, and obturation of root canal system cannot be accomplished properly unless the working length (WL) is correctly determined. Underestimation of the WL can lead to insufficient debridement of the root canal; whereas, overestimation may result in damage to the periapical tissues, which will delay or prevent healing. [1] Optimal healing condition with minimal contact between the obturation material and the apical tissue is achieved when root canal treatment terminates at the apical constriction.

Traditional methods for establishing WL have been the use of anatomical averages and knowledge of anatomy, tactile sensation, moisture on a paper point, and radiography. The most popular method of WL determination has been the use of radiographs. This method has many advantages like direct observation of the anatomy of the root canal system, the number and curvature of roots, the presence or absence of disease, and in addition it can act as an initial guide for WL estimation. [2] There are, however, a number of limitations associated with it; such as distortion, shortening and elongation, interpretation variability, lack of three-dimensional representation, technique sensitivity and subjectivity, [3] the danger of ionizing radiation, and errors of superimposition caused by producing a two-dimensional representation from a three-dimensional object. [4] The accuracy of radiographic methods of length determination also depends on the radiographic technique used. Sheaffer et al., [5] revealed that higher density radiographs were more desirable for measuring WL. Forsberg [6] reported that tooth length determined by the bisecting angle technique, either correctly or incorrectly angulated, was less accurate than the paralleling technique. Even when a paralleling technique is used, elongation of images has been found to be approximately 5%. [7]

Although it is generally accepted that the minor apical foramen and apical constriction is on an average located 0.5-1.0 mm short of the radiographic apex, [8] there are wide variations in the relationship of these landmarks that would result in under or over preparation of canals with an obvious impact on the position of the root filling. [9] Thus, a WL 1 mm short of the radiographic apex may result in over or under instrumentation and this often used 'rule' is not predictable or reliable.

One of the innovations in root canal treatment has been the development and production of electronic devices for detecting the canal terminus. Main advantages of electronic apex locators (EALs) are that these measure the root canal length to apical foramen, not the radiographic apex. They are easy and fast to operate, and have a good accuracy. Artificial perforations can be recognized and radiation can be reduced. [10] Earlier devices were inaccurate in root canals containing moisture, vital pulp tissue, blood, or remnants of canal irrigants. [11],[12] The acceptance of EALs is widely increasing, especially with the introduction of the third and fourth generations. [13] Third-generation EALs have more powerful microprocessors and are able to process mathematical quotient and algorithm calculations required to give accurate readings. The fourth-generation EALs do not process the impedance information as a mathematical algorithm, but instead they take the resistance and capacitance measurements separately and compare them with a database to determine the distance to the apex of the root canal. [14] Modern EALs work by using different frequencies, determining the ratio between the different electric potentials proportional to each impedance. There is no need to dry canal before using EALs because they work in the presence of electrolytes. [15]

Raypex5 (VDW, Munich, Germany) is a fourth generation EAL that uses the two alternating current frequencies (400 Hz and 8 kHz) and determine the WL via an impedance ratio. The Raypex5 passes the two frequencies in succession. [16] The manufacturer claims that using only one frequency at a time, in combination with obtaining measurements on the basis of the root mean square values of the signals, increases the accuracy of measurement and the reliability of the device. [17]

Several in vitro[18],[19] and ex vivo[20] studies have investigated radiographic method and EALs solely or in comparison to each other, but in vivo studies that compare these two methods with each other in a truly clinical condition are scarce. The purpose of this study was to evaluate the effect of WL determination by radiograph or EAL on the adequacy of the final WL.

 Materials and Methods

The sample size was calculated by setting the power of the study to 95%, and level of significance α = 0.05, which gave a minimum number of 153 canals for this two treatment parallel-design study. Patient aged 20-45 years who presented for primary endodontic therapy to the Department of Conservative Dentistry and Endodontics, Kothiwal Dental College and Research Centre, Moradabad were selected. Ethical approval was gained from the ethical committee of college. Only the teeth with single patent canal were included in the study to prevent error in WL determination due to superimposition of canals in radiography. After obtaining informed written consent form from each patient, 153 teeth were randomly allocated to two groups, that is, the radiography and EAL group. The randomization was done using a computer-generated sequence of random numbers by an independent statistician. All of the cases were treated by one endodontist. Also, teeth with no apical patency and radiographic signs of root resorption were excluded.

Preoperative periapical radiograph using paralleling angle technique using Rinn XCP holder was taken. It resulted in a constant angulation for all the radiographs taken for the same tooth. Under local anesthesia and isolation with rubber dam, caries and existing restorations were removed. Access cavity was prepared using high speed air rotor headpiece and diamond bur (Dentsply Maillefer), with water coolant in each tooth and a straight line access was achieved. The cusps or the incisal edges of the teeth were flattened with a diamond bur to obtain a stable reference point for all measurements. The crowns were marked with a marker to serve as a reference for the placement of the rubber stop. Endodontic access was obtained, and the pulp tissue was removed with a barbed broach. The coronal portion of each canal was flared with Gates Glidden burs #1, # 2, and # 3 (Dentsply Maillefer). Then the canal was irrigated with saline solution and excess was removed from the pulp chamber using cotton pellet. The pulp chamber was dried gently with air and sterile cotton pellets were used to dry the tooth surfaceand eliminate excess irrigant, with no attempt at drying the canal.

The steps followed for each group were as follows:

Group 1 (radiographic WL determination)

The working file was placed to the estimated length after access cavity preparation and the WL radiograph was taken by paralleling angle technique using Rinn XCP holder. A grid of1mm pitch (Bluedent, India) was superimposed on X-ray film while taking radiograph. The primary WL was determined to be 1 mm short of the radiographic apex.Canal preparation was done up to this WL, the master cone was inserted to this length, and a master cone radiograph was taken with superimposed grid using the paralleling angle technique.The measurement was recorded as final obturation and recorded.

Group 2 (EAL)

The Raypex5 was used in accordance with the manufacturer's instructions. The no. 15 K file was placed to the estimated length after access cavity preparation according to preoperative radiograph, attaching the file clip of Raypex5, and moving toward the apex until the red indicator shows the apex and retracted until the flashing green bars appeared. Measurements were considered to be valid if the reading remained stable for at least 5 s. The unstable measurements were recognized when the scale bars on the display of the Raypex5 jumped from one point to the other.Canal preparation was done up to this WL, the master cone was inserted to this length, and a master cone radiograph was taken with grid using the paralleling angle technique.The measurement was recorded as final obturation and recorded.

The master cone radiographs were evaluated by an endodontist blinded to group allocation of each case and graded as follows: (a) short (shorter than 2 mm from radiographic apex), (2) acceptable (within 0-2 mm from radiographic apex), and (c) over (beyond the radiographicapex) [Figure 1].{Figure 1}

Statistical analysis was performed with Statistical Package for Social Sciences (SPSS) 20.0 software. Descriptive statistics were expressed as number and percentage. Pearson chi-square test was used to determine for differences between groups at a significance level of P < 0.05.

 Observations and Results

The results of length adequacy in each group for master cone are summarized in [Table 1]. There were a higher percentage of acceptable cases (92.1%) in Group 2 as compared to (83.11%) Group 1, but the difference was not statistically significant. There were also a higher percentage of short cases (5.26%) in Group 2 as compared to (3.94%) Group 1, with no statistically significant difference. There was a lower percentage of over cases (2.63%) in Group 2 as compared to (13.15%) Group 1, and the difference was statistically significant.{Table 1}


Many studies have been carried out with the Raypex5 under in vitro conditions, [18],[19],[20] but at present the validity of measurements made with in vitro models remains unknown. Marjanovic et al., [21] observed that there are significant differences between the electrical properties of in vitro and in vivo models. As a consequence, extrapolation from in vitro studies to the clinical setting might not be appropriate. By comparison, in vivo studies in which EALs are used to determine the WL emulate what happens in the clinical situation.

The end result was evaluated by radiography, which is an intrinsic problem associated with such kinds of study, because radiography is the only universally accepted, available, and meaningful method of length adequacy assessment in the clinic. We decided to compare the results with paralleling angle technique, since it is more accurate and results in less distortion of image. It is also easier to standardize the radiographs. This is due to the use of a positioning instrument which allows the positioning of the film in approximately the same position at different appointments. Moreover, head position is also not very critical in this technique. Because of the paralleling instrument, with its aiming ring, it is easy to properly align the X-ray beam, no matter how the tube head is positioned.

The difficulties in accurately determining the apical point to which a root filling should extend are well recognized, with differences observed between the position of the anatomical apex and the radiographic apex. Nevertheless, it is widely accepted that placement of the root filling within 2 mm of the radiographic apex significantly affects the success of root-treated teeth. [1]

Most of the previous studies have classified the various extents of instrumentation into three categories for statistical analyses as; >2 mm short of radiographic apex (short), 0-2 mm within the radiographic apex (flush), and extruded beyond the radiographic apex (long).

Most of them found that this factor had significant influence on the success rates. Flush root fillings were associated with higher success rates than short root fillings or long root fillings. [1],[22] Therefore, this interval was chosen for our study as a reasonable and practical criterion for evaluating the length adequacy on radiographs.

The Raypex5 apex locator, which is a fourth generation apex locator, was chosen as it is easy to use even in wet canals, and has a high level of accuracy. In this study Raypex5, which like other impedance ratio apex locators shows a blinking red alarm when the file tip has just passed the apical foramen, was used. When the file tip was withdrawn just to the green zone, it indicates that the file is at apical constriction. Our method, which demands the file to pass through the apical foramen, ensures the operator of a patent canal and a definitive measurement as a result.

Endodontist who evaluated the master cone radiographs was blinded to group allocation to reduce the bias in the study. This study showed a higher but not statistically significant rate of acceptable results (92.1%) regarding master cone radiography in the EAL group which is in agreement with previous studies.

Hoer and Attin [23] compared the accuracy of two EALs and radiography. They concluded that the EALs were more accurate in determining the WL within target interval that was between minor and major foramen as compared to radiography. However, this difference was not statistically significant, which is similar to the result of our study.

Similar results were also found in another study done by Jarad et al. [24] They evaluated in vivo ability of Raypex5 in determining the WL compared with WL radiographs taken by paralleling angle technique. The results revealed that there were more (91%) acceptable results obtained using Raypex5 combined with a master cone gutta-percha (GP) radiograph as compared to conventional radiographic method, but the difference was not statistically significant.

Another study done by Kocak et al[25] also concluded that EALs are more accurate than radiography, but with no statistical difference.

In our study, there was significantly less over estimation of WL in EAL group, which is more unfavorable than under estimation. This result is in agreement to that of an in vivo study conducted by Ravanshad et al., [2] they compared the Raypex5 and bisecting angle technique of radiography in their study and concluded that EALs are superior in reducing the overestimation of root canal length.

Similar findings were also shown by El Ayouti et al. [4] They showed that EALs can prevent over instrumentation, even when WL seems within the acceptable range on radiography.

Another study done by Vieyra and Acosta [26] also compared the accuracy of Raypex5, Root ZX, Elements Diagnostic, and Precision AL apex locators with radiography. They also concluded that EALs were more accurate than radiographs and would reduce the risk of over instrumenting and filling beyond the apical foramen.

In our study, the length adequacy of master cone was considered as the final outcome of root canal treatment. Radiography is only universally accepted available, and meaningful method of length adequacy assessment in clinics. However, there is repeated radiation exposure, during and immediately after endodontic treatment. The adverse effect of radiation was investigated on area in the path of ionizing radiations including, the oral tissues, periodontal tissues, human embryos, and fetuses in pregnant women. Therefore, reducing the number of radiographs is crucial to prevent the patients from repeated exposure of ionizing radiation.

Neena et al., [10] reported that EALs were comparable to conventional radiographs in determining the WL without radiation. Similarly, Ravanshad et al[2] reported that the results of endodontic treatment using EALs are quite comparable to radiographic length measurements and the average number of radiographs taken was recorded significantly lower when EALs were used during WL determination.


The results of endodontic treatment using the Raypex5 EAL are quite comparable, if not superior, to radiographic length measurement regarding the rates of acceptable and short cases. Furthermore, in addition to reducing the radiographic exposure, EALs are superior in reducing overestimation of the root canal length.


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