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 Table of Contents  
Year : 2020  |  Volume : 10  |  Issue : 3  |  Page : 208-214

Comparison of the diagnostic accuracy of cone-beam computed tomography and periapical radiography in determining endodontic working length: An in vitro study

1 Department of Conservative Dentistry and Endodontics, Manipal College of Dental Sciences, Mangalore, Affiliated to Manipal Academy of Higher Education, Mangaluru, Karnataka, India
2 Department of Oral Medicine and Radiology, Manipal College of Dental Sciences, Mangalore, Affiliated to Manipal Academy of Higher Education, Mangaluru, Karnataka, India

Date of Submission20-May-2019
Date of Decision09-Nov-2019
Date of Acceptance05-Dec-2019
Date of Web Publication27-Aug-2020

Correspondence Address:
Dr. Kundabala Mala
Department of Conservative Dentistry and Endodontics, Manipal College of Dental Sciences, Mangalore, Affiliated to Manipal Academy of Higher Education, Mangalore - 575 001, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/sej.sej_57_19

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Introduction: The present study was undertaken to determine the accuracy of working length using cone-beam computed tomography and Ingle's method and to compare it with actual working length using visual method.
Materials and Methods: A total number of 52 single-rooted human teeth mounted on blocks of dental stone were subjected to cone-beam computed tomography (CBCT) by tracing a line between the apical foramen and the corresponding cusp tip from the scans taken before instrumentation. The measurement was taken in two planes in preoperative periapical radiographs. Working length was calculated using Ingle's method from periapical radiographs. The actual working length was measured using visual method under magnification (×2.5). All the measurement procedures were performed by an endodontist and a radiologist. Data were analyzed using SPSS software version 15.
Results: One sample t-test was applied to compare between the actual working length determined by the visual method and the working length determined by CBCT, and Ingle's method showed that there was no statistically significant difference (P > 0.05) between the groups. Inter-examiner reliability test using Cronbach's alpha showed a good agreement between the radiologist and the endodontist for both periapical radiography and CBCT.
Conclusion: The preoperative CBCT is better than Ingle's method in determining working length within a narrow range of ±0.5 mm. If preoperative CBCT scans are available, the dentist should make the use of the scan for determining the working length instead of exposing them for repetitive radiographs.

Keywords: Cone-beam computed tomography, Ingle's method, intraoral radiograph, working length determination

How to cite this article:
Basaiwala AK, Mala K, Ahmed J, Shetty N, Gupta A. Comparison of the diagnostic accuracy of cone-beam computed tomography and periapical radiography in determining endodontic working length: An in vitro study. Saudi Endod J 2020;10:208-14

How to cite this URL:
Basaiwala AK, Mala K, Ahmed J, Shetty N, Gupta A. Comparison of the diagnostic accuracy of cone-beam computed tomography and periapical radiography in determining endodontic working length: An in vitro study. Saudi Endod J [serial online] 2020 [cited 2021 Jan 27];10:208-14. Available from: https://www.saudiendodj.com/text.asp?2020/10/3/208/293580

  Introduction Top

An adequate and proper access to the entire root canal system, thorough disinfection of root canal system, shaping the canal in such a way to reach all the parts of canal and to seal the system three-dimensionally to get fluid-tight seal will definitely lead to the successful outcome of root canal therapy and prevent re-infection. However, success in all these steps depends on the establishment of accurate working length. Previous studies have been done to evaluate microscopically the distance between minor diameter and major diameter and found to be 0.5–1.0 mm.[1] The term working length is used to denote the distance between the apical limit of instrumentation and the stable point from which measurement is to be made coronally. This length is typically determined in millimeters. It is here that the endometric endodontics comes into play. Inaccurate root canal measurements will lead incomplete instrumentation or overinstrumentation to under/overobturation which may affect the outcome of root canal therapy.[2] Inaccuracy in the determination of exact working length causes the irritation of periapical tissues that may prevent optimum healing of periradicular tissues.[3],[4],[5],[6]

Different methods such as intraoral periapical radiographs (IOPAs), electronics, and tactile have been used for accurate detection of the position of minor apical constriction area and to measure the working length. There is good evidence of working length determination using conventional measurement methods with apex locators and IOPA radiographs in the literature.[7],[8],[9],[10],[11],[12]

The most widely used method for the determination of working length is by radiographic method. For endodontic treatment of teeth, radiography plays an indispensable role. Since endodontic therapy was a blind process before the era of surgical microscope, the clinical assessment of endodontic treatment used to be done by IOPA examination. There are various advantages of preoperative radiography such as internal anatomy of the root canal system could be studied along with the number and curvature of roots, the presence or absence of periapical lesions, and tentative working length estimation. Intraoral radiography can be technique sensitive and cannot be fully dependable for working length determination since there is a chance of elongation of radiograph which resulted in over measurement. Furthermore, there may be subjectivity in the evaluation of radiographs in addition to hazards of ionizing radiation and errors of superimposition of tissues in crucial areas.[8],[10],[13],[14],[15],[16]

Recently, cone-beam computed tomography (CBCTs) were established in dental offices because of multiplanar formation, three-dimensional (3D) image of internal structures, clear view of extensions of lesions, reduction in dose of X-ray irradiation, and reduction in scanning time compared to previous generations of CTs.[17],[18],[19] In spite of limited field of view, CBCT provides good spatial resolution and a high-quality 3D diagnostic image in all planes of the region acquired from the data. Hence, this study was planned to determine the accuracy of working length using CBCT and Ingle's method and to compare it with actual working length using visual method.

  Materials and Methods Top

The presentin vitro study was carried out in the Department of Conservative Dentistry and Endodontics and Department of Oral Medicine and Radiology, after taking the ethical approval from the Institutional Ethics Committee #13142.

The sample size was calculated based on available data (with reference value of 0.859 and mean difference of 0.51) using SPSS 15.0 software at 95% confidence interval and 90% power. Based on this, a total of 52 single-rooted human extracted teeth with Type 1 canals were selected for the study. Confirmation of Type 1 canal anatomy(a single canal from pulp chamber to the canal terminus) was done using both: Intraoral periapical radiograph (IOPAR) and all the planes of CBCT images and 20,21].

Inclusion criteria

  • Extracted human single-rooted teeth stored in normal saline
  • Teeth with closed apices and moderately curved canals <25° (angle of curvature measured using Weine's method for IOPA radiographs and based on three mathematical points determined using Planmeca Romexis® software.[21],[20]

Exclusion criteria

  • Teeth with severely curved canal >25°
  • Incompletely formed apices
  • Calcified canal
  • Fractured teeth
  • Internal and external resorption
  • Endodontically manipulated.

The Occupational Safety and Health Administration guidelines were followed for sample collection and storage. Teeth were then sterilized and handled according to the Centers for Disease Control and Prevention recommendations and guidelines.[22],[23] All teeth were mounted on blocks of equal dimensions in Type 4 dental stone with three teeth in each block. All the mounted specimens were then subjected to CBCT scan using Planmeca ProMax 3D Mid (Helsinki, Finland) with operating parameters set at 10.0 mA and 90 kV, voxel size of 0.3 mm, and exposure time of 12 s [Figure 1], followed by good undistorted preoperative radiographs to serve as an initial guide for working length determination using Ingle's method. Images were analyzed using a Dell 380 Precision workstation and an18-inch LCD Dell monitor with resolution of 1024 × 768 pixels (Dell Computer Corporation, Round Rock, TX, USA). Access cavity was prepared in all the teeth with the help of access opening Endo axis and Endo Z burs (Dentsply Maillefer). Canal orifice was located with the help of DG 16 explorer (Ash Endodontic Probe DG16, Dentsply Sirona, USA) and was enlarged up to no. 3 Gates-Glidden drill (Dentsply Maillefer). Initial lengths were measured from the preoperative radiographs taken before instrumentation. After subtracting 1 mm for safety allowance, all teeth were prepared up to no. 20 K-hand file (Mani-K hand files). Thirty milliliters of 3% solution of sodium hypochlorite and 1 ml of RC-Prep (Patterson Dental, Saint Paul, MN, USA) were used alternatively as irrigants during preparation. The canals were then blotted dry with absorbent paper points (Hygienic Absorbent Paper Points – White, Coltene), and a no. 20 K-file was introduced up to the measured working length and an IOPA radiograph was exposed with a paralleling technique using a film holder (Rinn XCP; Dentsply, Elgin, IL, USA). kV –Kilovoltage is power of the machine 8mA- current used 0.17 Seconds is the time of exposre. The radiographs were then developed in an automatic processor (Velopex Intra-X). A clear radiograph was then evaluated using a viewer box with the aid of an X-ray viewer under × 2 magnification for the determined working length and values were recorded. All the specimens were then demounted and the actual working lengths were determined by visual method under × 2.5 magnification using a magnifying loupe (Zeiss Magnifiers). A silicon stopper was adjusted to the corresponding reference point. The instrument is withdrawn from the canal and length is measured in mm scale. Thereafter, 0.5 mm is deducted from the obtained length which is the actual working length of root canal.
Figure 1: Working length determination of teeth using conebeam computed tomography at different planes

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Working length determination

Working length determination is done using preoperative CBCT scans using e-Vol DX software (Bauru, SP, Brazil) to define the apical foramen in axial plane. Then, distance between the apical foramen and the corresponding cusp tip before the start of canal instrumentation is measured in sagittal plane. Sometimes, measurements were taken in two planes when the cusp tip and the apical foramen were not visible in one plane.[24],[25] In periapical radiographs, working length was determined using Ingle's method.[26] The actual working length was measured using visual method under magnification (×2.5).[27],[28]

Evaluation of the images

Images were analyzed by an oral radiologist and an endodontist simultaneously. Initially, the IOPA radiographs were analyzed, followed by the CBCT images. The disagreements between examiners in interpretation if any were resolved by thorough discussion and consensus. Data were statistically analyzed using the Social Sciences software package version 15 (SPSS Inc., Chicago, IL, USA). The “P” value was set at < 0.05 to indicate statistical significance. The descriptive statistics were derived for working length by CBCT, radiographic method, and the actual working length. Intra-examiner reliability was measured.

  Results Top

[Table 1] shows the mean and standard deviation values of working length measured from periapical radiographs and CBCT by the oral radiologist and endodontist and actual working length by visual method. One sample t-test was applied to check the association between the actual working length determined by the visual method and the working length determined by CBCT and IOPAs. It was found that there was no statistically significant difference (P > 0.05) between the actual working length and the working length determined by CBCT and PAs [Table 2].
Table 1: Descriptive statistics derived for working length by cone-beam computed tomography, radiographic method, and the actual working length

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Table 2: One-sample t-test to check association between different groups and actual working length

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Frequency distribution showed that around 76.73% of times the radiologist measured the working length by Ingle's method with a difference of ±0.5 mm of actual working length while the endodontist measurement was 77% of the times. Hence, frequency distribution tests for periapical radiography showed that there is no difference between the radiologist and the endodontist while measuring the working length closer to the actual working length. When CBCT was evaluated by radiologist, 86% of the time and when evaluated by endodontist 94.2% of the time, measurements were within ±0.5 mm from the actual working length.

  Discussion Top

Accurate working length determination is one of the most crucial steps during root canal treatment. A number of methods have been used to determine the accuracy of the working length which includes radiographs, electronic apex locator, tactile sense, and visualization of moisture or bleeding points at the tip of paper points.[29],[30],[31] Radiographs lack consistency, and there is always an interpretation variability associated with it.[32]

To overcome the shortcomings of periapical radiography, CBCT might be used which provides a 3D information of the tooth. In modern endodontic practice, CBCT has proven its diagnostic potential and is a valuable tool in diagnosis and treatment planning. With the help of CBCT, slices in sagittal, coronal, and axial planes can be observed without any superimposition of anatomical structures. CBCT locates the apical foramen, i.e., the region where the root canal space exists and meets the periodontal space more accurately.[33]

This study was conducted to compare the diagnostic accuracy of two radiographic techniques using periapical radiograph and CBCT in determining the endodontic working length and compare both with actual working length.

The present study is in agreement with the study done by Sherrard et al., which showed that the tooth length and root length measurements taken using CBCT were similar to actual working length with no statistically significant difference with the mean differences being <0.3 mm,[34] whereas periapical radiographic measurements were significantly underestimated the root lengths (mean difference, 2.58 mm; P = 0.001) and overestimated tooth lengths (mean difference, 2.58 mm; P = 0.056). Mean differences between the three measurements using three different CBCT voxel sizes were all <0.25 mm. The intraclass correlation between the periapical and CBCT measurements were all above 0.995. The study concluded that the CBCT scans are as accurate and reliable as actual working length measured under magnification.[34]

In the present study, radiographic apex was taken into consideration as a landmark when working length was determined using Ingle's method. It was observed that only 23.1% of times both the radiologist and the endodontist measured the working lengths accurately coincided with actual working length. Within a range of 0 to ±0.5 mm from the actual working length, both the radiologist and the endodontist measured the working length 76.73% and 77% of the times, respectively [Table 3].
Table 3: Frequency distribution of PA radiographs when analyzed by radiologist and endodontist

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For determination of working length using CBCT, apical foramen was taken into consideration for termination of instrumentation. The results were contrasting to IOPA radiographic method, 67.3% of times endodontist could determine the working length accurately to actual working length, whereas radiologist could do the same only 40%. of the time. In a range ±0.5 from the actual working length, the percentage was much higher, i.e., around 94.2% by the endodontist and 86% by the radiologist [Table 4]. This shows that CBCT measures the working length closer (within 0 to ±0.5 mm range) to actual working length, whereas IOPA radiographs measured the working length only 77% of times by both the examiners (within 0 to ±0.5 mm range) closer to actual working length. This shows that CBCT scans are more reliable in working length determination than periapical radiographs.
Table 4: Frequency distribution of cone-beam computed tomography scans when analyzed by radiologist and endodontist

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The present study is in agreement with the study done by Connert et al. where the precision of CBCT to determine the working length was evaluated.[35] The measurement given by CBCT was then compared with the original working length obtained by visual method. It was found that the coefficient of repeatability, reproducibility, and inter-evaluator agreement was <0.5 mm and measurements obtained with CBCT were precise. The mean of absolute differences between CBCT and real working length was 0.41 mm (99% confidence interval: 0.31–0.52 mm).[35] Similarly, in the present study also, the measurements obtained with CBCT were precise to the actual working length with a mean of absolute difference 0.21 mm for the oral radiologist and 0.19 mm for the endodontist. This suggests excellent repeatability, reproducibility, and interoperator agreement between the radiologist and the endodontist.

Frequency distribution test for CBCT showed that the endodontist can keep the working length closer to actual working length compared to the radiologist. The intraclass correlation between a CBCT radiologist and a (PA) Periapical radiologist was 0.959 and the intraclass correlation between a CBCT endodontist and a PA endodontist was 0.943 [Table 5]. Interexaminer reliability using Cronbach”s alpha showed that there is a good agreement between the radiologist and the endodontist for both working length determination methods with periapical radiography as well as CBCT [Table 6]. Mean difference of 0.06 mm and 0.02 mm which is of negligible clinical significance when working length was determined by radiologist and endodontist using periapical radiographic method and CBCT respectively. Cox et al. were the first to check any variability in radiographic determination of working length among investigators with different clinical backgrounds. However, no definite correlation was made between their findings and the clinical expertise of the accessors.[36] In a recently reported study in which clinical experience of different evaluators in estimating the root canal length was checked, it was found that there was no significant difference.[37] Since periapical radiographs cannot locate the apical constriction or minor diameter area precisely, they showed significantly different results from CBCT scans in identifying the actual working length located within +0.5 mm distance from the apex.
Table 5: Intraclass correlation between cone.beam computed tomography radiologist and PA radiologist and endodontist

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Table 6: Agreement between two examiners with cone-beam computed tomography and PAs

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Although CBCT has lower image resolution than periapical radiographs, its advantage lies in its ability to identify anatomic landmarks in several dimensions. However, its indication should be critically evaluated for every image particularly to those requiring endodontic treatment and it must be determined whether spatial imaging is necessary or a conventional periapical radiograph alone will serve the purpose.[38] Moreover, radiation dose, scattering, and cost of CBCT must be considered before advising a CBCT. Preoperative CBCT is advantageous in complex cases such as teeth with complex anatomies requiring root canal treatment, in diagnosis and treatment planning of nonodontogenic pathologic conditions which are in close proximity with teeth, resorptive lesions etc.[39],[40] In these cases when CBCT scans have already been performed, reformatted CBCT slices can be made use off, which will place the root canal of the analyzed tooth in a axial/coronal/sagittal view. This helps in the measurement of endodontic working length and could replace an additional need of periapical radiograph required for determining working length.[20]

CBCT scans should be used judiciously during the root canal treatment because of its excessive radiation exposure compared to IOPA radiographs. Determination of working length should be done clinically with the help of electronic apex locators as their readings are more accurate, with a confirmatory periapical radiograph.[8] On the other hand, if in cases preexisting CBCT scans are available, the dentist should take advantage of this additional information and determine the exact working length using this more reliable method.

  Conclusion Top

Within the limitations of this study, it was concluded that CBCT was better than periapical radiography in determining working length within a narrow range of ±0.5 mm. Moreover, periapical radiograph with Ingle's technique was reliable within its limitation. If preoperative CBCT scans are available, the dentist should make the use of the CBCT scan to determine the exact working length, instead of taking a preoperative and working length radiographs.

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Conflicts of interest

There are no conflicts of interest.

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  [Figure 1]

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]


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