Home Print this page Email this page Users Online: 527
Home About us Editorial board Search Ahead of print Current issue Archives Submit article Instructions Subscribe Contacts Login 

 Table of Contents  
Year : 2013  |  Volume : 3  |  Issue : 2  |  Page : 57-64

Radiographic assessment of endodontic working length

1 Division of Endodontics, King Abdulaziz University, Jeddah, Saudi Arabia
2 Department of Oral Rehabilitation, Sir John Walsh Research Institute, University of Otago, Dunedin, NewZealand

Date of Web Publication13-Sep-2013

Correspondence Address:
Nicholas P Chandler
School of Dentistry, University of Otago, P.O. Box 647, Dunedin 9054
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/1658-5984.118145

Rights and Permissions

The use of radiographs for working length determination is usual practice in endodontics. Exposing radiographs following the principles of the paralleling technique allows more accurate length determination compared to the bisecting-angle method. However, it has been reported that up to 28.5% of cases can have the file tip extending beyond the confines of the root canals despite an acceptable radiographic appearance. The accuracy of radiographic working length determination could be affected by the location of the apical foramen, tooth type, canal curvature and superimposition of surrounding structures. Variations among observers by virtue of training and experience may also influence the accuracy of the procedure. The interpretation of radiographs could be affected by film speed and viewing conditions, with the superiority of digital imaging over conventional radiography for working length determination remaining debatable. The combination of several methods is recommended for acquiring the most accurate working length.

Keywords: Electronic apex locator, endodontics, radiography, root canal treatment, working length

How to cite this article:
Alothmani OS, Friedlander LT, Chandler NP. Radiographic assessment of endodontic working length. Saudi Endod J 2013;3:57-64

How to cite this URL:
Alothmani OS, Friedlander LT, Chandler NP. Radiographic assessment of endodontic working length. Saudi Endod J [serial online] 2013 [cited 2022 Aug 12];3:57-64. Available from: https://www.saudiendodj.com/text.asp?2013/3/2/57/118145

  Introduction Top

The search strategy for this review involved a combined manual and electronic investigation of references published in English. The former was run over the Medline via Ovid interface to identify articles published from 1948 to November 2012 using the search terms: Apical foramen (AF), apical constriction (AC), cemento-dentinal junction, root apex, anatomic apex, radiographic apex, major diameter, minor diameter and outcome of root canal treatment. The latter search involved a cross-check of the electronic results with review articles and textbook chapters to identify possible relevant publications.

There are two radiographic exposure techniques used for conventional and digital intra-oral radiography; the bisecting-angle technique and paralleling technique.

The vertical angulation during the bisecting-angle technique is determined by directing the X-ray beam perpendicular to an imaginary line bisecting the angle formed between the film and the long axis of the tooth. This method usually results in some linear distortion (elongation or shortening) depending on the accuracy of vertical angulation. It is also accompanied by dimensional distortion, due to the angular relation formed between the film and the tooth. Objects positioned away from the film will be shortened, while those located nearer the film will be less affected. Overall, this technique depends on operator experience and lacks consistency. [1]

The second exposure method is the paralleling technique where the film is placed parallel to the tooth and the X-ray beam is directed perpendicular to the film. This method minimizes dimensional distortion, with parallelism dictated by local anatomy. It is often helpful to increase the film-tooth distance in order to achieve parallelism, although this might not be necessary in the mandibular molar region. To minimize the loss of sharpness associated with the long film-tooth distance, a long cone must be used to increase the distance between the X-ray source and film. [1],[2]

  Length Measurements with Both Techniques Top

The mean radiographic tooth length of anterior teeth was found to be longer than the actual tooth length when the paralleling technique was used. The radiographic length was magnified by 5.4%. [3] Another study reported that, when the paralleling technique was used, 85% of the radiographic lengths of anterior teeth were longer than the actual length, 14% were shorter and only 1% of the lengths were exactly the same. The radiographic tooth length ranged from 1.3 mm short of actual length to 2.1 mm longer. [4] However, when radiographic length magnification associated with the paralleling technique was taken into consideration, the mean radiographic length was shorter than the mean actual length by 0.14 (±0.05) mm. [5] Tooth length determination with the paralleling technique was more accurate than with the bisecting-angle method. Nevertheless, both resulted in elongation of all roots, except for the mesio-buccal and disto-buccal roots of maxillary molars which were shortened when the bisecting-angle principle was used. [6] Magnification is inherent to the central projection principle used for intra-oral radiography. [4],[5]

The radiographic working length (WL) produced by both techniques has been compared. Chunn et al., [7] reported that the paralleling and bisecting-angle techniques gave comparable WLs and the slightly better performance of the former would be clinically irrelevant. The paralleling technique depicted the distance between an intra-canal marker and the root tip more consistently and with fewer errors. Varying the vertical angulation influenced the radiographic position of the intra-canal marker, especially with the bisecting-angle technique. [8],[9] The likelihood of over-instrumentation and overfilling with the bisecting-angle technique is high, as it depicts a shorter than actual file tip position, resulting in longer adjustments than required. Even when the file appears beyond the apex of the tooth, length subtraction would be shorter than required. [10] An in vitro comparison of conventional and digital images obtained using the paralleling technique showed that digital images resulted in over-estimation of the actual file length by 2.81-7.58%, while the same value for conventional images was 1.13%. [11]

The paralleling technique with a beam-aiming device resulted in a significantly lower frequency of incorrect vertical angulations, cone cuts and incorrect film placements during WL determination when compared with the bisecting-angle technique. Nevertheless, the beam-aiming device required experience for correct use. [12] Images taken with a beam-aiming device were more diagnostic than those obtained with a hemostat or the patient's finger supporting the film. [6],[13] Even when radiographs were taken with the bisecting-angle method the use of a film holder gave better standardization, less variation in tooth length measurements on follow-up and improved intra-examiner consistency. [14]

  Accuracy of the Radiographic WL Top

The most commonly employed radiographic WL determination method is that of Ingle. [15],[16] Ingle's method depends on estimating the distance between the file tip and the radiographic apex and adjusting it until the file tip is 0.5-1 mm short of the radiographic apex. [17] One in vivo study compared the accuracy of several radiographic methods for WL determination including those of Best, Bergman, Bramante and Ingle when the bisecting-angle technique was used. Best's method depends on securing a 10 mm steel pin to the labial surface of the tooth and parallel to its long axis before obtaining the radiograph. The radiograph is related to a gauge allowing tooth length determination. Bergman's method is based on calculating the real tooth length based on the radiographic appearance of a 25 mm probe that has an acrylic stop which allows it to penetrate 10 mm in the canal. Bramante introduced a technique that utilized stainless steel probes of different gauges and lengths bent at one end to form a right angle. A radiograph is obtained with the probe in place, then tooth length could be calculated (similar to Bergman's method) or the distance between the probe end and the radiographic apex used to determine the adjustment needed (similar to Ingle's method). The results of the study showed that the best length determination was obtained using Ingle's technique. [18]

Several studies examined the accuracy of the radiographic WL and related the file tip position to the AF. It was found that placing the file exactly at the radiographic apex resulted in a mean radiographic WL beyond the AF by 0.25 (±0.19) mm, with 97% of the measurements being within ±0.5 mm of the AF. [19] Setting the WL 1 mm short of the radiographic apex resulted in 60% of the measurements being within the ±0.5 mm range from the AF, although only 16% were at the AF. The mean radiographic WL was coronal to the AF by 0.1 (±2.11) mm. [20] Radiographic WL resulted in measurements beyond the AF in 19-28.5% of cases, regardless of an acceptable radiographic appearance. [7],[21],[22],[23] All these studies involved the paralleling technique.

Other researchers have related the radiographic file tip position to the AC. These studies showed that adjusting the WL 1 mm short of radiographic apex precisely detected the AC in 15-18% of the teeth. [24],[25] In 68% of anterior and premolar teeth, setting the WL 1 mm short of the radiographic apex positioned the file tip beyond the AC, with the file tip exactly at the AC in the remaining 32%. [26] Another study reported a higher accuracy of the WL when set to 1 mm short of the radiographic apex. The AC was precisely detected in 43% of the teeth. This high rate was attributed to the ideal projection geometry obtainable using extracted teeth. [27]

Hassanien et al., [28] studied 10 mandibular premolars and related the radiographic position of the file tip to the position of the cemento-dentinal junction, AF and AC in vivo. The WL was adjusted to be 0.5-mm short of the radiographic apex, the files were cemented in place and the teeth extracted. The mean radiographic WL was coronal to all three landmarks by 0.26 (±0.03) mm, 0.56 (±0.03) mm, and 0.64 (±0.08) mm, respectively. [28]

The position of the file tip in relation to the radiographic apex was consistent regardless of the images being exposed bucco-lingually or mesio-distally. [23],[29] File tip position on radiographs has been reported to be shorter than its actual position. [7],[8],[18],[23],[29],[30],[31],[32],[33] Only one study reported the opposite. [34]

  Factors Influencing the Accuracy of Radiographic WL Top

Location of the AF

File position in radiographic WL determination is related to the radiographic apex. [17] The AF is not always situated over the apex and is frequently found on the buccal or lingual sides of the root tip. Several studies have reported that radiographs could result in erroneous WL determination as a result of this anatomical feature. [7],[8],[30],[35],[36],[37],[38],[39],[40],[41],[42]

Tooth type and canal curvature

Radiographic WL determination might be more accurate for anterior teeth because the degree of AF deviation in anterior teeth is usually less than posterior teeth. [32] Indeed, the frequency of WL leading to instrumentation beyond the AF in premolars and molars was 51% and 22%, respectively, while this never occurred in anterior teeth. [21] In contrast, another study found the radiographic method to be more accurate in premolars compared to anterior teeth and molars. [43]

It has been reported that as the curvature of the apical part of the root increases, the chances for erroneous radiographic WL also increased. [8],[31] Specifically, when the angle of curvature of palatal roots of the maxillary first and second molars increased above 25°, the discrepancy between actual tooth length, radiographic tooth length and file length increased to more than 0.5 mm. [30] Conversely, the estimation of WL for the mesial canals of mandibular molars did not significantly differ from their actual length, regardless of the degree of canal curvature. [11]

Palatal and mesiobuccal roots of maxillary molars were associated with the highest incidence of inaccurate radiographic WL compared with other roots in vitro[21] and in vivo. [18],[44] The in vivo radiographic WL measurements of the distobuccal and palatal roots of maxillary first and second molars were within ±0.5 mm from the AF in 88.5% of the teeth. Longer measurements were seen in 9.6% while shorter measurements were seen in 1.9% of the sample. The accuracy of the method in distobuccal roots was higher than the palatal roots. [45]

Radiographic WL in maxillary molars may be complicated by the superimposition of the zygomatic arch when the bisecting-angle technique is used. [46] This helps explain why the highest discrepancy in radiographic WL assessment among different observers was seen during evaluations of the palatal root of maxillary molars. [47] Newer digital radiography systems might overcome this problem by image manipulation. [48]

Observer variability and clinical experience

Cox and coworkers [49] compared the agreement of nine observers; three endodontists, three oral radiologists, and three general practitioners with the adjustment needed for best radiographic WL. Assessors were asked to identify the distance needed to place the file tip 0.5-mm short of radiographic apex or short of where the AF was perceived. Excellent agreement of the nine assessors, defined as ±0.5-mm variation from the actual adjustment, was achieved for only 68% of the images. [49] Although the subjects were given identical instructions, their implementation varied. This may be because of differences in their clinical experience, which were not investigated. Recently, this factor was investigated and it was reported that the agreement of endodontists, restorative dentists, general practitioners, endodontic postgraduates and undergraduate students was high, and that the difference in clinical experience did not influence their interpretation. [50] Another study found that the accuracy of estimating the adjustment needed for radiographic WL was directly related to and significantly influenced by clinical experience. [51]

Film speed and viewing conditions

E-speed film was found to be as good as D-speed for radiographic WL determination when a size 15 file was used. [52] Although the accuracy of WL determination with D-, E- and F-speed films was similar, D-speed film received a higher subjective rating than other types regarding the clarity of a size 10 hand file. [47] Another study found that the use of E-speed film was significantly better than F-speed and equal to D-speed when size 10 and 15 files were used for WL determination. Again, D-speed film received better subjective scoring than the others. [53]

The position of size 8 and 10 files was statistically more accurately identified on D-speed film than E-speed film in both in vitro and in vivo conditions. [54],[55]

Optimum radiographic interpretation requires the radiograph to be mounted in a light-masking frame, extraneous light from the viewer be blocked and the amount of reflected light from the film reduced by dimming room lights. [56] Magnification is also recommended. [57],[58] Viewing box illumination intensity was found to be insignificant. [59] The use of a viewing box and masking allowed more accurate file length determination than when no masking was done. Further, viewing the images on a light box with masking and magnification provided higher accuracy than when no masking/magnification was used. There was no difference in the estimation of file length when films were viewed on a light box and masked with or without magnification. [50] This implies that blocking extraneous light might be more important than using magnification during file length estimation.

Digital radiography for WL determination

The first intraoral digital radiography system introduced was RadioVisio Graphy (RVG; Trophy Radiologie, Vincennes, France). [60] Since then, continuous development and improvements have been achieved and new digital systems have been introduced. [61] Digital images can be acquired directly using solid-state receptors such as charge-coupled devices (CCD) and complementary metal oxide semi-conductors (CMOS). Semi-direct capture is achieved via photo-stimulable phosphor (PSP). The indirect capture is acquired by flatbed scanner or digital camera. [61]

RVG, a CCD-based digital system, has been compared with conventional films for WL determination. RVG was as good as E-speed film for the determination of file length adjustment when a size 10 file was used. [62] Another study found that E-speed films were statistically better for WL determination when file size 15 was used, although the difference might not be clinically relevant. [63] D-speed and E-speed films were statistically better than RVG images for the detection of size 10 and 15 files, although image manipulation improved the performance of RVG to comparable levels. [54] Nevertheless, in vivo testing of the same three modalities revealed that D-speed films were significantly better than original and modified RVG images. Original RVG images were significantly worse than E-speed films, while no difference was found between the modified digital images and E-speed films. [55] However, this study did not use identical projection geometry to obtain the radiographs. When this was ensured, there was no difference between the WL of mandibular molars obtained from RVG images and D-speed films. In fact, there was no significant difference between radiographic length and actual length. [64]

The error margin of radiographic WL determination using the regular digital images of two CMOS-based systems, the RVG 6000 system (Kodak Dental Systems, Atlanta, USA) and Schick CDR system (Schick Technologies, NY, USA) was lower than the conventional, indirectly digitized F-speed film. Contrast enhancement of the digital images provided better visibility and improved the interpretation of the position of files of size 10 and 15. [48]

E-speed films were better than the CCD-based Sens-A-Ray (Regam Medical Systems AB, Sundsvall, Sweden) images for WL determination, especially when the digital images were viewed on the monitor. [63] Another study found that estimation of WL on Sens-A-Ray and Vixa (Gendex Dental Systems, Hatfield, USA) images was better than or equal to E-speed films. [65]

Another digital modality is the PSP marketed as Digora (Soredex Orion Corporation, Helsinki, Finland). This system was recommended for WL measurements, even at low radiation dosage. [66] Length adjustments obtained from Digora images were consistent with those obtained from E-speed films. Digital image manipulation allowed better delineation of the fine tips of files compared to conventional images. [67] In contrast, tip clarity of a size 6 file was significantly worse on Digora images than for E-speed films although manipulated images were evaluated. [68] Digora and RVG were inferior to D-speed film for WL determination although their accuracy improved when larger files were used. [69] File sizes 15 and 20 were more accurately visualized on digital images than sizes 8 and 10. [70],[71],[72] The accuracy of file length determination using the PSP-based sensors improved when the images were acquired with high spatial resolution and high contrast together with an appropriate endodontic filter. [73]

The image quality of a PSP-based system (Vistascan; Dürr Dental GmbH, Bissingen, Germany) was superior to a CCD-based system (Sidexis; Sirona Dental Systems GmbH, Bensheim, Germany). The latter required lower radiation but it was associated with more retakes. [74] Images obtained by three digital systems were assessed by six observers to determine WL. The highest error was with the PSP-based system (DenOptix, Gendex Dental Systems) followed by the CCD-based system (Visualix II, Gendex Dental Systems). The CMOS-based system (Schick CDR) was the best among the three systems. [75] Another study concluded that CMOS and CCD (CygnusRay MPS, Cygnus Technologies, Scottsdale, USA) images were better than the PSP (Digora) images to determine file length. [76]

It is important to note that all these studies compared the performance of different systems and attributed variations to differences in image clarity. A factor overlooked is that evaluation of image clarity also depends on observer perception and experience, and most evaluated earlier digital models. Newer brands overcame many of their limitations. [61]

Image manipulation is the strength of digital radiography; [48],[77] however, enhancement did not always result in better interpretation when compared to conventional films. [54],[55],[62],[68],[78] Thus, image enhancement should be task specific. [61] Although digital images are instantly available, their manipulation takes time and requires experience. [63]

From the above it can be concluded that digital radiography was found to be comparable to conventional radiography for WL determination especially when larger files were used. Image manipulation and enhancement is mandatory for optimum interpretation. Digital radiographs are exposed at a lower radiation dose, reducing patient exposure to ionizing radiation. Nair and Nair [61] recommended the use of CCD or CMOS systems for endodontic purposes.

Recommended WL determination technique

Recent guidelines recommend a combination of electronic and radiographic methods for WL determination. [79] This is in line with several studies which have recommended that an electronic apex locator (EAL) reading should be radiographically confirmed to reduce the chances of erroneous WL determination. [21],[27],[80],[81],[82],[83],[84],[85],[86],[87],[88],[89],[90],[91] This recommendation is further supported by the complexity and variability of the apical part of the root canal, which makes it obligatory to utilize multiple WL determination techniques in the same canal. [40],[41],[92]

The higher accuracy of the combined method has been demonstrated. In 51% of premolars, radiographic WL determination resulted in long measurements although they were radiographically acceptable. When the EAL was used, this frequency dropped to 21%. The combination of the two methods resulted in a further reduction of long measurements to only 14%. [93] EAL measurements were ±0.5 mm from the AC in 84% of the teeth. The combined method raised the accuracy to 96%. [81]

Conflicts in the length measurements given by the two techniques have also been reported. The mean length given by the EAL was beyond the radiographic apex by 0.66 mm and measurements ranged from 2.13-mm short of radiographic apex to 3.14 mm beyond it. [80] Another study reported that the mean length measured by the EAL was 1.08 (±0.73) mm short of the radiographic apex with recordings ranging from 4.1 mm short of the radiographic apex to 2 mm beyond it. [83] If the radiographic image of the indicated EAL length appeared to be well short of the radiographic apex, the EAL reading should be chosen as this should be closer to the vicinity of the AC. [80],[94] However, it is not always mandatory to follow the electronic length. [91] The quality guidelines of the ESE state that if the radiographic length is short by more than 3 mm of the desired position, the length should be adjusted and confirmed by another radiograph. [79] It might also be helpful to use tactile sensation in such situations. [84]

Another advantage of the combined method is the reduction in the number of radiographs needed for WL determination, meaning clinical time and radiation hazards are reduced. [20],[88],[95],[96] This was especially true for maxillary molars. [97] In addition, EALs offer the advantage of measuring the canal to the level of its terminus instead of its radiographic apex. [98] Meanwhile, the radiographic method has the advantages of being able to inspect root anatomy and document it in patient records. [45],[95]

It was recently reported that canal lengths measured on existing cone-beam computed tomography (CBCT) images were highly correlated with electronic lengths. [99],[100] More studies are required before implementing CBCT as a method for WL determination.

  Conclusions Top

The paralleling technique is the recommended exposure technique for radiographic WL determination. The accuracy of WL determination is affected by several factors, so a combination of methods is recommended for determining the best working length.

  References Top

1.Updegrave WJ. Simplifying and improving intraoral dental roentgenography. Oral Surg Oral Med Oral Pathol 1959;12:704-16.  Back to cited text no. 1
2.Updegrave WJ. The paralleling extension-cone technique in intraoral dental radiography. Oral Surg Oral Med Oral Pathol 1951;4:1250-61.  Back to cited text no. 2
3.Vande Voorde HE, Björndahl AM. Estimating endodontic working length with paralleling radiographs. Oral Surg Oral Med Oral Pathol 1969;27:106-10.  Back to cited text no. 3
4.Langland OE, Sippy FH. A study of radiographic longitudinal distortion of anterior teeth using the paralleling technique. Oral Surg Oral Med Oral Pathol 1966;22:737-49.  Back to cited text no. 4
5.Larheim TA, Eggen S. Determination of tooth length with a standardized paralleling technique and calibrated radiographic measuring film. Oral Surg Oral Med Oral Pathol 1979;48:374-8.  Back to cited text no. 5
6.Bhakdinaronk A, Manson-Hing LR. Effect of radiographic technique upon prediction of tooth length in intraoral radiography. Oral Surg Oral Med Oral Pathol 1981;51:100-7.  Back to cited text no. 6
7.Chunn CB, Zardiackas LD, Menke RA. In vivo root canal length determination using the Forameter. J Endod 1981;7:515-20.  Back to cited text no. 7
8.Forsberg J. Radiographic reproduction of endodontic "working length" comparing the paralleling and the bisecting-angle techniques. Oral Surg Oral Med Oral Pathol 1987;64:353-60.  Back to cited text no. 8
9.Forsberg JA. Comparison of the paralleling and bisecting-angle radiographic techniques in endodontics. Int Endod J 1987;20:177-82.  Back to cited text no. 9
10.Forsberg J. Estimation of the root filling length with the paralleling and bisecting-angle techniques performed by undergraduate students. Int Endod J 1987;20:282-6.  Back to cited text no. 10
11.Mentes A, Gencoglu N. Canal length evaluation of curved canals by direct digital or conventional radiography. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002;93:88-91.  Back to cited text no. 11
12.Kazzi D, Horner K, Qualtrough AC, Martinez-Beneyto Y, Rushton VE. A comparative study of three periapical radiographic techniques for endodontic working length estimation. Int Endod J 2007;40:526-31.  Back to cited text no. 12
13.Gound TG, DuBois L, Biggs SG. Factors that affect the rate of retakes for endodontic treatment radiographs. Oral Surg Oral Med Oral Pathol 1994;77:514-8.  Back to cited text no. 13
14.Andreasen FM, Andreasen JO. Diagnosis of luxation injuries: The importance of standardized clinical, radiographic and photographic techniques in clinical investigations. Endod Dent Traumatol 1985;1:160-9.  Back to cited text no. 14
15.Katz A, Tamse A, Kaufman AY. Tooth length determination: A review. Oral Surg Oral Med Oral Pathol 1991;72:238-42.  Back to cited text no. 15
16.McDonald NJ. The electronic determination of working length. Dent Clin North Am 1992;36:293-307.  Back to cited text no. 16
17.Ingle JI. Endodontic instruments and instrumentation. Dent Clin North Am 1957;1:805-22.  Back to cited text no. 17
18.Bramante CM, Berbert A. A critical evaluation of some methods of determining tooth length. Oral Surg Oral Med Oral Pathol 1974;37:463-73.  Back to cited text no. 18
19.Ounsi HF, Haddad G. In vitro evaluation of the reliability of the Endex electronic apex locator. J Endod 1998;24:120-1.  Back to cited text no. 19
20.Brunton PA, Abdeen D, Macfarlane TV. The effect of an apex locator on exposure to radiation during endodontic therapy. J Endod 2002;28:524-6.  Back to cited text no. 20
21.ElAyouti A, Weiger R, Löst C. Frequency of overinstrumentation with an acceptable radiographic working length. J Endod 2001;27:49-52.  Back to cited text no. 21
22.Welk AR, Baumgartner JC, Marshall JG. An in vivo comparison of two frequency-based electronic apex locators. J Endod 2003;29:497-500.  Back to cited text no. 22
23.Cianconi L, Angotti V, Felici R, Conte G, Mancini M. Accuracy of three electronic apex locators compared with digital radiography: An ex vivo study. J Endod 2010;36:2003-7.  Back to cited text no. 23
24.Pratten DH, McDonald NJ. Comparison of radiographic and electronic working lengths. J Endod 1996;22:173-6.  Back to cited text no. 24
25.Vieyra JP, Acosta J, Mondaca JM. Comparison of working length determination with radiographs and two electronic apex locators. Int Endod J 2010;43:16-20.  Back to cited text no. 25
26.Vieyra JP, Acosta J. Comparison of working length determination with radiographs and four electronic apex locators. Int Endod J 2011;44:510-8.  Back to cited text no. 26
27.Hoer D, Attin T. The accuracy of electronic working length determination. Int Endod J 2004;37:125-31.  Back to cited text no. 27
28.Hassanien EE, Hashem A, Chalfin H. Histomorphometric study of the root apex of mandibular premolar teeth: An attempt to correlate working length measured with electronic and radiograph methods to various anatomic positions in the apical portion of the canal. J Endod 2008;34:408-12.  Back to cited text no. 28
29.Mancini M, Felici R, Conte G, Costantini M, Cianconi L. Accuracy of three electronic apex locators in anterior and posterior teeth: An ex vivo study. J Endod 2011;37:684-7.  Back to cited text no. 29
30.Kim-Park MA, Baughan LW, Hartwell GR. Working length determination in palatal roots of maxillary molars. J Endod 2003;29:58-61.  Back to cited text no. 30
31.Stein TJ, Corcoran JF. Radiographic "working length" revisited. Oral Surg Oral Med Oral Pathol 1992;74:796-800.  Back to cited text no. 31
32.Williams CB, Joyce AP, Roberts S. A comparison between in vivo radiographic working length determination and measurement after extraction. J Endod 2006;32:624-7.  Back to cited text no. 32
33.Arora RK, Gulabivala K. An in vivo evaluation of the Endex and RCM Mark II electronic apex locators in root canals with different contents. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1995;79:497-503.  Back to cited text no. 33
34.Kaufman AY, Keila S, Yoshpe M. Accuracy of a new apex locator: An in vitro study. Int Endod J 2002;35:186-92.  Back to cited text no. 34
35.Burch JG, Hulen S. The relationship of the apical foramen to the anatomic apex of the tooth root. Oral Surg Oral Med Oral Pathol 1972;34:262-8.  Back to cited text no. 35
36.Palmer MJ, Weine FS, Healey HJ. Position of the apical foramen in relation to endodontic therapy. J Can Dent Assoc 1971;37:305-8.  Back to cited text no. 36
37.Langeland K. The histopathological basis in endodontic treatment. Dent Clin North Am 1967:491-520.  Back to cited text no. 37
38.Gutierrez JH, Aguayo P. Apical foraminal openings in human teeth: Number and location. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1995;79:769-77.  Back to cited text no. 38
39.Martos J, Lubian C, Silveira LF, de Castro LA, Ferrer Luque CM. Morphologic analysis of the root apex in human teeth. J Endod 2010;36:664-7.  Back to cited text no. 39
40.Olson AK, Goering AC, Cavataio RE, Luciano J. The ability of the radiograph to determine the location of the apical foramen. Int Endod J 1991;24:28-35.  Back to cited text no. 40
41.Bla?koviæ-?ubat V, Mariæiæ B, ?utalo J. Asymmetry of the root canal foramen. Int Endod J 1992;25:158-64.  Back to cited text no. 41
42.von der Lehr WN, Marsh RA. A radiographic study of the point of endodontic egress. Oral Surg Oral Med Oral Pathol 1973;35:105-9.  Back to cited text no. 42
43.Chen E, Kaing S, Mohan H, Ting SY, Wu J, Parashos P. An ex vivo comparison of electronic apex locator teaching models. J Endod 2011;37:1147-51.  Back to cited text no. 43
44.Krajczár K, Marada G, Gyulai G, Tóth V. Comparison of radiographic and electronical working length determination on palatal and mesio-buccal root canals of extracted upper molars. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;106:e90-3.  Back to cited text no. 44
45.Hembrough JH, Weine FS, Pisano JV, Eskoz N. Accuracy of an electronic apex locator: A clinical evaluation in maxillary molars. J Endod 1993;19:242-6.  Back to cited text no. 45
46.Tamse A, Kaffe I, Fishel D. Zygomatic arch interference with correct radiographic diagnosis in maxillary molar endodontics. Oral Surg Oral Med Oral Pathol 1980;50:563-5.  Back to cited text no. 46
47.Sheaffer JC, Eleazer PD, Scheetz JP, Clark SJ, Farman AG. A comparison of D-, E-, and F-speed conventional intraoral radiographic films in endodontic measurement. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002;93:337-40.  Back to cited text no. 47
48.Radel RT, Goodell GG, McClanahan SB, Cohen ME. In vitro radiographic determination of distances from working length files to root ends comparing Kodak RVG 6000, Schick CDR, and Kodak Insight Film. J Endod 2006;32:566-8.  Back to cited text no. 48
49.Cox VS, Brown JC, Bricker SL, Newton CW. Radiographic interpretation of endodontic file length. Oral Surg Oral Med Oral Pathol 1991;72:340-4.  Back to cited text no. 49
50.Orafi I, Worthington HV, Qualtrough AJ, Rushton VE. The impact of different viewing conditions on radiological file and working length measurement. Int Endod J 2010;43:600-7.  Back to cited text no. 50
51.Alothmani OS, Friedlander LT, Monteith BD, Chandler NP. Influence of clinical experience on the radiographic determination of endodontic working length. Int Endod J 2013;46:211-6.  Back to cited text no. 51
52.Brown R, Hadley JN, Chambers DW. An evaluation of Ektaspeed plus film versus ultraspeed film for endodontic working length determination. J Endod 1998;24:54-6.  Back to cited text no. 52
53.Sheaffer JC, Eleazer PD, Scheetz JP, Clark SJ, Farman AG. Endodontic measurement accuracy and perceived radiograph quality: Effects of film speed and density. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2003;96:441-8.  Back to cited text no. 53
54.Ellingsen MA, Harrington GW, Hollender LG. Radiovisiography versus conventional radiography for detection of small instruments in endodontic length determination. Part 1: In vitro evaluation. J Endod 1995;21:326-31.  Back to cited text no. 54
55.Ellingsen MA, Hollender LG, Harrington GW. Radiovisiography versus conventional radiography for detection of small instruments in endodontic length determination II. In vivo evaluation. J Endod 1995;21:516-20.  Back to cited text no. 55
56.Welander U, McDavid WD, Higgins NM, Morris CR. The effect of viewing conditions on the perceptibility of radiographic details. Oral Surg Oral Med Oral Pathol 1983;56:651-4.  Back to cited text no. 56
57.Brynolf I. Improved viewing facilities for better roentgenodiagnosis. Oral Surg Oral Med Oral Pathol 1971;32:808-11.  Back to cited text no. 57
58.Weisman MI. A superior magnifier for viewing radiographs. J Endod 1980;6:885.  Back to cited text no. 58
59.Mileman PA, Purdell-Lewis DJ, van der Weele LT, Leertouwer HL. Diagnostic variation caused by differences in viewbox illumination and visual ability. Dentomaxillofac Radiol 1984;13:51-8.  Back to cited text no. 59
60.Mouyen F, Benz C, Sonnabend E, Lodter JP. Presentation and physical evaluation of RadioVisioGraphy. Oral Surg Oral Med Oral Pathol 1989;68:238-42.  Back to cited text no. 60
61.Nair MK, Nair UP. Digital and advanced imaging in endodontics: A review. J Endod 2007;33:1-6.  Back to cited text no. 61
62.Leddy BJ, Miles DA, Newton CW, Brown CE Jr. Interpretation of endodontic file lengths using RadioVisioGraphy. J Endod 1994;20:542-5.  Back to cited text no. 62
63.Hedrick RT, Brent Dove S, Peters DD, McDavid WD. Radiographic determination of canal length: Direct digital radiography versus conventional radiography. J Endod 1994;20:320-6.  Back to cited text no. 63
64.Ong EY, Pitt Ford TR. Comparision of Radiovisiography with radiographic film in root length determination. Int Endod J 1995;28:25-9.  Back to cited text no. 64
65.Versteeg KH, Sanderink GC, van Ginkel FC, van der Stelt PF. Estimating distances on direct digital images and conventional radiographs. J Am Dent Assoc 1997;128:439-43.  Back to cited text no. 65
66.Borg E, Gröndahl HG. Endodontic measurements in digital radiographs acquired by a photostimulable storage phosphor system. Endod Dent Traumatol 1996;12:20-4.  Back to cited text no. 66
67.Cederberg RA, Tidwell E, Frederiksen NL, Benson BW. Endodontic working length assessment: Comparison of storage phosphor digital imaging and radiographic film. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998;85:325-8.  Back to cited text no. 67
68.Friedlander LT, Love RM, Chandler NP. A comparison of phosphor-plate digital images with conventional radiographs for the perceived clarity of fine endodontic files and periapical lesions. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002;93:321-7.  Back to cited text no. 68
69.Lozano A, Forner L, Llena C. In vitro comparison of root-canal measurements with conventional and digital radiology. Int Endod J 2002;35:542-50.  Back to cited text no. 69
70.Martinez-Lozano MA, Forner-Navarro L, Sánchéz-Cortes JL, Llena-Puy C. Methodological considerations in the determination of working length. Int Endod J 2001;34:371-6.  Back to cited text no. 70
71.Vandre RH, Pajak JC, Abdel-Nabi H, Farman TT, Farman AG. Comparison of observer performance in determining the position of endodontic files with physical measures in the evaluation of dental X-ray imaging systems. Dentomaxillofac Radiol 2000;29:216-22.  Back to cited text no. 71
72.Piepenbring ME, Potter BJ, Weller RN, Loushine RJ. Measurement of endodontic file lengths: A density profile plot analysis. J Endod 2000;26:615-8.  Back to cited text no. 72
73.de Oliveira ML, de Souza Pinto GC, Ambrosano GM, Tosoni GM. Effect of combined digital imaging parameters on endodontic file measurements. J Endod 2012;38:1404-7.  Back to cited text no. 73
74.Farrier SL, Drage NA, Newcombe RG, Hayes SJ, Dummer PM. A comparative study of image quality and radiation exposure for dental radiographs produced using a charge-coupled device and a phosphor plate system. Int Endod J 2009;42:900-7.  Back to cited text no. 74
75.Athar A, Angelopoulos C, Katz JO, Williams KB, Spencer P. Radiographic endodontic working length estimation: Comparison of three digital image receptors. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;106:604-8.  Back to cited text no. 75
76.Oliveira ML, Ambrosano GM, Almeida SM, Haiter-Neto F, Tosoni GM. Efficacy of several digital radiographic imaging systems for laboratory determination of endodontic file length. Int Endod J 2011;44:469-73.  Back to cited text no. 76
77.Gluskin AH. Anatomy of an overfill: A reflection on the process. Endod Top 2009;16:64-81.  Back to cited text no. 77
78.Fuge KN, Stuck AM, Love RM. A comparison of digitally scanned radiographs with conventional film for the detection of small endodontic instruments. Int Endod J 1998;31:123-6.  Back to cited text no. 78
79.European Society of Endodontology. Quality guidelines for endodontic treatment: Consensus report of the European Society of Endodontology. Int Endod J 2006;39:921-30.  Back to cited text no. 79
80.Dunlap CA, Remeikis NA, BeGole EA, Rauschenberger CR. An in vivo evaluation of an electronic apex locator that uses the ratio method in vital and necrotic canals. J Endod 1998;24:48-50.  Back to cited text no. 80
81.Kim E, Marmo M, Lee CY, Oh NS, Kim IK. An in vivo comparison of working length determination by only Root-ZX apex locator versus combining Root-ZX apex locator with radiographs using a new impression technique. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;105:e79-83.  Back to cited text no. 81
82.Nguyen HQ, Kaufman AY, Komorowski RC, Friedman S. Electronic length measurement using small and large files in enlarged canals. Int Endod J 1996;29:359-64.  Back to cited text no. 82
83.Pascon EA, Marrelli M, Congi O, Ciancio R, Miceli F, Versiani MA. An in vivo comparison of working length determination of two frequency-based electronic apex locators. Int Endod J 2009;42:1026-31.  Back to cited text no. 83
84.Shabahang S, Goon WW, Gluskin AH. An in vivo evaluation of Root ZX electronic apex locator. J Endod 1996;22:616-8.  Back to cited text no. 84
85.Fouad AF, Krell KV, McKendry DJ, Koorbusch GF, Olson RA. A clinical evaluation of five electronic root canal length measuring instruments. J Endod 1990;16:446-9.  Back to cited text no. 85
86.Vajrabhaya L, Tepmongkol P. Accuracy of apex locator. Endod Dent Traumatol 1997;13:180-2.  Back to cited text no. 86
87.Siqueira JF Jr. Reaction of periradicular tissue to root canal treatment: Benefits and drawbacks. Endod Topics 2005;10:123-47.  Back to cited text no. 87
88.Ravanshad S, Adl A, Anvar J. Effect of working length measurement by electronic apex locator or radiography on the adequacy of final working length: A randomized clinical trial. J Endod 2010;36:1753-6.  Back to cited text no. 88
89.Aggarwal V, Singla M, Kabi D. An in vitro evaluation of performance of two electronic root canal length measurement devices during retreatment of different obturating materials. J Endod 2010;36:1526-30.  Back to cited text no. 89
90.de Vasconcelos BC, do Vale TM, de Menezes AS, Pinheiro-Junior EC, Vivacqua-Gomes N, Bernardes RA, et al. An ex vivo comparison of root canal length determination by three electronic apex locators at positions short of the apical foramen. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010;110:e57-61.  Back to cited text no. 90
91.Mayeda DL, Simon JH, Aimar DF, Finley K. In vivo measurement accuracy in vital and necrotic canals with the Endex apex locator. J Endod 1993;19:545-8.  Back to cited text no. 91
92.Dummer PM, McGinn JH, Rees DG. The position and topography of the apical canal constriction and apical foramen. Int Endod J 1984;17:192-8.  Back to cited text no. 92
93.ElAyouti A, Weiger R, Löst C. The ability of Root ZX apex locator to reduce the frequency of overestimated radiographic working length. J Endod 2002;28:116-9.  Back to cited text no. 93
94.Lucena-Martín C, Robles-Gijón V, Ferrer-Luque CM, Navajas-Rodríguez de Mondelo JM. In vitro evaluation of the accuracy of three electronic apex locators. J Endod 2004;30:231-3.  Back to cited text no. 94
95.Fouad AF, Reid LC. Effect of using electronic apex locators on selected endodontic treatment parameters. J Endod 2000;26:364-7.  Back to cited text no. 95
96.Alves AM, Felippe MC, Felippe WT, Rocha MJC. Ex vivo evaluation of the capacity of the Tri Auto ZX to locate the apical foramen during root canal retreatment. Int Endod J 2005;38:718-24.  Back to cited text no. 96
97.Chandler NP, Koshy S. Radiographic practices of dentists undertaking endodontics in New Zealand. Dentomaxillofac Radiol 2002;31:317-21.  Back to cited text no. 97
98.Kobayashi C. Electronic canal length measurement. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1995;79:226-31.  Back to cited text no. 98
99.Janner SF, Jeger FB, Lussi A, Bornstein MM. Precision of endodontic working length measurements: A pilot study investigation comparing cone-beam computed tomography scanning with standard measurement techniques. J Endod 2011;37:1046-51.  Back to cited text no. 99
100.Jeger FB, Janner SF, Bornstein MM, Lussi A. Endodontic working length measurement with preexisting cone-beam computed tomography scanning: A prospective, controlled clinical study. J Endod 2012;38:884-8.  Back to cited text no. 100

This article has been cited by
1 Measuring the Canal Length - A Review
Simran Verma,Mandeep S. Grewal,Anshul Arora,Ashtha Arya,Vipul Gupta
Journal of Evolution of Medical and Dental Sciences. 2021; 10(33): 2824
[Pubmed] | [DOI]
2 Endodontic management of a two rooted canine with two root canals
European Journal of Oral and Maxillofacial Surgery. 2021; 5(2)
[Pubmed] | [DOI]
3 Comparative Evaluation of Working Length Using Conventional Radiographic Method, Radiovisiography, and Apex Locator in Single-rooted Permanent Teeth
KR Indushekar, Neha Sheoran, Divesh Sardana, Bhavna G Saraf, Megha Chawla, Tanum Goel
Journal of Oral Health and Community Dentistry. 2021; 15(2): 49
[Pubmed] | [DOI]
4 Impact of Apical Patency on Accuracy of Electronic Apex Locators: In Vitro Study
Nelly Abdelsalam,Nasr Hashem
Journal of Endodontics. 2020;
[Pubmed] | [DOI]
5 Ex vivo investigation on the postoperative integrity of the apical constriction after the sole use of electronic working length determination
Michael Wolgin,Markus J. Grundmann,Jörg P. Tchorz,Wilhelm Frank,Andrej M. Kielbassa
Journal of Dentistry. 2017;
[Pubmed] | [DOI]


Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
Access Statistics
Email Alert *
Add to My List *
* Registration required (free)

  In this article
Length Measureme...
Accuracy of the ...
Factors Influenc...

 Article Access Statistics
    PDF Downloaded1558    
    Comments [Add]    
    Cited by others 5    

Recommend this journal