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| Year : 2007 | Volume
: 18
| Issue : 2 | Page : 60-62 |
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| Evaluation of working length determination methods: An in vivo / ex vivo study |
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Muthu Shanmugaraj, Rajendran Nivedha, Rajan Mathan, Sundaresan Balagopal
Department of Conservative Dentistry and Endodontics, Sri Ramachandra Dental College and Research Institute (Deemed University), Porur, Chennai, India
Click here for correspondence address and email
| Date of Submission | 26-Nov-2006 |
| Date of Decision | 04-Jan-2007 |
| Date of Acceptance | 10-Jan-2007 |
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 Abstract | | |
This comparative study was done to determine the accuracy in measuring the working length of root canal using tactile method, electronic apex locator and radiographic method, in viv o, and comparing the lengths so measured to the actual working length, ex vivo , after extraction. Thirty single-rooted teeth scheduled for extraction were selected for the study. After obtaining the consent from patients, a preoperative radiograph was taken and access opening was done. Working length was determined by tactile method, by using Ingle's radiographic method and by using a Foramatron-IV digital apex locator. The teeth were then extracted and the actual working length was determined by placing an endodontic file in the root canal 0.5 mm short of the apex. The results indicated that among the three methods, the electronic apex locator showed the highest accuracy and the highest reliability for working length determination. Keywords: Electronic apex locator, radiographic tooth length, working length determination
How to cite this article:
Shanmugaraj M, Nivedha R, Mathan R, Balagopal S. Evaluation of working length determination methods: An in vivo / ex vivo study. Indian J Dent Res 2007;18:60-2 |
How to cite this URL:
Shanmugaraj M, Nivedha R, Mathan R, Balagopal S. Evaluation of working length determination methods: An in vivo / ex vivo study. Indian J Dent Res [serial online] 2007 [cited 2023 Sep 22];18:60-2. Available from: https://www.ijdr.in/text.asp?2007/18/2/60/32421 |
The determination of the working length and its maintenance during cleaning and shaping procedures are key factors for successful endodontic treatment. The procedure for establishment of working length should be performed with skill, using techniques that have been proven to give valuable and accurate results and by methods that are practical and efficacious.
Radiographic method described by Ingle is one of the most common and reliable methods used in determining the working length. However, accuracy is difficult to achieve in this technique because the apical constriction cannot be identified; and the variables in techniques, angulation and exposure distort this image and lead to error due to laterally situated foramina.[1],[2] In addition, there is radiation hazard both to the patients and the dental personnel. The observer's bias in radiographic interpretation may lead to errors.
The tactile perception because of the simplicity of the technique and its virtual effectiveness are factors that motivate a few clinicians in endodontic practice to still follow this technique. But this technique is in general inaccurate in root canals with immature apex, excessive curvature and if the canal is constricted throughout its length.
The electronic root canal working length determination has become increasingly popular as it eliminates many of the problems associated with radiographic methods. Its most important advantage over radiographic method is that it can measure the length of the root canal to the end of cementodentinal junction.[3] It is more accurate, easy and fast, with no requirements of X-ray exposures. But its accuracy is influenced by electrical condition of the canal, and it is inaccurate in teeth with wide-open apex and calcified canals.
The possible variation between the radiographic apex and anatomic foramen with various techniques of determining the working length should be compared and analyzed with that of the electronic apex, to evaluate its accuracy. So this in vivo and ex vivo study was done to determine the accuracy in measuring the working length of root canal using tactile method, electronic apex locator and radiographic method, in vivo, and comparing the lengths so measured to the actual working length, ex vivo, after extraction.
| Materials and Methods | |  |
Thirty human single-rooted teeth scheduled for extraction with mature apices were selected for the study. Informed written consent was obtained from each patient before treatment. Teeth with open apices, calcification in the pulp chamber or root canal and resorped apex were excluded from the study.
A good quality preoperative radiograph was taken employing the extension cone paralleling technique by using Rinn XCP instruments, which minimizes dimensional distortion and presents the objects being radiographed in their true anatomical relationship and size. The reference point was marked on the preoperative radiograph at the incisal edge, and the tooth length was measured using a graduated metal scale from the reference point to the radiographic apex; the measurements were then recorded.
Working length determination by tactile method
Access opening was made under local anesthesia with rubber dam isolation followed by extirpation of pulp. The canal was irrigated using 3% sodium hypochlorite solution and finally flushed copiously with distilled water. No. 15 K-file was introduced into the canal until an increase in tactile resistance was detected.[1],[4] The root canal orifices were widened and coronal preflaring was done with Gates Glidden drills. Rubber stop was adjusted on the file in such a way that it touched the reference point (the incisal edge). The 15 K-file was carefully withdrawn and the distance from the tip of the file to the rubber stop was measured using a graduated metal scale; the values were noted down and registered as tactile working length (TWL).
Working length determination by radiographic method [Ingle's method]
A file with a length 1 mm less (safety factor) than the tooth length as noted from the preoperative radiograph was kept in the root canal and a diagnostic radiograph was taken. On the radiograph, the difference between the end of the file and the apex was measured. This amount was added / subtracted to the original measured length. From this adjusted length of tooth, 1 mm was subtracted to confirm with the cementodentinal junction. This value was registered as radiographic working length (RWL).
Working length determination by Foramatron-IV digital apex locator
After tactile working length determination, the canal was irrigated using 3% sodium hypochlorite solution and finally flushed copiously with distilled water. Then the canal was thoroughly dried with paper points and the outer surface of the tooth was cleaned and dried using air syringe and cotton, as the low resistance pathways from file to oral mucosa may cause false readings.
The lip contact of the instrument was attached to the patient's lower lip. No. 15 K-file was taken and the unit's cable was clipped to its metal shank. The Foramatron-IV digital apex locator was turned on and the file was inserted into the root canal. As the instrument moved apically in the canal, the digital display indicated the distance from the tip of the file to the apical constriction in tenths of a millimeter. When the instrument reached the apical constriction, the apex locator gave out signals in the following three ways:
- A digital display reading - '0'
- A pulsing audition
- A flashing light
If the instrument penetrated the constriction, a caution light, a continuous alarm, as well as a flashing 'E' signal on the digital readout, provided the warning. When the Foramatron-IV apex locator signaled the apical constriction, the rubber stop was adjusted on the file or the reamer shaft in such a way that it touches the reference point. The instrument was carefully withdrawn and the distance from the tip of the instrument to the rubber stop was measured using a graduated metal scale; the value was noted down and registered as electronic working length (EWL).
Actual working length determination after extraction
After determining the working length by the above three methods, the teeth were extracted and an endodontic file was inserted into the root canal until the tip of the file was just visible at the apical foramen. The stopper was adjusted to the reference point and the file was withdrawn. The canal length was determined and the working length was established by deducting 0.5 mm from this length; these readings were registered as actual working length (AWL).
The values obtained by the different methods were cross tabulated with the levels of coincidence of AWL values. The reliability analysis was also done to analyze the reliability level of each group with the AWL.
The working lengths determined by various methods were compared with the AWL, and their levels of coincidence were calculated as follows:
Exact coincidence : Zero difference between the value obtained by any of the methods and the value obtained using the AWL method.
Acceptable coincidence: 0.5 mm decrease in measurement when compared with that obtained using AWL method.
Non-acceptable coincidence: >0.5 mm short of the actual working length or more than the AWL.
| Results | | |
The levels of coincidence obtained by the different working length determination methods and reliability analysis for various methods vis-a-vis actual working length method are tabulated [Table - 1],[Table - 2].
The results show that the EWL method gives the highest rate of exact coincidence followed by RWL method, and the least accuracy was obtained by tactile working length method. The results of the radiographic and AWL are in agreement with other studies[5],[6]
| Discussion | | |
Foramatron-IV digital apex locator is a self-calibrating AFA (All Fluid Allowed) device. It calculates the impedance between the file and the mucosa and it uses that impedance to compute the distance of the file tip to the apex.[7] In this study, the accuracies of various clinical methods of determination of working length were compared to the most probable location of the apical foramen or apical constriction after extraction.[8],[9] This was intended to provide a simple and accurate means of direct measurement, without altering the root anatomy.
Various studies have been conducted to test the accuracy of apex locators. They differ in the brand of apex locator used, the methods used to compare the devices and the parameters used for comparison. Most results indicate that the electronic method was 80 to 94% accurate, depending on the method of comparison.[2],[8],[10],[11],[12]
Earlier observations by Kuttler[13] showed that when a file tip is 1 mm short of anatomic apex, it will be within a range at which the apical constriction is generally located. However, it is felt appropriate to subtract 0.5 mm from the tooth length of each tooth to measure the actual length, as per many studies.[11],[14],[15] Our observations revealed that the electronic method values were 80% coincident with, or 86.7% within 0.5 mm of, actual working length, which is a clinically acceptable difference.[16]
The result of this study is in agreement with a similar study done by Van T Himel and Chris Cain[17] using Foramatron-IV in comparison with actual working length; they obtained an accuracy of 80-86% when considering within 1 mm of apex. In our study an accuracy of 86.7% was obtained within 0.5 mm of the canal length.
Results from this study indicate that the sole use of tactile method is generally depreciated because of its nonreliability (33.3%). Though the use of radiographs is well established, it has inherent limitations of projecting a three-dimensional object in a two-dimensional radiograph. This study proves that Foramatron-IV apex locator is more accurate (86.7%) in determining the working length than conventional radiographs (76.6%). However, the exact location of working length with respect to CDJ can be determined only by histological methods. Thus, further studies are required, with histological analysis, to confirm the accuracy of various new electronic methods of working length determination.
With the continuous advancements in the technology of electronic apex locator, we may not be far from determining the CDJ by electronic methods. These electronic devices thus prove to be a vital tool in endodontic working length determination for modern dental practice.
| References | | |
| 1. | Ingle JI, Bakland LK. Endodontics, 5th ed. Elsevier: Canada; 2002.  |
| 2. | Katz A, Tamse A, Kaufman Y. Tooth length determination: A review. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1991;72:238-42. |
| 3. | Koyabayashi C. Electronic canal length measurement. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1995;79:226-31. |
| 4. | Seidberg BH, Alibrandi BU, Fine H, Logue B. Clinical investigation of measuring lengths of root canals with an electronic device and with digital-tactile sense. J Am Dent Assoc 1975;90:379-87. |
| 5. | 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. [PUBMED] |
| 6. | Olson AK, Goerig AC, Cavataio RE, Luciano J. The ability of radiograph to determine the location of the apical foramen. Int Endod J 1991;24:28-35. [PUBMED] |
| 7. | Nguyen QH, Kaufman AY, Komorowski RC, Friedman S. Electronic length measurement using small and large files in enlarged canals. Int Endod J 1996;29:359-64. |
| 8. | Mayeda DL, Simon JH, Aimar DF, Finley K. In-vivo measurement accuracy in vital and necrotic canals with the Endex apex locator. J Endodon 1993;19:545-8. |
| 9. | Arora RK, Gulabivala K. An in-vitro evaluation of the Endex and RCM Mark II electronic apex locators in root canal with different contents. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1995;79:497-503. [PUBMED] |
| 10. | Busch LR, Leonard RC, Goldstein LG. Determination of the accuracy of the Sono-Explorer for establishing endodontic measurement control. J Endod 1976;10:295-7. |
| 11. | McDonald JN, Hovland J. An evaluation of the apex locator Endocater. J Endod 1990;16:5-8. |
| 12. | Pallares A, Faus V. An in-vivo comparative study of two apex locators. J Endodon 1994;20:576-9. |
| 13. | Kuttler Y. Microscopic investigation of root apexes. J Am Dent Assoc 1955;50:544-52. [PUBMED] |
| 14. | Weine FS. Endodontic therapy. 5th ed. Mosby - Year Book Inc: USA; 1996. |
| 15. | Leddy BJ, Miles DA, Newton CW, Brown CE Jr. Interpretation of endodontic file lengths using radiovisiography. J Endodon 1994;20:542-5. |
| 16. | Frank AL, Torabinejad M. An in-vivo evaluation of Endex electronic apex locator. J Endod 1993;19:177-9. [PUBMED] |
| 17. | Himel VT, Cain C. An evaluation of two electronic apex locators in a dental student clinic. Quintessence Int 1993;24:803-6. |
Correspondence Address:
Rajendran Nivedha
Department of Conservative Dentistry and Endodontics, Sri Ramachandra Dental College and Research Institute (Deemed University), Porur, Chennai
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/0970-9290.32421
[Table - 1], [Table - 2] |
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