Journal of Conservative Dentistry
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Year : 2013  |  Volume : 16  |  Issue : 5  |  Page : 458-461
An in vitro stereomicroscopic comparative evaluation of a combination of apex locator and endodontic motor with an integrated endodontic motor

1 Department of Conservative Dentistry and Endodontics, Gitam Dental College and Hospital, Visakhapatnam, Andhra Pradesh, India
2 Department of Conservative Dentistry and Endodontics, Vishnu Dental College, Bhimavaram, Andhra Pradesh, India
3 Department of Periodontics, Institute of Dental Sciences, Bhubaneshwar, Odisha, India

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Date of Submission03-Feb-2013
Date of Decision14-May-2013
Date of Acceptance12-Jul-2013
Date of Web Publication3-Sep-2013


Objective: To compare the efficacy of an integrated apex locator and an apex locator and endodontic motor assembly in maintaining the working length when operated under autoreverse mode.
Study Design: Thirty distobuccal roots of intact maxillary first molars were taken and access cavities were prepared. The teeth were divided into Group I: Prepared with TCM Endo V and Group II: Prepared with ProPex and NSK assembly. The instrumentation was ended in ProTaper F3 file, which was cemented in the canal. The roots were sectioned, observed under a stereomicroscope and the distance from instrument tip to the apical foramen was measured.
Results: Mean difference in the deviation of two groups was 0.075 mm, P = 0.34 (>0.05) which was statistically insignificant when assessed with unpaired t-test.
Conclusion: The assembly of ProPex-NSK Endo-mate DT and the apex locating endomotor TCM Endo V Nouvag are clinically acceptable.

Keywords: Endodontic motor; ProPex apex locator; stereomicroscope; TCM Endo V Nouvag endodontic motor

How to cite this article:
Swarupa C H, Sajjan GS, Sashi Kanth Y V. An in vitro stereomicroscopic comparative evaluation of a combination of apex locator and endodontic motor with an integrated endodontic motor. J Conserv Dent 2013;16:458-61

How to cite this URL:
Swarupa C H, Sajjan GS, Sashi Kanth Y V. An in vitro stereomicroscopic comparative evaluation of a combination of apex locator and endodontic motor with an integrated endodontic motor. J Conserv Dent [serial online] 2013 [cited 2021 Apr 11];16:458-61. Available from:

   Introduction Top

The most important objective of root canal therapy is to minimize the number of microorganisms and pathological debris in the root canal system within a precise apical limit.

In order to perform this crucial step, the apical limit is generally set near the apical constriction of the canal, which is the narrowest part with the smallest diameter of blood supply in the canal; thus creating the smallest wound site possible and best healing condition. [1],[2],[3],[4],[5]

Apical constriction may be disrupted iatrogenically because of improper working length determination, which facilitates increased apical extrusion of dentinal debris, endodontic irrigants, and filling materials; all of which predisposes to inflammatory response and delay in healing. [6],[7] Neither radiographic nor tactile methods can adequately determine the constriction, [8],[9] while electronic apex locators (EALs) are claimed to be capable of accurate measurement and give the exact location. [10],[11]

Determination of the working length is not going to do the job, the next crucial step is maintaining it all throughout the consequent procedures: Root canal instrumentation and obturation. The continuous monitoring of working length is important during the procedure, especially in curved canals. The endodontic instrument causes increased dentine removal from the inner wall of curved canals that straightens the root canal. Failures to adjust the working length can lead to negative side effects. [12],[13] In this context, an endodontic motor with a built-in apex locator would be of immense help. TCM Endo V Nouvag is one of the similar kinds of gadgets available, while others like NSK Endo-mate DT does not have a built-in apex locator, but has a provision to be connected to any other apex locator. ProPex was the apex locator of choice in this study. These devices also have torque control and speed setting features.

As there are a large number of EALs and endodontic motors in the market, the question arises as to whether these two stand-alone devices might be used in combination as an apex locating endodontic motor. The external connection can give rise to increased manual errors in completing the circuit and may be cumbersome to work within a busy clinical practice. [14]

Hence, this in vitro study was designed to evaluate these systems in measuring and maintaining the working length.

   Materials and Methods Top

Thirty distobuccal roots of intact maxillary first molar were taken and examined under Dental Operating Microscope (Carl Zeiss) under 2.5× magnification to confirm the apex formation and to rule out fractures and apical resorption; then radiographed with RVG (Satelec, X-Mind) to confirm the presence of single canal. The selected teeth were stored in 10% formalin solution and then washed in saline.

Access cavities were prepared to expose the root canal system with copious irrigation with 3% sodium hypochlorite and negotiated to patency by using a no. 10 K-file. The teeth were divided into two equal groups: I and II.

Group I: The working length determination and biomechanical preparation were done with TCM Endo V Nouvag
Group II: The working length was determined with ProPex (Dentsply) and biomechanical preparation was performed with NSK Endo-mate DT.

The teeth were embedded in an alginate model developed to demonstrate electronic working length and to perform instrumentation procedures. The alginate model was constructed using a metallic jaw filled with a layer of dental plaster followed by a layer of alginate above it and the teeth were then embedded into the alginate. As the roots were surrounded by alginate, they simulated the periodontal ligament in the clinical situation. All the measurements were made within 1 h of the model preparation.

The two gadgets were used as per the manufacturer's instructions and working length was determined using the respective EALs and radiographs; then biomechanical preparation was performed in a crown down technique with ProTaper files (Dentsply Maillifer). The preparations were made to end in F3 finishing file in all the roots.

The autoreverse mechanism was activated and the working length was set in both the groups at 1 mm short of the apical foramen.

After the preparation, the last finishing file used - F3 was carefully introduced into the canal to the preset distance and fixed in place with cold cure acrylic resin (DPI Cold Cure). The teeth were then carefully removed from the alginate model and the last 4 mm of the distobuccal root was ground along their long axis with diamond disks and then by Soflex disks (3M ESPE) until the file is exposed. The roots were then photographed with a digital camera attached to the stereomicroscope (Olympus, SZX 16) at 1.25× magnification and the images analyzed with an image analysis software (IMAGE PRO PLUS, Version 6.2, Media Cybernatics, USA). The file tip and the apical foramen were identified, and the measuring dialogue was set in millimeters and adjusted to three decimal places followed by measurement of the distance from instrument tip to the apical foramen for each root [Figure 1]. The observations were made by two experienced observers not involved with the study and an average of the two observations was taken whenever there was a difference between the two.
Figure 1: Image analysis software application

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The observations obtained were subjected to statistical analysis and the software application used was Statistical Package for Social Sciences (SPSS), version 16 (IBM, USA).

   Results Top

  • The mean distance between the file tip and apical foramen was observed to be:
    TCM Endo V: 0.521 mm
    NSK Endo-mate DT: 0.594 mm
  • The mean deviation of individual groups was calculated using paired t-test and it was observed that:
Mean deviation of TCM Endo V group was 0.478 mm (P < 0.01)
Mean deviation of NSK Endo-mate DT group was 0.403 mm (P < 0.01)
Both of which were statistically significant.

The mean difference in the deviation of two groups is 0.075 mm, P = 0.34 (>0.05) which was statistically insignificant when calculated using unpaired t-test. [Figure 2].
Figure 2: Graphical representation of mean deviation between file tip and apical foramen between TCM Endo V Nouvag (Group I) and NSK Endo-mate DT and ProPex assembly (Group II)

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   Discussion Top

The establishment and maintenance of the apical limit of instrumentation is undoubtedly an important step of the biomechanical preparation. An accurate working length contributes to a safe and effective instrumentation. There is a vast literature supporting the apical constriction to be the ideal location for the apical limit of instrumentation. [15],[16]

Unfortunately, canal preparation is adversely influenced by the highly variable root canal anatomy and the relative inability of the operator to visualize the anatomy from radiographs. A study by Pineda and Kuttler [2] showed that the apical foramen is situated away from the anatomic apex in 83% of the teeth examined, while there are also studies that have shown that apical constriction may not exist in 50% of the cases. [1],[2],[6]

In these situations, an EAL is of great help in determining the working length. However, mere determination of working length would not suffice, it has to be maintained throughout the biomechanical preparation. In this context an apex locator and endomotor combination will be of immense help for the clinician.

Recently, highly sophisticated endodontic motors have been introduced which pride themselves as having an autoreverse control system which is primed in a fraction of a second, so as to prevent overinstrumentation and further stress fatigue damage in the Ni-Ti rotary instruments. When the maximum torque value is reached or when the set minimum distance from the apex is reached, the motor will reverse the rotation and the instrument turns in anticlockwise direction and automatically exits from the canal. [13],[17] However, not all the endodontic motors have a built-in apex locator, while a few have a provision to be connected to any other apex locator.

An inbuilt and fully automated endodontic motor is easy to use and less time consuming. But in reality, the impedance of a root is complex, electronic devices or the earthing of the endodontic motor may interfere with electrical circuit of the EAL. [14]

Consequently, this in vitro study has been designed to evaluate the efficacy of an endodontic apex locating motor, that is, TCM Endo V Nouvag and an endodontic motor connected to an apex locator, that is, NSK Endo-mate DT connected to ProPex apex locator in maintaining the working length, when operated under autoreverse mode.

The TCM Endo V Nouvag has more than one function. It can be used as an EAL and/or as an endodontic motor.

NSK Endo-mate DT is an endodontic motor which can be connected to any other apex locator, ProPex has been the apex locator of choice owing to its proven accuracy in root canal length measurements. [18],[19],[20],[21],[22]

However, both the endomotors are integrated with auto reverse function, which is activated when the instrument tip reaches the perceived apical terminus and when there are exciding torque values as in the case of Nouvag and Endoamte DT, respectively. This triggers reversal of clockwise rotary motion into counterclockwise motion, thus preventing further penetration.

Alginate was chosen as the embedding medium because it has been demonstrated to have good electroconductive properties and remains around the roots simulating the periodontal ligament with its colloidal consistency. The easy achievement and preparation, combined with its low cost, made it the medium of choice. [23]

The ProTaper system features a short sequence of instruments, all the instrumentation procedures were performed till F3 file which presents a tip diameter of 0.30 mm and taper of 0.09 mm/mm, which does not influence the results as there are studies which have shown that small and larger files used in determining the electronic working length did not affect the accuracy of the results when the files were much smaller than the diameter of the canal. [2]

In the current study, using both endomotors at a distance 1 mm short of the apex gave a mean deviation of 0.478 mm with TCM Endo V and 0.403 mm with Endo-mate DT-ProPex combination, which was statistically significant with P < 0.01. While the mean difference in the deviation of these two groups was statistically insignificant with P > 0.05.

The autoreverse mechanism which is one of the safety mechanisms inbuilt in these gadgets should definitely prevent the instrument from proceeding beyond the preset distance which is 1 mm in our study; the instruments were found to deviate by 0.478 mm in group I and in group II by 0.403 mm. Though the files were still confined within the foramen, if the preset distance is further less than 1 mm; there is every chance for the instrument to go beyond the foramen.

This shows that the autoreverse mechanism should be used with caution and is not wholly reliable as claimed by the manufacturers.

The results which we obtained in our study corroborates with other studies which tested the efficiency of various other endomotors integrated with autoreverse mechanism. [24],[25]

However, in all these studies the gadgets that were tested were all endomotors with built-in apex locators, ours is one of the very few studies of its kind which has tested the efficiency of an endomotor that is connected to an apex locator.

   Conclusion Top

The following conclusions are drawn from the study:

  • The assembly of ProPex-NSK Endo-mate DT and the apex locating endomotor TCM Endo V Nouvag are clinically acceptable with neither of them superior over the other
  • The autoreverse function of the endodontic motors must be used with caution.
As in the current study when the autoreverse function was set to activate at 1 mm, the gadgets were found to exhibit this function at a distance greater than 1 mm but still confined within the foramen, so when the preset distance is further less than 1 mm there is every chance for overinstrumentation.

The astute clinician must be aware of this before choosing any of these gadgets and considering time as an important constrain and if affordable, an inbuilt system should be the gadget of choice.

   References Top

1.Baug D, Wallace J. The role of apical instrumentation in root canal treatment: A review of the literature. J Endod 2005;31:333-40.  Back to cited text no. 1
2.Carnerio E, Bramante CM, Picoli F, Letra A, da Silva Neto UX, Menezes R. Accuracy of root length determination using Tri Auto ZX and ProTaper instruments: An in vitro study. J Endod 2006;32:142-4.  Back to cited text no. 2
3.Martos J, Ferrer-Luque CM, González-Rodriguez MP, Castro LA. Topographical evaluation of the major apical foramen in permanent human teeth. Int Endod J 2009;42:329-34.  Back to cited text no. 3
4.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. 4
5.Sjogren U, Hagglund B, Sundqvist G, Wing K. Factors affecting the long-term results of endodontic treatment. J Endod 1990;16:498-504.  Back to cited text no. 5
6.Tinaz AC, Alacam T, Uzun O, Maden M, Kayaoglu G. The effect of disruption of apical constriction on periapical extrusion. J Endod 2005;31:533-5.  Back to cited text no. 6
7.Gutiérrez JH, Brizuela C, Villota E. Human teeth with periapical pathosis after overinstrumentation and overfilling of the root canals: A scanning electron microscope study. Int Endod J 1999;32:40-8.  Back to cited text no. 7
8.Olson AK, Goerig 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. 8
9.Weine FS. Calculation of working length. In: Weine FS, editor. Endodontic Therapy. 6 th ed. USA: Mosby; 2004. p. 240-65.  Back to cited text no. 9
10.Almenar García A, Forner Navarro L, Ubet Castelló V, Miñana Laliga R. Evaluation of a digital radiography to estimate working length. J Endod 1997;23:363-5.  Back to cited text no. 10
11.Ozsezer E, Inan U, Aydin U. In vivo evaluation of ProPex electronic apex locator. J Endod 2007;33:974-7.  Back to cited text no. 11
12.Topuz O, Uzun O, Tinaz AC, Sadik B. Accuracy of the apex locating function of TCM Endo V in simulated conditions: A comparison study. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2007;103:e73-6.  Back to cited text no. 12
13.Castellucci A. Schilder's technique for shaping the root canal system. In: Castellucci A, editor. Endodontics. 1 st ed, vol 2. USA: Edizioni Odontoiatriche Il Tridente; 2005. p. 438-69.  Back to cited text no. 13
14.Altenburger MJ, Cenik Y, Schirrmeister JF, Wrbas KT, Hellwig E. Combination of apex locator and endodontic motor for continuous length control during root canal treatment. Int Endod J 2009;42:368-74.  Back to cited text no. 14
15.Ricucci D. Apical limit of root canal instrumentation and obturation, part 1. Literatue review. Int Endod J 1998;31:384-93.  Back to cited text no. 15
16.Ricucci D, Langeland K. Apical limit of root canal instrumentation and obturation, part 2. A histological study. Int Endod J 1998;31:394-409.  Back to cited text no. 16
17.Gopikrishna V, Abarajithan. Working length determination. In: Kohli A, editor. Textbook of Endodontics, 1 st ed. USA: Elsevier; 2010. p. 144-53.  Back to cited text no. 17
18.Goldberg F, Frajlich S, Kuttler S, Manzur E, Briseño-Marroquín B. The evaluation of four electronic apex locators in teeth with simulated horizontal oblique root fractures. J Endod 2008;34:1497-9.  Back to cited text no. 18
19.Kqiku L, Hoxha V, Städtler P. Determination of working length with three different apexlocators. Acta Stomatol Croat 2007;41:49-56.  Back to cited text no. 19
20.Fan W, Fan B, Gutmann JL, Bian Z, Fan MW. Evaluation of the accuracy of three electronic apex locators using glass tubules. Int Endod J 2006;39:127-35.  Back to cited text no. 20
21.Plotino G, Grande NM, Brigante L, Lesti B, Somma F. Ex vivo accuracy of three electronic apex locators: Root ZX, Elements Diagnostic Unit and Apex Locator and ProPex. Int Endod J 2006;39:408-14.  Back to cited text no. 21
22.Steffen H, Splieth CH, Behr K. Comparison of measurements obtained with hand files or the Canal Leader attached to electronic apex locators: An in vitro study. Int Endod J 1999;32:103-7.  Back to cited text no. 22
23.Baldi JV, Victrnio FR, Bernardes RA, de Moraes IG, Bramante CM, Garcia RB, et al. Influence of embedding media on the assessment of electronic apex locators. J Endod 2007;33:476-9.  Back to cited text no. 23
24.Grimberg F, Banegas G, Chiacchio L, Zmener O. In vivo determination of root canal length: A preliminary report using the Tri Auto ZX apex-locating handpiece. Int Endod J 2002;35:590-3.  Back to cited text no. 24
25.Uzun O, Topuz O, Tinaz C, Nekoofar MH, Dummer PM. Accuracy of two root canal length measurement devices integrated into rotary endodontic motors when removing gutta-percha from root-filled teeth. Int Endod J 2008;41:725-32.  Back to cited text no. 25

Correspondence Address:
C H Swarupa
Door No. 34-13-38, Rossilloon Street, Gnanapuram, Visakhapatnam, Andhra Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0972-0707.117506

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