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Accuracy of electronic apex locators in comparison to actual length—an in vivo study
Journal of Dentistry (2005) 33, 619–625
www.intl.elsevierhealth.com/journals/jden
Accuracy of electronic apex locators in comparison to actual length—an in vivo study C. Haffnera,*, M. Folwacznya, K. Gallerb, R. Hickela a
Department of Restorative Dentistry, Ludwig–Maximilians University, Goethestrasse 70, D-80336 Munich, Germany b Departement of Restorative Dentistry, University of Regensburg, Franz-Josef Strauss Allee 11, D-93042 Regensburg, Germany Received 16 January 2004; received in revised form 12 November 2004; accepted 28 November 2004
KEYWORDS Working length; Endodontic; Measurement precision; Determination; Apical foramen
Summary Objectives: The measurement precision of four electronic apex locators (Root ZX, Morita, Tokyo, Japan; Endy, Loser, Leverkusen, Germany; Justy II, Hager– Werken, Duisburg, Germany; Endox Lysis, Milan, Italy) was examined in the present in vivo study. Methods: The root canal length of 40 single-rooted and multi-rooted teeth was determined with the four devices prior to tooth extraction. To determine the actual root canal length, the apical third was longitudinally sectioned, the root canal instrument was positioned and the apex was examined using a microscope. Results: The average measurement deviation (GSD) in relation to the apical constriction was 0.3 mm (G0.6) for the Root ZX, 0.7 mm (G1.0) for the Endy, 0.2 mm (G0.7) for the Justy II and 1.3 mm (G1.7) for the Endox. The limit of G0.5 mm from the apical constriction was attained by the Root ZX in 78%, by the Endy in 67%, by the Justy II in 80% and by Endox in 31% of all measurements. Conclusions: The latest generation of apex locaters provide the clinician with an accurate and useful adjunct for the determination of root canal length. Q 2005 Elsevier Ltd. All rights reserved.
Introduction In endodontic treatment the determination of the working length comprises one of the most critical steps and is still difficult to achieve under clinical
* Corresponding author. Tel.: C49 89 51607614; fax: C49 89 51607631. E-mail address: [email protected] (C. Haffner).
circumstances.1,2 Radiography is the traditional method of obtaining information on the anatomy of the root canal and its surrounding tissue.3,4 The exact determination is achieved using hand instruments and the subsequent translation with the assistance of gauges.5 However, radiography is sensitive both in its exposure and interpretation. Goldman, Pearson and Darzenta6 examined 253 cases and found agreement among observers in less than half, with the most disagreement being found in maxillary molars.
0300-5712/$ - see front matter Q 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.jdent.2004.11.017
620
C. Haffner et al.
In 1962, Sunada7 developed the first apex locator based on the assumption that there is a constant resistance of 6.5 kU at a defined current (amperage) between the periodontal membrane and oral mucosa. The device worked with direct current. The apex was located as soon as the resistance determined with a probe (hand instrument) corresponded to the device’s integrated resistance of 6.5 kU.7 To improve the measurement procedure, direct current was replaced by alternating current, and the frequencies used were varied and sometimes isolated.8 In addition, bipolar and oscillating electrodes were used.9,10 Integrated resistance adjustment was dropped, as it proved to be untenable.11 In 1984, the difference method was introduced by Yamashita as a new principle of measurement. This method used two different frequencies for the first time with two matching resistances and impedances. The apical constriction was determined from the difference between the two.12 Kobayashi and Suda13 improved this idea of relative impedance measurement and introduced the ‘ratio method’ in 1991, creating an impedance quotient instead of a difference. The description of this principle initiated the development of the latest endometric devices. For 20 years, investigations have been performed to assess their clinical application.14 Results based on clinical studies has only rarely been reported in the literature. In the present study, the accuracy of four different endometric devices to determine the working length was assessed in vivo. The extent to which the endometrically measured working length differed from the actual root canal length was determined.
Materials and methods The investigation was carried out by a single operator who was taught to use the different types of electronic apex locators (EALs) according to the operator’s manual. Four standard endometric devices were investigated under common clinical circumstances. Three devices operating on the basis of the ratio method were chosen,1–3 and one system as an older device.4 (1) (2) (3) (4)
Root ZX (J. Morita Corporation, Tokyo, Japan) Endy (Co. Loser, Leverkusen, Germany) Justy II (Co. Hager–Werken, Duisburg, Germany) Endox (Co. Lysis, Milan, Italy)
Forty root canals were measured prior to tooth extraction for periodontal, endodontic, prosthetic
or orthodontic reasons. No selection was made in respect of the type of tooth in order to maintain usual clinical conditions. Prior to measurement and extraction, local anesthesia was administered. The access cavity was made. In case of coronal bleeding out of the cavity, the tooth’s vitality was rated as positive. If not, it was rated as negative. The measurements were carried out one by one in the following order: (1) Root ZX, (2) Endy, (3) Justy II and (4) Endox. The root canals were rinsed with H2O2 (3%,) in order to avoid any ionized milieu inside the root canal. Immediately prior to electronic determination of the working-length each root canal was dried with paper points. Root canals showing residual humidity were classified as ‘moistened’, otherwise they were judged as ‘dry’. K-Files (Dentsply-Maillefer, Konstanz, Germany, ISO sized 15, length 28 mm) were used as active electrodes, with the exception of the Endox device, for which special needles (stainless steel, diameter 150 mm, length 28 mm) are provided by the manufacturer. The length was determined very carefully and its reproducibility was verified. A reference point was marked at the coronal part of the tooth crown using a fine paint marker. A metal stop was placed at this coronal reference point under display control on the basis of the acoustic signal (Endox). The apex or the apical constriction then appeared on the display of the particular device (Root ZX, Endy, Justy). After removing the file from the canal, the length was determined by holding the file next to a steel ruler and reading the length with a degree of accuracy of 0.5 mm (G0.02 mm). After extraction and storage in isotonic sodium chloride solution, teeth were sectioned longitudinally. The section was done parallel to the tooth’s axes in the apical third of the root with a handpiece and a diamond cutting cut-off wheel. Very thin slices were removed carefully one after the other. As the root canal became visible through a thin residual dentine layer, this was manually removed with a Hedstroem file (Dentsply-Maillefer, Konstanz) and the root canal was longitudinally exposed. Each canal was examined under a stereo light microscope at a magnification of 10-fold. An ISO 15 K-file (DentsplyMaillefer, Konstanz) was inserted into the canal until the tip reached the apical constriction. After placing the stop at the coronal reference point, the file was removed and the length was read off a steel ruler.
Statistical analysis Statistical evaluation was performed compiling an analysis of variance, carried out for the four
Accuracy of electronic apex locators in comparison to actual length—an in vivo study
621
Figure 1 (a) Stereo light microscope investigation (magnification 10!) of the apical third of tooth 31 after exposure of the root canal. (b) The same specimen with the file (ISO 15, K-file) up to the apical constriction.
endometric devices and the radiographic method (LSD test). The Kolmogorov–Smirnov test was applied to show whether the results of measurement were consistent with a normal distribution curve. Finally, the extent to which certain initial parameters influence the readings was investigated (t-test for independent spot checks).
Results Accuracy of working length determination Root canal length could be determined for all the teeth. Depending on an adequate access cavity and therefore the visible entrance of root canal, the active electrode (K-file, ISO 15) could be pushed far enough inside the root canal. The actual root canal length could be determined by microscopic investigation (Fig. 1). The Justy II provides the most accurate results. The average (GSD) for the Root ZX was at 0.3 (G0.6) mm to the apical constriction, for Endy 0.7 (G1.0) mm for Justy 0.2 (G0.7) mm and for Endox 1.3 (G1.7) (Table 1). Using the endometric devices, the apical constriction was localized exactly with the Root ZX in 45%, with Endy in 18%, with Justy II in 45% and with Endox in 20% compared to the actual
length, determined with the microscope. Within the limits of G0.5 mm to the apical constriction, the Root ZX succeeded in 78%. Twenty-two percent of the measurements, rated ‘outside the limit’, were situated apically to the defined limit, which means these lengths were too long. No length was too short of the determined limit. Endy succeeded within the limits of G0.5 mm in 67%, 30% of measurements were too long, 3% too short. Justy II was within the limits in 80% of all cases, 8% of all measurements were too long, 12% were short. Endox determined the length within the limits in only 31%, with 6% too long but 63% too short (Table 1). Overall, the following ranking regarding the accuracy of measurement was obsereved: (1) Justy II, (2) Root ZX, (3) Endy and (4) Endox. A significant difference was shown between Root ZX and Endy, as well as between Justy II and Endy, but not between Justy II and Root ZX. Endox was significantly different from Root ZX and Justy II (Table 2).
Impact of initial parameters on working length determination Various initial parameters that are reported to influence an accurate measurement of the EAL were investigated:
Table 1 Mean value (mm) (GSD) of the difference between the actual length of the root canal and the working length as aobtained with the four EAL. Root ZX Mean value (mm) SD Number exactly at apex Number within G0.5 mm
a
0.3 G0.6 18 (45%) 31 (78%)
Endy a
0.7 G1.1 7 (18%) 27 (67%)
Justy II b
0.2 G0.7 18 (45%) 32 (80%)
Endox 1.3b G1.7 8 (20%) 13 (31%)
Total number of samples with exact location of apex and determination of the working length within G0.5 mm. a Measurement was judged as too long. b Measurement was judged as too short.
622
Table 2
C. Haffner et al.
Comparison of accuracy of working length determination achieved with the four different EALs. Root ZX
p-value (exactly at apex) Root ZX – Endy 0.016 Justy II 0.822 p-value (within G0.5 mm) Root ZX – Endy 0.453 Justy II 1.00
Endy
Justy II
Endox
0.016 – 0.016
0.822 0.016 –
0.032 1.00 0.032
0.453 – 0.309
1.00 0.309 –
0.453 0.811 0.309
p-values as obtained with Pearsons–Chi-square-test.
Influence of diagnosis ‘vital’ or ‘non vital’
Discussion
With respect to the influence of ‘vital’ and ‘nonvital’ teeth on the measurement, the results showed highly significant differences between the two groups for the Root ZX and Endy (pZ0.008), respectively (pZ0.009), whereas no significant differences were shown for Justy and Endox (pZ0.176 and pZ0.585) (Table 3).
The present study was performed under authentic clinical conditions. Endodontic treatment requires cleaning and shaping and finally obturation of the root canal system.15 Controversy remains about the working length and the terminal point of root canal treatment.16 In the present study, the working length was determined in relation to the apical constriction according to the guidelines of the European Society of Endodontics (ESE).17 The apical constriction could be determined with sufficient accuracy with the light microscope. Some recent investigations have determined the accuracy of measurement of EALs.7,18 However, only a few investigations on the accuracy of measurement as compared to the root canal measurement with the actual root canal length.19 Electronic apex locators have traditionally afforded some latitude of acceptable error in locating the apex. Thus, radiographic locations within the G0.5 mm range to the apex are considered by some as the strictest acceptable range.18,20 Other studies rely on a more lax clinical range of G1.0 mm to the foramen.21 In the present study, the measurements attained within the tolerance limits of G0.5 mm are considered highly accurate. The use of EALs requires reduction or even the avoidance of mistakes by
Influence of type of tooth Comparing the groups regarding the type of tooth (single-rooted, multi-rooted) and the influence on measurement, a statistically significant difference was shown only for Endox (pZ0.039) (Table 4).
Influence of the humidity in the root canal The t-test showed a high statistical significance for the Root ZX and the Endy in sufficient measurement of root canal length taking into consideration the humidity inside the root canal (pZ0.009 and pZ0.009). The milieu inside the root canal did not have any significant influence on the length determination with Justy II and Endox (pZ0.168 and pZ0.734) (Table 5). Table 3
Influence of the factor ‘clinical diagnosis’ on the accuracy of working length determination.
Number of specimen ‘vital’ WL vs. AL (vital) SD (vital) Number of specimen ‘nonvital’ WL vs. AL (nonvital) SD (nonvital) p-value (vital vs. non-vital)
Root ZX
Endy
Justy II
Endox
29 0.4 mma G0.6 mm 11 0.0 mmb G0.4 mm 0.008
29 1.2 mma G1.126 mm 11 0.0 mmb G0.4 mm 0.009
29 0.0 mmb G0.693 mm 11 0.4mmb G0.5 mm 0.176
29 1.4mmb G1.7 mm 11 1.1 mmb G1.2 mm 0.585
p-values as obtained with the t-test. WL, working length; AL, actual length of root canal. a Measurement was judged as too long. b Measurement was judged as too short.
Accuracy of electronic apex locators in comparison to actual length—an in vivo study Table 4
623
Influence of the factor ‘type of tooth’ on the accuracy of working length determination.
Number of specimen ‘single-rooted’ WL vs. AL (single-rooted) SD (single-rooted) Number of specimen ‘multi-rooted’ WL vs. AL (multi-rooted) SD (multi-rooted) p-value (single- vs. multi-rooted)
Root ZX
Endy
Justy II
Endox
27 0.0 mma G0.6 mm 13 0.0 mma G0.6 mm 0.312
27 0.7 mma G1.120 mm 13 0.8 mma G1.0 mm 0.720
27 0.2 mmb G0.7 mm 13 0.1 mma G0.4 mm 0.660
27 0.9 mmb G1.4 mm 13 2.2 mmb G1.5 mm 0.039
p-values as obtained with the t-test. WL, working length; AL, actual length of root canal. a Measurement was judged as too long. b Measurement was judged as too short.
the operator. Katz et al.5 have described sources of error which preclude precise measurement. Our calibrated operator ensured the correct use of the EALs avoiding any complications by technical inadequacies (low battery level, disconnection of neutral electrode, guarantee of sufficient electrical circuit) or deficient clinical handling (contact of the active electrode with a conductive coronal filling). The root canals were rinsed with H2O2 in order to avoid an ionized milieu inside the root canal system.22,23 Recently, the Root ZX has been object of multiple in vitro as well as in vivo investigations.10,24,25 Studies were also performed with regard to measurement precision within G0.5 mm from the anatomical constriction.5,26 The results ranged from about 82% up to 96%.10,25,27 In the present study, the results were below 77.50% in relation to the actual root canal length. The question as to which initial parameters may influence the results remains hard to answer. One of these parameters is the ‘vitality’ or the ‘nonvitality’ of the examined tooth. Teeth with necrotic tissue in the root canal and increasing destruction of the periodontal ligament and the apex-surrounding alveolar bone showed different impedance readings than canals with vital content.28 The user Table 5
manual for the Root ZX informs the user that apical inflammation might influence the length determination. In ‘non-vital’ teeth, the characteristic constriction at the cemento-dentinal junction might be destroyed by apical resorption. Focusing on this aspect, different methods of investigation result in different appraisals. Teeth with necrotic content proved to have poorer measurements,24,26 while other studies showed no significant difference between the measurements on teeth with vital and nonvital canal contents.28,30 The length determination hardly differs between single- or multi-rooted teeth. Only the Endox showed statistically significant differences between single- and multi-rooted teeth but in general this device clearly shows poorer results than the other three devices. There were also no equivalent results in the comparison of moist and dry canals. However, the impression during the clinical procedure was that the measurement in dry canals was more straightforward and could be done faster. In moist root canals, there more often seemed to be a bouncing needle on the display. Root ZX and Endy were shown to have a significantly higher accuracy in dry canals, but there was no difference for Justy II and Endox. Justy II even showed higher accuracy in moist root canals.
Influence of the factor ‘humidity’ on the accuracy of working length determination.
Number of specimen ‘dry’ WL vs. AL (dry) SD (dry) Number of specimen (moistened) WL vs. AL (moistened) SD (moistened) p-value (dry vs. moistened)
Root ZX
Endy
Justy II
Endox
10 0.2a G0.3 30 0.4 mmb G0.6 mm 0.002
10 0.0 G0.4 30 1.0 mmb G1.1 mm 0.009
10 0.4a G0.5 30 0.1 mma G0.7 mm 0.168
10 1.2 mma G1.3 30 1.4 mma G1.7 mm 0.734
p-values as obtained with the t-test. WL, working length; AL, actual length of root canal. a Measurement was judged as too short. b Measurement was judged as too long.
624 Root ZX determined the root canal length as too long in 40%, Endy even in 66.7%. Similar results for Root ZX are found in the literature25 with the recommendation to subtract 0.5 mm from the working length determined. Since a slightly short root canal instrumentation and final obturation has a better prognosis than over-instrumentation and overfilling,31 we concur with this. Justy II determined length too short in 40%. Over-instrumentation with this device is relatively rare. Measurement with the Endox system was rated ‘too short’ in 74.3%, whereas the main problem during the measurement seemed to be blood inside the root canal. Furthermore, Endox showed the largest number of failures, i.e. a reading was not possible without sufficient drying of the root canal in several cases. The Endox system requires the vaporization of pulpal tissue inside the root canal under endometric control. Due to the effect of the frequent impulse around the tip of the active electrode, the system prevents over-instrumentation, measurement is known to be too short by 1– 1.5 mm. In addition, the system was used with an integrated older endometric device. In the light of the present results, the following aspects must also be discussed. Crucial for appraisal of the measurement results is the boundary to the physiological foramen determined in the evaluation. This limit was set as narrow as possible in order to determine the actual success rate. Ideally, only those results which located the physiological apex exactly can be termed successful. This was the case in 45% for the Root ZX, in 17.9% for the Endy, in 45% for the Justy II and in 20% for the Endox. For clinical application of EAL, the success rate would have to be compared with those of common methods. The endometric length determination has the advantage of ideally determining the physiological foramen. In the radiographic length determination, the root canal instrumentation has to follow the determination of the radiographic apex. As the distance between radiographic and physiological apex can vary, the error rate goes mostly undetected. Though the given numbers for the accuracy of radiographic length determination imply a multitude of inaccuracies,28 the frequent success of the endodontic treatment remains undisputed. Overall the devices of the latest generation therefore provide results comparable to those obtained in conventional radiographic length determination. However, radiographs will continue to provide us with important information beyond length determination, such as root configuration, curvatures and surrounding bone structures. Based on the present data we recommend the combined
C. Haffner et al. application of radiographs and EALs preferably using the following sequence: (1) radiograph for diagnostic reason, (2) electronic root canal length determination and (3) radiograph for confirmation of electronically determined working length. In conclusion, the present data revealed different accuracy in working length determination of the four EALs that have been evaluated herein. Whereas Justy II provides the most accurate results, Root ZX, Endy and Endox showed inferior quality of working length measurement. Overall, based on our present findings modern EALs offer a reliable method for endodontic working length determination.
References 1. Inoue N, Skinner DH. A simple and accurate way to measuring root canal length. Journal of Endodontics 1985;11:421–7. 2. Ketterl W. Length measurement of the root canal. Deutsche ¨rztliche Zeitschrift 1977;32:464–6. Zahna 3. Bramante CM, Berbert A. A critical evaluation of some methods of determing tooth length. Oral Surgery Oral Medicine Oral Pathology 1974;37:463–73. 4. Forsberg J. Radiographic reproduction of endodontic ‘working length’ comparing the paralleling and the bisecting-angle techniques. Oral Surgery Oral Medicine Oral Pathology 1987;64:353–60. 5. Katz A, Tamse A, Kaufman AY. Tooth length determination: a review. Oral Surgery Oral Medicine Oral Pathology 1991;72: 238–42. 6. Goldman M, Pearson AH, Darzenta N. Endodontic successwho’s reading the radiograph? Oral Surgery Oral Medicine Oral Pathology 1972;33:432–7. 7. Sunada I. Mesurement of tooth length. Nihon Shika Ishikai Zasshi 1976;28:1055–9. 8. Vob A. The determination of root canal length with the use of ¨rztliche Zeitsactual endometrical device. Deutsche Zahna chrift 1990;45:219–22. 9. Ushiyama J. New principle and method for measuring the root canal length. Journal of Endodontics 1983;9:97–104. 10. Pahncke D, Scheffler T, Sobkowiak E, Unger H, Vrana J. Electrical measurement of the length of root canals 2: New electric method for determining the apical foramen. Zahn Mund Kieferheilkunde Zentralblatt 1986;74:240–4. 11. Huang L. An experimental study of the principle of electronic root canal measurement. Journal of Endodontics 1987;13: 60–4. 12. Pilot TF, Pitts TL. Determination of impedance changes at varying frequencies in relation to root canal file position and irrigant. Journal of Endodontics 1997;23:719–24. 13. Kobayashi C, Suda H. New electronic canal measuring device based on the ratio method. Journal of Endodontics 1994;20: 111–4. 14. Lauper R, Lutz F, Barbakow F. An in vivo comparison of gradient and absolute impedance electronic apex locators. Journal of Endodontics 1996;22:260–3. 15. Friedman S. Treatment outcome and prognosis of endodontic therapy. In: Ørstavik D, Pitt Ford TR, editors. Essential endodontology-prevention and treatment of apical periodontitis. Oxford: Blackwell Science; 1998. p. 367–401.
Accuracy of electronic apex locators in comparison to actual length—an in vivo study 16. Gutmann JL, Leonhard JE. Problem solving in endodontic working-length determinations. Compendium Continuing Education in Dentistry 1995;16:288–302. 17. European Society of Endodontics. Quality guidelines of endodontic treatment. International Endodontic Journal 1994;27:115–24. 18. Fouad AF, Krell KV, McKendry DJ, Koorbusch GF, Olson RA. A clinical evaluation of five electronic root canal length measuring instruments. Journal of Endodontics 1990;16: 446–9. 19. Shabahang S, Goon WWY, Gluskin AH. An in vivo evaluation of Root ZX electronic apex locator. Journal of Endodontics 1996;22:616–8. 20. Ricard O, Roux D, Bourdeau L, Woda A. A clinical evaluation of the accuracy of the Evident RCM Mark II apex locator. Journal of Endodontics 1991;17:567–9. 21. Keller ME, Brown CE, Newton CW. A clinical evaluation of the Endocater—an electronic apex locator. Journal of Endodontics 1991;17:271–4. 22. Fouad AF, Krell KV. An in vitro comparison of five root canal length measuring instrument. Journal of Endodontics 1989; 15:573–7. 23. Stein TJ, Corcoran JF. Nonionizing method of locating the apical constriction (minor foramen) in root canals. Oral Surgery Oral Medicine Oral Pathology 1991;71:96–9.
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24. Jenkins JA, Walker 3rd WA, Schindler WG, Flores CM. An in vitro evaluation of the accuracy of the root ZX in the presence of various irrigants. Journal of Endodontics 2001; 27:209–11. 25. Negm MM. Clinical evaluation of a new method for determining tooth length without radiographs. Oral Surgery Oral Medicine Oral Pathology 1983;56:415–20. 26. Arora K, Gulabivala K. An in vivo evaluation of the Endex and RCM Mark II electronic apex locators in root canals with different contents. Oral Surgery Oral Medicine Oral Pathology 1995;79:497–503. 27. Pagavino G, Pace R, Baccetti T, A SEM. study of in vivo accuracy of the Root ZX electronic apex locator. Journal of Endodontics 1998;24:438–41. 28. 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. Journal of Endodontics 1998;24:48–50. 30. Forsberg J. Radiographic reproduction of endodontic ‘working-length’ comparing the paralleling and the bisecting-angle techniques. Oral Surgery Oral Medicine Oral Pathology 1987;64:353–60. 31. Sjo ¨gren U, Hagglund B, Sundquist G, Wing K. Factors affecting the long-term results of endodontic treatment. Journal of Endodontics 1990;16:498–504.
www.intl.elsevierhealth.com/journals/jden
Accuracy of electronic apex locators in comparison to actual length—an in vivo study C. Haffnera,*, M. Folwacznya, K. Gallerb, R. Hickela a
Department of Restorative Dentistry, Ludwig–Maximilians University, Goethestrasse 70, D-80336 Munich, Germany b Departement of Restorative Dentistry, University of Regensburg, Franz-Josef Strauss Allee 11, D-93042 Regensburg, Germany Received 16 January 2004; received in revised form 12 November 2004; accepted 28 November 2004
KEYWORDS Working length; Endodontic; Measurement precision; Determination; Apical foramen
Summary Objectives: The measurement precision of four electronic apex locators (Root ZX, Morita, Tokyo, Japan; Endy, Loser, Leverkusen, Germany; Justy II, Hager– Werken, Duisburg, Germany; Endox Lysis, Milan, Italy) was examined in the present in vivo study. Methods: The root canal length of 40 single-rooted and multi-rooted teeth was determined with the four devices prior to tooth extraction. To determine the actual root canal length, the apical third was longitudinally sectioned, the root canal instrument was positioned and the apex was examined using a microscope. Results: The average measurement deviation (GSD) in relation to the apical constriction was 0.3 mm (G0.6) for the Root ZX, 0.7 mm (G1.0) for the Endy, 0.2 mm (G0.7) for the Justy II and 1.3 mm (G1.7) for the Endox. The limit of G0.5 mm from the apical constriction was attained by the Root ZX in 78%, by the Endy in 67%, by the Justy II in 80% and by Endox in 31% of all measurements. Conclusions: The latest generation of apex locaters provide the clinician with an accurate and useful adjunct for the determination of root canal length. Q 2005 Elsevier Ltd. All rights reserved.
Introduction In endodontic treatment the determination of the working length comprises one of the most critical steps and is still difficult to achieve under clinical
* Corresponding author. Tel.: C49 89 51607614; fax: C49 89 51607631. E-mail address: [email protected] (C. Haffner).
circumstances.1,2 Radiography is the traditional method of obtaining information on the anatomy of the root canal and its surrounding tissue.3,4 The exact determination is achieved using hand instruments and the subsequent translation with the assistance of gauges.5 However, radiography is sensitive both in its exposure and interpretation. Goldman, Pearson and Darzenta6 examined 253 cases and found agreement among observers in less than half, with the most disagreement being found in maxillary molars.
0300-5712/$ - see front matter Q 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.jdent.2004.11.017
620
C. Haffner et al.
In 1962, Sunada7 developed the first apex locator based on the assumption that there is a constant resistance of 6.5 kU at a defined current (amperage) between the periodontal membrane and oral mucosa. The device worked with direct current. The apex was located as soon as the resistance determined with a probe (hand instrument) corresponded to the device’s integrated resistance of 6.5 kU.7 To improve the measurement procedure, direct current was replaced by alternating current, and the frequencies used were varied and sometimes isolated.8 In addition, bipolar and oscillating electrodes were used.9,10 Integrated resistance adjustment was dropped, as it proved to be untenable.11 In 1984, the difference method was introduced by Yamashita as a new principle of measurement. This method used two different frequencies for the first time with two matching resistances and impedances. The apical constriction was determined from the difference between the two.12 Kobayashi and Suda13 improved this idea of relative impedance measurement and introduced the ‘ratio method’ in 1991, creating an impedance quotient instead of a difference. The description of this principle initiated the development of the latest endometric devices. For 20 years, investigations have been performed to assess their clinical application.14 Results based on clinical studies has only rarely been reported in the literature. In the present study, the accuracy of four different endometric devices to determine the working length was assessed in vivo. The extent to which the endometrically measured working length differed from the actual root canal length was determined.
Materials and methods The investigation was carried out by a single operator who was taught to use the different types of electronic apex locators (EALs) according to the operator’s manual. Four standard endometric devices were investigated under common clinical circumstances. Three devices operating on the basis of the ratio method were chosen,1–3 and one system as an older device.4 (1) (2) (3) (4)
Root ZX (J. Morita Corporation, Tokyo, Japan) Endy (Co. Loser, Leverkusen, Germany) Justy II (Co. Hager–Werken, Duisburg, Germany) Endox (Co. Lysis, Milan, Italy)
Forty root canals were measured prior to tooth extraction for periodontal, endodontic, prosthetic
or orthodontic reasons. No selection was made in respect of the type of tooth in order to maintain usual clinical conditions. Prior to measurement and extraction, local anesthesia was administered. The access cavity was made. In case of coronal bleeding out of the cavity, the tooth’s vitality was rated as positive. If not, it was rated as negative. The measurements were carried out one by one in the following order: (1) Root ZX, (2) Endy, (3) Justy II and (4) Endox. The root canals were rinsed with H2O2 (3%,) in order to avoid any ionized milieu inside the root canal. Immediately prior to electronic determination of the working-length each root canal was dried with paper points. Root canals showing residual humidity were classified as ‘moistened’, otherwise they were judged as ‘dry’. K-Files (Dentsply-Maillefer, Konstanz, Germany, ISO sized 15, length 28 mm) were used as active electrodes, with the exception of the Endox device, for which special needles (stainless steel, diameter 150 mm, length 28 mm) are provided by the manufacturer. The length was determined very carefully and its reproducibility was verified. A reference point was marked at the coronal part of the tooth crown using a fine paint marker. A metal stop was placed at this coronal reference point under display control on the basis of the acoustic signal (Endox). The apex or the apical constriction then appeared on the display of the particular device (Root ZX, Endy, Justy). After removing the file from the canal, the length was determined by holding the file next to a steel ruler and reading the length with a degree of accuracy of 0.5 mm (G0.02 mm). After extraction and storage in isotonic sodium chloride solution, teeth were sectioned longitudinally. The section was done parallel to the tooth’s axes in the apical third of the root with a handpiece and a diamond cutting cut-off wheel. Very thin slices were removed carefully one after the other. As the root canal became visible through a thin residual dentine layer, this was manually removed with a Hedstroem file (Dentsply-Maillefer, Konstanz) and the root canal was longitudinally exposed. Each canal was examined under a stereo light microscope at a magnification of 10-fold. An ISO 15 K-file (DentsplyMaillefer, Konstanz) was inserted into the canal until the tip reached the apical constriction. After placing the stop at the coronal reference point, the file was removed and the length was read off a steel ruler.
Statistical analysis Statistical evaluation was performed compiling an analysis of variance, carried out for the four
Accuracy of electronic apex locators in comparison to actual length—an in vivo study
621
Figure 1 (a) Stereo light microscope investigation (magnification 10!) of the apical third of tooth 31 after exposure of the root canal. (b) The same specimen with the file (ISO 15, K-file) up to the apical constriction.
endometric devices and the radiographic method (LSD test). The Kolmogorov–Smirnov test was applied to show whether the results of measurement were consistent with a normal distribution curve. Finally, the extent to which certain initial parameters influence the readings was investigated (t-test for independent spot checks).
Results Accuracy of working length determination Root canal length could be determined for all the teeth. Depending on an adequate access cavity and therefore the visible entrance of root canal, the active electrode (K-file, ISO 15) could be pushed far enough inside the root canal. The actual root canal length could be determined by microscopic investigation (Fig. 1). The Justy II provides the most accurate results. The average (GSD) for the Root ZX was at 0.3 (G0.6) mm to the apical constriction, for Endy 0.7 (G1.0) mm for Justy 0.2 (G0.7) mm and for Endox 1.3 (G1.7) (Table 1). Using the endometric devices, the apical constriction was localized exactly with the Root ZX in 45%, with Endy in 18%, with Justy II in 45% and with Endox in 20% compared to the actual
length, determined with the microscope. Within the limits of G0.5 mm to the apical constriction, the Root ZX succeeded in 78%. Twenty-two percent of the measurements, rated ‘outside the limit’, were situated apically to the defined limit, which means these lengths were too long. No length was too short of the determined limit. Endy succeeded within the limits of G0.5 mm in 67%, 30% of measurements were too long, 3% too short. Justy II was within the limits in 80% of all cases, 8% of all measurements were too long, 12% were short. Endox determined the length within the limits in only 31%, with 6% too long but 63% too short (Table 1). Overall, the following ranking regarding the accuracy of measurement was obsereved: (1) Justy II, (2) Root ZX, (3) Endy and (4) Endox. A significant difference was shown between Root ZX and Endy, as well as between Justy II and Endy, but not between Justy II and Root ZX. Endox was significantly different from Root ZX and Justy II (Table 2).
Impact of initial parameters on working length determination Various initial parameters that are reported to influence an accurate measurement of the EAL were investigated:
Table 1 Mean value (mm) (GSD) of the difference between the actual length of the root canal and the working length as aobtained with the four EAL. Root ZX Mean value (mm) SD Number exactly at apex Number within G0.5 mm
a
0.3 G0.6 18 (45%) 31 (78%)
Endy a
0.7 G1.1 7 (18%) 27 (67%)
Justy II b
0.2 G0.7 18 (45%) 32 (80%)
Endox 1.3b G1.7 8 (20%) 13 (31%)
Total number of samples with exact location of apex and determination of the working length within G0.5 mm. a Measurement was judged as too long. b Measurement was judged as too short.
622
Table 2
C. Haffner et al.
Comparison of accuracy of working length determination achieved with the four different EALs. Root ZX
p-value (exactly at apex) Root ZX – Endy 0.016 Justy II 0.822 p-value (within G0.5 mm) Root ZX – Endy 0.453 Justy II 1.00
Endy
Justy II
Endox
0.016 – 0.016
0.822 0.016 –
0.032 1.00 0.032
0.453 – 0.309
1.00 0.309 –
0.453 0.811 0.309
p-values as obtained with Pearsons–Chi-square-test.
Influence of diagnosis ‘vital’ or ‘non vital’
Discussion
With respect to the influence of ‘vital’ and ‘nonvital’ teeth on the measurement, the results showed highly significant differences between the two groups for the Root ZX and Endy (pZ0.008), respectively (pZ0.009), whereas no significant differences were shown for Justy and Endox (pZ0.176 and pZ0.585) (Table 3).
The present study was performed under authentic clinical conditions. Endodontic treatment requires cleaning and shaping and finally obturation of the root canal system.15 Controversy remains about the working length and the terminal point of root canal treatment.16 In the present study, the working length was determined in relation to the apical constriction according to the guidelines of the European Society of Endodontics (ESE).17 The apical constriction could be determined with sufficient accuracy with the light microscope. Some recent investigations have determined the accuracy of measurement of EALs.7,18 However, only a few investigations on the accuracy of measurement as compared to the root canal measurement with the actual root canal length.19 Electronic apex locators have traditionally afforded some latitude of acceptable error in locating the apex. Thus, radiographic locations within the G0.5 mm range to the apex are considered by some as the strictest acceptable range.18,20 Other studies rely on a more lax clinical range of G1.0 mm to the foramen.21 In the present study, the measurements attained within the tolerance limits of G0.5 mm are considered highly accurate. The use of EALs requires reduction or even the avoidance of mistakes by
Influence of type of tooth Comparing the groups regarding the type of tooth (single-rooted, multi-rooted) and the influence on measurement, a statistically significant difference was shown only for Endox (pZ0.039) (Table 4).
Influence of the humidity in the root canal The t-test showed a high statistical significance for the Root ZX and the Endy in sufficient measurement of root canal length taking into consideration the humidity inside the root canal (pZ0.009 and pZ0.009). The milieu inside the root canal did not have any significant influence on the length determination with Justy II and Endox (pZ0.168 and pZ0.734) (Table 5). Table 3
Influence of the factor ‘clinical diagnosis’ on the accuracy of working length determination.
Number of specimen ‘vital’ WL vs. AL (vital) SD (vital) Number of specimen ‘nonvital’ WL vs. AL (nonvital) SD (nonvital) p-value (vital vs. non-vital)
Root ZX
Endy
Justy II
Endox
29 0.4 mma G0.6 mm 11 0.0 mmb G0.4 mm 0.008
29 1.2 mma G1.126 mm 11 0.0 mmb G0.4 mm 0.009
29 0.0 mmb G0.693 mm 11 0.4mmb G0.5 mm 0.176
29 1.4mmb G1.7 mm 11 1.1 mmb G1.2 mm 0.585
p-values as obtained with the t-test. WL, working length; AL, actual length of root canal. a Measurement was judged as too long. b Measurement was judged as too short.
Accuracy of electronic apex locators in comparison to actual length—an in vivo study Table 4
623
Influence of the factor ‘type of tooth’ on the accuracy of working length determination.
Number of specimen ‘single-rooted’ WL vs. AL (single-rooted) SD (single-rooted) Number of specimen ‘multi-rooted’ WL vs. AL (multi-rooted) SD (multi-rooted) p-value (single- vs. multi-rooted)
Root ZX
Endy
Justy II
Endox
27 0.0 mma G0.6 mm 13 0.0 mma G0.6 mm 0.312
27 0.7 mma G1.120 mm 13 0.8 mma G1.0 mm 0.720
27 0.2 mmb G0.7 mm 13 0.1 mma G0.4 mm 0.660
27 0.9 mmb G1.4 mm 13 2.2 mmb G1.5 mm 0.039
p-values as obtained with the t-test. WL, working length; AL, actual length of root canal. a Measurement was judged as too long. b Measurement was judged as too short.
the operator. Katz et al.5 have described sources of error which preclude precise measurement. Our calibrated operator ensured the correct use of the EALs avoiding any complications by technical inadequacies (low battery level, disconnection of neutral electrode, guarantee of sufficient electrical circuit) or deficient clinical handling (contact of the active electrode with a conductive coronal filling). The root canals were rinsed with H2O2 in order to avoid an ionized milieu inside the root canal system.22,23 Recently, the Root ZX has been object of multiple in vitro as well as in vivo investigations.10,24,25 Studies were also performed with regard to measurement precision within G0.5 mm from the anatomical constriction.5,26 The results ranged from about 82% up to 96%.10,25,27 In the present study, the results were below 77.50% in relation to the actual root canal length. The question as to which initial parameters may influence the results remains hard to answer. One of these parameters is the ‘vitality’ or the ‘nonvitality’ of the examined tooth. Teeth with necrotic tissue in the root canal and increasing destruction of the periodontal ligament and the apex-surrounding alveolar bone showed different impedance readings than canals with vital content.28 The user Table 5
manual for the Root ZX informs the user that apical inflammation might influence the length determination. In ‘non-vital’ teeth, the characteristic constriction at the cemento-dentinal junction might be destroyed by apical resorption. Focusing on this aspect, different methods of investigation result in different appraisals. Teeth with necrotic content proved to have poorer measurements,24,26 while other studies showed no significant difference between the measurements on teeth with vital and nonvital canal contents.28,30 The length determination hardly differs between single- or multi-rooted teeth. Only the Endox showed statistically significant differences between single- and multi-rooted teeth but in general this device clearly shows poorer results than the other three devices. There were also no equivalent results in the comparison of moist and dry canals. However, the impression during the clinical procedure was that the measurement in dry canals was more straightforward and could be done faster. In moist root canals, there more often seemed to be a bouncing needle on the display. Root ZX and Endy were shown to have a significantly higher accuracy in dry canals, but there was no difference for Justy II and Endox. Justy II even showed higher accuracy in moist root canals.
Influence of the factor ‘humidity’ on the accuracy of working length determination.
Number of specimen ‘dry’ WL vs. AL (dry) SD (dry) Number of specimen (moistened) WL vs. AL (moistened) SD (moistened) p-value (dry vs. moistened)
Root ZX
Endy
Justy II
Endox
10 0.2a G0.3 30 0.4 mmb G0.6 mm 0.002
10 0.0 G0.4 30 1.0 mmb G1.1 mm 0.009
10 0.4a G0.5 30 0.1 mma G0.7 mm 0.168
10 1.2 mma G1.3 30 1.4 mma G1.7 mm 0.734
p-values as obtained with the t-test. WL, working length; AL, actual length of root canal. a Measurement was judged as too short. b Measurement was judged as too long.
624 Root ZX determined the root canal length as too long in 40%, Endy even in 66.7%. Similar results for Root ZX are found in the literature25 with the recommendation to subtract 0.5 mm from the working length determined. Since a slightly short root canal instrumentation and final obturation has a better prognosis than over-instrumentation and overfilling,31 we concur with this. Justy II determined length too short in 40%. Over-instrumentation with this device is relatively rare. Measurement with the Endox system was rated ‘too short’ in 74.3%, whereas the main problem during the measurement seemed to be blood inside the root canal. Furthermore, Endox showed the largest number of failures, i.e. a reading was not possible without sufficient drying of the root canal in several cases. The Endox system requires the vaporization of pulpal tissue inside the root canal under endometric control. Due to the effect of the frequent impulse around the tip of the active electrode, the system prevents over-instrumentation, measurement is known to be too short by 1– 1.5 mm. In addition, the system was used with an integrated older endometric device. In the light of the present results, the following aspects must also be discussed. Crucial for appraisal of the measurement results is the boundary to the physiological foramen determined in the evaluation. This limit was set as narrow as possible in order to determine the actual success rate. Ideally, only those results which located the physiological apex exactly can be termed successful. This was the case in 45% for the Root ZX, in 17.9% for the Endy, in 45% for the Justy II and in 20% for the Endox. For clinical application of EAL, the success rate would have to be compared with those of common methods. The endometric length determination has the advantage of ideally determining the physiological foramen. In the radiographic length determination, the root canal instrumentation has to follow the determination of the radiographic apex. As the distance between radiographic and physiological apex can vary, the error rate goes mostly undetected. Though the given numbers for the accuracy of radiographic length determination imply a multitude of inaccuracies,28 the frequent success of the endodontic treatment remains undisputed. Overall the devices of the latest generation therefore provide results comparable to those obtained in conventional radiographic length determination. However, radiographs will continue to provide us with important information beyond length determination, such as root configuration, curvatures and surrounding bone structures. Based on the present data we recommend the combined
C. Haffner et al. application of radiographs and EALs preferably using the following sequence: (1) radiograph for diagnostic reason, (2) electronic root canal length determination and (3) radiograph for confirmation of electronically determined working length. In conclusion, the present data revealed different accuracy in working length determination of the four EALs that have been evaluated herein. Whereas Justy II provides the most accurate results, Root ZX, Endy and Endox showed inferior quality of working length measurement. Overall, based on our present findings modern EALs offer a reliable method for endodontic working length determination.
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