- Email: [email protected]
Influence of Instrument Size on the Accuracy of Different Apex Locators: An In Vitro Study
Basic Research—Technology
Influence of Instrument Size on the Accuracy of Different Apex Locators: An In Vitro Study Benjamín Briseño-Marroquín, PhD, MS, DDS,* Santiago Frajlich, DDS,† Fernando Goldberg, DDS,† and Brita Willershausen, PhD, DDS* Abstract The aim of this in vitro investigation was to determine the accuracy of 4 different electronic apex locators (EALs) with 3 different instrument sizes. For this study 146 roots were embedded in an agar solution. Electronic measurements were made to the physiologic foramen (apical constriction) with the Elements Apex Locator, Justy II, Raypex 5, and ProPex II and K-type files sizes 08, 10, and 15. Statistical significances were calculated with the sign test (P ⬍ .001). Exact measurements to the physiologic foramen were made with the Elements Apex Locator, 36.99%, 39.04%, and 44.93%; Justy II, 38.62%, 32.41%, and 43.41%; Raypex 5, 42.76%, 39.31%, and 39.06%; and ProPex II, 38.62%, 43.45%, and 40.63% of the time with instrument sizes 08, 10, and 15, respectively. No significant differences were found between the actual working length and EALs/instrument size. A nonsignificant higher number of unstable measurements were observed in all EALs with instrument size 15. (J Endod 2008;34:698 –702)
Key Words Apex locators, instrument size, working length
From the *Department of Operative Dentistry, Johannes Gutenberg University, Mainz, Germany; and †Universidad USAL/AOA, Buenos Aires, Argentina. Address requests for reprints to Benjamín Briseño Marroquín, Department of Operative Dentistry, Johannes Gutenberg University, Augustusplatz 2, 55131 Mainz, Germany. E-mail address: [email protected]. 0099-2399/$0 - see front matter Copyright © 2008 by the American Association of Endodontists. doi:10.1016/j.joen.2008.02.019
698
Briseño-Marroquín et al.
S
uccess or failure of endodontic treatment depends, among other parameters, on an accurate determination of the working length. Electronic apex locators (EALs) are a routinely used procedure in endodontic practice (1); yet their accuracy has been reported to vary from 35% (2) to 100% (3). The operating systems of the EALs (frequency or impedance quotient) and different investigative methodologies explain the higher accuracy obtained with the current generation of devices. It is difficult to draw conclusions on the basis of the results obtained with the new generation EALs because of research variables that can influence the results such as the lack of an accurate terminology used in the different investigations. For example, the working length landmark has been described as apical foramen, constriction, apical region or terminus, major and minor diameter or foramen, actual length, apical constriction, anatomic apex or end, apex, or foramen. Furthermore, it has been determined under direct or microscopic visualization and subtracting 0.5–1 mm as soon as the measuring instrument was “apically” visible (3–11). Yet some manufacturers claim that the working length determination is made when the instrument tip is between the anatomic (major) and physiologic (minor constriction) foramina, allowing the operator to decide which is the right point on the basis of his own clinical experience. It is widely accepted that the apical constriction or physiologic foramen is the point to which the cleaning and shaping procedures and root canal filling materials should terminate (12–15). Thus, independent of the capability of an EAL to localize a certain morphologic landmark or area, the physiologic foramen is the landmark that an operator is attempting to determine before the endodontic procedures in the root canal. Although it is morphologically difficult to determine the exact location of the physiologic foramen, there is a need in this type of research to define an exact landmark to which the working length can be determined. The aim of this study was to investigate whether the size/diameter of the measuring instrument had an influence on the accuracy of 4 different EALs.
Materials and Methods The crowns of 146 teeth were removed through separation at the cementoenamel junction level. In case of teeth with 2 or more roots, the roots were then separated at the furcation level. Only roots that showed under magnification (30⫻) completely formed apices, a well-defined physiologic foramen (apical constriction), no signs of resorption, and were patent with a 06 size K-type file (Dentsply Maillefer, Ballaigues, Switzerland) were included in the study. The root canals were immersed in sodium hypochlorite during 24 hours and dried with paper points to reduce moisture excess and make sure that they did not contain any tissue remnants. No distinction was made concerning the root type, origin, length, curvature degree, or internal anatomic characteristics, but these variables were recorded. Each root was fixed in a plastic tube (44 mm height, 14 mm diameter), which contained a buffered agar-agar solution with a constant pH of 7.3. A stainless steel rod (30 mm length, 1.5 mm diameter) was fixed 5 mm from the bottom plane of each tube. The stainless steel rod was connected to the negative pole of the EALs. The EALs investigated were Justy II (Hager & Werke GmbH, Duisburg, Germany), Raypex 5 (VDW, Munich, Germany), Elements Apex Locator (SybronEndo, Glendora, CA), and ProPex II (Dentsply Maillefer). They were used according to the manufacturers’ recommendations.
JOE — Volume 34, Number 6, June 2008
Basic Research—Technology Electronic measurements were made with instrument sizes (and sequence) 08 and 10 K-type files and 15 Flexofile (Dentsply Maillefer). The files were connected to the corresponding EAL and gradually introduced until the LCD and corresponding acoustic signal indicated that the instruments had reached the specific working length. Each root canal was measured once with each device and instrument size. A measurement was determined to be unstable when the reading of the EAL did not remain stable for at least 5 seconds. The actual working length was established after the electronic measurements were made by introducing a No. 10 K-type file (Dentsply Maillefer) under a stereomicroscope (30⫻) by an independent operator until the tip of the file reached the physiologic foramen. The resulting electronic measurements were compared with the actual working length. Unstable measurements were not considered for statistical evaluation of the results. As a result of the nonsymmetrical distribution (skewness ⬎1), the results were analyzed with the sign test. The results could not be adjusted for multiple testing; thus, the P value should be considered as a descriptive one.
Results The distribution of measurements is shown in Figs. 1–3. The statistical analysis of the results and number of unstable measurements are expressed in Table 1. An exact measurement to the physiologic foramen was made between 32.41% (Justy II, No. 10) to 44.93% (Elements Apex Locator, No. 15). If a tolerance of ⫾0.5 mm was allowed, the accuracy reached was Elements Apex Locator, 85.62%, 82.19%, and 85.51%; Justy II, 73.10%, 80.00%, and 85.27%; Raypex 5, 80.00%, 82.07%, and 85.59%; and ProPex II, 83.45%, 88.28%, and 91.41% with instrument sizes 08, 10, and 15, respectively. If a tolerance of ⫾1.00 mm was allowed, the accuracy reached was Elements Apex Locator, 93.84%, 95.21%, and 96.38%; Justy II, 84.83%, 90.34%, and 96.12%; Raypex 5, 96.55%, 95.17%, and 96.88%; and ProPex II, 93.79%, 95.86%, and 97.66% with instrument sizes 08, 10, and 15, respectively. Measurements of more than ⫾1.00 were made between 2.34% (ProPex II, No. 15; and Raypex 5, No. 15) to 9.66% (Justy II, No. 10)
and 15.17% (Justy II, No. 08). The statistical analysis showed differences only between the instrument sizes 08 and 15 (.002) and sizes 10 and 15 (⬍.0005) in the Justy II group and between instrument sizes 10 and 15 (.028) in the Elements Apex Locator group. A relatively high number of unstable measurements was observed with instrument size 15 (8.22%–12.33%) and all EALs (Table 1).
Discussion Although the use of EALs is part of routine endodontic therapy, their ability to determine the localization of the physiologic foramen is controversial. In vivo studies allow an electronic and radiographic determination of the working length before tooth extraction and in vitro determination of the actual working length (16 –18). However, it is difficult to obtain a large number of teeth, which would allow a reliable statistical analysis of the data obtained, and to conduct series of measurements with different EALs and instrument sizes and under different root canal environments. In vitro studies allow the inclusion of a large number of teeth and the possibility to maintain or reproduce the research variables such as root canal content and morphology at any time. In this study the root canal content was controlled by removing the excess moisture. Our results cannot support the claims made by the manufacturers and results obtained in other investigations that the accuracy of the EALs lies approximately between 50%– 88% (3, 19 –22). This might well be explained as a result of the different research parameters and landmark definitions used in the different investigations. In this research we were able to define the exact position of the physiologic foramen through selective teeth inclusion. Our results are partially supported by the results of different reports (3, 19) in which it was shown that exact measurements could not be made in more than 40%– 47% of the cases, regardless of the instrument size used. The results also showed that if a tolerance of ⫾0.5 mm was given, the devices’ accuracy increased considerably to between 69.6%–91.2%, also regardless of the instrument size used. A similar EAL accuracy increase, although proportionally different, has also been reported (3, 20 –25). We are of the opinion that
Measurements distribution / Instrument # 08 70
Elements Apex Locator Justy II Raypex 5 ProPex II
60
Absolute Frequency
50
40
30
20
10
0 >1.50
1.50
1.00
0.50 0.00 -0.50 -1.00 Distance to physiological foramen (mm)
-1.50
>-1.50
Figure 1. Distribution of the absolute measurement frequency obtained with size 08 instruments (n ⫽ 146). The values represent the results obtained from the subtraction between the electronic and actual working lengths.
JOE — Volume 34, Number 6, June 2008
Accuracy of Apex Locators
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Basic Research—Technology Measurements distribution / Instrument # 10 70
Elements Apex Locator Justy II Raypex 5 ProPex II
60
Absolute Frequency
50
40
30
20
10
0 >1.50
1.50
1.00
0.50
0.00
-0.50
-1.00
-1.50
>-1.50
Distance to physiological foramen (mm)
Figure 2. Distribution of the absolute measurement frequency obtained with size 10 instruments (n ⫽ 146). The values represent the results obtained from the subtraction between the electronic and actual working lengths.
a tolerance of ⫾0.5 mm can be allowed because this accuracy level cannot be reached with any other working length determination method. One hundred percent accuracy levels could not be achieved in this investigation, even if a tolerance of ⫾1.00 mm (84.83%, Justy II, No. 08 to 97.66%, ProPex II, No. 15) was allowed.
The results of this investigation showed that even though no statistical differences were obtained (they are considered descriptive), the mean values of all EALs and instruments proved to be short (negative) to the physiologic foramen. A tendency to make shorter measurements with all devices and instruments, rather than longer ones, can be ob-
Measurements distribution / Instrument # 15 70
Elements Apex Locator Justy II Raypex 5 ProPex II
60
Absolute Frequency
50
40
30
20
10
0 >1.50
1.50
1.00
0.50
0.00
-0.50
-1.00
-1.50
>-1.50
Distance to physiological foramen (mm)
Figure 3. Distribution of the absolute measurement frequency obtained with size 15 instruments (n ⫽ 146). The values represent the results obtained from the subtraction between the electronic and actual working lengths.
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JOE — Volume 34, Number 6, June 2008
Basic Research—Technology TABLE 1. Statistical Analysis of the Electronic Measurements (mm/n ⫽ 146) Elements Apex Locator Justy II Raypex 5 ProPex II Elements Apex Locator Justy II Raypex 5 ProPex II Elements Apex Locator Justy II Raypex 5 ProPex II
Ø
Mean
SD
Maximum
Minimum
UM
08 08 08 08 10 10 10 10 15 15 15 15
⫺0.28 ⫺0.60 ⫺0.30 ⫺0.17 ⫺0.39 ⫺0.40 ⫺0.35 ⫺0.09 ⫺0.30 ⫺0.22 ⫺0.24 ⫺0.12
0.92 1.06 0.59 0.93 0.79 0.65 0.71 0.88 0.81 0.55 0.53 0.90
4.50 2.00 2.00 8.00 2.00 2.50 2.00 8.00 3.50 2.00 1.50 8.50
⫺5.0 ⫺6.50 ⫺3.00 ⫺2.00 ⫺5.50 ⫺2.50 ⫺4.00 ⫺1.50 ⫺5.50 ⫺2.00 ⫺2.00 ⫺1.50
0 1 1 1 0 1 1 1 12 17 18 18
The values represent the results obtained from the subtraction between the electronic and actual working lengths. Ø and UM represent the instrument size and absolute number of unstable measurements made with each EAL and instrument size, respectively. SD, standard deviation.
served through the number of measurements made at the 0.0-mm level, which were always similar but higher than the ones at the ⫺0.5 mm level and higher in comparison with all other measuring levels, with exception of the Elements Apex Locator (No. 08) and Justy II (No. 10), in which the numbers of shorter measurements (⫺0.5 mm) were the highest ones. The numbers of shorter measurements were always higher when compared with the longer ones at the 0.5- and 1.0-mm levels. The instrument sequence used in this study ensured that the morphologic characteristics of the root canals were not modified, thus eliminating a possible uncontrollable investigation variable. The inclusion purpose of an instrument size 08 was merely to observe whether a fine instrument or the increasing instrument size could influence the electronic determination of the working length. Instrument sizes 10 and 15 are commonly used to verify the root canal patency and to make the first electronic working length determination. Our results support the ones obtained by Herrera et al. (26), in which a higher accuracy tendency was not observed with any of the EALs as the instrument size increased. It has been reported that unstable measurements were caused by the root canal content and the individual characteristics of the EALs tested (9), or that a nonsignificant tendency to make longer measurements in vitro was observed, depending on the embedding medium of the root canals (27). Yet even though the research parameters were identical for all devices and instrument sizes and to some extent contrary to the existing literature (28), a tendency to make unstable measurements with instrument size 15 was observed. It should be stressed that in this investigation an unstable measurement does not necessarily mean a wrong (too short or too long) measurement. This tendency could be explained as a result of the higher friction experienced by this instrument in root canals with a relatively small diameter. A suitable research model will be developed to address the reason for this variable.
Conclusions The results of this investigation showed the following: (1) a higher frequency tendency to make unstable measurements with size 15 instruments; (2) a tendency of all investigated devices and instruments to make shorter rather than longer measurements; and (3) that instrument sizes 08, 10, and 15 have no influence on the accuracy during working length determination with any of the investigated EALs.
JOE — Volume 34, Number 6, June 2008
References 1. Nekoofar MH, Ghandi MM, Hayes SJ, Dummer PM. The fundamental operating principles of electronic root canal length measurement devices. Int Endod J 2006;39:595– 609. 2. Welk AR, Baumgartner JC, Marshall JG. An in vivo comparison of two frequencybased electronic apex locators. J Endod 2003;29:497–500. 3. Plotino G, Grande NM, Brigante L, Lesti B, Somma F. Ex vivo accuracy of three electronic apex locators: Root ZX, Elements Diagnostic Unit, Apex Locator and ProPex. Int Endod J 2006;39:408 –14. 4. Alves AM, Felippe MC, Felippe WT, Rocha MJ. 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. 5. Kaufman AY, Keila S, Yoshpe M. Accuracy of a new apex locator: an in vitro study. Int Endod J 2002;35:186 –92. 6. ElAyouti A, Kimionis I, Chu AL, Lost C. Determining the apical terminus of root-end resected teeth using three modern apex locators: a comparative ex vivo study. Int Endod J 2005;38:827–33. 7. Erdemir A, Eldeniz AU, Ari H, Belli S, Esener T. The influence of irrigating solutions on the accuracy of the electronic apex locator facility in the Tri Auto ZX handpiece. Int Endod J 2007;40:391–7. 8. 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. 9. Venturi M, Breschi L. A comparison between two electronic apex locators: an in vivo investigation. Int Endod J 2005;38:36 – 45. 10. Lucena-Martin C, Robles-Gijon V, Ferrer-Luque CM, de Mondelo JM. In vitro evaluation of the accuracy of three electronic apex locators. J Endod 2004;30:231–3. 11. 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;103:73– 6. 12. Grove C. Why canals should be filled to the dentinocemental junction. J Am Dent Assoc 1930;17:293– 6. 13. Katz A, Tamse A, Kaufman AY. Tooth length determination: a review. Oral Surg Oral Med Oral Pathol 1991;72:238 – 42. 14. Ricucci D. Apical limit of root canal instrumentation and obturation, part 1: literature review. Int Endod J 1998;31:384 –93. 15. Ricucci D, Langeland K. Apical limit of root canal instrumentation and obturation, part 2: a histological study. Int Endod J 1998;31:394 – 409. 16. 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. 17. Lauper R, Lutz F, Barbakow F. An in vivo comparison of gradient and absolute impedance electronic apex locators. J Endod 1996;22:260 –3. 18. Pallares A, Faus V. An in vivo comparative study of two apex locators. J Endod 1994;20:576 –9. 19. Hoer D, Attin T. The accuracy of electronic working length determination. Int Endod J 2004;37:125–31. 20. Hör D, Krusy S, Attin T. Ex vivo comparison of two electronic apex locators with different scales and frequencies. Int Endod J 2005;38:855–9. 21. Tselnik M, Baumgartner JC, Marshall JG. An evaluation of Root ZX and Elements Diagnostic Apex locators. J Endod 2005;31:507–9.
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Basic Research—Technology 22. Wrbas KT, Ziegler AA, Altenburger MJ, Schirrmeister JF. In vivo comparison of working length determination with two electronic apex locators. Int Endod J 2007;40:133– 8. 23. D’Assuncao FL, de Albuquerque DS, de Queiroz Ferreira LC. The ability of two apex locators to locate the apical foramen: an in vitro study. J Endod 2006;32:560 –2. 24. 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.
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25. Goldberg F, Marroquin BB, Frajlich S, Dreyer C. In vitro evaluation of the ability of three apex locators to determine the working length during retreatment. J Endod 2005;31:676 – 8. 26. Herrera M, Abalos C, Planas AJ, Llamas R. Influence of apical constriction diameter on Root ZX apex locator precision. J Endod 2007;33:995– 8. 27. Baldi JV, Victorino FR, Bernardes RA, et al. Influence of embedding media on the assessment of electronic apex locators. J Endod 2007;33:476 –9. 28. 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.
JOE — Volume 34, Number 6, June 2008
Influence of Instrument Size on the Accuracy of Different Apex Locators: An In Vitro Study Benjamín Briseño-Marroquín, PhD, MS, DDS,* Santiago Frajlich, DDS,† Fernando Goldberg, DDS,† and Brita Willershausen, PhD, DDS* Abstract The aim of this in vitro investigation was to determine the accuracy of 4 different electronic apex locators (EALs) with 3 different instrument sizes. For this study 146 roots were embedded in an agar solution. Electronic measurements were made to the physiologic foramen (apical constriction) with the Elements Apex Locator, Justy II, Raypex 5, and ProPex II and K-type files sizes 08, 10, and 15. Statistical significances were calculated with the sign test (P ⬍ .001). Exact measurements to the physiologic foramen were made with the Elements Apex Locator, 36.99%, 39.04%, and 44.93%; Justy II, 38.62%, 32.41%, and 43.41%; Raypex 5, 42.76%, 39.31%, and 39.06%; and ProPex II, 38.62%, 43.45%, and 40.63% of the time with instrument sizes 08, 10, and 15, respectively. No significant differences were found between the actual working length and EALs/instrument size. A nonsignificant higher number of unstable measurements were observed in all EALs with instrument size 15. (J Endod 2008;34:698 –702)
Key Words Apex locators, instrument size, working length
From the *Department of Operative Dentistry, Johannes Gutenberg University, Mainz, Germany; and †Universidad USAL/AOA, Buenos Aires, Argentina. Address requests for reprints to Benjamín Briseño Marroquín, Department of Operative Dentistry, Johannes Gutenberg University, Augustusplatz 2, 55131 Mainz, Germany. E-mail address: [email protected]. 0099-2399/$0 - see front matter Copyright © 2008 by the American Association of Endodontists. doi:10.1016/j.joen.2008.02.019
698
Briseño-Marroquín et al.
S
uccess or failure of endodontic treatment depends, among other parameters, on an accurate determination of the working length. Electronic apex locators (EALs) are a routinely used procedure in endodontic practice (1); yet their accuracy has been reported to vary from 35% (2) to 100% (3). The operating systems of the EALs (frequency or impedance quotient) and different investigative methodologies explain the higher accuracy obtained with the current generation of devices. It is difficult to draw conclusions on the basis of the results obtained with the new generation EALs because of research variables that can influence the results such as the lack of an accurate terminology used in the different investigations. For example, the working length landmark has been described as apical foramen, constriction, apical region or terminus, major and minor diameter or foramen, actual length, apical constriction, anatomic apex or end, apex, or foramen. Furthermore, it has been determined under direct or microscopic visualization and subtracting 0.5–1 mm as soon as the measuring instrument was “apically” visible (3–11). Yet some manufacturers claim that the working length determination is made when the instrument tip is between the anatomic (major) and physiologic (minor constriction) foramina, allowing the operator to decide which is the right point on the basis of his own clinical experience. It is widely accepted that the apical constriction or physiologic foramen is the point to which the cleaning and shaping procedures and root canal filling materials should terminate (12–15). Thus, independent of the capability of an EAL to localize a certain morphologic landmark or area, the physiologic foramen is the landmark that an operator is attempting to determine before the endodontic procedures in the root canal. Although it is morphologically difficult to determine the exact location of the physiologic foramen, there is a need in this type of research to define an exact landmark to which the working length can be determined. The aim of this study was to investigate whether the size/diameter of the measuring instrument had an influence on the accuracy of 4 different EALs.
Materials and Methods The crowns of 146 teeth were removed through separation at the cementoenamel junction level. In case of teeth with 2 or more roots, the roots were then separated at the furcation level. Only roots that showed under magnification (30⫻) completely formed apices, a well-defined physiologic foramen (apical constriction), no signs of resorption, and were patent with a 06 size K-type file (Dentsply Maillefer, Ballaigues, Switzerland) were included in the study. The root canals were immersed in sodium hypochlorite during 24 hours and dried with paper points to reduce moisture excess and make sure that they did not contain any tissue remnants. No distinction was made concerning the root type, origin, length, curvature degree, or internal anatomic characteristics, but these variables were recorded. Each root was fixed in a plastic tube (44 mm height, 14 mm diameter), which contained a buffered agar-agar solution with a constant pH of 7.3. A stainless steel rod (30 mm length, 1.5 mm diameter) was fixed 5 mm from the bottom plane of each tube. The stainless steel rod was connected to the negative pole of the EALs. The EALs investigated were Justy II (Hager & Werke GmbH, Duisburg, Germany), Raypex 5 (VDW, Munich, Germany), Elements Apex Locator (SybronEndo, Glendora, CA), and ProPex II (Dentsply Maillefer). They were used according to the manufacturers’ recommendations.
JOE — Volume 34, Number 6, June 2008
Basic Research—Technology Electronic measurements were made with instrument sizes (and sequence) 08 and 10 K-type files and 15 Flexofile (Dentsply Maillefer). The files were connected to the corresponding EAL and gradually introduced until the LCD and corresponding acoustic signal indicated that the instruments had reached the specific working length. Each root canal was measured once with each device and instrument size. A measurement was determined to be unstable when the reading of the EAL did not remain stable for at least 5 seconds. The actual working length was established after the electronic measurements were made by introducing a No. 10 K-type file (Dentsply Maillefer) under a stereomicroscope (30⫻) by an independent operator until the tip of the file reached the physiologic foramen. The resulting electronic measurements were compared with the actual working length. Unstable measurements were not considered for statistical evaluation of the results. As a result of the nonsymmetrical distribution (skewness ⬎1), the results were analyzed with the sign test. The results could not be adjusted for multiple testing; thus, the P value should be considered as a descriptive one.
Results The distribution of measurements is shown in Figs. 1–3. The statistical analysis of the results and number of unstable measurements are expressed in Table 1. An exact measurement to the physiologic foramen was made between 32.41% (Justy II, No. 10) to 44.93% (Elements Apex Locator, No. 15). If a tolerance of ⫾0.5 mm was allowed, the accuracy reached was Elements Apex Locator, 85.62%, 82.19%, and 85.51%; Justy II, 73.10%, 80.00%, and 85.27%; Raypex 5, 80.00%, 82.07%, and 85.59%; and ProPex II, 83.45%, 88.28%, and 91.41% with instrument sizes 08, 10, and 15, respectively. If a tolerance of ⫾1.00 mm was allowed, the accuracy reached was Elements Apex Locator, 93.84%, 95.21%, and 96.38%; Justy II, 84.83%, 90.34%, and 96.12%; Raypex 5, 96.55%, 95.17%, and 96.88%; and ProPex II, 93.79%, 95.86%, and 97.66% with instrument sizes 08, 10, and 15, respectively. Measurements of more than ⫾1.00 were made between 2.34% (ProPex II, No. 15; and Raypex 5, No. 15) to 9.66% (Justy II, No. 10)
and 15.17% (Justy II, No. 08). The statistical analysis showed differences only between the instrument sizes 08 and 15 (.002) and sizes 10 and 15 (⬍.0005) in the Justy II group and between instrument sizes 10 and 15 (.028) in the Elements Apex Locator group. A relatively high number of unstable measurements was observed with instrument size 15 (8.22%–12.33%) and all EALs (Table 1).
Discussion Although the use of EALs is part of routine endodontic therapy, their ability to determine the localization of the physiologic foramen is controversial. In vivo studies allow an electronic and radiographic determination of the working length before tooth extraction and in vitro determination of the actual working length (16 –18). However, it is difficult to obtain a large number of teeth, which would allow a reliable statistical analysis of the data obtained, and to conduct series of measurements with different EALs and instrument sizes and under different root canal environments. In vitro studies allow the inclusion of a large number of teeth and the possibility to maintain or reproduce the research variables such as root canal content and morphology at any time. In this study the root canal content was controlled by removing the excess moisture. Our results cannot support the claims made by the manufacturers and results obtained in other investigations that the accuracy of the EALs lies approximately between 50%– 88% (3, 19 –22). This might well be explained as a result of the different research parameters and landmark definitions used in the different investigations. In this research we were able to define the exact position of the physiologic foramen through selective teeth inclusion. Our results are partially supported by the results of different reports (3, 19) in which it was shown that exact measurements could not be made in more than 40%– 47% of the cases, regardless of the instrument size used. The results also showed that if a tolerance of ⫾0.5 mm was given, the devices’ accuracy increased considerably to between 69.6%–91.2%, also regardless of the instrument size used. A similar EAL accuracy increase, although proportionally different, has also been reported (3, 20 –25). We are of the opinion that
Measurements distribution / Instrument # 08 70
Elements Apex Locator Justy II Raypex 5 ProPex II
60
Absolute Frequency
50
40
30
20
10
0 >1.50
1.50
1.00
0.50 0.00 -0.50 -1.00 Distance to physiological foramen (mm)
-1.50
>-1.50
Figure 1. Distribution of the absolute measurement frequency obtained with size 08 instruments (n ⫽ 146). The values represent the results obtained from the subtraction between the electronic and actual working lengths.
JOE — Volume 34, Number 6, June 2008
Accuracy of Apex Locators
699
Basic Research—Technology Measurements distribution / Instrument # 10 70
Elements Apex Locator Justy II Raypex 5 ProPex II
60
Absolute Frequency
50
40
30
20
10
0 >1.50
1.50
1.00
0.50
0.00
-0.50
-1.00
-1.50
>-1.50
Distance to physiological foramen (mm)
Figure 2. Distribution of the absolute measurement frequency obtained with size 10 instruments (n ⫽ 146). The values represent the results obtained from the subtraction between the electronic and actual working lengths.
a tolerance of ⫾0.5 mm can be allowed because this accuracy level cannot be reached with any other working length determination method. One hundred percent accuracy levels could not be achieved in this investigation, even if a tolerance of ⫾1.00 mm (84.83%, Justy II, No. 08 to 97.66%, ProPex II, No. 15) was allowed.
The results of this investigation showed that even though no statistical differences were obtained (they are considered descriptive), the mean values of all EALs and instruments proved to be short (negative) to the physiologic foramen. A tendency to make shorter measurements with all devices and instruments, rather than longer ones, can be ob-
Measurements distribution / Instrument # 15 70
Elements Apex Locator Justy II Raypex 5 ProPex II
60
Absolute Frequency
50
40
30
20
10
0 >1.50
1.50
1.00
0.50
0.00
-0.50
-1.00
-1.50
>-1.50
Distance to physiological foramen (mm)
Figure 3. Distribution of the absolute measurement frequency obtained with size 15 instruments (n ⫽ 146). The values represent the results obtained from the subtraction between the electronic and actual working lengths.
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JOE — Volume 34, Number 6, June 2008
Basic Research—Technology TABLE 1. Statistical Analysis of the Electronic Measurements (mm/n ⫽ 146) Elements Apex Locator Justy II Raypex 5 ProPex II Elements Apex Locator Justy II Raypex 5 ProPex II Elements Apex Locator Justy II Raypex 5 ProPex II
Ø
Mean
SD
Maximum
Minimum
UM
08 08 08 08 10 10 10 10 15 15 15 15
⫺0.28 ⫺0.60 ⫺0.30 ⫺0.17 ⫺0.39 ⫺0.40 ⫺0.35 ⫺0.09 ⫺0.30 ⫺0.22 ⫺0.24 ⫺0.12
0.92 1.06 0.59 0.93 0.79 0.65 0.71 0.88 0.81 0.55 0.53 0.90
4.50 2.00 2.00 8.00 2.00 2.50 2.00 8.00 3.50 2.00 1.50 8.50
⫺5.0 ⫺6.50 ⫺3.00 ⫺2.00 ⫺5.50 ⫺2.50 ⫺4.00 ⫺1.50 ⫺5.50 ⫺2.00 ⫺2.00 ⫺1.50
0 1 1 1 0 1 1 1 12 17 18 18
The values represent the results obtained from the subtraction between the electronic and actual working lengths. Ø and UM represent the instrument size and absolute number of unstable measurements made with each EAL and instrument size, respectively. SD, standard deviation.
served through the number of measurements made at the 0.0-mm level, which were always similar but higher than the ones at the ⫺0.5 mm level and higher in comparison with all other measuring levels, with exception of the Elements Apex Locator (No. 08) and Justy II (No. 10), in which the numbers of shorter measurements (⫺0.5 mm) were the highest ones. The numbers of shorter measurements were always higher when compared with the longer ones at the 0.5- and 1.0-mm levels. The instrument sequence used in this study ensured that the morphologic characteristics of the root canals were not modified, thus eliminating a possible uncontrollable investigation variable. The inclusion purpose of an instrument size 08 was merely to observe whether a fine instrument or the increasing instrument size could influence the electronic determination of the working length. Instrument sizes 10 and 15 are commonly used to verify the root canal patency and to make the first electronic working length determination. Our results support the ones obtained by Herrera et al. (26), in which a higher accuracy tendency was not observed with any of the EALs as the instrument size increased. It has been reported that unstable measurements were caused by the root canal content and the individual characteristics of the EALs tested (9), or that a nonsignificant tendency to make longer measurements in vitro was observed, depending on the embedding medium of the root canals (27). Yet even though the research parameters were identical for all devices and instrument sizes and to some extent contrary to the existing literature (28), a tendency to make unstable measurements with instrument size 15 was observed. It should be stressed that in this investigation an unstable measurement does not necessarily mean a wrong (too short or too long) measurement. This tendency could be explained as a result of the higher friction experienced by this instrument in root canals with a relatively small diameter. A suitable research model will be developed to address the reason for this variable.
Conclusions The results of this investigation showed the following: (1) a higher frequency tendency to make unstable measurements with size 15 instruments; (2) a tendency of all investigated devices and instruments to make shorter rather than longer measurements; and (3) that instrument sizes 08, 10, and 15 have no influence on the accuracy during working length determination with any of the investigated EALs.
JOE — Volume 34, Number 6, June 2008
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