- Email: [email protected]
Ex Vivo Evaluation of the Accuracy of Electronic Foramen Locators in Root Canals with an Obstructed Apical Foramen
Basic Research—Technology
Ex Vivo Evaluation of the Accuracy of Electronic Foramen Locators in Root Canals with an Obstructed Apical Foramen Bruno Carvalho de Vasconcelos, DDS, MSc, PhD,* Rebeca Dibe Verı´ssimo Chaves, DDS, MSc,† Nilton Vivacqua-Gomes, DDS, MSc, PhD,† George T accio de Miranda Candeiro, DDS, MSc, PhD,† ‡ Ricardo Affonso Bernardes, DDS, MSc, PhD, Rodrigi Ricci Vivan, DDS, MSc, PhD,§ and Marco Antonio Hungaro Duarte, DDS, MSc, PhD§ Abstract Introduction: The objective of the present study was to evaluate the accuracy of electronic foramen locators (EFLs), Root ZX II (RZX; J. Morita, Tokyo, Japan), Propex II (Dentsply Maillefer, Ballaigues, Switzerland), and Apex ID (AID; SybronEndo, Glendora, CA), in root canals with an obstructed apical foramen (OAF) and to compare them with those 1.0 mm short of the apical foramen (AF; 1.0) and at the AF (0.0). Methods: Thirty human mandibular molars had their coronal and cervical preparations accessed. Then, the AFs were standardized (250 mm). Electronic root canal measurements were performed for the 1.0 and 0.0 working lengths, and the canals were obstructed with dentinal debris. The distance to the AF displayed by the EFLs was then recorded. The last instrument used was fixed with a cyanoacrylatebased adhesive; the apical portions of the roots were scraped, allowing for the determination of the distance between the tips of the instruments and the AFs. Results: The precision rates at 0.0, 1.0, and the OAF were 94.7%, 43.9%, and 1.8% (RZX); 93.0%, 54.4%, and 54.4% (Propex II); and 93.0%, 68.5%, and 75.4% (AID), respectively (0.5 mm). No significant differences were found between the devices at 0.0; however, for the measurements at 1.0 and the OAF, the AID offered significantly better results than RZX (P < .05). Conclusions: The absence of foraminal patency caused by dentin debris obstruction affects the accuracy of the EFLs differently, suggesting distinctive interactions with their operating mechanisms. (J Endod 2015;41:1551–1554)
Key Words Apical patency, electronic foramen locators, working length
E
lectronic foramen locators (EFLs) are considered to be the best tools for determining the actual length of root canals during endodontic therapy (1–3). Precision values of up to 100% have been attributed to these devices; however, an important factor that affects the precision of these instruments is the apical limit that they can be introduced to in root canals during endodontic therapy (3–6). The vast majority of the ELFs that are available today work by using the relationship between impedance measurements at 2 or more frequencies (1, 3, 7). This impedance is composed by the association of resistive and capacitive factors; however, the limitation of the apical extent of penetration significantly impairs the resistive factor, which may cause the reduction of precision values of these devices (3, 7). Root canals have been successfully measured with electronic devices using the apical foramen (AF) as a reference point (the distance from the cervical reference point to the apical periodontium) (1, 6, 8). However, the AFs are not always accessible or patent (9–11), thereby rendering the determination of the correct working length difficult. This occurrence may be anatomically provided by an apical delta or a strong lateral foraminal opening or may be caused by the sedimentation of dentinal debris that is produced during instrumentation procedures (9–11). Moreover, in this situation, periapical radiographs do not provide additional information because of the mismatch between the locations of the AFs and the radiographic vertices (12). There is no information in the literature regarding the precision of EFLs in such situations, which represents an unintentional limitation of apical extension during electronic root canal measurements. The present study aimed to assess the accuracy of 3 EFLs that use different operating mechanisms, Root ZX II (J. Morita, Tokyo, Japan), Propex II (Dentsply Maillefer, Ballaigues, Switzerland), and Apex ID (SybronEndo, Glendora, CA), in teeth without foraminal patency, which is provided by dentinal plugs, and to compare them with measurements that are 1.0 mm short of ( 1.0) and at the AF (0.0).
Materials and Methods Thirty human inferior molars that were clinically indicated for extraction were collected for this study under the approval of the Committee of Ethics in Research (protocol #615.857/2014). Teeth with fully formed roots that were compatible with Vertucci type IV configurations were included in the study, whereas teeth with roots showing moderate or severe curvature (>25 ), large foramina (200 mm), or radicular fractures were replaced.
*From the School of Dentistry of Sobral, Federal University of Ceara, Campus Sobral, Sobral, Ceara; †School of Dentistry of Ceara, S~ao Leopoldo Mandic University, Campus Fortaleza, Fortaleza, Ceara; ‡Brazilian Dental Association, Taguatinga, Federal District; and §Department of Dentistry, Endodontics and Dental Materials Bauru Dental School, University de S~ao Paulo, Bauru, S~ao Paulo, Brazil. Address requests for reprints to Dr Bruno Carvalho de Vasconcelos, School of Dentistry of Sobral, Federal University of Ceara, Campus Sobral, CEP 62010-590, Sobral, CE, Brazil. E-mail address: [email protected] 0099-2399/$ - see front matter Copyright ª 2015 American Association of Endodontists. http://dx.doi.org/10.1016/j.joen.2015.06.009
JOE — Volume 41, Number 9, September 2015
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Basic Research—Technology Coronary access was performed using diamond tips (#1013, #3081; KG Sorensen, Cotia, Brazil); after access, the deletion parameters were tested in the mesial canals by catheterization with manual K-files (Dentsply Maillefer). A clinical microscope (16 magnification; Alliance, Campinas, Brazil) was used to determine the real length of the teeth (RLT), obtain foraminal patency, and set the diameter of the AF. Subsequently, the diameters of the AFs were standardized using a #25 manual instrument (Dentsply Maillefer). Cervical preparation of the canals was performed using S1 and SX ProTaper instruments (Dentsply Maillefer), which penetrated up to 5.0 mm short of the RLT. The canals were irrigated with 1.0 mL 2.5% sodium hypochlorite solution (Biodin^amica, Ibipor~a, Brazil) between each instrument using a specific needle and syringe (Navitip; Ultradent, South Jordan, UT); the foraminal patency was also confirmed at this point. The 30 teeth were then divided into groups of 5 teeth that were tied together for support. The apical portions of the teeth were immersed in alginate (Jeltrate; Dentsply, Petropolis, Brazil) along with the lip clip of the EFL. The electronic root canal lengths were measured in fresh alginate, alternating the order of the use of the EFLs with manual files fitted to the canal at the adjusted lengths.
Measurements 1.0 mm Short of the AF (AF 1.0) The file penetrated into the canal until the instrument displayed a 1.0-mm measurement on the LCD monitor; then, it was removed from the canal and measured. Both Propex II and Apex ID provided numeric measurement information on their LCD monitors, whereas for Root ZX II, the indicator bar was calibrated to this position. Measurements at the AF (RLT) Measurements at the AF were performed through the introduction of manual instruments until ‘‘0.0’’ and/or ‘‘Apex’’ were displayed on LCD monitors by Propex II and Apex ID; Root ZX II had its indicator bar calibrated for this position. Both determinations ( 1.0 and 0.0) were performed with manual instruments that were introduced into the root canals until the desired length was identified by the device. The ELFs were then decoupled, and rubber stops were adjusted to the occlusal reference levels to allow the penetration of the file into the root canal to be measured. Each measurement was verified using a digital caliper (0.001 mm; Mitutoyo, Suzano, Brazil) and duly registered. Measurements in Canals with an Obstructed AF The root canals were aspirated followed by the scraping of the cervical thirds with Hedstroem manual files (Dentsply Maillefer) to produce dentinal debris. This was then compressed in the apical portion of the root canal until the loss of AF patency was verified; the dentin
plugs measured approximately 0.5 mm (0.2 mm). With the AFs obstructed, electronic measurements were taken in a manner similar to that described for the previous determinations. However, when the instrument could no longer be inserted apically (ie, it reached the plug), it was removed from the canal, and the extent of penetration was measured as described earlier. The distance to the AF displayed by the devices was also registered for future comparisons. After the measurements, the last instrument used was reinserted into the canal and fixed by means of a cyanoacrylate-based adhesive (Super Bonder; Loctite of Brazil, S~ao Paulo, Brazil). The apexes of the roots were subjected to wear in the buccolingual direction, respecting the curvatures, to allow for digital photography using a clinical microscope at 25 magnification. The images were analyzed using ImageJ software (National Institutes of Health, Bethesda, MD) to calculate the errors for each EFL; the RLTs were estimated on the basis of the sum of the calculated errors in the software and the extent of penetration by the fixed instrument. Negative and positive values were specified for readings below and beyond the set levels (0.0 mm and 1.0 mm), respectively. The difference between the calculated error and the measurement displayed by the EFL during determination was defined as the mean error in the canals without patency. Absolute values were considered for statistical analysis, which was performed using the Kruskall-Wallis and Dunn tests for multiple comparisons. The chi-square test was used for the analysis of possible differences between the percentages of acceptable measures offered by the devices. For all tests, the significance level was set to 5%.
Results Table 1 presents the average, standard deviation, median, and minimum and maximum error values of the determinations performed by the EFLs. No statistically significant differences between devices were found for the measurements at 0.0 mm. However, at 1.0 mm short of the AF and in the canals with an obstructed foramen, the results measured with Apex ID were significantly different from those with Root ZX II (P < .05). Significant differences were also observed between Propex II and Root ZX II (P < .05) in the canals without foraminal patency. The distribution of measurements obtained from the EFLs at 0.0 mm and 1.0 mm are presented in Tables 2 and 3. Considering a margin of tolerance of 0.5 mm, the chi-square test did not show statistically significant differences between the percentages of the foraminal level accuracy (c2 = 0.82), whereas statistically significant differences were observed between Apex ID and the other devices (c2 < 0.01) for measurements 1.0 mm below the AF. Table 4 presents the divergence between the actual positions of the tips of the instruments and the positions displayed by the EFLs. The analysis performed using the chi-square test, observing the same parameters applied previously,
TABLE 1. Error (mm) from Device Measurements at Different Working Lengths and in Canals with an Obstructed Apical Foramen 0.0
1.0 Margin
Device Root ZX II Propex II Apex ID
Mean* 0.23 0.23 0.25
SD 0.17 0.18 0.19
Median* a,A
0.20 0.20a,A 0.23a,A
Min
Margin
Max Mean*
0.84 0.60 0.95 0.46 0.73 0.48
Obstructed foramen
0.56 0.48 0.40
SD 0.28 0.30 0.25
Median* b,B
0.52 0.47ab,B 0.38a,B
Min
Margin
Max Mean*
0.21 1.18 0.58 1.05 0.71 1.17
1.20 0.54 0.37
SD 0.43 0.42 0.34
Median* b,C
1.15 0.45a,B 0.27a,AB
Min 2.22 1.33 1.64
Max 0.29 0.0 0.1
Max, maximum; Min, minimum; SD, standard deviation. Different superscript lowercase letters indicate statistically significant differences according to the Kruskall-Wallis and Dunn tests (P < .05), considering each condition. Different superscript uppercase letters indicate statistically significant differences according to the Kruskall-Wallis and Dunn tests (P < .05), considering each device at different conditions. *Mean error and median calculated in terms of absolute values of the determinations.
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Basic Research—Technology TABLE 2. File Tip Position Relative to the Apical Foramen for Measurements Performed to 0.0 Distance from apical foramen (mm) < 0.51* 0.50 to 0.01* 0.00 0.01–0.50 >0.51
Root ZX II
Propex II
Apex ID
n
%
n
%
n
%
2 29 0 25 1
3.5 50.9 0.0 43.8 1.8
4 34 0 19 0
7.0 59.7 0.0 33.3 0.0
4 24 2 27 0
7.0 42.1 3.5 47.4 0.0
*Negative value indicates file position short (or coronal) to the apical foramen.
TABLE 3. File Tip Position during Measurements Performed Short of the Apical Foramen ( 1.0 mm) Distance from apical foramen (mm) <
2.01* 2.0 to 1.51* 1.50 to 1.01* 1.00 0.99 to 0.50 0.49 to 0.00 >0.01
Root ZX II
Propex II
Apex ID
n
%
n
%
n
%
0 3 1 0 24 25 4
0.0 5.2 1.8 0.0 42.1 43.9 7.0
0 2 6 0 25 21 3
0.0 3.5 10.5 0.0 43.9 36.9 5.2
0 3 13 1 25 13 2
0.0 5.2 22.8 1.8 43.9 22.8 3.5
*Negative value indicates file position short (or coronal) to the
showed statistically significant differences between all 3 devices (P < .05).
Discussion The present study evaluated the accuracy of 3 ELFs ex vivo in cases in which it is impossible to reach the foraminal patency of mesial canals in molars. The ELFs evaluated were Root ZX II, which is considered to be the gold standard; Propex II; and Apex ID. All 3 devices operate differently with regard to their frequencies and/or the relationship between the measured impedances. To the best of our knowledge, there are no studies in the literature evaluating the accuracy of EFLs in canals without patency; moreover, the accuracy of the EFL Apex ID has not been reported to date. In the present study, foraminal patency was deliberately lost to verify the accuracy of the EFLs in this condition; however, there was no intention to extrapolate the present results for all possibilities of this occurrence. The obliteration of the AFs with dentin debris produced a physical barrier that prevented the reach of the AF, thus disallowing the proper measurement of the impedance resistive factor by the devices. However, differences related to the density and humidity produced by dentinal plugs and physiological dentin could be considered to be possible differentiation factors that could provide dissimilar results. Root ZX II works by measuring the ratio of the impedances measured simultaneously at frequencies of 0.4 and 8.0 kHz (6, 8, 13, 14), whereas Propex II uses the mean square roots of the impedances at frequencies of 0.5 and 8.0 kHz (6, 15, 16). These impedances are separately and simultaneously measured and compared with the reference values stored in the device’s memory. The operating mechanism of Apex ID, which has only recently been introduced into the market, has not been described in the literature; however, it is known that the operating mechanism of this device is similar to that of Root ZX II, but Apex ID operates at frequencies of 0.5 and 5.0 kHz (17). However, according to the manufacturer, its firmware is more developed than that of the EFLs available (17). In the present study, the results obtained from the root canal length determinations using the 3 EFLs at 0.0 mm are in agreement with those in the literature, with indices close to 100% precision (3, 6, 13, 15, 16, 18–20). In addition, the slight mean error values (0.20–0.23 mm) show the accuracy of these devices when used to determine RLTs up to the AF regardless of the root canal anatomy or mechanism used. Our findings show that the accuracy of Apex ID can be compared with that of some of the best available devices (0.23 mm, 93%). In relation to the determinations at the 1.0 position, the percentages of accuracy and average error values were negatively influenced irrespective of the device used. All comparisons between the measurements performed at 0.0 and 1.0 showed significant differences. These findings agree with several studies that showed this behavior for JOE — Volume 41, Number 9, September 2015
1.0-mm position.
measurements that were made short of the AF (3–6). It has been shown that the inability to reach the limit of the AF affects the interpretation of the resistive factor, which is one of the components of the impedance calculated by EFLs (7). This was observed in the present study independent of the interpretation mechanism used by the devices. Despite the reduction of the precision values presented by Apex ID, it still offered the best results at this level (0.38 mm, 68.5%), with a statistically significant difference than Root ZX II (0.52 mm, 49.1%). Because there is a lack of similar studies evaluating the accuracy of EFLs on root canals without foraminal patency in the literature, it was difficult to compare the results of our study; however, the accuracy of the tested devices appeared to be affected differently by the inability to reach the AF because of an obstruction. The results obtained with Root ZX II were significantly lower than those observed without the obstruction and than the other EFLs at both levels (0.0 and 1.0). This suggests that the presence of dentin plugs, which make the passage of a current through the root canal difficult, and the inability to reach the AF significantly interfered with the accuracy of this device. As for Propex II, the values obtained in canals with an obstructed foramen were similar to those obtained at 1.0, suggesting that the inability of the file tip to reach the AF caused by an obstruction did not lead to additional errors by the device. The results offered by Apex ID in the canals without patency were similar to those observed at 0.0, suggesting that the impossibility of accessing the AF because of an obstruction does not influence its operating mechanism. Moreover, closure of the periodontium appears to improve the accuracy of the device for determining the length of the root canal compared with the limitation of the 1.0 position. Although the mesial root canal of inferior molars was used to examine the accuracy of the 3 EFLs in this study, it did not appear to interfere with the measurement error or the accuracy values of the devices. However, the absence of foraminal patency because of the clogging of the AF produced distinct behaviors between the 3 EFLs. These results suggest that the operating mechanisms of the 3 devices are TABLE 4. Error Distribution between the Real Length and the Actual Length Presented in the Device Displays Considering the Measurements in Canals with an Obstructed Foramen (dentin plugs of 0.5 0.2 mm) Divergence (mm) between the real length and the display
Root ZX II
Propex II
Apex ID
n
%
n
%
n
%
<
10 24 22 1 0
17.5 42.1 38.6 1.8 0.0
2 7 17 30 1
3.5 12.3 29.8 52.6 1.8
2 1 11 43 0
3.5 1.8 19.3 75.4 0.0
1.51* 1.01 to 1.50* 0.51 to 1.00* 0.01 to 0.50* 0.00
*Negative value indicates file position short (or coronal) to the apical foramen.
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Basic Research—Technology influenced by this clinical condition; therefore, it is important that a professional using these devices is aware of this limitation to define protocols that make it possible to obtain more satisfactory results.
Conclusion In accordance with the findings from this study, it can be concluded that the absence of foraminal patency provided by a dentinal debris obstruction has different effects on the accuracy of the 3 EFLs evaluated. Although the accuracy of Root ZX II was significantly reduced, the accuracy of Propex II was slightly lower than that found at 0.0 mm. Apex ID did not appear to suffer any interference in the presence of a foraminal obstruction. Furthermore, no differences were observed among the devices when the instrument reached the apical foramen.
Acknowledgments Supported by FUNCAP (#PJP-0072-00098.01.00/12). The authors deny any conflicts of interest related to this study.
References 1. Martins JN, Marques D, Mata A, Caram^es J. Clinical efficacy of electronic apex locators: systematic review. J Endod 2014;40:759–77. 2. Khandewal D, Ballal NV, Saraswhati MV. Comparative accuracy of 2 electronic apex locators with conventional radiograph: an ex vivo study. J Endod 2015;41:201–4. 3. Vasconcelos BC, Frota LMA, Souza TA, et al. Evaluation of the maintenance of the apical limit during instrumentation with hybrid equipment in rotary and reciprocating modes. J Endod 2015;41:682–5. 4. Vasconcelos BC, Vale TM, Menezes AST, et al. An ex vivo comparison of root canal length determination by three electronic apex locators at positions short of the apical foramen. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010;110:e57–61. 5. Stober EK, Duran-Sindreu F, Mercande M, et al. An evaluation of Root ZX and iPex apex locators: an in vivo study. J Endod 2011;37:608–10.
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6. Vasconcelos BC, Bueno MM, Luna-Cruz SM, et al. Accuracy of five electronic foramen locators with different operating systems: an ex vivo study. J Appl Oral Sci 2013;21:132–7. 7. Nekoofar MH, Ghandi MM, Hayes SJ, Dummer PMH. The fundamental operating principles of electronic root canal length measurement devices. Int Endod J 2006;39:595–609. 8. Duran-Sidreu F, Stober E, Mercande M, et al. Comparison of in vivo and in vitro readings when testing the accuracy of the Root ZX apex locator. J Endod 2012;38: 236–9. 9. Sj€ogren U, H€agglund B, Sundqvist G, Wing K. Factors affecting the long-term results of endodontic treatment. J Endod 1990;16:498–504. 10. Pettiette MT, Delano EO, Trope M. Evaluation of success rate of endodontic treatment performed by students with stainless-steel k-files and nickel titanium hand-files. J Endod 2001;27:124–7. 11. Ng YL, Mann V, Gulabivala K. A prospective study of the factors affecting outcomes of nonsurgical root canal treatment: part 1: periapical health. Int Endod J 2011;44: 583–609. 12. Kuttler Y. Microscopic investigation of root apexes. J Am Dent Assoc 1955;50: 544–52. 13. Jacobson SJ, Westpalhen VPD, da Silva-Neto UX, et al. The accuracy in the control of the apical extent of rotary canal instrumentation using Root ZX and Protaper instruments: an in vivo study. J Endod 2008;34:1342–5. 14. Piasecki L, Carneiro E, Fariniuk LF, et al. Accuracy of Root ZX II in locating foramen in teeth with apical periodontitis: an in vivo study. J Endod 2011;37:1213–6. 15. Cianconi L, Angotti V, Felici R, et al. Accuracy of three electronic apex locators compared with digital radiography: an ex vivo study. J Endod 2010; 36:2003–7. 16. Mancini M, Felici R, Conti G, et al. Accuracy of three electronic apex locators in anterior and posterior teeth: an ex vivo study. J Endod 2011;37:684–7. 17. APEX ID. Owner’s manual. Glendora: SybronEndo; 2014. 18. Bernardes RA, Duarte MAH, Vasconcelos BC, et al. Evaluation of precision length determination with 3 electronic apex locators: Root ZX, Elements Diagnostic Unit, RomiApex D-30. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2007;104: e91–4. 19. Camargo EJ, Zapata RO, Medeiros PL, et al. Influence of preflaring on the accuracy of length determination with four electronic apex locators. J Endod 2009;35: 1300–2. 20. Wigler R, Huber R, Lin S, Kaufman AY. Accuracy and reliability of working length determination by Gold Reciproc motor in reciprocating movement. J Endod 2014;40:694–7.
JOE — Volume 41, Number 9, September 2015
Ex Vivo Evaluation of the Accuracy of Electronic Foramen Locators in Root Canals with an Obstructed Apical Foramen Bruno Carvalho de Vasconcelos, DDS, MSc, PhD,* Rebeca Dibe Verı´ssimo Chaves, DDS, MSc,† Nilton Vivacqua-Gomes, DDS, MSc, PhD,† George T accio de Miranda Candeiro, DDS, MSc, PhD,† ‡ Ricardo Affonso Bernardes, DDS, MSc, PhD, Rodrigi Ricci Vivan, DDS, MSc, PhD,§ and Marco Antonio Hungaro Duarte, DDS, MSc, PhD§ Abstract Introduction: The objective of the present study was to evaluate the accuracy of electronic foramen locators (EFLs), Root ZX II (RZX; J. Morita, Tokyo, Japan), Propex II (Dentsply Maillefer, Ballaigues, Switzerland), and Apex ID (AID; SybronEndo, Glendora, CA), in root canals with an obstructed apical foramen (OAF) and to compare them with those 1.0 mm short of the apical foramen (AF; 1.0) and at the AF (0.0). Methods: Thirty human mandibular molars had their coronal and cervical preparations accessed. Then, the AFs were standardized (250 mm). Electronic root canal measurements were performed for the 1.0 and 0.0 working lengths, and the canals were obstructed with dentinal debris. The distance to the AF displayed by the EFLs was then recorded. The last instrument used was fixed with a cyanoacrylatebased adhesive; the apical portions of the roots were scraped, allowing for the determination of the distance between the tips of the instruments and the AFs. Results: The precision rates at 0.0, 1.0, and the OAF were 94.7%, 43.9%, and 1.8% (RZX); 93.0%, 54.4%, and 54.4% (Propex II); and 93.0%, 68.5%, and 75.4% (AID), respectively (0.5 mm). No significant differences were found between the devices at 0.0; however, for the measurements at 1.0 and the OAF, the AID offered significantly better results than RZX (P < .05). Conclusions: The absence of foraminal patency caused by dentin debris obstruction affects the accuracy of the EFLs differently, suggesting distinctive interactions with their operating mechanisms. (J Endod 2015;41:1551–1554)
Key Words Apical patency, electronic foramen locators, working length
E
lectronic foramen locators (EFLs) are considered to be the best tools for determining the actual length of root canals during endodontic therapy (1–3). Precision values of up to 100% have been attributed to these devices; however, an important factor that affects the precision of these instruments is the apical limit that they can be introduced to in root canals during endodontic therapy (3–6). The vast majority of the ELFs that are available today work by using the relationship between impedance measurements at 2 or more frequencies (1, 3, 7). This impedance is composed by the association of resistive and capacitive factors; however, the limitation of the apical extent of penetration significantly impairs the resistive factor, which may cause the reduction of precision values of these devices (3, 7). Root canals have been successfully measured with electronic devices using the apical foramen (AF) as a reference point (the distance from the cervical reference point to the apical periodontium) (1, 6, 8). However, the AFs are not always accessible or patent (9–11), thereby rendering the determination of the correct working length difficult. This occurrence may be anatomically provided by an apical delta or a strong lateral foraminal opening or may be caused by the sedimentation of dentinal debris that is produced during instrumentation procedures (9–11). Moreover, in this situation, periapical radiographs do not provide additional information because of the mismatch between the locations of the AFs and the radiographic vertices (12). There is no information in the literature regarding the precision of EFLs in such situations, which represents an unintentional limitation of apical extension during electronic root canal measurements. The present study aimed to assess the accuracy of 3 EFLs that use different operating mechanisms, Root ZX II (J. Morita, Tokyo, Japan), Propex II (Dentsply Maillefer, Ballaigues, Switzerland), and Apex ID (SybronEndo, Glendora, CA), in teeth without foraminal patency, which is provided by dentinal plugs, and to compare them with measurements that are 1.0 mm short of ( 1.0) and at the AF (0.0).
Materials and Methods Thirty human inferior molars that were clinically indicated for extraction were collected for this study under the approval of the Committee of Ethics in Research (protocol #615.857/2014). Teeth with fully formed roots that were compatible with Vertucci type IV configurations were included in the study, whereas teeth with roots showing moderate or severe curvature (>25 ), large foramina (200 mm), or radicular fractures were replaced.
*From the School of Dentistry of Sobral, Federal University of Ceara, Campus Sobral, Sobral, Ceara; †School of Dentistry of Ceara, S~ao Leopoldo Mandic University, Campus Fortaleza, Fortaleza, Ceara; ‡Brazilian Dental Association, Taguatinga, Federal District; and §Department of Dentistry, Endodontics and Dental Materials Bauru Dental School, University de S~ao Paulo, Bauru, S~ao Paulo, Brazil. Address requests for reprints to Dr Bruno Carvalho de Vasconcelos, School of Dentistry of Sobral, Federal University of Ceara, Campus Sobral, CEP 62010-590, Sobral, CE, Brazil. E-mail address: [email protected] 0099-2399/$ - see front matter Copyright ª 2015 American Association of Endodontists. http://dx.doi.org/10.1016/j.joen.2015.06.009
JOE — Volume 41, Number 9, September 2015
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Basic Research—Technology Coronary access was performed using diamond tips (#1013, #3081; KG Sorensen, Cotia, Brazil); after access, the deletion parameters were tested in the mesial canals by catheterization with manual K-files (Dentsply Maillefer). A clinical microscope (16 magnification; Alliance, Campinas, Brazil) was used to determine the real length of the teeth (RLT), obtain foraminal patency, and set the diameter of the AF. Subsequently, the diameters of the AFs were standardized using a #25 manual instrument (Dentsply Maillefer). Cervical preparation of the canals was performed using S1 and SX ProTaper instruments (Dentsply Maillefer), which penetrated up to 5.0 mm short of the RLT. The canals were irrigated with 1.0 mL 2.5% sodium hypochlorite solution (Biodin^amica, Ibipor~a, Brazil) between each instrument using a specific needle and syringe (Navitip; Ultradent, South Jordan, UT); the foraminal patency was also confirmed at this point. The 30 teeth were then divided into groups of 5 teeth that were tied together for support. The apical portions of the teeth were immersed in alginate (Jeltrate; Dentsply, Petropolis, Brazil) along with the lip clip of the EFL. The electronic root canal lengths were measured in fresh alginate, alternating the order of the use of the EFLs with manual files fitted to the canal at the adjusted lengths.
Measurements 1.0 mm Short of the AF (AF 1.0) The file penetrated into the canal until the instrument displayed a 1.0-mm measurement on the LCD monitor; then, it was removed from the canal and measured. Both Propex II and Apex ID provided numeric measurement information on their LCD monitors, whereas for Root ZX II, the indicator bar was calibrated to this position. Measurements at the AF (RLT) Measurements at the AF were performed through the introduction of manual instruments until ‘‘0.0’’ and/or ‘‘Apex’’ were displayed on LCD monitors by Propex II and Apex ID; Root ZX II had its indicator bar calibrated for this position. Both determinations ( 1.0 and 0.0) were performed with manual instruments that were introduced into the root canals until the desired length was identified by the device. The ELFs were then decoupled, and rubber stops were adjusted to the occlusal reference levels to allow the penetration of the file into the root canal to be measured. Each measurement was verified using a digital caliper (0.001 mm; Mitutoyo, Suzano, Brazil) and duly registered. Measurements in Canals with an Obstructed AF The root canals were aspirated followed by the scraping of the cervical thirds with Hedstroem manual files (Dentsply Maillefer) to produce dentinal debris. This was then compressed in the apical portion of the root canal until the loss of AF patency was verified; the dentin
plugs measured approximately 0.5 mm (0.2 mm). With the AFs obstructed, electronic measurements were taken in a manner similar to that described for the previous determinations. However, when the instrument could no longer be inserted apically (ie, it reached the plug), it was removed from the canal, and the extent of penetration was measured as described earlier. The distance to the AF displayed by the devices was also registered for future comparisons. After the measurements, the last instrument used was reinserted into the canal and fixed by means of a cyanoacrylate-based adhesive (Super Bonder; Loctite of Brazil, S~ao Paulo, Brazil). The apexes of the roots were subjected to wear in the buccolingual direction, respecting the curvatures, to allow for digital photography using a clinical microscope at 25 magnification. The images were analyzed using ImageJ software (National Institutes of Health, Bethesda, MD) to calculate the errors for each EFL; the RLTs were estimated on the basis of the sum of the calculated errors in the software and the extent of penetration by the fixed instrument. Negative and positive values were specified for readings below and beyond the set levels (0.0 mm and 1.0 mm), respectively. The difference between the calculated error and the measurement displayed by the EFL during determination was defined as the mean error in the canals without patency. Absolute values were considered for statistical analysis, which was performed using the Kruskall-Wallis and Dunn tests for multiple comparisons. The chi-square test was used for the analysis of possible differences between the percentages of acceptable measures offered by the devices. For all tests, the significance level was set to 5%.
Results Table 1 presents the average, standard deviation, median, and minimum and maximum error values of the determinations performed by the EFLs. No statistically significant differences between devices were found for the measurements at 0.0 mm. However, at 1.0 mm short of the AF and in the canals with an obstructed foramen, the results measured with Apex ID were significantly different from those with Root ZX II (P < .05). Significant differences were also observed between Propex II and Root ZX II (P < .05) in the canals without foraminal patency. The distribution of measurements obtained from the EFLs at 0.0 mm and 1.0 mm are presented in Tables 2 and 3. Considering a margin of tolerance of 0.5 mm, the chi-square test did not show statistically significant differences between the percentages of the foraminal level accuracy (c2 = 0.82), whereas statistically significant differences were observed between Apex ID and the other devices (c2 < 0.01) for measurements 1.0 mm below the AF. Table 4 presents the divergence between the actual positions of the tips of the instruments and the positions displayed by the EFLs. The analysis performed using the chi-square test, observing the same parameters applied previously,
TABLE 1. Error (mm) from Device Measurements at Different Working Lengths and in Canals with an Obstructed Apical Foramen 0.0
1.0 Margin
Device Root ZX II Propex II Apex ID
Mean* 0.23 0.23 0.25
SD 0.17 0.18 0.19
Median* a,A
0.20 0.20a,A 0.23a,A
Min
Margin
Max Mean*
0.84 0.60 0.95 0.46 0.73 0.48
Obstructed foramen
0.56 0.48 0.40
SD 0.28 0.30 0.25
Median* b,B
0.52 0.47ab,B 0.38a,B
Min
Margin
Max Mean*
0.21 1.18 0.58 1.05 0.71 1.17
1.20 0.54 0.37
SD 0.43 0.42 0.34
Median* b,C
1.15 0.45a,B 0.27a,AB
Min 2.22 1.33 1.64
Max 0.29 0.0 0.1
Max, maximum; Min, minimum; SD, standard deviation. Different superscript lowercase letters indicate statistically significant differences according to the Kruskall-Wallis and Dunn tests (P < .05), considering each condition. Different superscript uppercase letters indicate statistically significant differences according to the Kruskall-Wallis and Dunn tests (P < .05), considering each device at different conditions. *Mean error and median calculated in terms of absolute values of the determinations.
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Basic Research—Technology TABLE 2. File Tip Position Relative to the Apical Foramen for Measurements Performed to 0.0 Distance from apical foramen (mm) < 0.51* 0.50 to 0.01* 0.00 0.01–0.50 >0.51
Root ZX II
Propex II
Apex ID
n
%
n
%
n
%
2 29 0 25 1
3.5 50.9 0.0 43.8 1.8
4 34 0 19 0
7.0 59.7 0.0 33.3 0.0
4 24 2 27 0
7.0 42.1 3.5 47.4 0.0
*Negative value indicates file position short (or coronal) to the apical foramen.
TABLE 3. File Tip Position during Measurements Performed Short of the Apical Foramen ( 1.0 mm) Distance from apical foramen (mm) <
2.01* 2.0 to 1.51* 1.50 to 1.01* 1.00 0.99 to 0.50 0.49 to 0.00 >0.01
Root ZX II
Propex II
Apex ID
n
%
n
%
n
%
0 3 1 0 24 25 4
0.0 5.2 1.8 0.0 42.1 43.9 7.0
0 2 6 0 25 21 3
0.0 3.5 10.5 0.0 43.9 36.9 5.2
0 3 13 1 25 13 2
0.0 5.2 22.8 1.8 43.9 22.8 3.5
*Negative value indicates file position short (or coronal) to the
showed statistically significant differences between all 3 devices (P < .05).
Discussion The present study evaluated the accuracy of 3 ELFs ex vivo in cases in which it is impossible to reach the foraminal patency of mesial canals in molars. The ELFs evaluated were Root ZX II, which is considered to be the gold standard; Propex II; and Apex ID. All 3 devices operate differently with regard to their frequencies and/or the relationship between the measured impedances. To the best of our knowledge, there are no studies in the literature evaluating the accuracy of EFLs in canals without patency; moreover, the accuracy of the EFL Apex ID has not been reported to date. In the present study, foraminal patency was deliberately lost to verify the accuracy of the EFLs in this condition; however, there was no intention to extrapolate the present results for all possibilities of this occurrence. The obliteration of the AFs with dentin debris produced a physical barrier that prevented the reach of the AF, thus disallowing the proper measurement of the impedance resistive factor by the devices. However, differences related to the density and humidity produced by dentinal plugs and physiological dentin could be considered to be possible differentiation factors that could provide dissimilar results. Root ZX II works by measuring the ratio of the impedances measured simultaneously at frequencies of 0.4 and 8.0 kHz (6, 8, 13, 14), whereas Propex II uses the mean square roots of the impedances at frequencies of 0.5 and 8.0 kHz (6, 15, 16). These impedances are separately and simultaneously measured and compared with the reference values stored in the device’s memory. The operating mechanism of Apex ID, which has only recently been introduced into the market, has not been described in the literature; however, it is known that the operating mechanism of this device is similar to that of Root ZX II, but Apex ID operates at frequencies of 0.5 and 5.0 kHz (17). However, according to the manufacturer, its firmware is more developed than that of the EFLs available (17). In the present study, the results obtained from the root canal length determinations using the 3 EFLs at 0.0 mm are in agreement with those in the literature, with indices close to 100% precision (3, 6, 13, 15, 16, 18–20). In addition, the slight mean error values (0.20–0.23 mm) show the accuracy of these devices when used to determine RLTs up to the AF regardless of the root canal anatomy or mechanism used. Our findings show that the accuracy of Apex ID can be compared with that of some of the best available devices (0.23 mm, 93%). In relation to the determinations at the 1.0 position, the percentages of accuracy and average error values were negatively influenced irrespective of the device used. All comparisons between the measurements performed at 0.0 and 1.0 showed significant differences. These findings agree with several studies that showed this behavior for JOE — Volume 41, Number 9, September 2015
1.0-mm position.
measurements that were made short of the AF (3–6). It has been shown that the inability to reach the limit of the AF affects the interpretation of the resistive factor, which is one of the components of the impedance calculated by EFLs (7). This was observed in the present study independent of the interpretation mechanism used by the devices. Despite the reduction of the precision values presented by Apex ID, it still offered the best results at this level (0.38 mm, 68.5%), with a statistically significant difference than Root ZX II (0.52 mm, 49.1%). Because there is a lack of similar studies evaluating the accuracy of EFLs on root canals without foraminal patency in the literature, it was difficult to compare the results of our study; however, the accuracy of the tested devices appeared to be affected differently by the inability to reach the AF because of an obstruction. The results obtained with Root ZX II were significantly lower than those observed without the obstruction and than the other EFLs at both levels (0.0 and 1.0). This suggests that the presence of dentin plugs, which make the passage of a current through the root canal difficult, and the inability to reach the AF significantly interfered with the accuracy of this device. As for Propex II, the values obtained in canals with an obstructed foramen were similar to those obtained at 1.0, suggesting that the inability of the file tip to reach the AF caused by an obstruction did not lead to additional errors by the device. The results offered by Apex ID in the canals without patency were similar to those observed at 0.0, suggesting that the impossibility of accessing the AF because of an obstruction does not influence its operating mechanism. Moreover, closure of the periodontium appears to improve the accuracy of the device for determining the length of the root canal compared with the limitation of the 1.0 position. Although the mesial root canal of inferior molars was used to examine the accuracy of the 3 EFLs in this study, it did not appear to interfere with the measurement error or the accuracy values of the devices. However, the absence of foraminal patency because of the clogging of the AF produced distinct behaviors between the 3 EFLs. These results suggest that the operating mechanisms of the 3 devices are TABLE 4. Error Distribution between the Real Length and the Actual Length Presented in the Device Displays Considering the Measurements in Canals with an Obstructed Foramen (dentin plugs of 0.5 0.2 mm) Divergence (mm) between the real length and the display
Root ZX II
Propex II
Apex ID
n
%
n
%
n
%
<
10 24 22 1 0
17.5 42.1 38.6 1.8 0.0
2 7 17 30 1
3.5 12.3 29.8 52.6 1.8
2 1 11 43 0
3.5 1.8 19.3 75.4 0.0
1.51* 1.01 to 1.50* 0.51 to 1.00* 0.01 to 0.50* 0.00
*Negative value indicates file position short (or coronal) to the apical foramen.
Apical Patency and Accuracy of Foramen Locators
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Basic Research—Technology influenced by this clinical condition; therefore, it is important that a professional using these devices is aware of this limitation to define protocols that make it possible to obtain more satisfactory results.
Conclusion In accordance with the findings from this study, it can be concluded that the absence of foraminal patency provided by a dentinal debris obstruction has different effects on the accuracy of the 3 EFLs evaluated. Although the accuracy of Root ZX II was significantly reduced, the accuracy of Propex II was slightly lower than that found at 0.0 mm. Apex ID did not appear to suffer any interference in the presence of a foraminal obstruction. Furthermore, no differences were observed among the devices when the instrument reached the apical foramen.
Acknowledgments Supported by FUNCAP (#PJP-0072-00098.01.00/12). The authors deny any conflicts of interest related to this study.
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