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Effect of preflaring on Root ZX apex locators
JOURNALOF ENDODONTICS Copyright © 1999 by The American Association of Endodontists
Printed in U.S.A. VOL. 25, No. 9, SEPTEMBER1999
CLINICAL ARTICLES Effect of Preflaring on Root ZX Apex Locators Jose L. Ibarrola, DDS, MS, Brent L. Chapman, DDS, James H. Howard, DDS, MS, Kenneth I. Knowles, DDS, MS, and Marvin O. Ludlow, DDS, MS
The Root ZX apex Iocator is an example of a generation of apex Iocators that identify the terminus of the canal by measuring a ratio between two electrical impedances. Studies have shown this device to have a high degree of accuracy. However, the manufacturer warns that the performance of these devices is limited by the presence of calcifications and dentinal shaving obstructions. An in vitro study was designed to determine if preflaring of canals would facilitate the passage of files to the apical foramen by eliminating cervical interferences and to see what effect this would have on the performance of the Root ZX apex Iocator. Thirty-two canals were divided into two groups. Group 1 was not manipulated before use of the Root Zx apex Iocator and served as control. In group 2, the canals were preflared before the use of the Root ZX apex Iocator. The working length files were secured in place and measured with the linear measurement tool used by the Visilog 5 imaging program. Results of this study suggest that preflaring of canals will allow working length files to more consistently reach the apical foramen (p = 0.015), which in turn increases the efficacy of the Root ZX apex Iocator.
taining solutions. A number of these devices have been introduced in the market. Studies have placed the accuracy of these devices in the range of 83% to 93.4% (4). Shabahang et al. (5) specifically tested the accuracy of the Root Zx apex Iocator (J. Morita Corp., Kyoto, Japan) in vivo and located the apical foramen of 26 vital teeth with an accuracy rate of 96.2%, while allowing 0.5 mm for margin of error. Lack of patency and accumulation of debris in canals have been reported as impediments tbr the establishment of accurate working lengths. Stabholtz et al. (6) analyzed the effect that prefiaring of canals might have on the tactile sensitivity of operators who attempted to manually locate the apical constriction, and tbund preflaring of canals to significantly enhance the tactile sensitivity of the investigators. They observed that the geatest binding of files occurred in the coronal third of canals and that by enlarging the canal orifices and eliminating cervical interferences, files could be passed more easily to the apices of teeth. Calcifications and accumulation of dentinN shavings are said to interfere with the performance of electronic apex locators (7), and it has also been shown that packing of debris in the apic'al third of the canal will affect the accuracy of these devices (8). It is not known what effect the elimination of cervical interferences has on the pedbrmance of electronic apex locators. An in vitro study was des;gned to determine it" preflating of canals would improve the efficacy of Root ZX apex locators. M A T E R I A L S AND M E T H O D S Sixteen mesial roots of mandibular molars were used for this study. Only roots with Weine's type III canal configuration were used, giving a total of 32 canals. The canals were then divided into 2 groups of 16 canals each. In group 1, the canals were not manipulated before utilization of the electronic apex locator and served as the control group. Group 2 was the experimental group in which the canals were preflared before using the electronic apex locator. An in vitro model similar to the one that Aurelio et al. (9) used to compare the accuracy of several electronic apex locators was used in this study. This model consists of a test tube filled with an agar suspension that was mixed with saline solution with a nail inserted at the bottom of the test tube to complete the circuit. In our study, the agar was substituted with commercial gelatin as described by Czerw et al. (10). After gaining access, the pulp chamber was irrigated with distilled water to remove any debris. Canals in group 2 were preflared with Profile .04 taper rotary instruments (Tulsa Dental Products, Tulsa, OK) sizes 9 to 6 in a crown-down fashion. Canals were again irrigated with distilled water. A #10 file was introduced into all of the canals, and the electronic apex locator was connected to the ground nail that was
In 1942, Suzuki (1) found the electrical resistance of the periodontal membrane and that of the oral mucosa to share a constant value of - 6 . 5 kiloOhms. In 1962, Sunada (2) applied this principle to clinical practice by incorporating this resistance value into the electronic circuitry that was contained in prototype electronic canal measuring devices. These devices allowed measurement of the canal length by comparing the electrical resistance that was built into the apex locator with the resistance between the tip of the file and that of the periodontal membrane. Ensuing technology that measured the ratio between two electrical impedances emitted from a probing instrument was applied to the circuitry of newer generation electronic apex locators. This allowed these devices to circumvent some of the limitations of electrical resistance type apex locators, which could not be used in the presence of electrolyte-containing solutions, such as sodium hypochlorite or blood, limiting their usefulness to relatively dry canals. Fouad et al. (3) showed that impedance type apex locators could be accurately used in the presence of various electrolyte-con-
625
626
Ibarrola et al.
Journal of Endodontics
TABLE 1. Distance (mm) from apical constriction to tip of file Prefiared Canals
Unflared Canals (Control)
0.00 -0.90 -0.21 0.28 0.00 0.00 0.19 0.00 -0.13 0.41 0.67 0.31 0.00 0.00 0.00 0.15
-0.16 0.00 0.22 0.48 0.00 1.09 0.30 0.04 1.95 0.19 1.73 0.13 0.00 0.23 0.34 0.20
inserted into the test tubes. After establishing apical patency, the files were clipped to the file holder of the apex locator and advanced apically until the indicator display showed that the apical foramen had been reached. The files were then secured in place by tkst applying cyanoacrylate cement, and then filling the pulp chamber with a fight-cured resin. Mesial roots were sectioned with a fissure bur ha a high-speed handpiece. These roots were then thinned with a sandpaper disc until the apical foramen and tip of the file became visible. Samples were analyzed with a Leica DML microscope that was calibrated at ×2.5 ma~litication and a measurement was made from the apical constriction to the tip of the file with the linear measurement tool used by the Visilog 5 imaging software progrmn (Noesis Vision, Quebec, Canada). Measurements were compiled and statistically analyzed. RESULTS The distances obtained in all samples, between the apical constriction and the tip of the file, are presented in Table 1. A negative number signified the distance that the file extended past the apical constriction. A t test, comparing the means of the two groups (Table 2), showed the preflared group to be significantly different from the control group (p = 0.015). The mean of the experimental group was 0.04 mm vs. 0.4 mm for the control group.
TABLE 2. t test: paired two samples for means Preflared Mean Variance Observations Pearson correlation Hypothesized mean difference df t Statistics p (T _-< t) one-tailed t critical one-tailed p (T <= t) two-tailed t critical two-tailed
0.048125 0.11227 16 0.279815 0 15 2.41343 0.014526 1.753051 0.029052 2.131451
Unflared 0.42125 0.386785 16
Statistical analysis shows that the Preflared results are significantly different from the Unflared results (P 0.015).
We also found the model described by Aurelio et al. (9) to be reliable when testing apex locators in vitro, because most of the samples were right at or within 0.5 mm from the apical constriction. In our opinion, the higher accuracy observed in the preflared group was due to the ability to more consistently have unimpeded access to the apex by removing interferences that were coronal to the apical third. It would have been of interest to see if measurements changed within the same canals before and after preflaring. However, this was not possible because the files had to be secured and the roots thinned in order to use the Visiliog 5 linear measurement tool. Overall, the Root ZX apex locator was found to be an accurate measuring instrument. In 14 of 16 pmflared samples, the apex locator reading was within 0.5 mm of the apical constriction. In the nonfl~ed group, the apex locator reading was within 0.5 mm in 13 of 16 samples. The results of this study showed a statistical difference between the means of the two groups, which suggests that more consistent results were obtained in the preflared group. However, the clinical significance of these findings might be limited, because measurements in both groups were comparable with a mean of 0.04 on the preflared group vs. 0.4 in the control group. Dr. Ibarrola is assistant professor, Department of Endodontics; Dr. Chapman is a former fourth-year student; Dr. Howard is associate professor, Comprehensive Dental Care; Dr. Knowles is associate professor, Department of Endodontics; and Dr. Ludlow is chairman, Department of Endodontics, Creighton University School of Dentistry, Omaha, NE. Address requests for reprints to Dr. Jose L Ibarrola, Creighton University School of Dentistry, 2500 California Plaza, Omaha, NE 68178.
DISCUSSION The results of this study show a statistical difference between the two groups. However, all canals where canal patency was maintained showed no measurable differences. ]'he statistical difference was due to three samples in the nortflared group that had an excessive deviation from the rest of the measurements. In all three of these canals, overall canal patency was compromised due to blockage of the canal by dentinal shavings limiting the ability of the measuring device to determine the location of the apical tbramen. It is interesting to note that this did not occur in any of the preflared samples. In preflaring the canals, the Profile (Tulsa Dental 15oducts) insmamentation system was used. Reddy and Hicks (l l) showed engine-driven rotxtrydevices to significantly reduce the amount of dentinal debris that is extruded apically when compared with step-back instrumentation. This could explain the more consistent results obtained in the group that was preflared. It is not known whether the same results can be obtained by preflaring the canals with Gates-Glidden drills. Our results were in agreement with Stabholtz et al. (6), in that the apical loramen could be reached more consistently by preflaring the canals before obtaining working length.
References 1. Suzuki K. Experimental studies on iontophoresis. J Jpn Stomato11942; 16:411. 2. Sunada I. New method for measuring the length of the root canal. J Dent Res 1962;41:365. 3. Fouad AF, Rivera EM, Krell KV. Accuracy of the Endex with variations in canal irrigants and foramen size. J Endodon 1993;2:63-7. 4. McDonald NJ. The electronic determination of working length. Dent Clin North Am 1992;36:293-307. 5. Shabahang S, Goon WWY, Gluskin AH. An in vivo evaluation of Root ZX electronic apex Iocator. J Endodon 1996;22:616-8. 6. Stabholz A, Rotstein I, Torabinejad M. Effect of preflaring on tactile detection of the apical constriction. J Endodon 1995;21:92-4. 7. J. Morita Mfg. Corp. Root ZX operation manual. J. Morita Mfg. Corp., 1994. 8. Rivera EM, Seraji MK. Effect of recapitulation on accuracy of electronically determined canal length. Oral Surg 1993;76:225-30. 9. Aurelio AA, Nahmias Y, Gerstein H. A model for demonstrating an electronic canal length measuring device. J Endodon 1983;9:568-9. 10. Czerw RJ, Fulkerson MS, Donnelly JC. An in vitro test of a simplified model to demonstrate the operation of electronic root canal measuring devices. J Endodon 1994;20:605-6. 11. Reddy SA, Hicks ME Apical extrusion of debris using two hand and two rotary instrumentation techniques. J Endodon 1998;24:180-3.
Printed in U.S.A. VOL. 25, No. 9, SEPTEMBER1999
CLINICAL ARTICLES Effect of Preflaring on Root ZX Apex Locators Jose L. Ibarrola, DDS, MS, Brent L. Chapman, DDS, James H. Howard, DDS, MS, Kenneth I. Knowles, DDS, MS, and Marvin O. Ludlow, DDS, MS
The Root ZX apex Iocator is an example of a generation of apex Iocators that identify the terminus of the canal by measuring a ratio between two electrical impedances. Studies have shown this device to have a high degree of accuracy. However, the manufacturer warns that the performance of these devices is limited by the presence of calcifications and dentinal shaving obstructions. An in vitro study was designed to determine if preflaring of canals would facilitate the passage of files to the apical foramen by eliminating cervical interferences and to see what effect this would have on the performance of the Root ZX apex Iocator. Thirty-two canals were divided into two groups. Group 1 was not manipulated before use of the Root Zx apex Iocator and served as control. In group 2, the canals were preflared before the use of the Root ZX apex Iocator. The working length files were secured in place and measured with the linear measurement tool used by the Visilog 5 imaging program. Results of this study suggest that preflaring of canals will allow working length files to more consistently reach the apical foramen (p = 0.015), which in turn increases the efficacy of the Root ZX apex Iocator.
taining solutions. A number of these devices have been introduced in the market. Studies have placed the accuracy of these devices in the range of 83% to 93.4% (4). Shabahang et al. (5) specifically tested the accuracy of the Root Zx apex Iocator (J. Morita Corp., Kyoto, Japan) in vivo and located the apical foramen of 26 vital teeth with an accuracy rate of 96.2%, while allowing 0.5 mm for margin of error. Lack of patency and accumulation of debris in canals have been reported as impediments tbr the establishment of accurate working lengths. Stabholtz et al. (6) analyzed the effect that prefiaring of canals might have on the tactile sensitivity of operators who attempted to manually locate the apical constriction, and tbund preflaring of canals to significantly enhance the tactile sensitivity of the investigators. They observed that the geatest binding of files occurred in the coronal third of canals and that by enlarging the canal orifices and eliminating cervical interferences, files could be passed more easily to the apices of teeth. Calcifications and accumulation of dentinN shavings are said to interfere with the performance of electronic apex locators (7), and it has also been shown that packing of debris in the apic'al third of the canal will affect the accuracy of these devices (8). It is not known what effect the elimination of cervical interferences has on the pedbrmance of electronic apex locators. An in vitro study was des;gned to determine it" preflating of canals would improve the efficacy of Root ZX apex locators. M A T E R I A L S AND M E T H O D S Sixteen mesial roots of mandibular molars were used for this study. Only roots with Weine's type III canal configuration were used, giving a total of 32 canals. The canals were then divided into 2 groups of 16 canals each. In group 1, the canals were not manipulated before utilization of the electronic apex locator and served as the control group. Group 2 was the experimental group in which the canals were preflared before using the electronic apex locator. An in vitro model similar to the one that Aurelio et al. (9) used to compare the accuracy of several electronic apex locators was used in this study. This model consists of a test tube filled with an agar suspension that was mixed with saline solution with a nail inserted at the bottom of the test tube to complete the circuit. In our study, the agar was substituted with commercial gelatin as described by Czerw et al. (10). After gaining access, the pulp chamber was irrigated with distilled water to remove any debris. Canals in group 2 were preflared with Profile .04 taper rotary instruments (Tulsa Dental Products, Tulsa, OK) sizes 9 to 6 in a crown-down fashion. Canals were again irrigated with distilled water. A #10 file was introduced into all of the canals, and the electronic apex locator was connected to the ground nail that was
In 1942, Suzuki (1) found the electrical resistance of the periodontal membrane and that of the oral mucosa to share a constant value of - 6 . 5 kiloOhms. In 1962, Sunada (2) applied this principle to clinical practice by incorporating this resistance value into the electronic circuitry that was contained in prototype electronic canal measuring devices. These devices allowed measurement of the canal length by comparing the electrical resistance that was built into the apex locator with the resistance between the tip of the file and that of the periodontal membrane. Ensuing technology that measured the ratio between two electrical impedances emitted from a probing instrument was applied to the circuitry of newer generation electronic apex locators. This allowed these devices to circumvent some of the limitations of electrical resistance type apex locators, which could not be used in the presence of electrolyte-containing solutions, such as sodium hypochlorite or blood, limiting their usefulness to relatively dry canals. Fouad et al. (3) showed that impedance type apex locators could be accurately used in the presence of various electrolyte-con-
625
626
Ibarrola et al.
Journal of Endodontics
TABLE 1. Distance (mm) from apical constriction to tip of file Prefiared Canals
Unflared Canals (Control)
0.00 -0.90 -0.21 0.28 0.00 0.00 0.19 0.00 -0.13 0.41 0.67 0.31 0.00 0.00 0.00 0.15
-0.16 0.00 0.22 0.48 0.00 1.09 0.30 0.04 1.95 0.19 1.73 0.13 0.00 0.23 0.34 0.20
inserted into the test tubes. After establishing apical patency, the files were clipped to the file holder of the apex locator and advanced apically until the indicator display showed that the apical foramen had been reached. The files were then secured in place by tkst applying cyanoacrylate cement, and then filling the pulp chamber with a fight-cured resin. Mesial roots were sectioned with a fissure bur ha a high-speed handpiece. These roots were then thinned with a sandpaper disc until the apical foramen and tip of the file became visible. Samples were analyzed with a Leica DML microscope that was calibrated at ×2.5 ma~litication and a measurement was made from the apical constriction to the tip of the file with the linear measurement tool used by the Visilog 5 imaging software progrmn (Noesis Vision, Quebec, Canada). Measurements were compiled and statistically analyzed. RESULTS The distances obtained in all samples, between the apical constriction and the tip of the file, are presented in Table 1. A negative number signified the distance that the file extended past the apical constriction. A t test, comparing the means of the two groups (Table 2), showed the preflared group to be significantly different from the control group (p = 0.015). The mean of the experimental group was 0.04 mm vs. 0.4 mm for the control group.
TABLE 2. t test: paired two samples for means Preflared Mean Variance Observations Pearson correlation Hypothesized mean difference df t Statistics p (T _-< t) one-tailed t critical one-tailed p (T <= t) two-tailed t critical two-tailed
0.048125 0.11227 16 0.279815 0 15 2.41343 0.014526 1.753051 0.029052 2.131451
Unflared 0.42125 0.386785 16
Statistical analysis shows that the Preflared results are significantly different from the Unflared results (P 0.015).
We also found the model described by Aurelio et al. (9) to be reliable when testing apex locators in vitro, because most of the samples were right at or within 0.5 mm from the apical constriction. In our opinion, the higher accuracy observed in the preflared group was due to the ability to more consistently have unimpeded access to the apex by removing interferences that were coronal to the apical third. It would have been of interest to see if measurements changed within the same canals before and after preflaring. However, this was not possible because the files had to be secured and the roots thinned in order to use the Visiliog 5 linear measurement tool. Overall, the Root ZX apex locator was found to be an accurate measuring instrument. In 14 of 16 pmflared samples, the apex locator reading was within 0.5 mm of the apical constriction. In the nonfl~ed group, the apex locator reading was within 0.5 mm in 13 of 16 samples. The results of this study showed a statistical difference between the means of the two groups, which suggests that more consistent results were obtained in the preflared group. However, the clinical significance of these findings might be limited, because measurements in both groups were comparable with a mean of 0.04 on the preflared group vs. 0.4 in the control group. Dr. Ibarrola is assistant professor, Department of Endodontics; Dr. Chapman is a former fourth-year student; Dr. Howard is associate professor, Comprehensive Dental Care; Dr. Knowles is associate professor, Department of Endodontics; and Dr. Ludlow is chairman, Department of Endodontics, Creighton University School of Dentistry, Omaha, NE. Address requests for reprints to Dr. Jose L Ibarrola, Creighton University School of Dentistry, 2500 California Plaza, Omaha, NE 68178.
DISCUSSION The results of this study show a statistical difference between the two groups. However, all canals where canal patency was maintained showed no measurable differences. ]'he statistical difference was due to three samples in the nortflared group that had an excessive deviation from the rest of the measurements. In all three of these canals, overall canal patency was compromised due to blockage of the canal by dentinal shavings limiting the ability of the measuring device to determine the location of the apical tbramen. It is interesting to note that this did not occur in any of the preflared samples. In preflaring the canals, the Profile (Tulsa Dental 15oducts) insmamentation system was used. Reddy and Hicks (l l) showed engine-driven rotxtrydevices to significantly reduce the amount of dentinal debris that is extruded apically when compared with step-back instrumentation. This could explain the more consistent results obtained in the group that was preflared. It is not known whether the same results can be obtained by preflaring the canals with Gates-Glidden drills. Our results were in agreement with Stabholtz et al. (6), in that the apical loramen could be reached more consistently by preflaring the canals before obtaining working length.
References 1. Suzuki K. Experimental studies on iontophoresis. J Jpn Stomato11942; 16:411. 2. Sunada I. New method for measuring the length of the root canal. J Dent Res 1962;41:365. 3. Fouad AF, Rivera EM, Krell KV. Accuracy of the Endex with variations in canal irrigants and foramen size. J Endodon 1993;2:63-7. 4. McDonald NJ. The electronic determination of working length. Dent Clin North Am 1992;36:293-307. 5. Shabahang S, Goon WWY, Gluskin AH. An in vivo evaluation of Root ZX electronic apex Iocator. J Endodon 1996;22:616-8. 6. Stabholz A, Rotstein I, Torabinejad M. Effect of preflaring on tactile detection of the apical constriction. J Endodon 1995;21:92-4. 7. J. Morita Mfg. Corp. Root ZX operation manual. J. Morita Mfg. Corp., 1994. 8. Rivera EM, Seraji MK. Effect of recapitulation on accuracy of electronically determined canal length. Oral Surg 1993;76:225-30. 9. Aurelio AA, Nahmias Y, Gerstein H. A model for demonstrating an electronic canal length measuring device. J Endodon 1983;9:568-9. 10. Czerw RJ, Fulkerson MS, Donnelly JC. An in vitro test of a simplified model to demonstrate the operation of electronic root canal measuring devices. J Endodon 1994;20:605-6. 11. Reddy SA, Hicks ME Apical extrusion of debris using two hand and two rotary instrumentation techniques. J Endodon 1998;24:180-3.