A COMPARATIVE EVALUATION OF THE ACCURACY OF THIRD GENERATION ELECTRONIC APEX LOCATOR (ROOT ZX) IN PRESENCE OF VARIOUS INTRACANAL IRRIGANTS.

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1 A COMPARATIVE EVALUATION OF THE ACCURACY OF THIRD GENERATION ELECTRONIC APEX LOCATOR (ROOT ZX) IN PRESENCE OF VARIOUS INTRACANAL IRRIGANTS. YOGESH GOEL* SHASHI RASHMI ACHARYA** KUNDABALA M.*** VASUDEV BALLAL**** ABSTRACT This study aimed to evaluate the accuracy of Root ZX in determining working length in presence of normal saline, 0.2% chlorhexidine and 2.5% of sodium hypochlorite. Thirty extracted, single rooted, single canal human teeth were used. Teeth were sectioned at CEJ and actual canal length determined. Then working length measurements were obtained with Root ZX in presence of normal saline, 0.2% chlorhexidine and 2.5% NaOCl. The working length obtained with Root ZX were compared with actual canal length and subjected to statistical analysis. No statistical significant difference was found between actual canal length and Root ZX measurements in presence of normal saline and 0.2% chlorhexidine. Highly statistical difference was found between actual canal length and Root ZX measurements in presence of 2.5% of NaOCl, however all the measurements were within the clinically acceptable range of ± 0.5mm. Overall Root ZX measurements were within 0.5mm of the actual canal length 100% of the time. The results of this study indicate that the Root ZX accurately determine the working length even in presence of intra canal irrigating solutions. Key words: Electronic Apex Locator, Root ZX, working length, intracanal irrigating solutions Introduction Electronic apex locators have been used clinically for over 0 years as an aid in deciding where canal preparation and obturation should terminate. Suzuki 1 in 1942 first studied the flow of current through teeth. He found that a constant electric resistance was obtained between an electrode attached to a root canal instrument and one applied to the oral mucous membrane. In 1962, Sunada determined this constant electrical resistance to be 6.5 kilo ohms and stated that it is possible to use this value of resistance in the estimation of root canal length 2. Huang later suggested, in 1987, that principle of electronic apex locators (EALs) do not depend on the resistance of biological tissues, but rather on the physics of electricity. The Root ZX, marketed by J. Morita Corporation, uses the ratio method for measuring the root canal length. The ratio method simultaneously measures the impedances of the canal contents using two different frequencies (400 Hz and 8 khz) and calculates the quotient of the impedances. This quotient is used to denote the position of the file inside the canal 4. The * Post Graduate Student, ** Associate Professor, *** Professor and Head, **** Assitant Professor, Dept. of Conservative Dentistry and Endodontics. Manipal College of Dental Sciences, Manipal. Karnataka. 28

2 manufacturer says that Root ZX is accurate even when the canal is filled with electrolytes, such as sodium hypochlorite, saline, tap water or hydrogen peroxide. Shabahang et al in a 1996 clinical study found the root ZX to be accurate within ± 0.5 mm 96.2% of the time in presence of saline 5. However, the 1998 clinical survey by Dunlap et al which did include sodium hypochlorite irrigation, reported a 82.% accuracy of Root ZX within ± 0.5 mm 6. Chlorhexidine has now become the irrigant of choice along with NaOCl. However there is paucity of research regarding the accuracy of Root ZX in presence of commonly used endodontic irrigant chlorhexidine. The purpose of the study was to examine the accuracy of Root ZX in the presence of sodium hypochlorite, chlorhexidine and saline. MATERIALS AND METHODS The in vitro model chosen for this research project was based on the model designed by Donnelly 7. This model consists of mixing one package of sugar free gelatin (Bakers Ind Ltd.) with 0.9% sodium chloride used as a substitute for tap water. The warmed solution was then poured into plastic cup and refrigerated for at least 2 hours to allow the liquid to gel. Thirty single rooted extracted teeth with mature apices and no resorptive defects were used in this study. Teeth were sectioned at CEJ and canal patency verified with size 10 K file (Dentsply, Malliefer). The actual canal lengths were determined by placing a size 15 K file into the canal until the tip of the file was just visible at apical foramen using x magnification (Carl Zeiss). Coronal third of each canal was enlarged using Gates Glidden drills in crown down manner. Canals were irrigated with distilled water during the access preparation and flaring. All the specimens were stored in distilled water until working length determination done using Root ZX. The tip of metal clip of Root ZX were placed into the gelatin and stabilized. For each tooth, the canal was dried with paper points. The 0 specimens were divided into three groups of 10 teeth each. For group 1 the teeth were irrigated with 0.9% sodium chloride (normal saline). For group 2 the irrigating solution used was 0.2% chlorhexidine and 2.5% sodium hypochlorite was used as irrigating solution for group. Canals were irrigated with 5ml irrigating syringe and 24 gauge needle. The tip of the tooth was placed into the gelatin. Root ZX was turned on and file holder was attached to no 10 K file. The length were measured according to the manufacturer s instruction (Root ZX owner s manual). While holding the apex of the tooth into gelatin, the file was inserted slowly into the canal until the device indicated the apex location. For each group, the measurements were taken three times per tooth and recorded. The difference between root ZX measurements and the actual canal length was calculated for each tooth and the mean values were calculated for each group. The mean value was subjected to statistical analyses using One Sample T Test. Intergroup statistical analysis was done using ANOVA and TUKEY HSD test. Results and Analysis The values for actual canal length for all the thirty specimens are given in table 1. 29

3 Table 2, and 4 show the values of working length as determined by Root ZX and difference with the actual canal length for group 1, 2 and respectively. The mean values of difference between the actual canal length and Root ZX measurements for all the three groups are given in Table 5. In Group 1 (normal saline), the mean Root ZX measurement was -5 mm from the actual canal length with a standard deviation of In group 2 (0.2% CHX), the mean Root ZX measurement was 5 mm from the actual canal length with a standard deviation of In group (2.5% NaOCl), the mean Root ZX measurement was 0.4 mm from the actual canal length with a standard deviation of Statistical analysis using One Sample T Test (table 6) showed no statistical significant difference between actual canal length and length obtained by Root ZX for group 1 (p = 1.0). Also no statistical significant difference was found between group 2 and the actual canal length (p = 1.0). However, a high statistical difference was found between actual canal length and length obtained by Root ZX for group (p < 01). Intergroup statistical analysis (table 7) showed no statistical significant difference between group 1 and group 2 (p = 1.0). But a high statistical difference was found between group 1 and group (p < 01) and between group 2 and group (p < 01). The results indicate that Root ZX was accurate within ± 0.5 mm 100% of the time with all the three test irrigants. DISCUSSION The Electronic Apex Locator (EAL) helps in accurately determining the location of the apical foramen. Kuttler 8 and Green 9 have shown that the apex coincides with the anatomical foramen not more than 50% of the time. This limits the usefulness of radiographs, even, if the quality is excellent to determine working length. An excellent adjunct, therefore, is the use of an EAL. The present study, used an in vitro model as described by Donnelly 7 to obtain accurate measurements. The advantages of the model were its simplicity, ease of use and the ability to have strict control over the tested experimental condition. A disadvantage of the model is its inability to fully simulate in vivo conditions. However, Huang s finding tend support to the use of in vitro models in evaluating electronic apex locators. He concluded that when tip of the file passes through narrow apical foramen, the physical properties of the foramen itself produce the electrical resistance gradient. This resistance gradient is not caused by the biological characteristics of the periodontium as was discussed by Sunada 2. Previous studies have shown that EALs often yield inaccurate results in the presence of fluids 10. However, the use of irrigants and their benefits in endodontics have been clearly proven, and most clinicians use irrigants for their antimicrobial and tissue dissolving capabilities. Chlorhexidine has now become the irrigant of choice along with sodium hypochlorite due to the antimicrobial efficiency and less toxicity. However, there is paucity of research regarding the accuracy of EAL in presence of Chlorhexidine 11. It is of great importance that a clinician has confidence in the 0

4 accuracy of EAL, even in the presence of an irrigant. The results of this study showed that, Root ZX is 100% accurate within 0.5 mm from the apical foramen. The ± 0.5 mm to the foramen range has been considered as the strictest acceptable range (Foud et al , Ricard et al ). Thus, measurements attained within this tolerance are considered highly accurate. Although statistical significant difference was found between the Root ZX measurement in presence of 2.5% NaOCl and the actual canal length, all the measurements were within the clinically acceptable range of 0.5 mm. This variation with 2.5% NaOCl can be attributed to higher electroconductivity of NaOCl and to the fact that rate of change of impedance in presence of highly electroconductive solution was not large enough at the apical foramen to result in a clinically detectable reading (Kim et al 14 ). Working length determination using Root ZX have shown to be superior compared to radiographic measurements 15,16. Visualization of root canal curvature on radiographs is difficult and the radiographic assessment of file position in case of eccentric foramen is also scarcely reliable. In teeth with lateral foramen, the radiographic method to locate the apex is again poorly reliable. Furthermore, radiographs free of distortion are extremely difficult to obtain. Anatomic structures such as maxillary sinus and the zygomatic arch can also interfere with accurate radiographic visualization of the roots 17. So this limits the usefulness of radiographs to determine the working length. Root ZX has shown to be reliable method to determine the working length. The results of the study demonstrated that the Root ZX was able to consistently determine the location of the apical foramen (within approximately 0.5mm) in the presence of any of the tested irrigants. To conclude 1) Root ZX is a reliable tool to determine the working length. 2) Root ZX is accurate within ± 0.5 mm in presence of normal saline, 0.2% chlorhexidine and 2.5% NaOCl in determing the working length. Specimen no Table 1. Actual Canal Length Actual canal length Specimen no Actual canal length Specimen no Actual canal length Table 2. Root ZX measurement and difference with the actual canal length for Group 1 ( normal saline) Specimen no Root ZX measurement Difference 1

5 Table. Root ZX measurement and difference with the actual canal length for Group 2 (0.2%chlorhexidine). Specimen no Root ZX measurement Difference Table 4. Root ZX measurement and difference with the actual canal length for Group (2.5% NaOCl) Specimen no Root ZX measurement Table 5.Mean of difference Groups 1-0.9% Sodium chloride 2-0.2% Chlorhexidine -2.5% NaOCl Difference Mean ± Standard Deviation - 5 ± ± ± i j Table 6 : One Sample T Test Groups Group 1 Group 2 Group Table 7 : ANOVA and TUKEY HSD Test Mean difference(i-j) p <.001 Significance p 1.00 < < 01 < 01 < 01 REFERENCES: 1. Suzuki K. Experimental study on iontophoresis. Jpn J Stomatol 1942;16: Sunada I. New method for measuring length of the root canal. J Dent Res 1962;41: Huang L. An experimental study of the principle of electronic root canal measurement. J Endodon 1987;1: Kobayashi C, Suda H. New electronic canal length measuring device based on the ratio method. J Endodon 1994; 20: Shabahang S, Goon WW, Gluskin AH. An in vivo evaluation of Root ZX electronic apex locator. J Endodon 1996; 22: 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 Endodon 1998; 24: Donnelly JC. A simplified model to demonstrate the operation of electronic root canal measuring devices. J Endodon 199; 19: Kuttler Y. Microscopic investigation of the root apex. J Am Dent Assoc 1955;50: Green D. Stereomicroscopic study of the root apices of 400 maxillary and mandibular teeth. Oral Surg 1956;9: Frank AL, Torabinejad T. An in vivo evaluation of Endex electronic apex locator. J Endodon 199;19: Jenkins JA, Walker WA, Schindler WG, Flores CH.An invitro evaluation of the accuracy of the Root ZX in the presence 2

6 of various irrigants. J Endodon 2001; 27: Fouad AF, Krell KV, Mckendry DJ, Koorbusch GF, Olson RA. A clinical evaluation of five electronic root canal length measurement instruments. J Endodon 1990; 16: Ricard O, Roux D, Bourdeau L, Woda A. Clinical evaluation of the accuracy of the evident RCM Mark II apex locator. J Endodon 1991; 17: Kim DW, Nam KC, Lee SJ. Development of a frequency dependent type apex locator with automatic compensation. Crit Rev Biomed Eng 2000;28: Fouad AF, Reid LC. Effect of using apex locators on selected endodontic treatment parameters (abstract).j Endodon 1994; 24: Pratten DM, McDonald NJ. Comparison of radiographic & electronic working lengths. J Endodon 1996; 22: Tamse A, Kaffe I, Fishel D. Zygomatic arch interference with correct radiographic diagnoses in maxillary molar endodontics. Oral Surg 1980; 90: EDITOR S NOTE In the contents page of our last issue, the name of Dr. Gopikrishna was wrongly printed due to printing error. Dr. Gopikrishna is hereby acknowledged as the author of Newer Classification of Endodontic Flaps and Co-author of the following articles: 1. In-vitro Evaluation of Apical Microleakage of Thermafil and Obtura II Heated Gutta Percha in comparison with Cold Lateral Condensation Using Fluid Filtration System 2. Gutta-Percha - An untold story The editorial board welcomes donation or advertisements Back Outer Cover Rs. 15,000/- Front Inner Cover Rs.10,000/- Back Inner Cover Rs.10,000/- Full Page Colour Rs.5,000/- Full Page B/W Rs.,000/- The amount is payable at Mangalore by D.D. / Cheque / Pay Order in favour of Endodontology. The out-station Cheques should include Rs. 50/-