|Year : 2015 | Volume
| Issue : 1 | Page : 24-28
Accuracy of Root ZX apex locator in primary teeth with different root canal irrigants: An in vivo study
P Poornima, Gaurav Ramchandani, IE Neena, NM Roshan, R Basavanna, NB Nagaveni
Department of Pedodontics and Preventive Dentistry, College of Dental Sciences, Davangere, Karnataka, India
|Date of Web Publication||4-Jun-2015|
I E Neena
Department of Pedodontics and Preventive Dentistry, College of Dental Sciences, Pavilion Road, Davangere - 577 004, Karnataka
Source of Support: None, Conflict of Interest: None
Objective: The aim of this in vivo study was to determine the accuracy of 3 rd generation apex locator (Root ZX) in determining the canal length in primary teeth with normal saline and 0.12% chlorhexidine as root canal irrigants. Study Design: A total of 36 primary anterior teeth with minimum of 2/3 rd root lengths (indicated for extraction) were selected for this study. Working length (WL) was measured in dry, saline and chlorhexidine mode respectively and the standardized WL was measured using stereomicroscope under ×30. The data were evaluated using one-way ANOVA and Tukey's post-hoc test using SPSS software version 19 (IBM Company). The critical value for statistical significance was 5%. Results : For teeth without root resorption, the accuracy of Root ZX was 83% in dry mode and 92% in saline and chlorhexidine mode. For root canals with resorption the accuracy of Root ZX was 67% in dry mode and 83% in saline and chlorhexidine mode within ± 1 mm. However these figures decreased to 17%, 58% and 75% without resorption and 0%, 17% and 50% with resorption respectively for within ± 0.5. No significant differences were detected between the three different modes with the tolerance ± 1 mm under without resorption. However, significant difference was found without resorption as well as with resorption under tolerance ± 0.5 mm. Conclusion: The study concluded that Root ZX electronic Root apex locator is accurate with tolerance ± 1 mm in determining the root canal length in primary teeth without root resorption under different root canal irrigants that is, saline and chlorhexidine.
Keywords: Primary teeth, resorption, root canal irrigants, Root ZX apex locator, working length
|How to cite this article:|
Poornima P, Ramchandani G, Neena I E, Roshan N M, Basavanna R, Nagaveni N B. Accuracy of Root ZX apex locator in primary teeth with different root canal irrigants: An in vivo study. Niger J Exp Clin Biosci 2015;3:24-8
|How to cite this URL:|
Poornima P, Ramchandani G, Neena I E, Roshan N M, Basavanna R, Nagaveni N B. Accuracy of Root ZX apex locator in primary teeth with different root canal irrigants: An in vivo study. Niger J Exp Clin Biosci [serial online] 2015 [cited 2017 May 24];3:24-8. Available from: http://www.njecbonline.org/text.asp?2015/3/1/24/158161
| Introduction|| |
The important measure during root canal treatment in primary teeth is determination of working length (WL) to minimize periapical injury and possible damage to the permanent successor germ.  WL determination can be done by digital tactile sense technique or by conventional radiographic method, but both techniques present some limitations. The digital tactile sense technique requires that the clinician be trained and have experience.  Radiography is traditionally used to obtain information about root canal anatomy, WL and the surrounding apical tissues. The accurate determination of root canal length radiographically is hindered because of the anatomical variations, interference of anatomical structures or errors in projection.  Moreover, it is often difficult to obtain a diagnostic radiograph in children because of poor patient cooperation and limited access to the mouth.  Specific problems which are characteristic of primary teeth include thin root canal walls further instrumentation of these canals may result in perforation or root fractures. In addition, the primary teeth resorb during eruption of their permanent successors also radiographic determination of canal length may give misleading results when lateral canals are present. One of the critical steps of pulpectomy in primary teeth is WL determination as there is presence of root resorption. Minor degrees of root resorption may not be obvious radiographically and more extensive resorption should be considered as a contraindication for root canal treatment. 
Use of electronic apex locator (Root ZX) for determining WL has reduced radiation dosage and time.  In 1918, Custer was the first to develop the idea that root canal length could be estimated by the use of an electrical current. The electrical resistance between the periodontal ligament and oral mucosa has a constant value that could be measured using electronic apex locator.  Most studies have focused on the investigation into these new technologies for determining the root canal length in permanent teeth. However this is probably more difficult in the primary dentition, because of its altered anatomy and various stages of apical resorption. 
Nevertheless, investigators report and recommend the necessity for further clinical studies.  The accuracy of electronic root canal measuring devices is influenced by moisture content in root canals and the diameter of apical foramen. The Root ZX (J. Morita, corp., Tokyo, Japan) (developed by Kobayashi and Suda) electronic apex locator, could able to detect narrowest diameter of the root canal under both wet and dry conditions. It uses the impedance ratio instead of impedance difference. Impedance values at two frequencies (8 and 0.4 kHz) and calculates a quotient of impedance by this method the measurements appear to be less accurate when the apical foramen is immature or large. Consequently, the wide foramen of resorbed canals in primary teeth might affect the electrical measurement of root canal length. Kielbasa et al. recommended using Root ZX in primary teeth that have undergone little or no resorption.  There are many published reports on the accuracy of determination of the WL with apex locators in permanent teeth but the information on primary teeth is limited. Most of the investigations are focused on in vitro evaluation but very few on clinical patients. Therefore the purpose of this in vivo study was to evaluate the accuracy of electronic apex locator in root canal length determination of primary teeth in the presence of different canal irrigants with or without root resorption.
| Materials and Methods|| |
A total of 36 primary teeth with minimum of 2/3 rd of root length present which were indicated for extraction were selected for the study. Teeth with radiographic evidence of root resorption of >1/3 were excluded from the study. Ethical clearance (Ref. No. CODS/2308/2010-2011) was obtained from the ethical committee of the institution. Informed written consent was signed by the parent or guardian of all the children who were included in the study. Local anesthesia was administered if required, and the study teeth were isolated with rubber dam. Endodontic access was made with #2 round carbide bur and the pulp extirpated with barbed broaches. The WL measurements were recorded by the following steps.
An access cavity was prepared and the pulp was extirpated completely from the chamber and canals. Then the canals were dried completely using paper points. A flat reference point was prepared and marked using a fine paint marker on the incisal surface of the teeth to allow for precise positioning of the test K-file for WL determination. K-files were used in this study due to the ability to lock the adjustable handle to the file creating an immovable stop. This feature allows precise file placement during testing. The size of the test K-file used was such that passive binding occurred as the file approached the estimated length.
In each tooth, electronic root length was first measured in dry mode. Root ZX electronic apex locator (EAL) was used to estimate the WL according to the manufacturer's protocol. No 15 K-type file with rubber stopper was connected to electrode and lip clip is attached to patients lip. The file is moved into the canal until it shows apex on liquid-crystal display screen and then it is retracted slowly till it is short of apex by 0.5 mm. The rubber stopper on the inserted file was then set to the incisal reference point. Later the file was removed, measured with a 0.5 mm precision endodontic ruler and registered as the electronic WL.
Saline was injected into the canal and electronic length was recorded after changing into wet mode according to the manufacturer's instruction. If the reading were stable for at least 5 s, then the electronic root canal length was measured and recorded.
Saline washed out from the canal with distilled water and then the canal was dried with paper points. 0.12% chlorhexidine was injected and then subsequently WL was measured.
After the WL determination of the teeth, extraction was carried out, and the standardized WL was measured with the help of stereomicroscope till the apical foramen or apical resorption bevel using a K-file with silicon stop. The length of the file was determined under computer scale and the actual length was taken by subtracting 0.5 mm and 1 mm separately.
| Results|| |
The data were evaluated using one-way ANOVA and Tukey's post-hoc test using SPSS software version 19 (IBM Company). The mean and standard deviation (in mm) of values obtained in teeth with resorption and without resorption in dry, saline and chlorhexidine are illustrated in [Table 1]. Mean root length values without root resorption and with root resorption are depicted in [Table 2] and [Table 3] respectively under different modes.
|Table 1: Comparison of mean root length values of dry, saline and CHX mode under SM with and without resorption|
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|Table 2: Comparison of mean root length values of dry, saline and CHX mode under SM in teeth without resorption|
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|Table 3: Comparison of mean root length values of dry, saline and CHX mode with SM in teeth with resorption|
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For Canals without Resorption
The accuracy of Root ZX was 83% in dry mode and 92% in saline as well as chlorhexidine mode. However when the tolerance was ± 0.5 mm, root canals without resorption showed 17% in dry mode, 58% in saline mode and 75% in chlorhexidine mode.
For Root Canals with Root Resorption
The accuracy of Root ZX was 67% in dry mode and 83% in saline and chlorhexidine mode (tolerance ± 1 mm). When under tolerance ± 0.5 mm was measured, it found to be 0%, 17% and 50% with dry, saline and chlorhexidine mode respectively.
| Discussion|| |
The present study showed that the Root ZX in dry mode was accurate 83% of the time while in saline and chlorhexidine mode accuracy was 92%; in teeth with resorption, the accuracy of Root ZX was 67% in dry mode and 83% in saline and chlorhexidine mode. The anatomic variations of the apical region make it difficult to locate the cemento dentinal junction (CDJ) and apical foramen. ,,, Determination of the apical foramen location, or WL analysis, has traditionally been performed using radiographic methods. However, there are limitations associated with image interpretation, like anatomical variations, interference of anatomical structures or errors in projection with radiographs. ,,
Various schools of thought exist for the determination of the root canal WL.
The importance of staying inside the root canal with the obturation and avoiding extrusion of material into the periapical tissues in order to obtain a higher success rate was stated by various research workers.  According to Schilder, the main aim of root canal treatment should be to debride and obturate till the apex, lateral canals, and apical ramifications. He opposed limitation of preparation at the CDJ at the apical constriction because he considered these as variables. Thus, it is too approximate to apply a mathematical or statistical formula (0.5, 1 or 2 mm). , Some recent investigations have determined the accuracy of measurement of electronic apex locators in primary teeth with and without resorption. However, only few investigations have been carried out to compare the electronic root canal measurements in presence of different root canal irrigants. Factors that may influence the accuracy of electronic apex locators are the size of apical foramen, type and size of measuring file, irrigation solution and electro conductivity of pulp.  The use of irrigating solutions is an important aspect of endodontic treatment. The irrigants investigated were saline and 0.12% chlorhexidine gluconate, which was suggested as an intracanal medicament (Kuruvilla and Kamath 1998, Lindskog et al, Segura et al. 1999). 
The present study was one of its first kind in vivo study done in primary teeth where different root canal irrigants that is, saline and 2% chlorhexidine were compared with the dry medium in measuring the canal length by Root ZX apex locator in 36 teeth. The main aim of the study was to check that, does the change in root canal irrigants have any influence on the WL determination in primary teeth undergoing physiologic root resorption and the teeth that were not showing any root resorption.
The results of this study showed that in every mode of measurement, the Root ZX EAL gives accurate results with statistically insignificant values in teeth with resorption and without resorption. These findings were also consistent with an in vitro study on permanent teeth done by Soujanya et al. that root canal irrigants did not influence their findings of Root ZX EAL; however they used saline, sodium hypochlorite and hydrogen peroxide as irrigants media; and an in vitro study on permanent teeth done by Kang and Kim where they checked the accuracy of seven different apex locators under different root canal irrigants viz. Saline, 5.25% ethylenediaminetetraacetic acid and at varying sizes of the apical foramen and concluded that Root ZX was accurate under different irrigants in root canal and varying sizes of the apical foramen. 
Nguyen et al. reported that different file size did not affect the accuracy of EAL. The study also concluded that if a potential error of + 1.0 mm from the apex was accepted as a tolerable range for the clinical application of electronic apex locator, than in determining the final WL in teeth without resorption. Our findings regarding the tolerance level was similar to the findings of a study done by Mesut Enes Odabas et al. who gave an accuracy of 95.82% within + 1.0 mm for root canals without resorption and an accuracy of 86.35% for root canals with resorption when the samples were analyzed in vivo. Another study done by Beltrame et al.  gave an accuracy of 92% both for root canals with and without resorption at a tolerance level of + 1.0 mm, similarly in vivo study done by Duran-Sindreu et al.  who found an overall accuracy of 100% of the time to + 1.0 mm. However in our study we tested accuracy along with different irrigant medias, which showed the values with resorption were comparatively less accurate than without resorption and chlorhexidine was found to be more accurate compared to dry and saline mode although not significant.
Studies done be Berman and Fleischman in 1984, Hulsmann and Pieper in 1989, Saito and Yamashita in 1990, Fouad et al. in 1993 and Kaufman and Katz in 1993, indicated that the electronic apex locator measurements in roots with a wider apical foramen were shorter than the actual canal length. This was claimed to be due to the fact that apical foramen was wide with flared canal configuration due to the immature root configuration.  However in the present study no such difference was found in the root length measurements in teeth which had root resorption or teeth without root resorption with the actual root length as measured by stereomicroscope. This may be attributed by the fact that when root length becomes shorter than 7 mm the apices tended to have an increase in vertical and horizontal resorption and consequently increase in diameter. The root lengths in the present study were on an average 13 mm. The results obtained in the present study were thus in confirmation with the studies done by Mente et al. and Kielbasa et al. in 2003 that the presence or absence of root resorption does not influence the findings on root length when measured by electronic apex locator. 
Huang had demonstrated that the moisture content of root canal does influence the accuracy of electronic root canal measurements, although when the foramen was sufficiently small, it did not disturb the accuracy of electronic root canal measurement.  However in the present study the irrigant medias used did not influence the findings of electronic apex locators in fact it gave a better result than a dry mode. These findings were consistent with the in vitro findings of studies done by Mull et al. and Carvalho et al. ,
| Conclusion|| |
Under the experimental conditions of this in vivo study the following conclusions can be drawn:
- When Root ZX apex locator was used to measure the root canal length in primary teeth in dry mode, with saline and chlorhexidine as root canal irrigants in teeth with and without resorption, the values obtained were statistically insignificant.
- Although, the measurement of EAL was more accurate in teeth without resorption than teeth with resorption and was more accurate with irrigants than under dry mode.
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[Table 1], [Table 2], [Table 3]