|Year : 2013 | Volume
| Issue : 3 | Page : 163-166
Accuracy of apex locator for root canal length determination of deciduous molars compared to conventional radiograph
G Sivadas1, P Sudha1, Ramya Shenoy2, Arathi Rao1, BS Suprabha1
1 Department of Paedodontics and Preventive Dentistry, Manipal College of Dental Sciences, Manipal University, Mangalore, Karnataka, India
2 Department of Public Health Dentistry, Manipal College of Dental Sciences, Manipal University, Mangalore, Karnataka, India
|Date of Web Publication||21-Apr-2014|
Department of Paedodontics and Preventive Dentistry, Manipal College of Dental Sciences, Manipal University, Mangalore, Karnataka
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: To assess whether apex locators are accurate in determining the root canal length in resorbing roots of deciduous tooth compared to the conventional radiographic method. Materials and Methods: Samples for the study included 30 primary maxillary and mandibular molar root canals in children of age group 5 to 12 years. Root canal lengths were determined with Conventional radiographs, Apex locator and direct measurements using stereomicroscope. Results: When the measurements from radiograph and apex locator were compared with direct measurements, they were non-significant with P value of 0.342 and 0.266 respectively and F value of 0.396 and 0.303, respectively. Conclusions: Apex locator and conventional radiograph both are proven to be accurate in working length determination in primary molars. Apex locators can thus be used in resorbing root canals of deciduous molars obtaining good results with no radiation hazard and processing difficulties.
Clinical Relevance to Interdisciplinary Dentistry
- Working length determination is one of the crucial steps for the final outcome of the endodontic procedure
- Apex locators work well in fully formed roots, but is it the same in cases of resorbing roots especially as seen in deciduous teeth
- The answer to the same question may be relevant in roots with external root resorption or in an immature root
Keywords: Apex locator, deciduous root canal, IOPA, resorbing roots
|How to cite this article:|
Sivadas G, Sudha P, Shenoy R, Rao A, Suprabha B S. Accuracy of apex locator for root canal length determination of deciduous molars compared to conventional radiograph. J Interdiscip Dentistry 2013;3:163-6
|How to cite this URL:|
Sivadas G, Sudha P, Shenoy R, Rao A, Suprabha B S. Accuracy of apex locator for root canal length determination of deciduous molars compared to conventional radiograph. J Interdiscip Dentistry [serial online] 2013 [cited 2019 Sep 15];3:163-6. Available from: http://www.jidonline.com/text.asp?2013/3/3/163/131209
| Introduction|| |
Working length determination forms one of the critical steps in endodontic treatment. Accurate determination of apical stop aids in limiting instrumentation within the confines of root canal and minimizes the damage to the developing tooth bud. The apex of the roots of deciduous teeth undergoes continuous change in the shape, dimension, and position. 
The irregular oblique resorption pattern in deciduous root canals makes it difficult to determine the apical foramen accurately. ,
Conventionally, radiographs are being used but this method has certain shortcomings like magnification and overlapping of images, difficulty in film placement and most of all to identify the exact foramina in a resorbing root. 
The apex locators are one of the breakthroughs that brought electronic science into the conventional endodontic practice. They operate on the basis of electrical impedance rather than visual inspection.  Apex locators are found to be accurate in the presence of canal contents, irrigating solutions, detection of perforations and also apical root resorptions. , Studies done on permanent teeth have reported more than 80% accuracy with electronic apex locators. ,
The purpose of the present study was to assess whether apex locators are accurate in determining the root canal length in resorbing roots of deciduous tooth compared to the conventional radiographic method.
| Materials and Methods|| |
The present study was an ex vivo study. Institutional Ethics Committee clearance and written consent from parents/guardians were obtained prior to the commencement of the study.
The sample for the study included deciduous maxillary and mandibular molars in children of age group 5 to 12 years, who visited the department clinic for their dental treatment. A sample size of 30 molar root canals which were equally distributed among maxilla and mandible were selected for the study.
Teeth indicated for extraction in healthy children for the following reasons:
- Prolonged retention (with succeedaneous tooth)
- Orthodontic purpose
- Teeth with non restorable crown
- Pathologic mobility due to severe bone resorption.
- Resorption more than half of root
- Teeth with calcified canals
- Medically compromised children.
Local anesthesia was administered and complete caries removal was done using a round bur. Standard endodontic access cavity was done using Endo access bur. Pulp extirpation was done using barbed broach and canals were irrigated with 0.9% sodium chloride solution. Working length was measured using conventional radiographs (A 70-kV, 8-mA X-ray device with 0.4-s exposure time, IOPA film- Kodak, Ultra Speed E film) and Apex locators (Root ZX, J. Morita). The teeth were then extracted, cleaned and immersed in 5.25% sodium hypochlorite solution. The direct measurement of the root canal was done using stereomicroscope (40×) (Leitz Microscope).
Working length determination
Working length was initially measured using conventional radiograph followed by apex locator. Cusp adjacent to the canal was taken as the occlusal reference, for example, mesiopalatal cusp for palatal canals. To avoid bias the three measurements were recorded by three investigators separately. All the investigators were calibrated before the study began. Each measurement was made thrice and average of two closest readings was recorded as final recording.
Determination of working length using Conventional radiograph
Using a No. 10 size file canal patency was established. Using the initial radiograph, approximate working length was measured. Silicone stopper was adjusted on a 15 or 20 size K file and the corresponding occlusal reference point was identified and noted. Radiograph was taken using paralleling technique where the film was placed parallel and 15 cm distant to the tube with the K-file in position. Assessment was made and measurements were recorded in the data sheet.
Determination of working length using Apex locator
Working length was determined using Root ZX apex locator. A K-file of size 15 was attached to the file holder and was gently inserted into to the canal until the display read ''apex''. If the reading was stable for at least 5 s, the silicone stopper was placed at the coronal reference and the electronic root canal length was measured using a 0.5-mm precision endodontic ruler, considering the actual root length. Care was taken to use the same reference point for both the radiographic and apex locater methods.
Determination of actual length using stereomicroscope
The actual canal length of each tooth was measured at 40× stereomicroscopy magnification. A K-file with a silicone stop was inserted into the root canal until its tip was visible at the apical foramen or first point of exit in case of oblique apical resorption. The silicone stop was placed at the coronal reference and the file was measured with a metallic endodontic ruler of 0.5-mm precision.
Descriptive statistics was carried out using SPSS v. 11.5 software (SPSS Inc, Chicago, USA) to find the difference between the values of each group. After that, comparison amongst the methods was also performed using one way ANOVA.
| Results|| |
The mean root length in as measured with radiographs was 13.36 ± 2.32 mm, apex locator was 13.06 ± 3.01 mm and with direct measurement was 13.06 ± 3.16 mm [Table 1]. When the direct measurements were compared with conventional radiographs and Apex Locator measurements, it was found to be non significant with P value of 0.342 and 0.266 respectively and F value of 0.396 and 0.303, respectively [Table 2].
Although there was no statistical significant difference in the canal length between the three groups, the Apex locator measurements were similar to direct measurement.
|Table 1: Descriptives of primary molars root canal length obtained using conventional radiograph, Apex locator and original length using stereomicroscope (mm) |
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|Table 2: Comparison between conventional radiograph, apex locator and direct measurements |
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| Discussion|| |
Working length determination is one of the crucial steps for the final outcome of the endodontic procedure. The use of apex locator has gained increasing popularity in recent years to avoid the hazards of radiation, technical and processing errors etc.  Modern apex locators are even able to determine an area between the minor and major apical foramina by measuring the impedance between the file tip and the canal with different frequencies enabling tooth length measurements in presence of electrical conductive media in the root canals. 
The Root ZX is a third generation electronic apex locator where no calibration is required and a microprocessor calculates the impedance quotient. They use multiple frequencies to determine the distance from the end of the canal. The change in electrical capacitance at the apical constriction is the basis for the operation of the device. 
Apex locators work well in fully formed roots, but are it the same in cases of resorbing roots especially as seen in deciduous teeth, in permanent roots with external root resorption or in an immature permanent root with open apex.
In the present study we have chosen resorbing deciduous molar roots for evaluation as the deciduous roots are more complex, where oblique type of resorptions are common.
The generally accepted indication for pulpectomy in primary teeth is that root resorption should not have exceeded one-third of root length. Therefore, only teeth that had root length more than two-thirds of the average root length were used. 
In the present study, since our aim was to measure the canal length, we did not substract 0.5 mm from the actual canal length as done in working length measurement. In the present study we selected No. 10 size K files as the tip was easily identifiable in the radiograph.  The specific file size used for canal length determination does not influence the accuracy of length determination by apex locator. 
The results of present study showed no statistical significant difference between conventional radiograph and apex locator in working length determination of primary molars.
Apex locators were found to be more accurate (significance) compared to the radiographs and thus significant result may be obtained by increasing the sample size.
Electronic apex locators are more accurate, safe, painless, and useful because it avoids unnecessary radiation. It proved to be a good alternative also for roots with resorbing root canals and so can be recommended for primary teeth. ,
| Conclusion|| |
From this study the following conclusions were drawn:
- Inter group comparison between Conventional radiograph and Apex locator showed no statistical difference between the two methods in working length determination
- Apex locators can be used in resorbing root canals of deciduous molars obtaining good results.
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[Table 1], [Table 2]