|Year : 2013 | Volume
| Issue : 6 | Page : 555-558
|An in vitro comparison of root canal length determination by DentaPort ZX and iPex apex locators
Nikhil Puri1, Rupali Chadha2, Pragya Kumar3, Komal Puri4
1 Department of Conservative Dentistry and Endodontics, Institute of Dental Studies and Technologies, Modinagar, Uttar Pradesh, India
2 Consultant Endodontist, New Delhi, India
3 Department of Conservative Dentistry and Endodontics, ITS Dental College, Muradnagar, Uttar Pradesh, India
4 Department of Periodontics, Institute of Dental Studies and Technologies, Modinagar, Uttar Pradesh, India
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|Date of Submission||07-May-2013|
|Date of Decision||22-Jul-2013|
|Date of Acceptance||08-Aug-2013|
|Date of Web Publication||2-Nov-2013|
| Abstract|| |
Aim: The aim of the present study is to evaluate and to compare the accuracy of two electronic apex locators (EALs): DentaPort ZX and iPex, at a position 0.5 mm short of the apical foramen.
Materials and Methods: Thirty single-rooted, mandibular premolar teeth were selected. Standard access cavities were prepared and the actual length (AL) was calculated. The samples were then embedded in alginate and the electronic measurements were determined and recorded.
Results: The results obtained showed that in determining the root canal length with a tolerance level of ±0.5 mm, i.e., AL ± 0.5 mm, DentaPort ZX was accurate in 93.3% of the samples and iPex was accurate in 90% of the samples at a position 0.5 mm short of the apical foramen.
Conclusion: A strong correlation was seen between the two electronic methods and AL and also in between the two EALs, showing the possibility of their use to measure the root canal length. No statistically significant difference was found between both the apex locators.
Keywords: Actual length; apex locator; DentaPort ZX; iPex
|How to cite this article:|
Puri N, Chadha R, Kumar P, Puri K. An in vitro comparison of root canal length determination by DentaPort ZX and iPex apex locators. J Conserv Dent 2013;16:555-8
|How to cite this URL:|
Puri N, Chadha R, Kumar P, Puri K. An in vitro comparison of root canal length determination by DentaPort ZX and iPex apex locators. J Conserv Dent [serial online] 2013 [cited 2020 Jan 25];16:555-8. Available from: http://www.jcd.org.in/text.asp?2013/16/6/555/120953
| Introduction|| |
Endodontic success depends upon the complete removal of pulp tissue, necrotic materials and microorganisms from the root canal. The cleaning, shaping and obturation of the root canal system cannot be accomplished accurately unless the working length (WL) is determined precisely. WL has been defined as, "the distance from a coronal reference point to the point at which canal preparation and obturation should terminate." Root fillings terminating at the apical constriction (AC) provide optimal healing conditions with minimal contact between the filling material and the apical tissue; thus, reducing tissue destruction, persisting inflammatory responses and foreign body reactions. 
Locating the AC clinically is problematic. Dummer et al.  concluded that it is impossible to locate the minor foramen clinically with certainty, because of its position and topography. The cementodentinal junction (CDJ) has also been suggested as the location for WL as it represents the transition between pulpal and periodontal tissues. The location of the CDJ is widely accepted as being 0.50-0.75 mm coronal to the apical foramen, but as with the AC, the exact location of the CDJ is impossible to identify clinically. 
Under instrumentation and over instrumentation affect the outcome of root canal treatment negatively.  Traditional methods for establishing root canal length include the use of radiographs, knowledge of anatomy and anatomical averages, tactile sensation and presence of moisture on a paper point. All these methods have limitations. Therefore, the search for a more accurate and predictable method of determining root canal length led to the invention of the electrical method. The original idea of using electronics to determine WL was introduced in 1918 by Custer.  An investigation by Suzuki in 1942,  reported that the electrical resistance between the periodontal ligament and the oral mucosa in vivo was a constant value of 6.5 kΩ. This led to the development of the first electronic apex locators (EALs) by Sunada in 1962. 
The first generation apex locators relied on the principle that electrical resistance between oral mucous membrane and periodontal ligament remained constantly 6.5 kΩ, regardless of the age of patient and type and shape of teeth.
The second generation EALs was characterized by a single frequency of alternating current to detect changes in the canal impedance, but the canal needed to be reasonably free of electrically conductive material for an accurate reading.
The third generation apex locators based on dual frequencies were then introduced. These units still use impedance measurement to measure the location within the canal, but have more powerful microprocessors. DentaPort ZX (J. Morita Mfg. Corp., Kyoto, Japan), is a third generation apex locator, which determines the position of the minor diameter by simultaneous measurement of impedance at two different frequencies (8 and 0.4 kHz). A quotient of impedance ("ratio method") is then calculated, which expresses the position of the file in the canal.  This device works on the same principle as the original Root ZX.
Fourth generation apex locators have been developed to further increase the accuracy of apex locators. These apex locators take the resistance and capacitance measurements simultaneously to determine the location of the file tip in the canal.  The recently introduced iPex apex locator (NSK Nakanishi Inc., Kanuma-City, Japan) is a multi-frequency apex locator, claimed to be a fourth generation apex locator.
The aim of this study is to compare and to evaluate the accuracy of third generation (DentaPort ZX) and fourth generation (iPex) apex locators, at a position 0.5 mm short of the apical foramen.
| Materials and Methods|| |
Thirty single-rooted, caries-free mandibular premolar teeth extracted for orthodontic purposes, were selected for the study. The extracted teeth were soaked in 5% sodium hypochlorite (NaOCl) for 6 h to remove the periodontal ligament and then stored in sterile 0.9% saline until used. The extracted teeth were carefully examined under ×5 magnifications using a magnifying glass, for the presence of any fracture and to confirm root apical closure. Per tooth, two preliminary radiographs using the Sopix radiovisiography system (Sopro, France) were taken in the buccolingual and mesiodistal directions, to evaluate the root canal anatomy, identify the radiographic apex and to exclude teeth with more than one canal. Teeth with resorption, fractures or open apices were also excluded.
Standard access cavities were prepared and occlusal edges of the samples were flattened to achieve reproducible stable reference points. After the identification of the root canal orifice, the canals were cleansed of debris by irrigating with 5 ml of 5% NaOCl using a syringe. The canal patency was evaluated using a size 10 K-file. Pulp tissues were extirpated using barbed broaches, without any attempt to enlarge the canal with the root canal instruments. The root canals were again irrigated with 5 ml of 5% NaOCl to remove the organic content of the root canal space.
To obtain the real length, a size 15 K-type stainless steel file was inserted into the canal until the file tip became just visible at the level of the apical foramen under ×5 magnification, using a magnifying glass. The file was measured with a digital caliper to the accuracy of 0.01 mm and from this length; 0.5 mm was subtracted and recorded as the "Actual Length" (AL).
The samples were then embedded up to the cemento-enamel junction in a plastic container containing freshly mixed alginate to simulate periodontium. All measurements were made within 2 hours with the alginate model kept sufficiently humid. For electronic measurement, a size 15 K-file connected to the EAL was used, with the lip electrode inserted into the alginate model. At first, canals were irrigated using 5% NaOCl and then cotton pellets held in tweezers were used to dry the tooth surface and eliminate excess irrigating solution. No attempt was made to dry the canal. Electronic measurements were obtained using the two EALs, DentaPort ZX and iPex. Both were used alternately and irrigation was performed between the uses of the apex locators.
Using the DentaPort ZX, the file was advanced within the root canal to just beyond the foramen, as indicated by the flashing "apex" bar and the continuous tone. The file was then withdrawn until there was an audible signal and a flashing bar between the "apex" and "1" marks, indicating that a position 0.5 mm short of the apical foramen was reached.
Using the iPex, the file was advanced within the root canal to just beyond the foramen as indicated by the flashing "apex" bar and the continuous tone. The file was then withdrawn until an audible signal and a flashing bar indicated that the 0.5 mm mark short of the apical foramen was reached.
Measurements were considered as valid if the reading remained stable for at least 5 seconds, otherwise the value was recorded as an unstable measurement due to inability of the EALs to reveal a constant reading. Measurements were repeated 3 times and the mean value was calculated and recorded for each sample and for each EAL. The recorded AL was compared with the values obtained with the EALs. The root canal lengths obtained by each method were recorded and were subjected to statistical analysis.
| Results|| |
Intergroup comparisons were carried out using the students-paired t test. Pearson's bivariate correlation analysis was used to see the correlation between the electronic measurement methods and AL.
The results of this study showed that the length measurement by DentaPort ZX was accurate in 93.3% of the samples and by iPex was accurate in 90% of the samples, within the range of ±0.5 mm from the AL.
Only two samples (6.7%) in the DentaPort ZX group and three samples (10%) in the iPex group had a range of difference of more than ±0.5 mm from the AL [Table 1].
|Tab le 1: Sample values falling within the range of ±0.5 mm from the actual length|
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The mean AL was measured as 19.05 ± 1.44 mm, whereas DentaPort ZX and iPex measured the length as 19.10 ± 1.49 and 18.97 ± 1.50 mm respectively. On comparing, the length measured by DentaPort ZX to the AL a mean difference of 0.05 ± 0.25 mm was observed, whereas the difference between AL and iPex was −0.08 ± 0.31 mm. On applying a paired t-test between the DentaPort ZX mean and the AL, the P value obtained was 0.311 and between the iPex mean and the AL, the P value obtained was 0.189, implying that there was no significant difference between both the values [Table 2].
|Table 2: Descriptive statistics of mean difference between actual length and length obtained by electronic measurement techniques|
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On applying Pearson's bivariate correlation analysis between the AL and both electronic measurement groups, the r-value obtained was 0.986 and 0.979 for the DentaPort ZX and the iPex groups respectively. This shows a very strong correlation between the electronic measurement methods and AL.
| Discussion|| |
Accurate determination of root canal length is a crucial factor that influences the outcome of root canal therapy. ,, The use of electronic devices to determine the WL has gained increasing popularity in recent years, particularly after the introduction of the latest generation of apex locators, which not only allow measurements in the presence of humidity, but also actually requires the presence of solution within the root canal to function properly.
The development and production of electronic devices for locating the canal terminus has been a major innovation in root canal treatment. The electronic method has shown equal or higher accuracy compared with the radiographic method in determining root canal length in in vivo studies and also reduced the total number of radiographs needed and thus the radiographic exposure. ,
The most extensively researched apex locator is the Root ZX, which is considered as the gold standard against, which the newer apex locators are being compared. In previous studies, the accuracy of the Root ZX has varied from 50% to 100% and it has shown high consistency even in the presence of various irrigants. ,,
Dentaport ZX works on the same principle as Root ZX and is marketed by the same company J. Morita, Japan. There is no difference between Dentaport ZX and Root ZX mechanism, except that the Dentaport ZX has an available port for attachment of endomotor.  The main purpose of this study was to evaluate the accuracy of two apex locators, Dentaport ZX and iPex apex locator.
In the present study, the actual canal length was determined by introducing the file into the canal up to the major foramen under magnification of ×5. , The AC was not used as a landmark; the major foramen was used since it could be located consistently. Reducing 0.5 mm from the length of the major foramen leads us to a point just before or at the AC and secures the operator from any over instrumentation as systematic working to the AC entails the risk of leaving tissue remains within the apical region and also this tissue may be diseased and may lead to the failure of the treatment.  This also provides measurements well within the clinically tolerable 0.5-1.0 mm range from the AC. ,,
Kaufman and Katz  proposed the alginate model for the electronic measurement by apex locators as it very well mimics the electric impedance of the human periodontium and has since then has been used in numerous in vitro studies for WL determination. ,,
In the present study, while advancing the file for electronic canal length measurement, the file was taken slightly beyond the apex as indicated by the apex locator and then retracted to a point where the device showed the file to lie 0.5 mm short of the apical foramen. This increases the reading accuracy of apex locators and ensures the operator of a patent canal. ,,
The results obtained showed that in determining the root canal length with a tolerance level of ±0.5 mm, i.e., AL ±0.5 mm, DentaPort ZX was accurate in 93.3% of the samples and iPex was accurate in 90% of the samples at a position 0.5 mm short of the apical foramen. There was no statistically significant difference between the two apex locators. This result is in agreement with the results obtained by de Vasconcelos et al. and Stφber et al. , Furthermore, in a study done by Stavrianos et al.  the DentaPort ZX was able to locate the apical foramen 95% of the time within ±0.5 mm under clinical conditions.
A strong correlation was seen between the two electronic methods and AL and also in between the two EALs, showing the possibility of their use to measure the root canal length. The results also demonstrated that none of the readings of both the apex locators were beyond the apical foramen, suggesting that the use of EALs prevents overestimation of root canal length, thus preventing over instrumentation.
| Conclusion|| |
Within the limitations of this study, no statistically significant difference was found between both the apex locators and both demonstrated adequate precision in determining root canal length. Further research is required to evaluate the accuracy of these apex locators in different clinical conditions.
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Department of Conservative Dentistry and Endodontics, Institute of Dental Studies and Technologies, Modinagar, Ghaziabad - 201 204, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
[Table 1], [Table 2]
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