1. health and fitness
2. disease

Original Article
ACCURACY OF ELECTRONIC APEX LOCATOR IN DETERMINING
THE WORKING LENGTH IN PRIMARY MOLARS WITH ROOT RESORPTION:
AN IN VITRO STUDY
1
MARIA SIKANDER, BDS, FCPS Trainee
2
ALIA AHMED, BDS, FCPS
3
SANA JALIL, BDS, FCPS Trainee
ABSTRACT
For successful endodontic outcome, correct working length has to be determined. The
third generation apex locators claim to be accurate regardless of physiologic root resorption. The objective of the study was to determine in vitro the accuracy of Dentaport ZX
(third generation apex locator) in determining the working length of primary molars with root resorption.
Thirty-two extracted primary molars with root resorption were obtained for this study. After
ascertaining the direct working length, Dentaport ZX was used to determine the working length of
roots of primary molars with root resorption .The Dentaport ZX was 86.9% accurate in determining
working length within ±0.0mm of coronal limit of resorbed primary molar root when compared with
direct method. The accuracy of Dentaport ZX in measuring working length in primary molars was
high and was not affected by physiologic root resorption.
Key Words: apex locator, working length, root canal, primary molar, physiologic root resorption.
INTRODUCTION
Virtually all elements of root canal therapy demand
strict length control to ensure that neither the root canal
system itself nor the periodontal ligament is damaged.
Correct length measurements minimize the extrusion of
potentially infected dentinal debris into the periapical
area1, 2, 3. Traditionally, the periapical radiograph has
been the primary method of canal length determination, but they expose the patient to ionizing radiation.
They are merely two dimensional images of a three-dimensional object. Small areas of resorption especially
on buccal or lingual aspects of the root are difficult to
assess radiographically4 . Interference of adjacent anatomic can often superimpose on the image of the root
apices of molar teeth, resulting in interpretive error5,6.
Furthermore, in children placement of large-sized sensor in their mouth is difficult and cause discomfort to
them. All these factors together have stimulated the
development of electronic root canal measuring devices
also known as electronic apex locators (EALs)5.
Third generation devices are largely frequency-based. Certain third generational devices use a
IIDC House No. 428, Street 16, Chaklala Scheme III, Rawalpindi.
E-mail: [email protected] Tel: 051-5153528
2
IIDC Professor, House No. 704, Street 70, I-8/3, Islamabad
3
IIDC House No. 219-B, Lane 7, Street 12, Chaklala Scheme III,
Rawalpindi
Received for Publication:
November 5, 2014
Accepted:
November 22, 2014
1
Pakistan Oral & Dental Journal Vol 34, No. 4 (December 2014)
ratio algorithm between two electrical currents and
are designed to make accurate readings regardless of
fluid electrolytes being present within the canal7, 8,9,10.
Kobayashi and Suda 11 have developed an EAL, the
Root-ZX (J. Morita CO., Tustin, CA) that is based on
the ratio method for measuring canal length. A study
by A.C.V. Mello-Moura et al. concluded that Root ZX
electronic apex locator performed best for the root canal
length determination in primary teeth 12. P.Nelson-Filho
et al. found that the electronic apex locator accurately
identify the working length in primary teeth regardless
of presence or absence of root resorption13.
The present study is aimed to evaluate Dentaport
Root ZX electronic apex locator, in vitro, for the accurate measurement of working length in primary molars
with root resorption and to compare this to the working
length measured by direct method.
METHODOLOGY
Thirty-two primary molars with the resorbed
roots were obtained from the department of Oral and
Maxillofacial Surgery at Islamic International Dental
Hospital (IIDH) Islamabad. The teeth were not endodontically treated or calcified and the root length was
not less than two-thirds of its full length. They were
stored in 10% formalin and rinsed in saline solution
before use. Each tooth was coded from number 1 to 32.
A periapical radiograph of each tooth was taken to rule
711
Accuracy of Electronic Apex Locator
out any previous endodontic treatment or morphological
alteration. After standard access cavity preparation
working length was determined both visually (direct
method) and with Dentaport ZX electronic apex locator
(EAL). Three readings were obtained, each after a 24
hour interval and average value was calculated.
For direct working length (DL) measurement a reference point was marked at the most coronal position of
the crown using fine point marker. A K-file with silicone
stop was introduced into the root canal until the tip was
visible at the most coronal limit of root apex. At this
point DL was calculated with the help of millimeter
ruler. For electronic working length (EL) measurement
the teeth were first fixed into saline-soaked sponge.
The root canals were also flooded with saline. Excess
saline from pulp chamber was removed using cotton
pellets. The lip clip was attached to the sponge and
the file holder to the metal shaft of the K-file (Mani)
used to determine DL. The K-file was advanced in the
canal until the display read “Apex”. A constant beep
is heard at that point. If the reading was stable for at
least 5 seconds the stop was adjusted against the same
reference point used for DL. The EL is recorded with
the help of millimeter ruler. The difference between
EL and DL was recorded. The value within ±0.0mm
was considered as a measurement of the accuracy of
Dentaport ZX apex locator.
RESULTS
primary teeth without root resorption, the reading is
maximized in the area of the apical constriction, as it is
the site where the pulpal tissue meets the periodontal
ligament. In primary teeth with root resorption the
apical area keeps changing constantly, it is possible
that the apical constriction is obliterated and apex
is wide open. Therefore, it is reasonable to infer that
inaccuracies may exist when EALs are used in cases
of primary teeth with root resorption.
Working length measurement of primary teeth
with or without root resorption has been carried out
by using a number of EALs5 .The Dentaport ZX used
in the present study is a third generation apex locator,
and claims to be accurate in the presence of different
canal conditions. The present study aimed to explore
the effect of physiologic root resorption in primary
molars on the accuracy of Dentaport ZX apex locator.
In this study sixty-one canals from the 32 teeth
were measured for accurate working length determination by Dentaport ZX apex locator. The accuracy of
Dentaport ZX apex locator was compared with direct
method in terms of comparing the difference i.e. DLEL. The results obtained are in accordance with the
studies of Angwaravong and Panitvisa16, Odabas et
al17, Leonardo et al18 , Pinhreiro et al19, and Beltrame
et al (2011)20 who reported high accuracy of EALs at
different levels of root resorption.
DISCUSSION
In the present study the sample size was thirty two
which is in agreement with Angwaravong and Panitvisai16 and Odabas et al17 studies. Angwaravong and
Panitvisai16 used thirty-three primary teeth in their
in-vitro study and Odabas et al17 used twenty-eight
primary teeth . Hence the results are very much comparable with the above mentioned studies.
Establishment of correct working length is an important stage in root canal treatment because instrumentation beyond or too short of apex can adversely
affect success 14. Historically, conventional radiography
has been primary means for establishing working
length in endodontic treatment but there are certain
limitations to this technique 15. Therefore, an alternate
method was developed, that uses electrical current for
working length determination2. EAL devices measure
the constant resistance or impedance value between the
patient’s oral mucosa and the periodontal ligament. In
The Root ZX and The Root ZX II (Morita) are the
common EALs used in primary teeth. Related investigations of this brand did not follow a single criterion in
determining the working length. For instance, Beltrame
et al20 evaluated the working length at “0.0” mark i.e.
Apex. Angwaravong and Panitvisai16 compared the
Root ZX measurement meter readings at “0.5” bar and
“Apex” and found that the error in locating the apical
foramen was smaller at meter reading “Apex” than
“0.5” bar. Odabas et al17 selected the “1” reading on
the apex locator’s display. In the present study “0.0”
The frequency and percentages of electronic working
length readings relative to DL are summarized in Table
1. In total the Dentaport ZX showed the accuracy as
DL 86.9% of the time.
TABLE 1: DIFFERENCE (EL-DL) IN MILLIMETERS
Valid
.00
.50
1.00
Total
Frequency
53
7
1
61
Percent
86.9
11.5
1.6
100.0
Pakistan Oral & Dental Journal Vol 34, No. 4 (December 2014)
Valid Percent
86.9
11.5
1.6
100.0
Cumulative Percent
86.9
98.4
100.0
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Accuracy of Electronic Apex Locator
mark i.e. Apex was selected as by Beltrame et al20 and
the results of their study were quite similar to our
study. However, Kielbassa et al.21 study results were
in contrast with our study.
A number of methods have been used to evaluate the accuracy of EALs e.g. its comparison with radiographic technique
and, in other studies, EAL was used clinically and the actual
lengths of canals were measured following extraction22. In this
in vitro research the electronic working length was measured
visually first and then with Dentaport ZX .This methodology
is similar to that of Angwaraong and Panitvisai (2009)16. The
overall accuracy of Dentaport ZX in this study compare well
with those from other in vivo studies in which accuracies range
from 80% to 100%10,16,17,22,23.
The most significant limitation of this study is that
it was done in vitro which allows us a well-controlled
environment for the study and the clinical situations
which offer multiple challenges cannot be taken into
account. The small sample size did not include the
anterior primary teeth. Increasing the number and
types of teeth will give extremely valid and reliable
statistical data. Secondly with the physiologic resorption the canals can begin to calcify thus accuracy of
EALs in such cases was not established. Thirdly the
histological sectioning of the teeth was not taken as
the “gold standard”. The actual working length was
measured visually that can vary from one individual
to the other.
CONCLUSION
It can be concluded that Dentaport ZX can measure the working length in primary molars with root
resorption with high accuracy and therefore is a reliable
alternative for conventional radiographic measurement
of working length.
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