1. Evaluation of the multifrequency electronic
apex locator Joypex 5 in primary teeth
E. J. N. L. Silva, D. R. Herrera,
E. J. Souza-Júnior & T. P. Rosa
European Archives of Paediatric
Dentistry
ISSN 1818-6300
Eur Arch Paediatr Dent
DOI 10.1007/s40368-013-0065-0
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3. Author's personal copy
Eur Arch Paediatr Dent
DOI 10.1007/s40368-013-0065-0
ORIGINAL SCIENTIFIC ARTICLE
Evaluation of the multifrequency electronic apex locator
Joypex 5 in primary teeth
´
E. J. N. L. Silva • D. R. Herrera • E. J. Souza-Junior
T. P. Rosa
•
Received: 16 February 2013 / Accepted: 19 June 2013
Ó European Academy of Paediatric Dentistry 2013
Abstract
Aim To evaluate ex vivo the accuracy of the multifrequency electronic apex locator (EAL) Joypex 5 in primary
molars.
Methods Fourteen primary molars were selected for a
total of 25 root canals. Working length measurements were
performed by direct observation (DO), using a 15 K-file
into the root canal until its tip was visible at the apical
foramen and electronically using the EALs Joypex 5. Data
were analysed statistically using the intraclass correlation
coefficient (ICC). To assess whether a significant difference in accuracy of the electronic apex locator existed, the
Student’s t test was performed at 5 % significance.
Results No statistical difference was observed between
the direct observation and the EAL measurement
(p 0.05). The ICC confirmed the agreement of different
methods to measure canal length. The R2 coefficient was
close to 1, denoting a strong agreement between measures
obtained with Joypex 5 and DO.
Conclusion The multifrequency EALs Joypex 5 showed
adequate accuracy in the root length determination of
primary teeth.
E. J. N. L. Silva
Endodontics Department, Grande Rio UniversityUNIGRANRIO, Rio de Janeiro, Brazil
E. J. N. L. Silva (&)
Rua Herotides de Oliveira,
´
´
61/902, Icaraı, Niteroi, RJ CEP 24230-230, Brazil
e-mail: nogueiraemmanuel@hotmail.com
´
D. R. Herrera Á E. J. Souza-Junior Á T. P. Rosa
Endodontics Department, Piracicaba Dentistry School,
Campinas State University-UNICAMP, Campinas, Brazil
Keywords Endodontics Á Electronic apex locator Á
Primary teeth
Introduction
Pulpectomies are indicated in cases of irreversible pulpitis,
necrosis or infections in primary teeth with at least 2/3 of
intact roots. The determination and maintenance of the
working length (WL) is an important step in root canal
treatment, ensuring an efficient chemo-mechanical preparation and a hermetic sealing of the root canal system
(Ricucci 1998). It is especially critical in primary teeth,
since over-instrumentation and over-filling of a primary
tooth can damage the permanent tooth germ and underinstrumentation and underfilling, on the other hand, is also a
risk factor that accounts for persistence of apical infection
(Kielbassa et al. 2003; Angwaravong and Panitvisai 2009;
Leonardo et al. 2009).
The most widely used method for the measurement of
working length for primary teeth is the use of conventional
and digital radiography. Several studies have demonstrated
the limitations of radiographs that include inconsistent
working length determination due to image distortion,
superposition of roots and adjacent anatomical structures
(e.g. permanent tooth germ), radiation exposure and patient
management (Katz et al. 1996; ElAyouti et al. 2001). The
advent of electronic apex locators (EALs) provides an
additional feature to the endodontic arsenal for determining
the correct odontometry. The latest generation of EALs
operates by measuring changes in impedance (alternating
current). For this, two or more different frequencies are
used and processed using different mathematical algorithms (Nekoofar et al. 2006). Many studies report a high
efficacy achieved by new generations of electronic apex
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Eur Arch Paediatr Dent
locators, even in adverse situations like the presence of
irrigating solutions, blood, and the existence of large
foramens as in primary teeth (Kielbassa et al. 2003;
Angwaravong and Panitvisai 2009; Leonardo et al. 2008;
Leonardo et al. 2009; Beltrame et al. 2011).
Recently, a new EAL has been introduced (Joypex 5,
Denjoy Dental Corporation, Changsha City, China). This
EAL adopts multiple frequencies and according to the
manufacturer it works more accurately than others EALs in
dry or wet canals (www.denjoy.cn). Although a recent
study demonstrated that this EAL is accurate in determining the working length in permanent teeth (Soares et al.
2013), little is known about the efficiency and accuracy of
this EAL in primary tooth. Therefore, the aim of this study
was to evaluate the accuracy of the EALs Joypex 5 in
primary molar teeth. The null hypothesis was that there
was no significant difference in the direct and EAL
measurement.
Materials and methods
Tooth selection and preparation
Fourteen primary molars were selected for a total of 25 root
canals. Tooth extraction was necessary as a result of one of
the following reasons: prolonged retention (no spontaneous
exfoliation), orthodontic purposes or no possibility of restoration after caries excavation. All selected teeth did not
show resorption more than 1/3rd the root length. Teeth
were stored in saline solution until use. Preliminary
radiographs were taken after extraction to evaluate root
canal anatomy, identify the radiographic apex and exclude
teeth with calcification, whose main canal was not visible
radiographically. The roots were numbered and stored in
sterile saline until use. After endodontic access cavity
preparation, a K-file (Dentsply Maillefer, Ballaigues,
Switzerland) with diameter compatible with that of the
canal diameter was passively introduced up to the apical
foramen or the most coronal limit of root resorption to
verify canal patency. No root canal preparation was
performed.
Direct measurement
For direct measurement of working length, a reference
point was first marked at the most coronal portion of the
tooth crown using a fine paint marker. Then, a 15 K-file
(Dentsply Maillefer, Ballaigues, Switzerland) with a silicon stop was passively introduced into the root canal until
its tip was visible at the apical foramen under a stereomicroscope at 948 magnification. After this, the file was
123
withdrawn until its tip lay tangential to the apical foramen.
The silicon stop was tangentially positioned to the occlusal
reference edge, which was recorded previously, and the file
was then removed. The distance between the file tip and
silicon stop was measured using a digital calliper with
0.01-mm resolution. Each procedure was repeated three
times, and the average was calculated and computed.
Electronic determination of working length
The electronic working length determination was undertaken using the Joypex 5 (DenjoyÒ, China). The teeth were
embedded in a plastic device containing 0.9 % saline.
Cotton pellets were used to remove excess saline from the
pulp chamber. The labial clip was inserted into the saline
solution, and a 15 K-file was adapted to the file holder. The
file holder was always positioned between the handle of the
file and the silicon stop. The file was introduced slowly into
the root canal until the EAL displayed the ‘0.0’ mark. The
silicon stop was shifted to the occlusal reference edge,
which was recorded previously, and the file was then
removed. The distance between file tip and silicon stop was
measured using a digital caliper with 0.01-mm resolution.
Each procedure was repeated three times, and the average
was calculated and computed.
Statistical analysis
The measurements (in mm) of direct and electronic
determination of the working length were made by an
experienced examiner, and were recorded in specific charts
for further comparison of the methods. Data were analysed
statistically using the intraclass correlation coefficient
(ICC). Mean and standard deviations of direct and electronic means were also calculated. To assess whether a
significant difference in accuracy of the electronic apex
locator existed, the Student’s t test was performed at 5 %
significance, using version 17 SPSS (Chicago, IL, USA).
Results
Figure 1 compares graphically the actual and electronic
working length measurements and shows a high intraclass
correlation (ICC = 0.98) between the direct and electronic
methods.
Table 1 shows the difference between the WL values by
direct measurement and EAL measurement. In 19.2 % of
the canals a full precision (difference of 0.0 mm) was
observed and, only in two cases, a difference[1.0 mm was
verified.

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Fig. 1 Direct measurements and electronic measurements in the
primary molar teeth. The intraclass correlation represents the
intersection of the two measurements that is indicated on the axes
X (direct measurement) and Y (electronic measurement). The dots that
coincide with the line represent that the two measurements had the
same values
Discussion
Root length determination is a crucial factor for a successful root canal treatment, especially in primary teeth
because of the unpredictable root anatomy (Fuks and
Eidelman 1991). Radiography as a method of determining
the working length has numerous shortcoming in which it
depends on the child’s co-operation, as well as the operator’s proficiency. In addition, minor degrees of resorption
may not be visible, and overlapped by adjacent anatomical
structures that could obscure the clarity of the image
(Kielbassa et al. 2003). Another problem associated with
intra-oral periapical radiographs is the positioning of the
film inside the child’s mouth. Furthermore, radiographic
assessment is difficult, particularly in cases where the
physiological resorption in primary teeth occurs on buccal
or lingual aspects of the root. Recently, electronic methods
for determining the root canal length, in both permanent
and primary teeth, have gained popularity amongst dentists
because of the hazards of radiation, the technical problems
associated with radiographic techniques and to avoid overinstrumentation beyond the root canal terminus (Fuks and
Eidelman 1991; ElAyouti et al. 2001; Brunton et al. 2002;
Schaeffer et al. 2005).
Several studies have reported the accuracy of EALs in
determining the WL, validating its clinical use as a simple
and effective alternative and optimising endodontic therapy
(Kielbassa et al. 2003; Leonardo et al. 2008; Angwaravong
and Panitvisai 2009; Leonardo et al. 2009; de Vardasca
Oliveira et al. 2010; Beltrame et al. 2011]. Recently, the
Joypex 5 was launched and according to the manufacturer
(www.denjoy.cn) it has an advanced electronic T-surge
circuit and uses multiple frequencies alternating current
rather than the dual frequency alternating current incorporated in the Root ZX II (Nekoofar et al. 2006; Soares
et al. 2013). Moreover, in the Joypex 5, the calculations of
the position of the file tip are based on measurements of
root mean square values of the signal, which expresses the
energy of the measured signal and is more immune to
various noises or signal distortions than the other parameters of the signal, such as amplitude or the different phases
used in other devices (Majeed and Subhi 2011). According
to the manufacturer, these combinations can increase the
measurement accuracy and the reliability of the device
(www.denjoy.cn).
The apical endpoint of root canals in primary teeth is
often uncertain as they do not always have a well-defined
apical constriction and physiological and pathological
resorptions occur (Azar and Mokhtare 2011; Ruschel et al.
2011). Owing to those inherent problems when using
EALs, many authors consider it acceptable for the measurement to be ±0.5 mm between the working length
obtained directly and that obtained electronically (Angwaravong and Panitvisai 2009; Leonardo et al. 2008;
Leonardo et al. 2009), whereas others have quoted a difference of ±1 mm (Kielbassa et al. 2003; Mello-Moura
et al. 2010). In the present study, the accuracy of the EAL
was assessed by taking into account both differences
(±0.5 mm and ±1 mm). The null hypothesis of the present
study was upheld because no significant difference was
observed in the direct and EAL measurements. This result
confirms the efficacy of this device to determine the WL. In
23 of 25 measurements, the difference between direct and
EAL measurement was lower than ±1.0 mm. In addition,
only two cases showed a greater difference than 1.0 mm,
demonstrating high efficacy of the Joypex 5 for determining WL. In this study, it was also possible to observe an
almost perfect correlation (ICC = 0.98) between the
results of this EAL with those of the direct method. In the
same way, previous reports using different EALs found
high correlations in primary teeth (Tosun et al. 2008;
Nelson-Filho et al. 2011; Saritha et al. 2012). The results
obtained for Joypex 5 in a previous study in permanent
teeth (ElAyouti et al. 2001) and those obtained in this study
Table 1 Difference distribution (in mm) of WL by direct measurement and EAL measurement
Difference
-1.50
1.00
0.50
0
0.50
1.00
1.50
Direct 9 EAL
2 (8.00 %)
2 (8.00 %)
6 (24.00 %)
5 (20.00 %)
7 (28.00 %)
3 (12.00 %)
0 (0.00 %)
Positive values represent a higher direct observation measurement and negative values represent a higher EALs measurement
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for primary teeth indicate its usefulness, and because of the
low cost of this device compared with traditional EALs.
Previous reports showed that the presence of root resorption did not interfere with the accuracy of EALs; therefore,
this variable was not tested in the present study (Kielbassa
et al. 2003; Mello-Moura et al. 2010; Tosun et al. 2008;
Nelson-Filho et al. 2011; Saritha et al. 2012).
Conclusion
The result of this study supports the use of Joypex 5 to
determine root length in primary teeth that require pulpectomy. The use of the electronic apex locator is quick,
comfortable, accurate, safe, painless, and does not involve
unnecessary radiation.
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