Basic Research—Technology
Comparison of Apical Extrusion of Sodium Hypochlorite
Using 4 Different Root Canal Irrigation Techniques
Emre I_ riboz, DDS, PhD, Koral Bayraktar, DDS, Dilek T€
urkaydın, DDS, PhD,
and Bilge Tarçın, DDS, PhD
Abstract
Introduction: We compared the apical extrusion of
sodium hypochlorite delivered with a 27-G needle, selfadjusting file (SAF), passive ultrasonic irrigation, or the
EndoVac system (SybronEndo, Orange, CA) during the
instrumentation and final irrigation of root canals.
Methods: Matched paired single-canal teeth were
divided into 8 groups. The experimental groups were needle irrigation size #30 (NI30) and #50 (NI50), SAF size #30
(SAF30) and #50 (SAF50), passive ultrasonic irrigation
size #30 (PUI30) and #50 (PUI50), and EndoVac size
#30 (EV30) and #50 (EV50). Teeth were embedded in
0.2% agarose gel (pH = 7.4) containing 1 mL 0.1% mCresol purple (Sigma-Aldrich, St Louis, MO), which
changes color at a pH level of 9.0. Root canals were irrigated with sodium hypochlorite and EDTA using
4 different techniques, and the amount of irrigant was
controlled. Standardized digital photographs were taken
20 minutes after the first irrigant was used and were
analyzed to determine the amount of extrusion (expressed as a percentage of total pixels). Results: The
amounts of apical extrusion obtained in the NI30, NI50,
SAF30, SAF50, PUI30, PUI50, EV30, and EV50 groups
were 30% (3/10), 50% (5/10), 20% (2/10), 70% (7/10),
40% (4/10), 40% (4/10), 10% (1/10), and 10% (1/10),
respectively. The overall extrusion frequency, regardless
of the apical preparation size, was 40% (8/20) for needle,
45% (9/20) for SAF, 40% (8/20) for ultrasonic irrigation,
and 10% (2/20) for EndoVac. Although the SAF group
showed more extrusion, the percentage of pixels was
significantly higher in the needle irrigation group
(P < .01). The EndoVac group showed significantly lower
extrusion values than the other techniques in terms of the
number of teeth and pixels (P < .05 and P < .01, respectively). Conclusions: The risk of apical extrusion is significantly lower with the EndoVac in comparison with the
3 other techniques. (J Endod 2015;41:380–384)
Key Words
Apical extrusion, EndoVac, irrigation, passive ultrasonic
irrigation, self-adjusting file
C
areful removal of vital and necrotic remnants of pulp tissue, debris, microorganisms, and microbial toxins from a root canal system is essential in endodontic treatment (1). However, debris is difficult to remove effectively using mechanical
instrumentation alone because the root canal system has a complex and irregular structure (2). Thus, root canal irrigation needs to be incorporated to enhance debridement
(3, 4). The purpose of root canal irrigation is to remove pulp tissue and
microorganisms from the root canal system and to remove debris and the smear
layer formed after mechanical instrumentation of the root canal (5).
Clinicians enlarge the canal space to better deliver irrigants, such as sodium
hypochlorite (NaOCl), to the apical third of the root canal system (6, 7). Current
techniques inadequately debride the entire root canal system (8–10). Indeed, it is
likely that irrigants do not predictably reach all aspects of the canal, especially the
apical third (11).
Irrigation solutions are often delivered with a 30- or 27-G endodontic slot-tipped
needle placed into the canal until just short of the apex (12). The difficulty with this
technique is that the depth of needle penetration is dependent on the size and
morphology of each canal. Predictable delivery of irrigants to the working length
(WL) is often not achieved with needle irrigation (13). If adequate positive pressure
is not used, irrigants may not reach close to the WL. If too much positive pressure is
used, the practitioner risks forcing irrigants past the terminus of the root canal, which
can produce tissue damage, pain, and swelling (14–17).
The self-adjusting file (SAF; ReDent Nova, Ra’anana, Israel) is hollow and designed
as a thin cylindrical nickel-titanium lattice that adapts to the cross-section of the root
canal. A single file is used throughout the procedure (18, 19). The resulting
circumferential pressure allows the file’s abrasive surface to gradually remove a thin,
uniform hard tissue layer from the entire root canal surface, resulting in a canal with
a similar cross-section but of larger dimensions (10, 20). This also holds true for
canals with an oval or flat cross-section, which will be enlarged to a flat or oval
cross-section of larger dimensions. The straightening of curved canals is also reduced,
so the original shape of the root canal is respected, both longitudinally and in the crosssection (21).
Recently, with its gradually increasing popularity, passive ultrasonic activation of
endodontic instruments has been suggested as a means to improve canal debridement
(22), canal disinfection (23), and canal sealing (24). Passive ultrasonic irrigation
(PUI) also has been recommended for removing Ca(OH)2 from the root canal (25).
However, whether PUI as an effective irrigation method causes extrusion of irrigant
from the apical foramen remains unknown.
The EndoVac (SybronEndo, Orange, CA) negative pressure irrigation system was
developed to address the procedural challenge of delivering irrigants safely to the WL.
An EndoVac placed to the WL resulted in significantly better debridement at 1 mm from
From the Faculty of Dentistry, Department of Endodontics, Marmara University, Istanbul, Turkey.
Address requests for reprints to Dr Emre _Iriboz, Faculty of Dentistry, Department of Endodontics, Marmara University, B€uy€ukçiftlik St No 6, Nişantaşı, Istanbul, Turkey.
E-mail address: [email protected]
0099-2399/$ - see front matter
Copyright ª 2015 American Association of Endodontists.
http://dx.doi.org/10.1016/j.joen.2014.11.003
380
I_riboz et al.
JOE — Volume 41, Number 3, March 2015
Basic Research—Technology
the WL compared with needle irrigation in teeth prepared to an ISO size
#36 or larger (26). Water was used to compare the safety of the available irrigation systems; the results showed no extrusion occurring in
any of the EndoVac samples (27). It has also been shown that an intracanal aspiration technique produced limited extrusion of the irrigant
compared with conventional needle irrigation (28). The purpose of
this investigation was to compare apical extrusion of NaOCl delivered
with a 27-G irrigation needle, the EndoVac, the SAF, or passive ultrasonic irrigation during both instrumentation and the final irrigation
of single-canal teeth.
Materials and Methods
In total, 42 pairs of single-canal bilaterally matching human teeth
were used as study groups, and 2 pairs were used as controls. After
extraction, the teeth were stored at room temperature in phosphatebuffered saline. A flat occlusal surface was made as a reference for
determining the WL, and the pulp chamber of each tooth was accessed
with a #2 round bur. The WL was determined as the point in which a #15
file was just visible at the root end with 20 magnification. The root
end was also inspected at the same magnification to verify closed
apices and the absence of root resorption or visible cracks. Teeth
with an apical diameter more than #30 as measured by a K-file were
excluded. Each pair of bilaterally matching teeth was randomly assigned
to either an apical size #30 or a size #50 group with 20 pairs in each.
The experimental groups were as follows: needle irrigation size
#30 (NI30) and #50 (NI50), SAF size #30 (SAF30) and #50
(SAF50), passive ultrasonic irrigation size #30 (PUI30) and #50
(PUI50), and EndoVac size #30 (EV30) and #50 (EV50). Two other
pairs of teeth were used as controls.
The teeth were fixed rigidly and secured to a modified flat-sided
clear plastic container (Deneysel Medical Devices, Istanbul, Turkey)
with dimensions of 4 3 3 cm using self-curing resin (Imicryl,
Konya, Turkey) and embedded in a gel. A #15 K-file was placed at
the WL in each canal to prevent the 0.2% agarose gel (Difco Laboratories, Sparks, MD; pH = 7.3–7.4) containing 1 mL 0.1% m-Cresol purple (Sigma-Aldrich, St Louis, MO) from getting into the canals. m-Cresol
purple has a pH-sensitive color change (from yellow at pH = 7.4 to purple at pH = 9). A color change to purple indicated the extrusion of
NaOCl (pH = 11.4) into the gel. All experiments were completed within
2 hours of the gel setting. Before instrumentation, a dental dam was
placed on each tooth to prevent observation of the gel by the operator.
Each of the teeth in the NI30, SAF30, PUI30, and EV30 groups were
instrumented to a size #30 master apical file with ProTaper Universal
rotary instruments (S1, S2, F1, F2, and F3; Dentsply, Ballaigues,
Switzerland). Each of the teeth in the NI50, SAF50, PUI50, and EV50
groups were instrumented to a #50 master apical file with ProTaper
Universal tapered files (S1, S2, F1, F2, F3, F4, and F5). Apical patency
was maintained by passing a #15 file to the WL after each rotary instrument in all groups.
Root canals were irrigated using 2 mL 5.25% NaOCl between all
instrument changes. The final irrigation was performed with 2 mL
5.25% NaOCl and then 2 mL 17% EDTA followed by 2 mL 5.25%
NaOCl. Irrigation in the needle groups was performed with a 27-G
slot-tipped endodontic needle (Monoject; Tyco Healthcare, Mettawa,
IL) and syringe. The needle was placed short of the binding point or
2 mm from the WL, and irrigants were delivered over 30 seconds. In
the SAF groups, irrigants were delivered through the SAF file according to the manufacturer’s protocol. In the passive ultrasonic irrigation
groups, irrigants were delivered as described in the manufacturer’s
directions (NSK Varios 970; NSK, Tokyo, Japan). In the EndoVac
groups, the irrigant was delivered via the delivery/evacuation tip at
JOE — Volume 41, Number 3, March 2015
the orifice level. Two matched pairs were used as positive and negative
controls to show color changes in the gel. One tooth in each pair was
the positive control; the other was the negative control. Positive and
negative control teeth were shaped at the WL to a size #30, at which
point a file of corresponding size was placed to length and the gel
was poured. After the gel had set, a 27-G endodontic slot-tipped needle was inserted into the positive control canals to the WL, and 0.5 mL
NaOCl was delivered over 30 seconds. Negative control teeth were
prepared as described for the positive controls except that they
were irrigated with 0.5 mL saline (pH = 7.2–7.4) over 30 seconds
at the WL. To standardize the time for diffusion of the dye, the gel
was photographed at precisely 20 minutes after the initial irrigation
with NaOCl. The gel was photographed digitally using a camera at a
fixed distance. The standardized photographs were analyzed using
Adobe Photoshop 7 (Adobe, San Jose, CA) to determine the area of
the color change (expressed in pixels) (Fig. 1). The total number
of pixels in each photograph was 3,630,168. The threshold showing
apical extrusion of NaOCl was determined to be the pixel number
greater than 2 standard deviations above the mean of the negative control group (477 pixels or 0.01% of the total area). The data were then
analyzed using the Kruskal-Wallis, Mann-Whitney U, chi-square, and
Fisher exact tests with the P value set at <.05.
Results
Positive controls had a mean affected area of 213,454 pixels or
5.88% of the total area. Negative controls had a mean affected area of
177 pixels or 0.01% of the total; this represents the outline of the roots
in the photographs analyzed. Comparison of the 2 controls using the
Mann-Whitney U test showed a significant difference (P < .05). The
amounts of apical extrusion in the NI30, NI50, SAF30, SAF50, PUI30,
PUI50, EV30, and EV50 groups were 30% (3/10), 50% (5/10), 20%
(2/10), 70% (7/10), 40% (4/10), 40% (4/10), 10% (1/10), and
10% (1/10), respectively. The overall extrusion frequency, regardless
of the apical preparation size, was 40% (8/20) for needle, 45%
(9/20) for SAF, 40% (8/20) for ultrasonic irrigation, and 10%
(2/20) for the EndoVac (Table 1). Although the SAF group resulted
in apical extrusion in more teeth, the percentage of pixels was significantly higher in the needle irrigation group (P < .01, Table 2). The EndoVac group showed significantly lower extrusion values than the other
techniques in terms of the mean number of teeth and pixels (P < .05
and <.01, respectively; Table 3).
Discussion
A sufficient volume of irrigant should be supplied to a mechanically instrumented space. However, it is difficult to irrigate the apical
portion of the root canal system sufficiently to achieve satisfactory
root canal debridement (29, 30).
The results of this study are consistent with those of Fukumoto et al
(28), Desai and Himel (27), and Neilsen and Baumgartner (26), who
concluded that negative pressure irrigation was a controlled, effective
method of delivering irrigants into the apical third of the canal system.
The results are also consistent with Brown et al (31) and Mitchell et al
(12), who showed that positive pressure irrigation may force irrigants
into the periapical tissues.
The amount of irrigant delivered between files and during the final
irrigation was controlled to allow for a direct comparison between the 4
delivery techniques. A pilot study determined that the maximum amount
of NaOCl evacuated by the microcannula when placed in a beaker was
0.8 mL per 30 seconds and the maximum amount of NaOCl that the
macrocannula could evacuate was 9 mL per 30 seconds. Irrigation of
2 mL per 30 seconds was used in this study because this allowed passive
Apical Extrusion of NaOCl Using 4 Irrigation Techniques
381
Basic Research—Technology
Figure 1. Digital photographs of apical extrusion of NaOCl using the EndoVac, passive ultrasonic irrigation, the SAF, and needle irrigation.
irrigation in the needle groups and provided adequate irrigation for the
microcannula.
Recommendations for the use of needle irrigation include not
binding the needle, not placing the needle to the WL, and using a gentle
delivery of irrigant to avoid forcing irrigants into the periapex (12). In
this study, the needle was not placed closer than 2 mm from the WL. In
contrast, the EndoVac was used at the WL as recommended by the
manufacturer. The results of this study reflect extrusion using the apical
extent of ‘‘safe’’ endodontic needle placement and the manufacturer’s
recommended location for the EndoVac at the WL.
Desai and Himel (27) compared extrusion using water as the irrigant in previously instrumented teeth open to atmospheric pressure.
In this study, teeth were embedded in gel, creating a closed system that
more closely resembles the in vivo environment. The teeth were instrumented and irrigated in a similar manner to that in the clinical
setting, and our results revealed that the frequency of extrusion
past the apex was increased significantly when needle irrigation
was used compared with the 3 other irrigation techniques. We also
showed that as the canal was instrumented to a larger apical diameter,
the likelihood that irrigants are extruded into the periradicular tissues
increased if needle irrigation was used. In contrast, the risk remained
constant if irrigation was performed using the EndoVac, regardless of
the apical preparation size.
Thorough cleaning of the root canal depends on effective irrigant delivery, solution agitation (32), and its direct contact with
the entire canal wall, particularly in the apical third (1, 32). SAF
uses an irrigation device (Vatea, ReDent-Nova) that provides
continuous flow of the irrigant during use. Because SAF is a hollow
file, the irrigant enters the full length of the canal and is activated
by the vibrating motion of the file’s metal lattice, reportedly facilitating its cleaning and debridement effects (18). We used the technique in our study for its continuous irrigation; however, the
TABLE 1. Number of Teeth Showing Apical Extrusion According to the Irrigation Technique
Irrigation needle
PUI
EndoVac
n (%)
n (%)
n (%)
n (%)
P value
8 (40.0)
12 (60.0)
9 (45.0)
11 (55.0)
8 (40.0)
12 (60.0)
2 (10.0)
18 (90.0)
.076*
Number of teeth
Extruded
No extrusion
SAF
PUI, passive ultrasonic irrigation; SAF, self-adjusting file.
*Chi-square test. P > .05.
382
_Iriboz et al.
JOE — Volume 41, Number 3, March 2015
Basic Research—Technology
Conclusions
TABLE 2. Pixel Percentages According to the Irrigation Technique
Pixel (%)
Irrigation needle
SAF
PUI
EndoVac
Mean ± SD
Median
P value
2.98 0.79
1.32 1.36
0.62 0.01
0.35 0.0
3.05
0.75
0.47
0.35
.004*
PUI, passive ultrasonic irrigation; SAF, self-adjusting file; SD, standard deviation.
Kruskal-Wallis test.
*P < .01.
Our results showed that needle irrigation should be our last choice
among these techniques because our pixel percentage data showed
that it extruded the most amount of irrigant. Our data suggested a
significantly lower frequency of extrusion of NaOCl using the EndoVac
compared with the 3 other techniques. Further research should
investigate the actual volume of irrigant reaching the apex with the
EndoVac.
Acknowledgments
The authors deny any conflicts of interest related to this study.
results revealed that SAF showed more apical extrusion than the
other techniques and considerably more than the EndoVac system.
This may be explained by the simultaneous effects of both the SAF
file and the continuous flow of the irrigation solution. The Vatea
pump ‘‘controls’’ the irrigation procedure, not the clinician, which
may lead to uncontrolled and uncalculated irrigation, and, as a
consequence, apical extrusion.
It is generally accepted that passive ultrasonic irrigation is more
effective than conventional syringe and needle irrigation in eliminating
pulp tissue and dentin debris. The difference may be caused by the fact
that ultrasound creates a higher irrigant flow rate in the canal during
irrigation, eliminating more debris and improving access by the chemical product to the accessory canals (33). Our results showed that, in
addition to these positive attributes, passive ultrasonic irrigation may
also push the NaOCl solution into periapical tissues (as do the other irrigation techniques) but showed significantly more apical extrusion than
the EndoVac technique.
Brunson et al (34) and de Gregorio et al (35) showed that an increase in the apical size resulted in a gain of irrigant volume. Similar to
this study (ie, the apical preparation size increased from 30 to 50), the
volume of irrigant significantly increased in the needle irrigation and
SAF groups, but the increase in the PUI and EndoVac groups was not
significant. These results show that the volume of irrigant delivered to
the apex and the volume of irrigant extruded beyond the apex may
correspond with each other, but they also may be irrelevant (36).
Our study presents 2 data variables: the frequency of apical extrusion and the number of pixels. The number of pixels directly corresponds to the amount of the extruded irrigant, which is more
important than the number of teeth showing extrusion because the
greater the amount of extrusion the greater the damage to the periapical
tissues (12, 37). Apical extrusion may occur in any irrigation procedure
as shown in our results, but if the amount of extrusion is small, the
periapical tissues would not be harmed, and the patients would show
no clinical symptoms (37).
TABLE 3. Pixel Percentages in the Study Groups
Pixel (%)
Group 1
Group 2
Group 3
Group 4
Group 5
Group 6
Group 7
Group 8
Mean ± SD
Median
P value
2.55 0.98
3.25 0.62
0.51 0.33
1.55 1.48
0.74 0.47
0.50 0.20
0.36 —
0.35 —
2.84
3.27
0.51
0.88
0.70
0.47
0.36
0.35
.023*
Kruskal-Wallis test.
*P < .05.
JOE — Volume 41, Number 3, March 2015
References
1. Zehnder M. Root canal irrigants. J Endod 2006;32:389–98.
2. Moodnik RM, Dorn SO, Feldman MJ, et al. Efficacy of biomechanical instrumentation: a scanning electron microscopic study. J Endod 1976;2:261–6.
3. Bystrom A, Sundqvist G. Bacteriologic evaluation of the efficacy of mechanical root
canal instrumentation in endodontic therapy. Scand J Dent Res 1981;89:321–8.
4. Ruddle CJ. Finishing the apical one third. Endodontic considerations. Dent Today
2002;21:66–70.
5. Baugh D, Wallace J. The role of apical instrumentation in root canal treatment: a
review of the literature. J Endod 2005;31:333–40.
6. Clegg MS, Vertucci FJ, Walker C. The effect of exposure to irrigant solutions on the
apical dentin biofilms in vitro. J Endod 2006;32:434–7.
7. Dunavant TR, Regen JD, Glickman GN. Comparative evaluation of endodontic irrigants against E. faecalis biofilms. J Endod 2006;32:527–31.
8. Svec TA, Harrison JW. Chemomechanical removal of pulpal and dentinal debris with
sodium hypochlorite and hydrogen peroxide vs normal saline. J Endod 1977;3:
49–53.
9. Salzgeber RM, Brilliant JD. An in vivo evaluation of the penetration of an irrigating
solution in root canals. J Endod 1977;3:394–8.
10. Metzger Z, Teperovich E, Zary R, et al. The self-adjusting File (SAF). Part 1:
respecting the root canal anatomy—a new concept of endodontic files and its implementation. J Endod 2010;36:679–90.
11. Walters MJ, Baumgartner JC, Marshall JG. Efficacy of irrigation with rotary instrumentation. J Endod 2002;28:837–9.
12. Mitchell RP, Yang S, Baumgartner JC. Comparison of apical extrusion of NaOCl using
the EndoVac or needle irrigation of root canals. J Endod 2010;36:338–41.
13. Chow TW. Mechanical effectiveness of root canal irrigation. J Endod 1983;9:475–9.
14. Becking AG. Complications in the use of sodium hypochlorite during endodontic
treatment. Report of three cases. Oral Surg Oral Med Oral Pathol Oral Radiol Endod
1991;71:346–8.
15. Hulsmann M, Hahn W. Complications during root canal irrigation—literature review and case reports. Int Endod J 2000;33:186–93.
16. Gernhardt CR, Eppendorf K, Kozlowski A. Toxicity of concentrated sodium hypochlorite used as an endodontic irrigant. Int Endod J 2004;37:272–80.
17. Kleier DJ, Averbach RE, Mehdipour O. The sodium hypochlorite accident: experience of diplomates of the American Board of Endodontics. J Endod 2008;34:
1346–50.
18. Metzger Z, Teperovich E, Cohen R, et al. The self-adjusting File (SAF). Part 3:
removal of debris and smear layer—a scanning electron microscope study.
J Endod 2010;36:697–702.
19. Hof R, Perevalov V, Eltanani M, et al. The self-adjusting file (SAF). Part 2: mechanical
analysis. J Endod 2010;36:691–6.
20. De-Deus G, Accorsi-Mendonça T, Silva LC, et al. Self-adjusting file cleaning-shapingirrigation system improves root-filling bond strength. J Endod 2013;39:254–7.
21. De-Deus G, Barino B, Marins J, et al. Self-adjusting file cleaning-shaping-irrigation
system optimizes the filling of oval-shaped canals with thermoplasticized gutta-percha. J Endod 2012;38(6):846–9.
22. Plotino G, Pameijer CH, Grande NM, Somma F. Ultrasonics in endodontics: a review
of the literature. J Endod 2007;33:81–95.
23. Carver K, Nusstein J, Reader A, Beck M. In vivo antibacterial efficacy of ultrasound
after hand and rotary instrumentation in human mandibular molars. J Endod 2007;
33:1038–43.
24. van der Sluis LWM, Wu MK, Wesselink PR. The evaluation of removal of calcium
hydroxide paste from an artificial standardized groove in the apical root canal using
different irrigation methodologies. Int Endod J 2007;40:52–7.
25. van der Sluis LWM, Shemesh H, Wu MK, Wesselink PR. An evaluation of the influence
of passive ultrasonic irrigation on the seal of root canal fillings. Int Endod J 2007;40:
356–61.
Apical Extrusion of NaOCl Using 4 Irrigation Techniques
383
Basic Research—Technology
26. Nielsen BA, Baumgartner JC. Comparison of the EndoVac system to needle irrigation
of root canals. J Endod 2007;33:611–5.
27. Desai P, Himel V. Comparitive safety of various intracanal irrigation systems. J Endod
2009;35:545–9.
28. Fukumoto Y, Kikuchi I, Yoshioka T. An ex-vivo evaluation of a new root canal irrigation technique with intracanal aspiration. Int Endod J 2006;39:93–9.
29. Baumgartner JC, Mader CL. A scanning electron microscopic evaluation of four root
canal irrigation regimens. J Endod 1987;13:147–57.
30. Albrecht LJ, Baumgartner JC, Marshall JG. Evaluation of apical debris removal using
various sizes and tapers of ProFile GT files. J Endod 2004;30:425–8.
31. Brown DC, Moore BK, Brown CE Jr. An in vitro study of apical extrusion of sodium
hypochlorite during endodontic canal preparation. J Endod 1995;21:587–91.
32. Gu LS, Kim JR, Ling J, et al. Review of contemporary irrigant agitation techniques and
devices. J Endod 2009;35:791–804.
384
_Iriboz et al.
33. van der Sluis LW, Wu MK, Wesselink PR. A comparison between a smooth wire and a
K-file in removing artificially placed dentine debris from root canals in resin blocks
during ultrasonic irrigation. Int Endod J 2005;38:593–6.
34. Brunson M, Heilborn C, Johnson DJ, Johnson N. Effect of apical preparation size and
preparation taper on irrigant volume delivered by using negative pressure irrigation
system. J Endod 2010;36:721–4.
35. de Gregorio C, Arias A, Navarrete N, et al. Effect of apical size and taper on volume of
irrigant delivered at working length with apical negative pressure at different root
curvatures. J Endod 2013;39:119–24.
36. Munoz HR, Camacho-Cuadra K. In vivo efficacy of three different endodontic irrigation systems for irrigant delivery to working length of mesial canals of mandibular
molars. J Endod 2012;38:445–8.
37. Psimma Z, Boutsioukis C, Kastrinakis E, Vasiliadis L. Effect of needle insertion depth
and root canal curvature on irrigant extrusion ex vivo. J Endod 2013;39:521–4.
JOE — Volume 41, Number 3, March 2015