former studies have shown that the dentin wall was covered with smear layer
after mechanical shaping of the root canals with instrument (1,2). Disregarding
of the controversy over retaining the smear layer it has been recognized that the
smear layer itself may be infected and may protect the bacteria within the
dentinal tubules (3). Smear layer not only contains organic components but also
have inorganic component in the form of dentin chips etc (1). The penetration
of intracanal disinfectants (4) and sealers into dentinal tubules were
prevented by smear layer, which affects the final seal of the root canal
filling (5, 6, 7).
are paramount for complete debridement of the root canals with mechanical procedures
(3). There is no single potent solution is appropriate for removing both
organic and inorganic parts of the smear layer. To eliminate this smear layer mix
of sodium hypochlorite (NaOCl) and strong chelating agent such as EDTA (Ethylenediaminetetraacetic acid) is
recommended (8). Crumpton et al. proposed
that complete evacuation of smear layer can be achieved by 17% EDTA for 1min
followed by 5.25% NaOCl (9,12). Till now there is no single solution which can
disinfect the root canal system as well as remove the smear layer. On the other
hand the application of strong chelating agent like EDTA for more than minute
and 1ml of volume has been reported to be associated with dentinal erosion
(Sybron Endo, Orange, CA) is a product introduced for eliminating the smear
layer. It contains 17% EDTA solution in conjunction with a cationic (Cetrimide)
and an anionic surfactant. SmearOFF (Vista Detal Products) is Proprietary EDTA
and Chlrohexidine mix. It is prepared with combination of wetting agents and
surface modifiers for best outcomes. These solutions are used only as final
Etridonic acid which is soft chelating agent appears
to have a nominal effect on dentine walls and still cut down smear layer. Lottanti et al.
showed that Etridonic acid (HEBP) can be used in combination
with NaOCl without affecting its proteolytic or antimicrobial properties (13,14). In contrast to EDTA, Etridonic
acid is a weak decalcifying agent and hence cannot be used as a mere final
rinse there for it is suggested that HEBP to be mixed with NaOCl to be used as
more complete root canal irrigation solution.
(innovationsendo, India) is a combination of NaOCl and HEBP. Chloroquick High
contains 18% HEBP and 5.25% NaOCl while Chloroquick Low contains 9% HEBP and 3%
NaOCl both be mixed with surfactant tween 80 for complete root canal irrigation
solution. There for this study aims to compare the efficacy of continuous soft
chelating irrigation protocol with Chloroquick solutions to conventional
irrigation protocol on smear layer removal in coronal, middle, and apical
thirds of the instrumented root canals.
freshly extracted human premolar teeth with single and straight root canal were
preferred and stored in distal water. Average root length of 12 mm were retained
by decoronating the teeth and then divided into 5 groups (n = 12) randomly. Working length was determined with
#10 K-files and deduction of 1mm was done from recorded root length.
irrigation protocol was pursued for three groups. After using each file and
before proceeding to the next canals were irrigated with 2 ml of 5.25% NaOCl.
After instrumentation, all teeth underwent final irrigation as follows:-
Group A(control, EDTA) –
1ml of 17% EDTA for 1 minute followed by 3 ml of 5.25% NaOCl.
Group B (Smear Clear)–
1 ml of Smear clear (Sybron Endo, Orange, CA) for 1 minute followed by 3 ml of
Group C (Smear OFF) –
1 ml of Smear OFF (Vista dental,) for 1 minute followed by 3 ml of 5.25% NaOCl.
soft chelating irrigation protocol was followed for 2 Groups. Group D- Chloroquick
Low (innovationsendo) and Group E – Chloroquick High (innovationsendo). After use of each file
canal was irrigated with 2 ml of respective Chloroquick solution. After
instrumentation, all teeth underwent final irrigation as follows:-
Group D (Chloroquick Low)
– 1 ml of Chloroquick Low solution (9%HEBP + 3%NaOCl) for 1 minute and final rinse with 3 ml same
Group E (Chloroquck High)
– 1 ml of Chloroquick High solution (18%HEBP + 5.25%NaOCl) for 1 minute and
final rinse with 3 ml of same solution.
In-between solutions, 5 ml of distilled water was
used for rinsing canal walls and solutions were introduced with the help of a
30-G side vented needle (innovationsendo), which penetrated within 1 to 2 mm
from the working length. In the end 5ml of distilled water were used to rinse
root canal walls which were dried with paper points.
In the end of entire procedure, two longitudinal
groves were prepared with the help of diamond disc without cutting into the
canal. Grooves were prepared on the buccal and lingual surfaces of each root.
Chisel was used for splitting the teeth. Then the specimens were mounted on the
metallic stubs and investigated under a scanning electron microscope (FEI
Quanta 200 FE-SEM MK2, Netherlands). Images were obtained at 2000× magnifications
at coronal (9 mm to apex), middle (6 mm to apex), and apical (3 mm to apex)
third of each specimen.
Scoring criteria was given by Torabinejad M, Khademi
AA et al. where scores were given as follow score 1 = no smear layer; all tubules were clean and open and smear
layer was absent on the surface of the canals; score 2 = moderate smear layer; smear layer was not present on the
surface of the canal, but debris were present in tubules; score 3 = heavy smear layer; the debris were observed in tubules and
smear layer enclosed the dentin wall surfaces.
An endodntist who was unaware of groups and coding
evaluated and scored all the images to exclude observer bias. Repeated
evaluation was done to ensure intra-examiner consistency.
statistics were expressed as numbers for each group. The efficacy of various
agents for smear layer removal was assessed by comparison of groups using
Kruskal Wallis ANOVA and Mann- Whitney U test. In the above tests, p value less
than or equal to 0.05 (p?0.05) was taken to be statistically significant. All
analyses were performed using SPSS software version 17.
The results for smear
layer scores in each group at coronal, middle and apical are conferred in Table
no 1, 2 and 3. The examination of the surface of root canal walls at coronal
third groups showed less or no smear layer (Fig. 1) and there was no statistically significant
samples at middle thirds shows no smear layer or minimal smear layer present
(Fig. 2) and there was no
statistically significant difference at middle layer of root canals (p_0.615). Chloroquick High group showed better smear layer removal at the apical thirds (Fig.
3). Chloroquick High shows statistically significantly better
(p_0.029) as compared to the other groups. Mann-Whitney U test shows that
Chloroquick High is able to remove better smear layer compared to Chloroquick Low
(p_0.028). Choloroquick Low has similar chelating
ability as compared to other solution there is no statically significant
difference at apical third.
This examination provides the insightful understanding
of smear layer abolition proceeding and capability of conventional irrigation
protocol and continuous soft chelating irrigation protocol. Satisfactory irrigation,
disinfection, and obturation are main principle of shaping. Accumulation of
smear layer is noticed while shaping of canals which need to abolish with the help
of irrigating solution. Whole activity needed from an irrigant to reduce smear
layer from dentin wall cannot be obtain by any sole irrigating solution.
Therefore, combined application of multiple irrigating solutions is obligatory for
optimal abolition of smear layer (5).Whereas Chloroquick solution is mix of
HEBP (a soft chelating agent) and NaOCl which can disinfect root canal as well
as reduces smear layer. Highlight of such combination of NaOCl and Etridonic
acid is that the NaOCl doesn’t surrender its biological, antibacterial and
tissue dissolving properties (13, 14), whereas the reduction and elimination of
the inorganic element is done with help of HEBP (11, 12).
Outcome of this current research demonstrate eradication
of smear layer was more decisive in middle and coronal third in comparison to
apical third. These results are in accordance with study done by Abbott PV, Heijkoop PS et al. and numerous studies, which have proved in past that
an effective cleaning action in the middle and coronal third of the root canals
even with numerous irrigation solutions, different volume, and time (15, 16).
In coronal and middle third areas where a larger canal diameter allows better
flow of solution and more time to be in contact with dentine wall which allows the
solution to remove smear layer comprehensively. (3,16).
of surfactant has been discussed and reviewed by numerous authors, in current
study SmearClear, SmearOFF and Chloroquick contains surfactant. Abou-Rass and
Patonai confirmed that reduction of surface tension of endodontic solutions
improved their flow into slender and narrow root canals (17). Therefore, an
improved penetration into apical narrow part of canals can be seen with
addition of surfactants to irrigation solution. In present study, SmearClear
and SmearOFF despite having additional surfactant doesn’t show the significant
removal of smear layer in apical third when compared to control group of 17%
EDTA, which does not have any addition surfactant. This result is in accordance
with the observations of Lui et al. (18) and also, other studies have shown
that calcium chelating ability of solution is not improved by reducing the surface
tension of the solution.
study results display that the continuous soft
chelating irrigation shows the significantly better removal of smear layer than
conventional irrigation protocol at apical third level when 18% HEBP was used
in combination with 5.25% NaOCl (Chloroquick High). Where 9% HEBP in
combination with 3% NaOCl (Chloroquick Low) did not show any significance
difference compared to conventional irrigation protocol groups. These results can
be attributed to chelating agent being more time in canal and also chelating
procedure is seen while instrumentation, unlike conventional irrigation
protocol where removal of smear layer is done only once instrumentation is
completed (19). Paque et al. demonstrated that the accumulation of hard tissue
debris in root canals when irrigated with amalgamation of NaOCl and HEBP was significantly less than irrigation
was performed with 2.5% NaOCl alone (20).Another advantage of this combination
is that it has better tissue dissolution capacity by keeping the hypochlorite-
hypochlorous acid equilibrium towards hypochlorite (21). This combination is
affective on inorganic as well as organic part of smear layer at same time.
of this study is in contrast to the recently published study by Aby
Kuruvilla et al. where 7%malic acid was
more effective in removing smear layer as compared to 17% EDTA and 18%
etidronic acid (22). This observation may be seen because 18% etidronic acid which
is soft chelating agent was merely used in a final rinse irrigation protocol
and not combined with sodium hypochlorite.
very few studies available on use of the continuous soft chelating agent for
smear layer removal. Future study should be aimed towards effect of both this
protocol on root canal walls. In present study, continuous soft chelating
irrigation protocol shows promising results.
Within the limitation of this in-vitro study
both the protocols conventional as well as continuous soft chelating irrigation
protocols were able to remove smear layer at coronal and middle third of the
root canals but at apical third only continues soft chelating irrigation
protocol performed with Chloroquick High shows better removal of smear.