Introduction there is no single solution which can

Introduction
  Various former studies have shown that the dentinal wall was
covered with smear layer after mechanical instrumentation of the root canals (1,2).
Regardless of the controversy over maintaining the smear layer it has been
demonstrated 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). Irrigants are paramount for successful debridement of the
root canals with mechanical procedures (3). There is no single solution is
efficient of removing both organic and inorganic parts of the smear layer. To
eliminate this smear layer combination of sodium hypochlorite (NaOCl) and
strong chelating agent such as Ethylenediaminetetraacetic acid (EDTA) is favored (8). It has been suggested
that smear layer was completely evacuated by 17% EDTA for 1min followed by 5.25%
NaOCl by Crumpton et al. (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 1minute
and 1ml of volume has been reported to be associated with dentinal erosion
(10,11). SmearClear (Sybron Endo, Orange, CA) is a product recently
introduced for removing 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 rinse.Etridonic acid which is soft chelating agent
appears to have a nominal effect on dentine walls yet can still reduce smear
layer Lottanti et al. 2009.
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. Chloroquick (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.  Materials
and methodsSixty freshly extracted human premolar teeth with straight
single root canal were selected and stored in distal water. To maintain
standard root length of 12 mm the teeth were decoronated and randomly divided
into 5 groups (n = 12). Measurements
of the working length were done by deducting 1mm from recorded root length with
#10 K-files (DentsplyMaillefer, Tulsa). Conventional irrigation protocol was followed 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
5.25% NaOCl.Group C (Smear OFF) –
1 ml of Smear OFF (Vista dental,) for 1 minute followed by 3 ml of 5.25% NaOCl.In continuous soft chelating irrigation protocol was
followed for 2 Groups D (Chloroquick Low) 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 solution. 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 two solution canals
were rinsed with 5 ml of distilled water and solutions were introduced into the
canals by means of a 30-G side vented needle, which penetrated within 1 to 2 mm
from the working length. In the end root canals were rinsed with 5ml of
distilled water and dried with paper points.Finally, on the buccal and
lingual surfaces of each root two longitudinal groves were prepared using
diamond disc without penetrating into the canal. The roots were then split into
two halves with a chisel. Then the specimens were mounted on the metallic
stubs, gold sputtered, and examined by a scanning electron microscope (FEI
Quanta 200 FE-SEM MK2, Netherlands). Images were taken at 2000× magnifications coronal
(9 mm to apex), middle (6 mm to apex), and apical (3 mm to apex) third of each
specimen. Scoring criteria given by Torabinejad
M, Khademi AA et al. where scores were given as follow score 1 = no smear
layer; no smear layer was detected on the surface of the root canals and all
tublues were open and clean; score 2 = moderate smear layer; no smear layer was
observed on the surface of thr root canal, but debris were present in tubules;
score 3 = heavy smear layer; the smear layer covered the root canal surfaces
and debris were present in tubules.All the images were scored by
an endodontist who was unaware of the groups and coding system to exclude
observer bias. Repeated evaluation was done to ensure intra examiner
consistency. Data were analyzed with the help of Kruskal-Wallis and Mann-
Whitney U tests; p values were computed and compared with thr p = 0.05 level. RESULTSDescriptive 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 presented 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 difference (p_0.643) Most 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.    DISCUSSIONThis study gives the
understanding of the process of smear layer removing ability of conventional
irrigation protocol and continuous soft chelating irrigation protocol. The main
objective of instrumentation is to promote effective irrigation, disinfection,
and filling. Smear layer production is seen while instrumentation procedures of
root canal which has to be eliminated with the use of irrigating solution. All
the functions required from an irrigant to remove smear layer from root canal
wall cannot be achieved by any single irrigating solution. Therefore, combined
use of 2 or several irrigating solutions is required for optimal removal of
smear layer (5). Whereas Chloroquick solution having HEBP as a soft chelating
agent and can be combined with NaOCl to become single solution for disinfecting
root canals. Highlight of such combination of NaOCl and HEBP is that the NaOCl
doesn’t loses its biological, antibacterial and tissue dissolving properties
(13, 14), whereas the reduction and removal of the inorganic matter is done
with HEBP (11, 12). Results of this present study
shows removal of smear layer was more efficient in coronal and middle third as
compared to apical third. This finding is in agreement with results of Abbott PV, Heijkoop PS et al.
study and many studies which have
proved in past that an effective cleaning action in the coronal and middle
third of the canals even with different irrigation solution, time, and volume
(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).             Role
of surfactant has been discussed by many authors, in present study SmearClear,
SmearOFF and Chloroquick have surfactant in the solution. Abou-Rass and Patonai
confirmed that reduction of surface tension of endodontic solutions improved
their flow into narrow root canals (17). Therefore, an addition of surfactants
to irrigation solution should improve its penetration into apical narrow part
of root canal. 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.             Present study results disply 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.              Result
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.  There are very few studies available on use of
the continuous soft chelating agent for smear layer removal. In present study,
continuous soft chelating irrigation protocol shows promising results.   CONCLUSION

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.