Keywords calcium hydroxide - cetrimide - chitosan - EndoVac - intracanal medicament
Introduction
Root canal treatment (RCT), the primary goal of endodontic treatment, is to prevent
and control pulpal and periradicular infections. Given the importance of microbes
in the etiology of these infections, it is evident that reducing or eliminating them
is critical to the success of endodontic therapy.[1 ] While mechanical preparation of infected root canals may remove microorganisms,
some bacteria hide in isthmuses, apical deltas, dentinal tubules, and ramifications
due to the root canal system's complexity. Thus, intracanal medicaments could help
eliminate these hidden bacteria.[2 ]
Calcium hydroxide (Ca(OH)2 ) is currently the most extensively used intracanal medication. Due to its well-documented
antibacterial efficacy against most endodontic infections, it is extensively used
as a root canal dressing between treatment sessions. The highly alkaline environment
created by Ca(OH)2 is unfavorable to most bacteria.[3 ]
Ca(OH)2 can be injected inside the root canal using a variety of carriers, including water,
carboxymethyl cellulose, glycerin, and silicone oil. The physical and chemical properties
of Ca(OH)2 are affected by the type of vehicle used. Calcium and hydroxyl ions are released
quickly in aqueous vehicles, whereas ionic dissociation takes longer in oily vehicles.[4 ]
Despite the efficacy of Ca(OH)2 as an intracanal medicament, certain bacterial species have been observed to be resistant
to total eradication, including Enterococcus faecalis .[2 ] In these scenarios, Ca(OH)2 paste with a silicone oil-based carrier containing 38% iodoform (Metapex [Meta Biomed,
Korea]) is preferred over Ca(OH)2 alone because it disinfects dentinal tubules infected with E. faecalis better.[5 ]
Before starting the obturation, the Ca(OH)2 medicament should be removed to avoid any interference with the obturating material
and to permit maximum adherence between the sealer and the root canal wall.[6 ] Silicone oil-based Ca(OH)2 is more difficult to remove than aqueous-based Ca(OH)2 due to lesser penetration of the irrigant through the silicone oil layer.[7 ]
It has been demonstrated that eliminating Ca(OH)2 intracanal medication requires sodium hypochlorite (NaOCl) (5.25%) followed by a
final rinse of ethylenediaminetetraacetic acid (EDTA) (17%).
For the removal of the remaining Ca(OH)2 from the root canal, a variety of root canal irrigants, including saline, NaOCl,
and EDTA, can be used alone or in conjunction with several techniques, including EndoVac,
EndoActivator, CanalBrush, Max-i-Probe needle, and passive ultrasonic irrigation in
conjunction with hand instrumentation.[8 ]
Chitosan nanoparticle (NP) is a nontoxic, biocompatible, biodegradable, and bioadhesive
natural polysaccharide produced by deacetylating chitin.[5 ] Similar to EDTA and citric acid, it displays chelation characteristics but with
significantly fewer negative effects.[9 ] The present study's purpose was to compare the efficacy of two irrigants (5.25%
NaOCl followed by a final rinse of 17% EDTA, 0.2% chitosan NPs) and two techniques
(conventional irrigation, EndoVac) for the removal of silicone oil-based Ca(OH)2 medicament (Metapex) from the apical third of the root canal.
Materials and Methods
Sample size was determined based on a pilot study, by calculating mean and standard
deviation. Ethical clearance was provided by institutional ethical committee (ABSM/EC66/2019)
dated October 15, 2019. Forty extracted single-rooted human premolars extracted for
orthodontic purposes were collected. The teeth included were caries free and with
a completely formed apex. The specimens were cleaned of soft tissue and calculus using
an ultrasonic device. A diamond disc (Confident Dental Equipments Ltd., India) was
used to decoronate each of the 40 samples to produce a standardized root length of
15 mm. The study of Alturaiki et al formed the basis for the methodology. Root canal
patency was established with a No. 15 K file (Dentsply Maillefer, Switzerland).[10 ] The working length (WL) was kept 1 mm short of the apex. The root canals were prepared
using ProTaper rotary files till F3 (Dentsply Maillefer).
Canals were routinely cleaned with 5 mL of 17% EDTA (Anabond Stedman, Chennai, India),
5 mL of distilled water, and 5 mL of 5.25% NaOCl (Coltene, Switzerland) between each
instrument. The needle was moved up and down inside the apical third during irrigation.
After the canal had been dried with paper points, the access cavity was sealed with
a cotton pellet and Cavit. The Metapex was then inserted into the root canal until
it came out from the apex. The samples were kept for a week at 37°C and 100% humidity.
Chitosan NP was dissolved in 100 mL of 1% acetic acid, yielding a 0.2% chitosan NP
solution. The provisional restoration was removed and the samples were randomly divided
into four groups:
Group 1 (conventional irrigation using 5.25% NaOCl and 17% EDTA, n = 10): The removal of CH was performed with a conventional irrigation needle with
5 mL of 5.25% NaOCl followed up by 5 mL of 17% EDTA. For 60 seconds, a continuous
flow was applied while moving the needle up and down within the apical third. By positioning
the rubber stopper 1 to 2 mm short of the operating length, the needle depth was standardized
for each canal.
Group 2 (conventional irrigation using 0.2% chitosan NPs, n = 10): The CH removal was done with 5 mL of 0.2% chitosan NPs and a conventional
irrigation needle with the same technique as described earlier.
Group 3 (EndoVac using 5.25% NaOCl and 17% EDTA, n = 10): Using the EndoVac device, the canals were irrigated for 30 seconds with each
solution, 5 mL of 5.25% NaOCl and 5 mL of 17% EDTA.
Group 4 (EndoVac using 0.2% chitosan NPs, n = 10): CH removal was performed using 0.2% chitosan NPs in combination with the EndoVac
system for 60 seconds.
The decoronated teeth are longitudinally sectioned before scanning electron microscopy
(SEM) analysis following pretreatment and Metapex implantation. A similar methodology
is used in this investigation as well. It is claimed that longitudinal sectioning
will result in a more precise measurement of the root canal residuals.[11 ]
After irrigant activation, the roots were divided into two halves buccolingually without
perforating the root canal and SEM analysis was performed for one half of each tooth
at a magnification of ×2,000 (Carl Zeiss Sigma FESEM 03-81) at the apical third ([Fig. 1 ]). For SEM analysis, the samples were dehydrated, then fixed on aluminum stubs, and
finally coated with gold sputtering. Two endodontists who were blinded to the samples
being tested evaluated the SEM photomicrographs for cleanliness. The degree of Ca(OH)2 medication removal and dentinal wall cleaning was assessed using a five-grade scoring
system.[10 ] They are as follows: Score 1: 80 to 100% CH removal (total cleanliness); Score 2:
60 to 80% CH removal (great cleanliness); Score 3: 40 to 60% CH removal (partial cleanliness);
Score 4: 20 to 40% CH removal (light cleanliness), and Score 5: 0 to 20% CH removal
(no cleanliness).
Fig. 1 Scanning electron microscopy images of the apical third of the root canal at ×2,000
magnification.
Results
The study followed the protocol of double blinding during the whole procedure, where
each sample was examined by two people blindly and evaluated. Sample size was 10 per
group. As four groups were included in this study, it gave an overall sample size
of 40. Where between group variance was 0.83, power was 80% and an α error of 5%,
which gave the required sample size of 40, where sample size per group is 10.
Since this was a qualitative analysis, chi-square test was done. The p -value associated with the chi-square test is less than 0.001, which is highly significant
([Table 1 ]). To compare the difference between each group, one-way analysis of variance was
done. On comparison of the degree of Ca(OH)2 removal, the highest mean is seen in Group 1 (4.3) followed by Group 2 (3.5), Group
3 (3), and the least value in Group 4 (1.7). This parameter is statistically significant
with a p -value of <0.001. To compare each group, post hoc analysis was done which indicates
significant differences between Groups 1 and 3, Groups 1 and 4, Groups 2 and 4, Groups
3 and 4 with a p -value of less than 0.05 for each.
Table 1
Depicting degree of calcium hydroxide removal
Degree of calcium hydroxide removal
Group
Total
Group 1
Group 2
Group 3
Group 4
Score 1
Count
0
0
0
4
4
% within group
0%
0%
0%
40%
10%
Score 2
Count
0
0
2
5
7
% within group
0%
0%
20%
50%
17.5%
Score 3
Count
2
5
6
1
14
% within group
20%
50%
60%
10%
35%
Score 4
Count
3
5
2
0
10
% within group
30%
50%
20%
0%
25%
Score 5
Count
5
0
0
0
5
% within group
50%
0%
0%
0%
12.5%
Total
Count
10
10
10
10
40
% within group
100%
100%
100%
100%
100%
Chitosan NPs showed the least mean canal cleanliness scores at the apical one-third
of the root canal when compared with the other irrigants along with EndoVac method
(1.7 ± 0.675). A significant difference in mean canal cleanliness scores was observed
in the four groups (p = 0.00).
The conventional needle irrigation method showed higher scores of canal cleanliness
in the apical area when compared with the EndoVac method with the irrigating solutions
used and a statistically significant difference was observed between the methods at
p < 0.05.
Results of the study indicated that there is statistical difference between the values
of the group with significant p -value. Ca(OH)2 removal with EndoVac using 0.2% chitosan NPs has shown better results as compared
with all the other groups.
Discussion
Intracanal medicaments reduce bacterial growth in the canal and prevent the spread
of infection within the root canal by acting as a physiochemical barrier. Ca(OH)2 is proven to be an effective intracanal medicament due to its excellent antimicrobial
properties, neutralization of bacterial endotoxins, and in periapical tissue repair.
The complete removal of intracanal medicaments might be impracticable many times due
to the morphological variations of the root and canal wall irregularities. Therefore,
in the current study, the extracted single-canal human premolars with straight roots
were used.[8 ]
[12 ]
The residual intracanal medicament may serve as an irritant causing failure of endodontic
treatment.[13 ] Additionally, when residual Ca(OH)2 interacts with zinc oxide and eugenol-based sealers, calcium eugenolate is created,
which is brittle in consistency and has a granulated structure due to which the sealer
penetration is hindered.
Moreover, the interaction of residual Ca(OH)2 with zinc oxide and eugenol-based sealers leads to the formation of calcium eugenolate.
The former, being brittle with a granular structure, impedes the sealer penetration
into the dentinal tubules, which can eventually impact the treatment outcome.[14 ] Hence, complete removal of the residual intracanal medicament before obturation
of the root canals has been suggested.[15 ]
Aqueous vehicles are the most often utilized carriers for Ca(OH)2 intracanal medication because they encourage quick ion liberation, while viscous
and oily vehicles release calcium and hydroxyl ions over longer periods, minimizing
the number of dressing-changing sessions. However, the use of intracanal medications
with oily vehicles may leave a residue on the root canal walls that will make it harder
for the sealer to attach to the walls, which will affect the treatment outcome.[16 ] A study done by Sokhi et al, to evaluate the effect of three CH-based intracanal
medicaments on the apical sealing ability of AH Plus—gutta-percha obturation, concluded
that the vehicle used to carry Ca(OH)2 intracanal medication may significantly influence the apical sealing ability of gutta-percha—AH
Plus obturated canals.[17 ]
[18 ]
Numerous studies have suggested the method of Ca(OH)2 removal from the root canal walls.[8 ]
[10 ] The most commonly used clinical technique for the removal of Ca(OH)2 intracanal medicament is by using the master apical file combined with numerous irrigants
such as normal saline, NaOCl, EDTA, alone and in combination.[18 ]
[19 ]
In the present study, the objective was to assess the efficacy of 5.25% NaOCl followed
by a final rinse of 17% EDTA and 0.2% chitosan NPs used with conventional irrigation
and EndoVac for the removal of Metapex from the apical third of the root canal by
SEM analysis. The outcomes showed that none of the techniques was successful in eliminating
the Ca(OH)2 medication from the apical third.
NaOCl has been commonly used in endodontics in various concentrations as the primary
root canal irrigant due to its antibacterial activity against a wide array of microorganisms,
including Enterococcus , Actinomyces , and Candida species, which are difficult to eliminate from the root canals. Based on the previous
studies, the best irrigation protocol for the removal of Ca(OH)2 intracanal medicament is by using 5.25% NaOCl and 17% EDTA.[8 ] During the canal preparation method, alternating between NaOCl and EDTA solutions
decreases debris formation and results in cleaner canals, according to various studies.
Chitosan's chelating mechanism on dentin has not been well documented. This bioactive
biopolymer, on the other hand, is commonly employed as a chelating agent to remove
heavy metals from wastewater. The chelating mechanism of chitosan has been explained
using two theories. To begin, the bridge model proposes that two or more chitosan
amino groups are attached to the same metal ion. Second, the pendant model implies
that just one amino group is used in the binding, and the metal ion is suspended from
the amino group.[20 ] The chelation of calcium ions in dentin, which results in the loss of inorganic
materials from the smear layer, could be caused by any of the two methods. A study,
done to investigate the ability of bioactive chitosan NPs to remove the smear layer
and inhibit bacterial recolonization on dentin, concluded that it could be used as
a final irrigant during RCT with the dual benefit of removing the smear layer and
inhibiting bacterial recolonization on root dentin.[21 ] Another study concluded that 17% EDTA is a potent chelating agent that can successfully
remove the smear layer but compromises the Ca/P ratio of dentin. However, 0.2% chitosan
and its NPs have comparable chelating effects and induce remineralization of the root
canal dentin.[22 ]
Various methods such as capturing images using a digital camera, stereomicroscope,
micro-computed tomography (CT), and cone beam CT have been used to assess the cleanliness
of the root canal walls. Most of the studies assessed the amount of residual intracanal
medicament in the canal walls by measuring the surface area of the residues on the
canal walls. The amount covered is then scored, and estimated through SEM, or by volumetric
analysis using spiral CT.[9 ]
SEM is considered a standard and the most reliable approach to examine and evaluate
canal cleanliness after the removal of Ca(OH)2 using various recent technologies along with irrigants. Nandini et al used volumetric
analysis with spiral CT to evaluate Ca(OH)2 elimination. The present work used SEM analysis to emphasize the condition of the
dentinal tubules despite the benefits of spiral CT, such as three-dimensional volume
measurements of the remaining Ca(OH)2 packed in the canal without root sectioning (open, eroded, and occluded).[11 ]
[23 ]
In the present study, the removal of Metapex from the apical third of the root canal
using conventional irrigation technique and EndoVac technique with 5.25% NaOCl followed
by a final rinse of 17% EDTA and 0.2% chitosan NPs was assessed. The comparison of
the effectiveness of the irrigants, as well as the techniques, was evaluated using
SEM in the apical third of the root canal. A five-grade scoring scale was used which
determines the extent of cleanliness of the canal by the percentage of Ca(OH)2 removed.[8 ]
[10 ]
Considering the irrigant used in the present study, 0.2% chitosan NPs was found to
be the most effective using the EndoVac technique. EndoVac has the advantage of producing
negative pressure and allowing for safe use up to the WL without irrigant extrusion
past the apical constriction of the canal. It makes use of a suction device with a
macro- or microcannula connected to it. A negative pressure is created by the cannula,
which is attached to a high-speed suction. This draws the irrigant to the cannula's
tip and pokes little holes in it to let the irrigation solution and debris escape.
A study conducted to compare the debridement efficacy of EndoVac irrigation versus
conventional needle irrigation in vivo concluded that EndoVac irrigation resulted
in significantly less debris at 1 mm from WL compared with conventional needle irrigation.[24 ] Another study done to compare the smear layer removal efficacy of 17% EDTA, 0.2%
chitosan NPs, and QMix 2in1 at apical third of root canal system, using EndoVac system
concluded that the final irrigation with QMix 2in1 solution aids in better smear layer
removal at the apical third of the root canal system, using EndoVac system irrigation
system.[25 ] The current study's findings are supported by prior research that indicates the
EndoVac system leaves substantially less debris behind than conventional irrigation
techniques when used with both irrigants.[21 ]
[26 ]
Conventional syringe irrigation has been widely used for the delivery of irrigants
due to the ease of control of the needle penetration depth into the canal space and
the quantity of the irrigant that is flushed through the canal. An irrigant's hydrodynamic
activation is enhanced by agitating the needle by moving it up and down within the
canal. It also reduces the chance of apical extrusion of the irrigant. The needle
placed within the canal should remain loose during irrigation to allow the backflow
of the irrigant, which also helps in the coronal displacement of the debris and avoids
the periapical extrusion of the irrigant.[27 ]
The most commonly used irrigation technology is still the conventional irrigation
technique due to several reasons such as its simplicity, ease of controlling the depth
of needle penetration, and irrigant volume flushed down through the canal. The results
of this study demonstrate the necessity for more sophisticated irrigation techniques,
such as EndoVac. Literature implies that using an agitation system can improve the
action of the irrigant, thereby improving its efficacy in removing Ca(OH)2.
[8 ]
Limitations and Future Directions
Limitations and Future Directions
While these in vitro findings are promising, they may not translate directly to clinical
situations due to the complexities present. In vivo studies are crucial to validate
these findings in a clinical context, as the current in vitro environment may not
fully represent real-world conditions. Another limitation of the present study was
less sample size, it can be done with a larger sample size. Future research should
explore other optimal concentrations of the different agents used, different agitation
techniques such as ultrasonic agitation, and potential synergistic effects with different
irrigants to maximize the medicament removal and treatment efficacy.
Conclusion
The present study has limitations as it is an in vitro study and should be performed
in a large number of samples in a simulated clinical environment. Within the limitations
of this study, it can be concluded that the EndoVac technique along with 0.2% chitosan
NPs proved to be the most effective in removing the silicone oil-based intracanal
medicament from the apical third of the root canal.
