Clinical Research

One-Visit Versus Two-Visit Root Canal Treatment:

Effectiveness in the Removal of Endotoxins
and Cultivable Bacteria
Ana Claudia C. Xavier, DDS, MSc, Frederico C. Martinho, DDS, MSc, PhD,
Adriana Chung, DDS, MSc, Luciane D. Oliveira, DDS, MSc, PhD,
Ant^
onio O.C. Jorge, DDS, MSc, PhD, M
arcia C. Valera, DDS, MSc, PhD,
and Cl
audio A.T. Carvalho, DDS, MSc, PhD

Abstract
Introduction: This clinical study was conducted to Key Words
compare the effectiveness of 1-visit versus 2-visit root Endotoxin, LAL, limulus amebocyte lysate assay, root canal
canal treatment in removing endotoxins and cultivable
bacteria from primarily infected root canals. Methods:
Forty-eight primarily infected root canals were selected
and randomly divided into 4 groups: G1, 1% NaOCl; G2,
O ne-visit and 2-visit root canal treatments have gained attention during recent
decades under different aspects, including healing rates, postobturation pain,
bacterial disinfection, as well as patient preferences (1–4).
2% chlorhexidine (CHX) gel; G3, 1% NaOCl + Ca(OH)2; It has long been known that the infectious disease involved in apical periodontitis
and G4, 2% CHX gel + Ca(OH)2 (all, n = 12). G1 and G2 is the result of the interplay between number of bacterial cells, microbial virulence, and
involved 1-visit treatment, whereas G3 and G4 involved host defense (5). Therefore, ideal antimicrobial treatment protocol for teeth with apical
2-visit treatment with the placement of Ca(OH)2 medica- periodontitis should be able to eliminate bacteria (3, 6, 7) as well as microbial
tion for 14 days. Samples were collected before and after virulence factors (7, 8), which might contribute to the perpetuation of periapical
root canal procedures. A chromogenic LAL assay test was inflammation process.
used to quantify endotoxins. Culture techniques were Lipopolysaccharide (LPS), generally referred to as endotoxin, major constituent of
used to determine bacterial counts. Results: Endotoxins the outer cell wall of gram-negative bacteria, is one of the most important virulent
and cultivable bacteria were detected in 100% of the factors participating in the development and maintenance of apical periodontitis
initial samples. All treatment protocols were effective in (9, 10). Clinical investigations have revealed the presence of endotoxin in 100% of
reducing bacterial load from infected root canals: G1 the root canal samples in primary (7, 8, 11–14) and secondary (14, 15) infectious
(1% NaOCl, 99.97%), G2 (2% CHX gel, 99.75%), G3 diseases showing apical periodontitis, with high levels related to the development of
(1% NaOCl + Ca(OH)2, 99.90%), and G4 (2% CHX gel clinical symptoms and larger area of bone destruction (7, 11–13).
+ Ca(OH)2, 96.81%), respectively (P < .05). No differ- Because of the high toxicity of endotoxin in vivo (10, 16) and in vitro (17), even
ences were found in bacterial load reduction when at very low concentrations, its removal/neutralization during endodontic treatment
comparing 1-visit and 2-visit treatment groups, irrespec- seems to be important for the healing process of periapical tissues of infected root
tive of the irrigant tested (P > .05). Higher median canals (8, 11).
percentage values of endotoxin reduction were achieved The root canal disinfection can be attained by treatment involving chemomechan-
in the 2-visit treatment groups (G3, 98.01% and G4, ical preparation, immediately followed by obturation (1-visit treatment) or supple-
96.81%) compared with 1-visit treatment groups (G1, mented by a previous interappointment intracanal medication (2-visit treatment) (3, 6).
86.33% and G2, 84.77%) (all P < .05). Conclusions: Previous studies evaluating the efficacy of chemomechanical procedures in
Both 1-visit and 2-visit root canal treatment protocols reducing/eliminating endotoxins from infected root canals by using sodium
were effective in reducing bacteria and endotoxins, but hypochlorite (NaOCl) (7, 8, 11) as well as chlorhexidine gel 2% (CHX) (11, 18)
they were not able to eliminate them in all root canals indicated that the mechanical debridement along with irrigation is able to reduce
analyzed. Furthermore, 2-visit root canal treatment proto- endotoxin contents z50% (by using conventional instrumentation) (7, 11, 18) and
cols were more effective in reducing endotoxins than z98% by using rotary nickel-titanium files (8). However, endotoxins were still de-
1-visit root canal treatment protocols. (J Endod tected in 100% of the root canal samples of infected teeth after instrumentation (8,
2013;39:959–964) 11, 18).

From the Department of Restorative Dentistry, Endodontic Division–UNESP-UNIV Estadual Paulista, S~ao Jose dos Campos Dental School, S~ao Jose dos Campos, S~ao
Paulo, Brazil.
Supported by the Brazilian agencies FAPESP (2008/54536-0, 2009/54621-0, 2012/19536-5), FAPERJ (E-26/110-265/2012), and CNPQ (10557/2011-6).
Address requests for reprints to Dr Frederico C. Martinho, S~ao Jose dos Campos Dental School, State University of S~ao Paulo–UNESP, Department of Restorative
Dentistry, Endodontic Division, Eng Francisco Jose Longo, 777, S~ao Jose dos Campos, 12245-000 SP, Brazil. E-mail address: frederico.martinho@fosjc.unesp.br
0099-2399/$ - see front matter
Copyright ª 2013 American Association of Endodontists.
http://dx.doi.org/10.1016/j.joen.2013.04.027

JOE — Volume 39, Number 8, August 2013 1-Visit vs 2-Visit Root Canal Treatment 959
Clinical Research
Calcium hydroxide [Ca(OH)2], the most commonly used amebocyte lysate (LAL) water according to the endotoxin dosage by
intracanal medication during 2-visit treatment, has been proven to be using the kinetic chromogenic LAL (Lonza, Walkersville, MD) assay.
effective against endotoxins as demonstrated by in vitro studies (19– This sampling procedure was repeated with 3 paper points that were
21). However, in clinical practice, controversy exists on whether pooled in a sterile tube containing 1 mL VMGA III transport medium
Ca(OH)2 medication can improve the removal or elimination of (23) for microbial cultivation.
endotoxins from infected root canals (18, 22). After accessing the pulp chamber and subsequent first endotoxin
There is currently no clinical study comparing the effectiveness of sampling, teeth were randomly divided into 4 groups: G1, 1% NaOCl
1-visit versus 2-visit root canal treatment protocol regarding the (n = 12); G2, 2% CHX gel (n = 12); G3, 1% NaOCl + calcium hydroxide
removal of endotoxins from primarily infected root canals with apical [Ca(OH)2] (n = 12) medication; and G4, 2% CHX gel + [Ca(OH)2]
periodontitis. medication (n = 12), with the first 2 groups involving 1-visit
Therefore, this clinical study was conducted to compare the treatment and the latter 2 involving 2-visit treatment.
effectiveness of 1-visit versus 2-visit root canal treatment in removing Next, the cervical and middle thirds of the root canals were
endotoxins and cultivable bacteria from primarily infected root canals. prepared with the crown-down technique by using Endo-Eze files
(Ultradent Products, South Jordan, UT) according to the manufacturer’s
Materials and Methods instructions. The Endo-Eze files were adapted to the Endo-Eze contra-
angle handpiece (Kavo do Brasil, Ltda, Saguaçu Joinville, SC, Brazil).
Patient Selection
K-files, size #15 or #20 (Dentsply-Maillefer), were always used between
Forty-eight patients attending the S~ao Jose dos Campos Dental each instrumentation. The lumen of the canal was identified by using
School (UNESP), S~ao Jose dos Campos (SP), Brazil for primary a K-file size #10 (Dentsply-Maillefer). Next, cervical interferences
endodontic treatment were included in the present study. A detailed were eliminated with the 13/.60 instrument of the Endo-Eze system
dental history was obtained from each patient. Those who had received according to the same principles of the crown-down pressureless tech-
antibiotic treatment during the last 3 months or who had any general nique. Instrumentation was continued by using oscillating 13/.45 file,
disease were excluded. The Human Research Ethics Committee of the K-file (#15 or 20), oscillating 13/.35 file, K-file (#15 or 20), and os-
S~ao Jose dos Campos Dental School (UNESP) approved the protocol cillating 10/.25 file until reaching a depth 3 mm shorter than the full
describing the sample collection for this investigation, and all volunteer length of the root canal, as calculated from preoperative radiographs.
patients signed an informed consent form. During preparation of the cervical and middle thirds, the root canal
All the selected teeth were single-rooted with primary endodontic was filled with selected auxiliary chemical substance, followed by irriga-
infection, showing the presence of 1 root canal and absence of tion and aspiration of 5 mL sterile apyrogenic saline after use of the
periodontal pockets deeper than 4 mm. None of the patients reported oscillating instrument. This procedure was repeated at each file change.
spontaneous pain. Teeth that could not be isolated with rubber dam The apical preparation was performed by using 4 manual K-files
were excluded. The following clinical/radiographic features were found (Dentsply-Maillefer), which ended in #35 to #45 size.
in root canals with primary endodontic infections investigated: pain on In the 1-visit 1% NaOCl group (G1), the use of each instrument was
palpation, 2 of 40, tenderness to percussion, 7 of 40, and size of followed by irrigation with 5 mL 1% NaOCl solution by means of a syringe
radiolucent area >3 mm, 29 of 40. (27-gauge needle). Before the second sampling after instrumentation,
NaOCl was inactivated with 5 mL sterile 0.5% sodium thiosulfate during
Sampling Procedures 1-minute period, which was then removed with 5 mL sterile/apyrogenic
Files, instruments, and all materials used in this study were treated water.
with Co60 gamma radiation (20 kGy for 6 hours) for sterilization and In the 1-visit 2% CHX gel group (G2), root canals were irrigated
elimination of preexisting endotoxins (EMBRARAD; Empresa Brasileira with a syringe (27-gauge needle) containing 1 mL of the substance
de Radiaç~ao, Cotia, SP, Brazil). The method used for disinfection of the before each instrument and immediately rinsed with 4 mL saline
operative field has been previously described (8, 10, 16). Briefly, the solution. Before the second sampling after instrumentation, 2% CHX
teeth were isolated with a rubber dam. The crown and surrounding activity was inactivated with 5 mL solution containing 5% Tween 80
structures were disinfected with 30% H2O2 (volume/volume for 30 and 0.07% (w/v) lecithin during 1-minute period, which was then
seconds), followed by 2.5% NaOCl for the same period of time and removed with 5 mL sterile/apyrogenic water.
then inactivated with 5% sodium thiosulfate. The sterility of the In the 2-visit 1% NaOCl group (G3) and 2-visit 2% CHX gel group
external surfaces of the crown was checked by taking a swab sample (G4), root canal irrigation was performed as described earlier, and
from the crown surface and streaking it on blood agar plates, which subsequently the canals were dried by using sterile/apyrogenic paper
were then incubated both aerobically and anaerobically. points and filled with freshly prepared paste of Ca(OH)2 in propylene
A 2-stage access cavity preparation was made without the use of glycol for a period of 14 days. The paste was inserted into the canals
water spray but under manual irrigation with sterile/apyrogenic saline with the aid of a lentulo spiral. Care was taken to properly fill the
solution and by using sterile/apyrogenic high-speed diamond bur. The root canal with the calcium hydroxide paste without any radiographi-
first stage was performed to promote a major removal of contaminants, cally visible air bubbles. The paste was condensed at the canal orifice
including carious lesion and restoration. In the second stage before level with the aid of a sterile cotton pellet. Next, the access cavities
entering the pulp chamber, the access cavity was disinfected according were properly closed with ionomer cement.
to the protocol described above. Sterility of the internal surface of the After 14 days with intracanal medication, the samples of G2 and G4
access cavity was checked as previously described, and all procedures had their surgical field isolated and disinfected, including removal of the
were performed aseptically. A first endotoxin sampling was taken by provisional restoration. Next, the root canals were irrigated with 10 mL
introducing sterile/apyrogenic paper points (size #15; Dentsply- saline solution, and calcium hydroxide antimicrobial activity was
Maillefer, Balaigues, Switzerland) into the full length of the canal, which neutralized with 0.5% citric acid. Afterward, another collection of bacte-
was determined radiographically, and retained in position during 60 rial material and endotoxins was performed.
seconds for sampling. Immediately afterward, the sample was placed At the end of instrumentation, root canals in all 4 groups were
in a pyrogen-free glass and immediately suspended in 1 mL limulus flooded with 17% EDTA during 3-minute period. EDTA was activated

960 Xavier et al. JOE — Volume 39, Number 8, August 2013

 Clinical Research
by using hand K-files. Next, a final rinse with 5 mL sterile/apyrogenic bacterial and endotoxin reductions found in all groups tested at
saline solution was performed. different sampling times.

Endotoxin Procedures Quantification of Endotoxin Concentration (LAL Assay)

Quantification of Endotoxins (LPS) by Kinetic Chromo- The standard curve for detection of endotoxins fulfilled the
criteria of linearity (r = 1). At the baseline, the LAL assay indicated
genic LAL Assay. The kinetic chromogenic LAL assay (Lonza) that endotoxins were detected in 100% of the root canals with a median
was used for quantification of endotoxins. Escherichia coli endotoxin value of 127 EU/mL (40 of 40), ranging from 5.47–394 EU/mL.
was used as standard. A positive control (root canal sample Individual median and range of values of endotoxins found in 1-visit
contaminated with a known amount of endotoxin) was included for treatment (G1, G2) and 2-visit treatment (G3, G4) groups at different
each sample to determine the presence or absence of interfering agents. sampling times are shown in Table 1. In the 1-visit treatment groups,
For the test, 100 mL apyrogenic water (reaction blank), 5 standard statically significant median percentage values of endotoxin reduction
endotoxin solutions (0.005–50 endotoxin units [EU]/mL), root canal were achieved after chemomechanical preparation (G1, 1% NaOCl,
samples, and positive controls (each root canal sample contaminated 86.33% and G2, 2% CHX, 84.77%) compared with the baseline
with a known concentration of endotoxin [10 EU/mL]) were added samples (all P < .05) (Fig. 1). After treatment, no endotoxins were
to a 96-well apyrogenic plate. The tests were carried out in quadrupli- detected in 6 of 12 root canals (50.00%) irrigated with 1% NaOCl
cate. The plate was incubated at 37 C  1 C for 10 minutes in a Kinetic- (G1) and 5 of 12 root canals (41.00%) irrigated with 2% CHX gel
QCL (Lonza) reader, which was coupled to a microcomputer by means (G2). After 14 days of Ca(OH)2 medication (2-visit treatment groups),
of the WinKQCL software. Next, 100 mL chromogenic reagent was added the median percentage values of endotoxin reduction found in G3
to each well. After the beginning of the kinetic test, the software [1% NaOCl + Ca(OH)2] and G4 [2% CHX + Ca(OH)2] were
continuously monitored absorbance at 405 nm in each microplate 98.01% and 96.81%, respectively (Fig. 1). No statistically significant
well and automatically calculated the log/log linear correlation between difference was found between G3 and G4 (P > .05). In G3 and G4,
reaction time of each standard solution and corresponding endotoxin endotoxins were not detected in 7 of 12 (58.33%) and 6 of 12
concentration. (50.00%) root canals investigated, respectively. Higher
median percentage values of endotoxin reduction were achieved in
Culture Procedure both 2-visit treatment groups compared with the 1-visit treatment
Determination of Cultivable Bacterial Counts (Culturing groups (P < .05).
Procedure). The method used for culture procedures in the
present study had been previously reported by the author (10). Determination of Cultivable Bacterial Counts
Briefly, the transport media containing the root canal samples (Culturing Procedure)
were thoroughly shaken for 60 seconds (Vortex; Marconi, Piraci- Bacteria were found in all initial samples of the 40 root
caba, S~ao Paulo, Brazil). Serial 10-fold dilutions were made up to canals investigated. In the baseline samples, CFU count ranged from
10 4 in tubes containing fastidious anaerobe broth (FAB; Lab M, 2  103 to 5.70  107 (median value, 1.6  106). Individual median
Bury, UK). Fifty microliters of the serial dilutions was plated onto and range of values of bacterial counts found in the 1-visit treatment
5% defibrinated sheep blood fastidious anaerobe agar (FAA; Lab (G1, G2) and 2-visit treatment groups (G3, G4) at different sampling
M) by using sterile plastic spreaders to culture nonselectively times are shown in Table 1. In the 1-visit treatment groups, significant
obligate anaerobes and facultative anaerobes. The plates were median percentage values of bacterial reduction were achieved after
incubated at 37 C in anaerobic atmosphere for up to 14 days. After chemomechanical preparation (1% NaOCl, 99.97%; 2% CHX,
this period, colony-forming units (CFUs) were visually quantified for 99.75%) compared with the baseline samples (all P < .05)
each plate. (Fig. 1). No statistically significant difference was found between the
median percentage values of bacterial reduction found in G1 and
G2 (P > .05). No cultivable bacteria were recovered from 3 of 12
Statistical Analysis root canals (25%) irrigated with 1% NaOCl (G1) and 3 of 12 root
The data collected (CFUs and endotoxin concentrations) were canals (25%) irrigated with 2% CHX gel (G2). After 14 days of
statistically analyzed by using SPSS for Windows (SPSS, Inc, Chicago, Ca(OH)2 medication (2-visit treatment groups), the median
IL). The Kolmogorov–Smirnov test showed that the distributions of percentage values of bacterial load reduction found in G3 [1% NaOCl
the studied variables deviated from normality. Friedman test was + Ca(OH)2] and G4 [2% CHX + Ca(OH)2] were 99.90% and 96.62%,
performed to compare the amount of bacteria and endotoxin contents respectively (Fig. 1). After 14 days of Ca(OH)2 medication, 4 of
before and after endodontic treatment. Wilcoxon test was used when 12 root canals (33%) in the 1% NaOCl group (G3) and 2 of 12 canals
significant differences were found between different sampling times. (16%) in the 2% CHX gel group (G4) yielded no cultivable bacteria.
Comparison among the root canal treatment groups (G1, G2, G3, and No differences were found in the median percentage values of bacterial
G4) was performed by using the Kruskal-Wallis test. Significance level load reduction by comparing 1-visit treatment (G1 and G2) with 2-visit
was always set at 5% (P < .05). treatment (G3 and G4) groups, irrespective of the irrigant tested
(P > .05) (Table 1).
Results
Sterility samples taken from the external and internal surfaces of Discussion
the crown and its surrounding structures, tested before and after Data obtained in the present study revealed that 2-visit treatment
entering the pulp chamber, showed no microbial growth. Table 1 protocol, which used either 1% NaOCl or 2% CHX gel as irrigant along
provides an overview of the endotoxin concentrations (EU/mL), amount with an interappointment medication with Ca(OH)2 for 14 days, re-
of cultivable bacteria (CFU/mL), range in values, number of endotoxin- sulted in statically significant improvement of endotoxin removal
positive and culture-positive samples, and percentage values of from primarily infected root canals compared with 1-visit treatment

JOE — Volume 39, Number 8, August 2013 1-Visit vs 2-Visit Root Canal Treatment 961
Clinical Research

7.2  102 (0–2.88  103)

2.2  102 (0–3.8  102)
After treatment

4.88 (0–36.5)
1.92 (0–15.1)
2-visit treatment

1.04  107 (8.0  103 to 2.8  102)

4.2  104 (8.0  103 to 3.6  106)
Before treatment

154 (5.47–394)
198 (22–196)

Figure 1. Distribution of percentage values of endotoxin and cultivable

bacteria reduction found in primary root canal infection after 1-visit and
2-visit root canal treatment.
TABLE 1. Effectiveness of 1- and 2-Visit Root Canal Treatment on Endotoxins (EU/mL) and Cultivable (CFU/mL) Bacteria by Using NaOCl and CHX Gel

protocol, thus confirming the importance of using an interappointment

dressing to enhance the endotoxin-detoxifying effects of the chemome-
chanical preparation.
In the present study, all initial samples were positive for the
G3
G4

G3
G4

presence of bacteria, and the number of CFU values per canal ranged
from 2  103 to 5.70  107, which is comparable to previous studies
(7, 18, 24, 25). In the 1-visit treatment protocol, although substantial
3.4  102 (0–2.0  103)
8.0  102 (0–4.0  102)

bacterial load reduction was achieved by mechanical debridement

After treatment

along with irrigation (in more than 99%), cultivable bacteria were still
15.65 (0–80.6)
19.75 (0–90.3)

detected in 25% of the root canals irrigated with either 1% NaOCl or 2%

CHX gel. The limited ability of root canal treatment to eliminate bacteria
has been demonstrated by previous studies in which cultivable bacteria
Median and range of values of endotoxins and cultivable bacteria found in root canals before and after 1- and 2-visit treatment protocol.

could still be recovered in z20%–60% of the infected teeth after

chemomechanical preparation with 1% NaOCl (6, 7, 26) or 2% CHX
(6, 18, 24), even after enhancing the antimicrobial effects of
chemomechanical debridement (27). The implications of bacterial
1-visit treatment

1.6  107 (2.0  103 to 5.7  107)

1.6  106 (4.0  103 to 6.2  106)

persistence in infected root canals after treatment procedures have

been discussed in endodontic literature (5, 28).
Despite the limited number of bacteria-free root canals achieved
Before treatment

after 2 weeks of Ca(OH)2 interappointment medication, particularly

in root canals irrigated with 1% NaOCl, statistically significant
114.5 (6.51–249)
146 (14.3–198)

percentage values of bacterial reduction were achieved with the

2-visit treatment protocol, thus corroborating previous investigations
(26, 29).
The limited ability of the 2-visit treatment protocol, even using
Ca(OH)2 interappointment medication, in enhancing the bacteria
elimination, which was demonstrated by the present study and previous
investigations (6, 18) involving sampling specimens by using paper
point and culture techniques, might be argued. Considering that one
G1
G2

G1
G2

of the main reasons to use an interappointment root canal dressing is

to allow time for the medication to diffuse and reach bacteria in
those areas inaccessible to chemomechanical preparation, the results
Cultivable bacteria (CFU/mL)

obtained by sampling specimen by using paper point (which remains

restricted to microbiological conditions of the lumen area of
the canal) are limited. In contrast, the notable improvement in
Endotoxins (EU/mL)

microbiological status of the root canal system achieved by 2-visit treat-

ment protocols along with interappointment medication with calcium
hydroxide compared with 1-visit protocol has been demonstrated by
histobacteriologic approach (3, 30, 31), which provides information
NaOCl

NaOCl
CHX

CHX

about the spatial location of residual bacteria, including those

present in areas distant from the lumen area, such as tubules,
isthmuses, and ramifications.

962 Xavier et al. JOE — Volume 39, Number 8, August 2013

 Clinical Research
Endotoxin was recovered from all root canal samples collected root canals irrigated with 1% NaOCl or 2% CHX gel, thus demonstrating
from primarily infected root canals, which is in agreement with previous low or no efficacy of the irrigant on endotoxins. No endotoxins were
studies (7, 11–13, 32). In the baseline samples, endotoxin was detected found in 7 of 12 root canals (58.33%) irrigated with NaOCl and 6 of
in a median value of 127 EU/mL, determined by the kinetic 12 root canals (50.00%) irrigated with 2% CHX gel. Such a finding is
chromogenic LAL assay (KQCl test). Early studies (7, 11) revealed in agreement with Oliveira et al (22), but in disagreement with Vianna
median values of endotoxins ranging from 272–228 EU/mL, et al (18), who reported that root canal dressing contributes to
determined by the end point–QCL method (QCL-1000 test). Because a reduction of endotoxin in only 1.4% compared with the reduction
of limitations of this method (14), further investigations used the observed after root canal instrumentation. Of note, the longer
analysis of endotoxin from primarily infected teeth by using kinetic tests, application of interappointment medication (for 14 days) in the present
both chromogenic (KQCL test) and turbidimetric (Pyrogent 5000 test), study and by Oliveira et al compared with Vianna et al (for 7 days)
indicating levels of endotoxins ranging from 569–6.955 EU/mL (22) seemed to be important for better in vivo endotoxin-detoxifying activity
and 7.49–19.10 EU/mL (12, 13, 32), respectively. In the present of Ca(OH)2. Previous in vitro studies (20, 21) demonstrated the
study, the levels of endotoxins were determined by the chromogenic ability of intracanal medication used for 14 days in neutralizing
test (KQCL test). Because of differences in the sensitivity of the tests endotoxins left behind after root canal instrumentation.
used for quantification of endotoxins, sampling techniques, and The ability of calcium hydroxide to neutralize endotoxins in root
further methodological aspects, it is difficult to reconcile the levels of canals when used as intracanal medication, which was demonstrated
endotoxins (14). by the present and previous studies (22, 34), has to do with its
After chemomechanical preparation, statistically significant ability to cleave the ester-linked hydroxy fatty acids bonds, greatly
median percentage values of endotoxin reduction were achieved by affecting the biological properties of LPS (35). Safavi and Nichols
using root canal instrumentation with oscillating Endo-Eze files, (35) and Barthel et al (36) demonstrated that calcium hydroxide
accomplished by 1% NaOCl (88.33%) as well as 2% CHX gel alters some biological properties of bacterial LPS, such as the ability
(84.77%). Considering the low or no efficacy of NaOCl (even at high to stimulate prostaglandin E2 and tumor necrosis factor-alpha
concentrations) (7, 11, 33) and the 2% CHX (19, 33) detoxifying production by monocytes, which is intimately related to periapical
activity, the reduction of endotoxins in more than 80% (irrespective tissue destruction.
of the irrigant) might be attributed to the mechanical action of In conclusion, both 1-visit and 2-visit root canal treatment proto-
the instruments against dentin walls and the flow and backflow cols were effective in reducing bacteria and endotoxins, but they were
of the irrigants. Previous studies evaluating the efficacy of not able to eliminate them in all root canals analyzed. Furthermore,
chemomechanical procedures in reducing/eliminating endotoxins 2-visit root canal treatment protocols were more effective in reducing
from infected root canals by using 2.5% NaOCl (8, 11, 15) or 2% endotoxins than 1-visit root canal treatment protocols.
CHX gel (11, 18) indicated that mechanical debridement along with
irrigation can reduce endotoxin contents in z50% by using
conventional instrumentation (7, 11, 18) and z98% by using Acknowledgments
rotary nickel-titanium files (8). The authors deny any conflicts of interest related to this study.
In the 1-visit treatment protocols, endotoxin was still detected in 6
of 12 root canals (50.00%) irrigated with 1% NaOCl (G1) and 5 of 12
root canals (41.00%) irrigated with 2% CHX gel (G2) at S2, thus References
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