• Main cause of endodontic failure- Microorganisms, either remaining in the
root canal space after treatment or re-colonizing the filled canal system.
• Primary endodontic treatment goal- optimize root canal disinfection and to
• Pulpitis is the host reaction to opportunistic pathogens from the oral
environment entering the endodontium.
• Vital pulp tissue can defend against microorganisms and is thus largely
noninfected until it gradually becomes necrotic. In contrast, the pulp space of
nonvital teeth with radiographic signs of periapical rarefaction always
harbors cultivable microorganisms.
• Consequently, the treatment of vital cases should focus on asepsis, i.e. the
prevention of infection entering a primarily sterile environment, which is the
apical portion of the root canal. Antisepsis, which is the attempt to remove all
microorganisms, is the key issue in nonvital cases.
• Success, longevity, and reliability of modern endodontic treatments-
effectiveness of endodontic files, rotary instrumentation, irrigating solutions,
and chelating agents to clean, shape, and disinfect root canals.
• The role of microorganisms in the development and perpetuation of pulp
and periapical diseases has clearly been demonstrated in animal models
and human studies.
• Elimination of microorganisms from infected root canals is a complicated
• The chances of a favourable outcome with root canal treatment are
significantly higher if infection is eradicated effectively before the root canal
system is obturated.
• However, if microorganisms persist at the time of obturation, or if they
penetrate into the canal after obturation, there is a high risk of treatment
• Self-aggregates of monobacterial morphotypes and coaggregates of
different bacterial morphotypes are also found adhering to teeth.
• The interbacterial spaces are occupied by an amorphous material,
spirochetes, and hyphal-like structures that are suggestive of fungi.
• Costerton et al. used the term “biofilm” to describe this clustering of
bacteria. Bacteria within a biofilm have increased resistance to a variety of
external hostile influences, such as the host defense responses, antibiotics,
antiseptics, and shear forces, compared with isolated bacterial cells.
* F. J. Vertucci, “Root canal anatomy of the human permanent teeth,” Oral Surgery Oral Medicine
and Oral Pathology, vol. 58, no. 5, pp. 589–599, 1984.
• Numerous measures have been described to reduce the number of
microorganisms in the root canal system, including the use of various
instrumentation techniques, irrigation regimens, and intracanal
• The use of chemical agents during instrumentation to completely clean all
aspects of the root canal system is central to successful endodontic
treatment. Irrigation is complementary to instrumentation in facilitating
the removal of pulp tissue and/or microorganisms.
• Irrigation dynamics plays an important role; the effectiveness of irrigation
depends on the working mechanism(s) of the irrigant and the ability to bring
the irrigant in contact with the microorganisms and tissue debris in the root
Root Canal Bacterium
• Primary root canal infections are polymicrobial, typically dominated by obligatory
• The most frequently isolated microorganisms before root canal treatment include
Gram-negative anaerobic rods, Gram-positive anaerobic cocci, Gram-positive
anaerobic and facultative rods, Lactobacillus species, and Gram-positive facultative
• The obligate anaerobes are rather easily eradicated during root canal treatment.
• Facultative bacteria such as nonmutans Streptococci, Enterococci, and Lactobacilli,
once established, are more likely to survive chemomechanical instrumentation and
root canal medication.
• Enterococcus faecalis has gained attention in the endodontic literature, as it can
frequently be isolated from root canals in cases of failed root canal treatments.
• Yeasts may also be found in root canals associated with therapy-resistant apical
Root Canal Irrigants
• It is generally believed that mechanical enlargement of canals must be
accompanied by copious irrigation in order to facilitate maximum
removal of microorganisms so that the prepared canal becomes as
bacteria-free as possible.
• Ideally an irrigant should provide a mechanical flushing action, be
microbiocidal and dissolve remnants of organic tissues without
damaging the periradicular tissues if extruded into the periodontium.
• In addition, the root canal irrigants should be biocompatible with oral
Ideal Requirement of Root Canal Irrigants
It appears evident that root canal irrigants ideally should
(i) have a broad antimicrobial spectrum and high efficacy against anaerobic and
facultative microorganisms organized in biofilms
(ii) dissolve necrotic pulp tissue remnants,
(iii) inactivate endotoxin,
(iv) prevent the formation of a smear layer during instrumentation or dissolve the latter
once it has formed,
(v) be systemically nontoxic,
(vi) be non caustic to periodontal tissues,
(vii) be little potential to cause an anaphylactic reaction.
• Have a broad antimicrobial spectrum and high efficacy against
anaerobic and facultative microorganisms organized in biofilms
● Dissolve necrotic pulp tissue remnants
● Inactivate endotoxin
● Prevent the formation of a smear layer during instrumentation or
dissolve the latter once it has formed.
Furthermore, as endodontic irrigants come in contact with vital tissues,
they should be systemically nontoxic, non caustic to periodontal tissues
and have little potential to cause an anaphylactic reaction.
Root Canal Irrigants , J Endod 2006;32:389–398
• A large number of substances have been used as root canal irrigants,
including acids (citric and phosphoric), chelating agent (ethylene
diaminetetraacetic acid EDTA), proteolytic enzymes, alkaline solutions
(sodium hypochlorite, sodium hydroxide, urea, and potassium hydroxide),
oxidative agents (hydrogen peroxide and Gly-Oxide), local anesthetic
solutions, and normal saline.
• The most widely used endodontic irrigant is 0.5% to 6.0% sodium
hypochlorite (NaOCl), because of its bactericidal activity and ability to
dissolve vital and necrotic organic tissue.
• However, NaOCl solutions exert no effects on inorganic components of
• Chelant and acid solutions have been recommended for removing the smear
layer from instrumented root canals, including ethylene diaminetetraacetic
acid (EDTA), citric acid, and phosphoric acid
• Sodium hypochlorite is the most commonly used
endodontic irrigant, despite limitations. None of the
presently available root canal irrigants satisfy the
requirements of ideal root canal irrigant. Newer root canal
irrigants are studied for potential replacement of sodium
Newer Root Canal Irrigants in Horizon: A Review
Sushma Jaju and Prashant P. Jaju
International Journal of Dentistry
Volume 2011 (2011), Article ID 851359, 9 pages
• Most commonly used irrigating solution
• Excellent antibacterial agent
• Capable of dissolving necrotic tissue, vital pulp tissue, organic components of
dentin and biofilms
• Bleach- disinfectant or bleaching agent
• Irrigant of choice in endodontics, efficacy against pathogenic organisms and
• low viscosity allowing easy introduction into the canal architecture*
• acceptable shelf life*
• easily available and inexpensive*
* Review: the use of sodium hypochlorite in endodontics — potential complications and their management
H. R. Spencer, V. Ike& P. A. Brennan:British Dental Journal 202, 555 - 559 (2007)
• Chlorine is one of the most widely distributed elements on earth. It is
not found in a free state in nature, but exists in combination with
sodium, potassium, calcium, and magnesium.
• In the human body, chlorine compounds are part of the nonspecific
• They are generated by neutrophils via the myeloperoxidase-mediated
chlorination of a nitrogenous compound or set of compounds.
• Potassium hypochlorite was the first chemically produced aqueous
chlorine solution, invented in France by Berthollet (1748-1822).
• Starting in the late 18th century, this solution was industrially
produced by Percy in Javel near Paris, hence the name “Eau de
• First, hypochlorite solutions were used as bleaching agents.
• Subsequently, sodium hypochlorite was recommended by Labarraque
(1777-1850) to prevent childbed fever and other infectious diseases.
• Based on the controlled laboratory studies by Koch and Pasteur,
hypochlorite then gained wide acceptance as a disinfectant by the end
of the 19th century.
• In World War I, the chemist Henry Drysdale Dakin and the surgeon
Alexis Carrel extended the use of a buffered 0.5% sodium hypochlorite
solution to the irrigation of infected wounds, based on Dakin’s
meticulous studies on the efficacy of different solutions on infected
• Beside their wide-spectrum, nonspecific killing efficacy on all microbes,
hypochlorite preparations are sporicidal, virucidal, and show far greater
tissue dissolving effects on necrotic than on vital tissues.
• These features prompted the use of aqueous sodium hypochlorite in
endodontics as the main irrigant as early as 1920.
• Other chlorine-releasing compounds have been advocated in
endodontics, such as chloramine-T and sodium dichloroisocyanurate.
• These, however, have never gained wide acceptance in endodontics,
and appear to be less effective than hypochlorite at comparable
• Reactive chlorine in aqueous solution at body temperature can, in essence,
take two forms: hypochlorite (OCl-) or hypochlorous acid (HOCl).
• The concentration of these can be expressed as available chlorine by
determining the electrochemical equivalent amount of elemental chlorine.
According to the following equations:
• Therefore, 1 mol of hypochlorite contains 1 mol of available chlorine.
• The state of available chlorine is depending on the pH of the solution.
• Above a pH of 7.6, the predominant form is hypochlorite, below this value it
is hypochlorous acid.
• Both forms are extremely reactive oxidizing agents.
• Pure hypochlorite solutions as they are used in endodontics have a pH of 12,
and thus the entire available chlorine is in the form of OCl-.
• However, at identical levels of available chlorine, hypochlorous acid is
more bactericidal than hypochlorite.
• One way to increase the efficacy of hypochlorite solutions could thus
be to lower their pH.
• One alternative approach to improve the effectiveness of hypochlorite
irrigants in the root canal system could be to increase the
temperature of low-concentration NaOCl solutions. This improves
their immediate tissue-dissolution capacity.
• Furthermore, heated hypochlorite solutions remove organic debris
from dentin shavings more efficiently than unheated counterparts.
• Ultrasonic activation of sodium hypochlorite has also been advocated,
as this would “accelerate chemical reactions, create cavitational
effects, and achieve a superior cleansing action”.
• However, results obtained with ultrasonically activated hypochlorite
versus irrigation alone are contradictory, both in terms of root canal
cleanliness and remaining microbiota in the infected root canal system
after the cleaning and shaping procedure.
• The observed effects of ultrasonic activation, if any, were relatively
• Ultrasonic energy may simply produce heat, thus rendering the
hypochlorite slightly more active.
MODE OF ACTION
• In use for almost a century
• Possesses broad spectrum antimicrobial activity against endodontic
microorganisms and biofilms, including microbiota difficult to eradicate from
root canals such as Enterococcus, Actinomyces and Candida
• Dissolves organic material such as pulp tissue and collagen
• Bacteria inside main root canal, lateral canals and dentinal tubules- if in
direct contact with irrigant- are destroyed.
• Sodium hypochlorite reacts with fatty acids and amino acids in dental pulp
resulting in liquefaction of organic tissue.
• There is no universally accepted concentration of sodium hypochlorite for
use as an endodontic irrigant.
• The antibacterial and tissue dissolution action of hypochlorite increases with
its concentration, but this is accompanied by an increase in toxicity.
• Dakin’s original 0.5% sodium hypochlorite solution was designed to
treat open (burnt) wounds, it was surmised that in the confined area of
a root canal system, higher concentrations should be used, as they
would be more efficient than Dakin’s solution
• The antibacterial effectiveness and tissue dissolution capacity of
aqueous hypochlorite is a function of its concentration.
• Severe irritations have been reported when such concentrated
solutions were inadvertently forced into the periapical tissues during
irrigation or leaked through the rubber dam
• Furthermore, a 5.25% solution significantly decreases the elastic
modulus and flexural strength of human dentin compared to
physiologic saline, while a 0.5% solution does not.
• The reduction of intracanal microbiota, on the other hand, is not any greater
when 5% sodium hypochlorite is used as an irrigant as compared to 0.5%.
• From in vitro observations, it would appear that a 1% NaOCl solution should
suffice to dissolve the entire pulp tissue in the course of an endodontic
• It must be realized that during irrigation, fresh hypochlorite consistently
reaches the canal system, and concentration of the solution may thus not
play a decisive role.
• Unclean areas may be a result of the inability of solutions to physically reach
these areas rather than their concentration.
• Hence, based on the currently available evidence, there is no rationale for
using hypochlorite solutions at concentrations over 1% wt/vol.
Infected dentin blocks- 0.25% sufficient to kill E.faecalis in 15 mins,
conc of 1% requires 1 hr to kill Candida albicans
* Ruff et al., in infected extracted teeth, found that 1 min application of 6%
NaOCl and 2% chlorhexidine equally effective in eliminating
microorganisms and statistically significantly superior to MTAD and 17%
EDTA in eliminating Candida albicans infections
• Commercially available household bleach- Clorox 6.15% NaOCl,
alkaline pH- 11.4, hypertonic
• Some authors recommend, dilution of clorox with 1% bicarbonate,
instead of water to bring down pH to a lower level.
• Others do not see any reduction in aggressiveness on fresh tissue
by buffering NaOCl and recommend dilution with water to obtain less
conc. irrigation solutions.
* Splangberg LSW, Haapasalo M: Rationale and efficacy of root canal medicaments
and root filling material with emphasis on treatment outcome.Endod Topics 2:35,2002
SUGGESTED IRRIGATION REGIMEN
• The chemicals used to clean infected canals should be administered in such
manner that they can unleash their full potential on their targets in the root
canal rather than act on each other.
• Hence, a hypochlorite solution should be employed throughout instrumentation,
without altering it with EDTA or citric acid.
• ‘Canals should always be filled with sodium hypochlorite’.
• This will increase the working time of the irrigant.
• In addition, cutting efficacy of hand instruments is improved and torsional load on
rotary nickel-titanium instruments is reduced in fluid-filled environments compared to
• On the other hand, corrosion of instruments in prolonged contact with hypochlorite
is an issue.
• Submersing instruments for hours in a hypochlorite solution will induce corrosion.
• However, no adverse effects should be expected during the short contact periods
when an instrument is manipulated in a root canal filled with hypochlorite.
• After the smear removing procedure a final rinse with an antiseptic solution
appears beneficial. The choice of the final irrigant depends on the next
treatment step, i.e. whether an inter visit dressing is planned or not.
• If calcium hydroxide is used for the interim, the final rinse should be sodium
hypochlorite, as these two chemicals are perfectly complementary. It
appears even advantageous to mix calcium hydroxide powder with the
sodium hypochlorite irrigant rather than with saline to obtain a more
• Chlorhexidie- promising agent to be used as a final irrigant. It has an
affinity to dental hard tissues, and once bound to a surface, has
prolonged antimicrobial activity, a phenomenon called substantivity.
• ‘Substantivity is not observed with sodium hypochlorite.’
1 min of 6% solution reduced biofilm by 7-8 orders of magnitude
15 min at 0.25% in contaminated dentin blocks
30 min at 0.5% and 2 min at 5.25% in direct contact with bacteria
• Actinomyces organisms-
1 min at 1% solution
10 sec at 0.5% in direct contact with bacteria
• Candida organisms-
1 hour at 1% or 5% solution on root dentin with smear layer
30 sec for both the 0.5% solutions to kill all cells in culture
1 min of 6% solution: no growth
• Principal ingredient- unbound chlorine, solution must be replenished
frequently during preparation to compensate for lower concentrations
and to constantly renew the fluid inside the root canal.
• More important- when canal is narrow and small, files must carry the
NaOCl to the apical third during instrumentation.
• 1% solution- effective, at dissolving tissue and providing an
• 6% commercial household bleach undiluted- substantial necrosis of
wound area and may result in serious clinical side effects.
• Diluted 1:1 or 1:3 ratio with water- 2.5% or 1% solution suitable for
clinical endodontic use.
Increasing efficacy of hypochlorite preparations
• Increasing temperature of low concentration NaOCl solutions- which
improve their immediate tissue-dissolution capacity.
• Heated hypochlorite solutions remove organic debris from dentin shavings
• Antimicrobial properties of heated NaOCl- bactericidal rates more than
doubled for each 5O rise in temperature in the range of 5-600.
Device for heating syringes filled with
irrigation solution before use.
Syringe warmer (Vista dental products,
Effect of heating on NaOCl
(0.5%) to dissolve pulp tissue,
positive control 5.25%.
(Sirtes G, Waltimo T, Schaetzle M, Zehnder
M: The effects of temperature on sodium
hypochlorite short-term stability, pulp
dissolution capacity and antimicrobial
efficacy. J Endod 31:669-671, 2005)
• Studies have shown that 1 min at 47oc is the cutoff exposure at which
osteoblasts can still survive, however, higher temperatures may infact be
sufficient to kill osteoblasts and other host cells.
• Warming of NaOCl to 50oc or 60oc increases collagen dissolution and
disinfecting potential, but it may also have severely detrimental effects on
NiTi instruments, causing corrosion of the metal surface after immersion for
Rotary instrument immersed for 2 hours in NaOCl heated to 60oc, showing severe
• A study using steady state planktonic E.fecalis cells, showed a
temperature rise of 25oc increased NaOCl efficacy by a factor of
• Capacity to dissolve human dental pulp using 1% NaOCl at 45oc
was found to be equal to that of a 5.25% solution at 20oc.
• Systemic toxicity of preheated low conc of NaOCl irrigants should
be less than that of a more concentrated unheated solution.
• NaOCl require an adequate working time to reach their potential.
• Chlorine, which is responsible for dissolving and antibacterial capacity of
NaOCl- unstable and consumed rapidly during the first phase of tissue
dissolution, probably within 2 mins.
• Optimal time a hypochlorite irrigant needs to remain in the canal system is
an issue yet to be resolved.
* Cohen- Pathways of the pulp, 10th edition
• Antimicrobial activity, dissolving of the remaining pulp tissues,
lubrication during mechanical instrumentation, availability and low
cost are the fundamental requirements for root canal irrigants
(Zehnder 2006, Haapasalo et al. 2010).
• Sodium hypochlorite-most common irrigant, other solutions mostly
used along with sodium hypochlorite, as a final rinse to enhance the
antimicrobial activity and substantivity against some resistant
bacteria, to decrease the caustic effect or to aid in removing the
(Zehnder 2006, Mohammadi & Abbott 2009, Haapasalo et al. 2010).
NaOCl has been reported to cause dentine discolouration, although
it is a bleaching agent.
This discolouration is a result of its contact with erythrocytes and its
high tendency to crystallize on the root dentine, which may mean
that it is difficult to completely remove from the canal (Gutie´rrez &
Guzma´n 1968). In addition, the combination of NaOCl with other
adjunct irrigating solutions has been found to cause marked tooth
Vivacqua-Gomes et al. (2002) observed a dark brown precipitate
when NaOCl was combined with chlorhexidine (CHX) gel. Other
authors have reported the same type of discolouration when
NaOCl has been used with CHX solutions (Basrani et al. 2007,
Marchesan et al. 2007, Bui et al. 2008, Akisue et al. 2010,
Krishnamurthy & Sudhakaran 2010, Nassar et al. 2011, Souza et
Discolouration when irrigants are combined.
(a) 2.63% NaOCl + 2% chlorhexidine (CHX) (dark brown precipitate);
(b) 18% EDTA + 2% CHX (cloudy blue);
(c) 2.63% NaOCl + 18% EDTA (no discolouration)
d) 2.63% NaOCl + 20% Citric acid (white precipitate and the solution turns cloudy after shaking).
This dark brown precipitate can stain the dentine, adhere to the floor of the pulp
chamber, access cavity and root canal walls and act as a residual film that may
compromise the diffusion of intra-canal medicaments into the dentine, disrupt the
adhesion of the root canal filling and favour coronal restoration breakdown
(Vivacqua-Gomes et al. 2002, Akisue et al. 2010)
Discolouration potential of NaOCl/CHX combination on the access cavity walls.
(b) Dark brown precipitate after NaOCl/CHX combination
(c) The precipitate becomes adherent to the access cavity walls (white arrow) and
crown fissures (red arrow) even after flushing with distilled water.
Basrani et al. (2007) examined this precipitate using X-ray photoelectron
spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry
(TOF-SIMS), and they found that it contains a significant amount of
This substance is carcinogenic and it can further degrade to 1-chloro-4-
nitrobenzene, which also is carcinogenic.
However, by using nuclear magnetic resonance (NMR), Thomas & Sem
(2010) reported that mixing NaOCl and CHX did not produce PCA at any
measurable quantity, but one of the CHX breakdown products may be further
metabolized to PCA (Nowicki & Sem 2011).
As a result of these possible hazards, Kim et al. (2012) examined the
chemical interaction between Alexidine (ALX), as a substitute for CHX, and
NaOCl using electrospray ionization mass spectrometry (ESIMS) and
scanning electron microscopy (SEM).
The results revealed that the association of ALX/NaOCl did not produce PCA
or any precipitate, and the mixing solutions of ALX and NaOCl resulted in a
slight discolouration ranging from light yellow to transparent as the ALX
In addition, this combination did not stain dentine and was easy to remove
from the root canal by irrigation.
NaOCl also reacts with MTAD (a mixture of a tetracycline isomer, an acid
[citric acid], and a detergent) (Dentsply Tulsa Dental, Tulsa, OK, USA), in the
presence of light, causing brown discolouration (Torabinejad et al. 2003).
This reaction may be caused by the dentinal absorption and release of the
doxycycline, present in MTAD, which will be exposed to NaOCl if it is used as
a final rinse after MTAD (Torabinejad et al. 2003).
Tay et al. (2006a) formation of yellow precipitate along the root canal walls when
NaOCl was used as an irrigant and then followed by the application of BioPure
MTAD as a final rinse.
They also observed red-purple staining of light-exposed, root-treated dentine when
the root canals were rinsed with 1.3% NaOCl as an initial rinse followed by MTAD as
the final rinse.
This photo-oxidative degradation process was probably triggered by the use
of NaOCl as an oxidizing agent which also resulted in partial loss of its
antimicrobial substantivity (Tay et al. 2006a,b).
The chemical reaction between NaOCl and citric acid, which leads to the
formation of a white precipitate, indicates a complex interaction between
NaOCl and MTAD that requires further investigations to validate the safety
and usefulness of this combination of irrigants.
Gonza´lez-Lo´pez et al. (2006) and Rasimick et al. (2008) have reported
interactions between CHX and EDTA irrigants with the formation of white to
Practitioners should choose irrigating solutions carefully to suit the clinical
condition that is being treated.
If CHX is chosen, then the insoluble dark brown precipitate, created when NaOCl and
CHX are mixed, can be avoided by incorporating a thorough intermediate flush
between each irrigant – this can be carried out with solutions such as saline or sterile
distilled water, followed by drying of the canal before the next solution is used
(Krishnamurthy & Sudhakaran 2010).
Absolute alcohol has also been suggested as an intermediate flush but its
biocompatibility with the periapical tissues and interactions with other irrigants remain
a concern (Krishnamurthy & Sudhakaran 2010, Valera et al. 2010)
Nassar et al. (2011) recommended the use of sodium ascorbate to prevent
the formation of this precipitate.
Ascorbic acid solution, as a reducing agent, has been advocated as an
intermediate flush between NaOCl and MTAD, to prevent the oxidation effect
of NaOCl and to avoid the photodegradation of the doxycycline that is present
in MTAD (Tay et al. 2006a). In addition, the possible interaction between
NaOCl and citric acid would be avoided.
A cloudy precipitate forms when EDTA and CHX are combined. Maleic acid
(MA), which has been found to be less cytotoxic and more effective in smear
layer removal than EDTA (Ballal et al. 2009a,b), can be used as a substitute
for EDTA, and the combination of MA and CHX has not shown any precipitate
formation or discolouration (Ballal et al. 2011).
Tooth discolouration associated with root canal irrigants
Irrigating solutions Type of discolouration Author/s – year
NaOCl (undiluted and 10%) Some discolouring effect Gutie´ rrez and Guzma´n (1968)
1% NaOCl +
2% chlorhexidine (CHX) gel Dark brown precipitate Vivacqua-Gomes et al. (2002)
MTAD + NaOCl (5.25–0.65%) Brown solution (NaOCl final rinse) Torabinejad et al. (2003)
17% EDTA + 1% CHX sol. Pink precipitate (CHX final rinse) Gonza´ lez-Lo´ pez et al. (2006)
2% CHX sol. + 17% EDTA White precipitate Rasimick et al. (2008)
1.54–6.15% NaOCl + MTAD Yellow precipitate (MTAD final rinse) Tay et al. (2006a) (Clinical application)
1.3% NaOCl + MTAD Red-purple (MTAD final rinse) Tay et al. (2006a) (In vitro study)
NaOCl + CHX sol. Light orange to dark brown Basrani et al. (2007), Marchesan et al(2007),
according to conc. Bui et al. (2008) Akisue et al. (2010),
Krishnamurthy & Sudhakaran (2010), Nassar et al. (2011)
2% CHX sol. + 15% Citric acid A white solution but returns Akisue et al. (2010)
colourless and easily removed
during irrigation with CHX
2% CHX gel + 5.25% NaOCl Discoloured enamel and dentine Souza et al. (2011)
2% CHX sol. + 5.25% NaOCl Discoloured dentine only Souza et al. (2011)
2% CHX gel + 5.25% NaOCl + 17% EDTA Discoloured enamel and dentine Souza et al. (2011)
2% CHX sol. + 5.25% NaOCl + 17% EDTA Discoloured dentine Souza et al. (2011)
• Unlikely to occur, since both sodium and chlorine are essential elements in
the physiology of human body
• Hypersensitivity and contact dermatitis- rare cases
• In cases of hypersensitivity- chlorhexidine should not be used either- due to
• Alternative irrigant- iodine potassium iodide, high antimicrobial efficacy
• Alcohol, tap water- less effective against microorganisms, do not dissolve
vital or necrotic pulp tissue.
• Ca(OH)2- temporary medicament, dissolves both vital and necrotic tissue.
• The allergic potential of sodium hypochlorite was first reported in 1940 by
Sulzberger and subsequently by Cohen and Burns.
• Caliskan et al. presented a case where a 32-year-old female developed rapid
onset pain, swelling, difficulty in breathing and subsequently hypotension
following application of 0.5 ml of 1% sodium hypochlorite. The patient
required urgent hospitalization in the intensive care unit and management
with intravenous steroids and antihistamines.
• Subsequent allergy skin scratch test performed two weeks after the patient
was discharged confirmed a highly positive result to sodium hypochlorite. The
usefulness of this test in suspected cases of sodium hypochlorite allergy
during endodontic treatment has been confirmed by Kaufman and Keila.
• Symptoms of allergy and possible anaphylaxis- urticaria, oedema, shortness
of breath, wheezing (bronchospasm) and hypotension.
• Urgent referral to a hospital following first aid management is recommended.
Review: the use of sodium hypochlorite in endodontics — potential complications and their
H. R. Spencer, V. Ike& P. A. Brennan:British Dental Journal 202, 555 - 559 (2007)
• To avoid extrusion and serious damage to periapical tissues,
irrigation needles should never be wedged into canals during
• Higher concentration NaOCl- more aggressive toward living tissue
and can cause severe injuries when forced into periapical area.
27 gauge needle 30 gauge side
Toxic effect of sodium hypochlorite on periradicular tissues.
After root canal treatment of the first molar, the patient reported pain
A. On a return visit, an abscess was diagnosed and incised.
B. Osteonecrosis was evident after 3 weeks.
These accidents can be prevented-
• Mark the working length on the irrigation needle with a bend or rubber stop
and passively expressing the solution from the syringe into the canal.
• Needle should be continuously moved up and down.
• It should remain loose in the canal, allowing a backflow of liquid.
• The goal is to rinse the suspended, concentrated dentinal filings out of the
pulp chamber and root canals as new solution is brought down into the most
apical areas by the endodontic instrument and capillary effect.
• Patency files should not be extended farther than the periodontal ligament
because they are possible sources of irrigant extrusion
Complications of accidental spillage
1) Damage to clothing
Accidental spillage of sodium hypochlorite is probably the most common accident
to occur during root canal irrigation.
Even spillage of minute quantities of this agent on clothing will lead to rapid,
The patient should wear a protective plastic bib, and the practitioner should
exercise care when transferring syringes filled with hypochlorite to the oral cavity.
2) Eye damage
Seemingly mild burns with an alkali such as sodium hypochlorite can result in
significant injury as the alkali reacts with the lipid in the corneal epithelial cells,
forming a soap bubble that penetrates the corneal stroma. The alkali moves rapidly
to the anterior chamber, making repair difficult. Further degeneration of the tissues
within the anterior chamber results in perforation, with endophthalmitis and
subsequent loss of the eye.
• Ingram recorded a case of accidental spillage of 5.25% sodium hypochlorite
into a patient's eye during endodontic therapy.
• The immediate symptoms included instant severe pain and intense burning,
profuse watering (epiphora) and erythema.
• Loss of epithelial cells in the outer corneal layer may occur.
• There may be blurring of vision and patchy colouration of the cornea.
• Immediate ocular irrigation with a large amount of water or sterile saline is
required followed by an urgent referral to an ophthalmologist.
• The referral should ideally be made immediately by telephone to the nearest
• The use of adequate eye protection during endodontic treatment should
eliminate the risk of occurrence of this accident, but sterile saline should
always be available to irrigate eyes injured with hypochlorite.
• It has been advised that eyes exposed to undiluted bleach should be irrigated
for 15 minutes with a litre of normal saline.
3) Damage to skin
• Skin injury with an alkaline substance requires immediate irrigation with water
as alkalis combine with proteins or fats in tissue to form soluble protein
complexes or soaps. These complexes permit the passage of hydroxyl ions
deep into the tissue, thereby limiting their contact with the water dilutant on the
• Water is the agent of choice for irrigating skin and it should be delivered at low
pressure as high pressure may spread the hypochlorite into the patient's or
4) Damage to oral mucosa
• Surface injury is caused by the reaction of alkali with protein and fats as
described for eye injuries above. Swallowing of sodium hypochlorite requires
the patient to be monitored following immediate treatment. It is worth noting
that skin damage can result from secondary contamination.
Review: the use of sodium hypochlorite in endodontics — potential complications and their management.
H. R. Spencer, V. Ike& P. A. Brennan:British Dental Journal 202, 555 - 559 (2007)
Complications arising from hypochlorite extrusion beyond the root
1) Chemical burns and tissue necrosis
• When sodium hypochlorite is extruded beyond the root canal into the peri-
radicular tissues, the effect is one of a chemical burn leading to a localised or
extensive tissue necrosis.
• Given the widespread use of hypochlorite, this complication is fortunately very
• A severe acute inflammatory reaction of the tissues develops.
• This leads to rapid tissue swelling both intra orally within the surrounding
mucosa and extra orally within the skin and subcutaneous tissues.
• The swelling may be oedematous, haemorrhagic or both, and may extend
beyond the region that might be expected with an acute infection of the affected
Bruising and oedema of patients who presented with hypochlorite extrusion into the
• Sudden onset of pain is a hallmark of tissue damage, and may occur
immediately or be delayed for several minutes or hours.
• Involvement of the maxillary sinus will lead to acute sinusitis.
• Associated bleeding into the interstitial tissues results in bruising and
ecchymosis of the surrounding mucosa and possibly the facial skin and
may include the formation of a hematoma.
• A necrotic ulceration of the mucosa adjacent to the tooth may occur as a
direct result of the chemical burn.
• This reaction of the tissues may occur within minutes or may be delayed
and appear some hours or days later.
• If these symptoms develop, urgent telephone referral should be made to
the nearest maxillofacial unit.
• Patients will be assessed by the on call maxillofacial team.
• Treatment is determined by the extent and rapidity of the soft tissue
swelling but may necessitate urgent hospitalization and administration of
intravenous steroids and antibiotics.
• Although the evidence for the use of antibiotics in these patients is
anecdotal, secondary bacterial infection is a distinct possibility in areas
of necrotic tissue and therefore they are often prescribed as part of the
overall patient management.
• Surgical drainage or debridement may also be required depending on
the extent and character of the tissue swelling and necrosis.
2) Neurological complications
- Paraesthesia and anaesthesia affecting the mental, inferior dental and
infra-orbital branches of the trigeminal nerve following inadvertent
extrusion of sodium hypochlorite beyond the root canals.
- Normal sensation may take many months to completely resolve.
- Facial nerve damage was first described by Witton et al. in 2005.
- In both cases, the buccal branch of the facial nerve was affected.
- Both patients exhibited a loss of the naso-labial groove and a down
turning of the angle of the mouth.
- Both patients were reviewed and their motor function was regained after
- Sensory and motor nerve deficit are not commonly associated with acute
- As there is no other current evidence in the literature it is possible that
these neurological complications were a direct result of chemical damage
by sodium hypochlorite, but further research (including nerve conduction
studies) is required.
3) Upper airway obstruction
The use of sodium hypochlorite for root canal irrigation without adequate isolation of
the tooth can lead to leakage of the solution into the oral cavity and ingestion or
inhalation by the patient.
This could result in throat irritation and in severe cases, the upper airway could be
Ziegler presented a case of a 15-month-old girl who presented in the accident and
emergency unit with acute laryngotracheal bronchitis, stridor and profuse drooling
from the mouth as a result of ingestion of a high concentration of household sodium
A similar clinical presentation might occur with the ingestion of any caustic
Opinion varies as to the best concentration of hypochlorite, with some practitioners
using undiluted household bleach. Fibre optic nasal tracheal intubation followed by
surgical decompression has been required to manage airway compromising
swelling arising within three hours of accidental exposure to sodium hypochlorite
during root canal treatment
• Plastic bib to protect patient's clothing
• Provision of protective eye-wear for both patient and operator
• The use of a sealed rubber dam for isolation of the tooth under
• The use of side exit Luer-Lok needles for root canal irrigation
• Irrigation needle a minimum of 2 mm short of the working length
• Avoidance of wedging the needle into the root canal
• Avoidance of excessive pressure during irrigation
Preventive measures that should be taken to minimize potential
complications with sodium hypochlorite
Placement of rubber stop on irrigation needle
• Needle must be side venting
• Hypodermic (end exiting) needles in root canal
irrigation risks accidental inoculation into the soft
• Luer-Lok style syringes and needles should be used,
as taper seat needles may dislodge in use, with
uncontrolled loss of the hypochlorite solution under
• Needle should not engage the sides of the canal, but
be loosely positioned within the canal.
• Needle should not reach the apical extent of the
• This technique may be facilitated by marking the
working length on the needle with a rubber stop.
irrigant delivered slowly with minimal pressure to
reduce the likelihood of forcing it through the apex.
Achieved by using your index finger rather than
thumb to depress the plunger.
• This will reduce the risk to periapical tissues by
inadvertent extrusion of irrigant.
Irrigate gently with normal saline. If normal saline is insufficient or unavailable, tap water
should be used
Refer for ophthalmology opinion
Wash thoroughly and gently with normal saline or tap water
Oral mucosa injuries
Copious rinsing with water
Analgesia if required
If visible tissue damage antibiotics to reduce risk of secondary infection
If any possibility of ingestion or inhalation refer to emergency department
Ice/cooling packs to swelling first 24 hours
Heat packs subsequently
Antibiotics to reduce the risk of secondary infection
Request advice or management from Maxillofacial Unit
Arrange review if to be managed in dental practice
Emergency management of accidental hypochlorite damage
• The dissolving effect of the endodontic medicaments calcium hydroxide
(Ca(OH)2) and sodium hypochlorite (NaOCI) on necrotic tissue was
• Pieces of necrotic porcine muscular tissue were placed in either a 0.5%
NaOCI solution (Dakin's solution), Ca(OH)2, mixed with water, or a
NaOCI solution following pretreatment in Ca(OH)2 for various time
• The tissue pieces placed in 0.5% NaOCI were not completely dissolved
after 12 days. When NaOCI solution was changed every 30 min, the
tissue was completely dissolved after 3 h.
• Pieces placed in Ca(OH)2 exhibited a marked swelling and a jelly-like
Effects of calcium hydroxide and sodium hypochlorite on the dissolution
of necrotic porcine muscle tissue
Gunna Hasselgren, Berit Olsson, Miomir Cvek
JOE, Volume 14, Issue 3, March 1988, Pages 125–127
• The increase in weight was maintained for 24 h, after which a
decrease was noted.
• After 12 days, the tissue was completely dissolved.
• Pretreatment with Ca(OH)2 for 30 min caused the tissue to dissolve in
NaOCI within 90 min. Pieces that were pretreated for 24 h or 7 days
dissolved within 60 min.
• As a control, tissue pieces were kept in isotonic saline solution and
these were not dissolved after 12 days.
• Apparently, long-term treatment with Ca(OH)2 can dissolve necrotic
tissue and pretreatment with Ca(OH)2 can enhance the tissue
dissolving effect of NaOCl.
Tissue-dissolving capacity and antibacterial effect of buffered and
unbuffered hypochlorite solutions
Matthias Zehnder, Daniel Kosicki, Hansueli Luder, Beatrice Sener, Tuomas Waltimo
Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology and Endodontology
Volume 94, Issue 6 , Pages 756-762, December 2002
• The goal of this study was to compare the dissolving potential of Dakin's
solution with that of equivalent buffered and unbuffered sodium hypochlorite
solutions on fresh and decayed tissues. In addition, the antimicrobial effect of
Dakin's solution and equivalent unbuffered hypochlorite was tested.
• Study Design. Tissue specimens were obtained from freshly dissected pig
palates. Unbuffered 2.5% and 0.5% sodium hypochlorite solutions and 0.5%
solutions buffered at a pH of 12 and a pH of 9 (Dakin's solution) were tested on
fresh and decayed tissue. Tissue decay was assessed histologically.
Antimicrobial testing was performed with Enterococcus faecalis in dentin
blocks and on filter papers.
• The 2.5% NaOCl solution was substantially more effective than the three 0.5%
solutions in dissolving the test tissues. Buffering had little effect on tissue
dissolution, and Dakin's solution was equally effective on decayed and fresh
tissues. No differences were recorded for the antibacterial properties of Dakin's
solution and an equivalent unbuffered hypochlorite solution.
• In contrast to earlier statements, the results of this study do not demonstrate
any benefit from buffering sodium hypochlorite with sodium bicarbonate
according to Dakin's method. An irrigation solution with less dissolving potential
may be obtained by simply diluting stock solutions of NaOCl with water.
• New concepts usually are overrated in initial studies when compared to
the gold standard.
• Some recent approaches to improve root canal debridement include
the use of laser light to induce lethal photosensitization on canal
microbiota, irrigation using electrochemically activated water, and
ozone gas infiltration into the endodontic system.
• However, in terms of killing efficacy on endodontic microbiota in
biofilms, there is good evidence that none of these approaches can
match a simple sodium hypochlorite irrigation.
1. Cohen’s PATHWAYS OF THE PULP- 10TH EDITION
2. Problem solving in Endodontics- fourth edition, GUTMANN, DUMSHA, LOVDAHL
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4. Review: the use of sodium hypochlorite in endodontics — potential complications and their
H. R. Spencer, V. Ike& P. A. Brennan:British Dental Journal 202, 555 - 559 (2007)
5. Tissue-dissolving capacity and antibacterial effect of buffered and unbuffered hypochlorite
Matthias Zehnder, Daniel Kosicki, Hansueli Luder, Beatrice Sener, Tuomas Waltimo
OOOOE, Volume 94, Issue 6 , Pages 756-762, December 2002
6. Newer Root Canal Irrigants in Horizon: A Review, Sushma Jaju and Prashant P. Jaju
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