Volume 3, Issue 1 - Winter 2012

A Case Report on Sodium Hypochlorite Accident During Root Canal Therapy

December 27, 2012


     A 34 year old male presented for routine root canal therapy on the Mandibular right first molar (tooth #30). His past medical history showed no significant contraindication for this procedure, no known drug allergies were noted, and he had a previous dental history of two root canals and multiple restorations. All risks, benefits, and alternative options were discussed with the patient. He preferred and consented to a root canal on tooth #30.  Prior to endodontic therapy, standard (formally known as universal) precautions were used for proper infection control, profound anesthesia, and rubber dam isolation. A clear radiographic image of the tooth was evaluated and studied. A conservative occlusal access for clear visualization of the three canals was prepared within normal endodontic protocol. Instrumentation of the canals included: 1) Broach files to remove inflamed and necrotic pulp tissue; and 2) K-files to shape the canals in order for proper fit of the master apical cone. Step back with recapitulation were utilized on each canal, the canals were irrigated with 5.25% sodium hypochlorite to ensure thorough disinfection. Immediately after the irrigation, the patient began sensing a sharp pain along the inferior border of his mandible. In a short period of time, the pain radiated to his pre-auricular region. The root canal procedure was terminated and managing the patient’s symptoms became the primary objective.

     Sodium hypochlorite is the most widely used endodontic irrigant, but can be an irritant to vital tissues. Most of the complications are the result of accidental extrusion of the solution through the apical foramen or accessory canals or perforations into the periradicular area. This report is a review of palliative treatment for this patients’ symptoms and further explores the protocol to follow in the case of a mild to severe sodium hypochlorite accident. The following guidelines for treating sodium hypochlorite accidents are compilations of the recommendations gathered and referenced from several case reports and articles from the Journal of Endodontics. The chemical properties of sodium hypochlorite, signs & symptoms of an accident, precautionary measures in avoiding this accident, post-accident treatment and management will be discussed.


Chemical Properties of Sodium Hypochlorite

     Sodium Hypochlorite, the chemical formula NaOCl, has a variety of uses. It has long been used as a biological disinfectant, dating back to World War I, where a 0.5% solution was used to clean contaminated wounds. In the 1920’s Dakin’s solution was created and first used as an intraoral irrigant for root canal therapy. It became a very popular material due to its effectiveness, cost efficiency, and abundance. Since then, sodium hypochlorite irrigation became a major factor in the success of root canal treatment (RCT).

    The chemical properties include a pH of 11 to 12.5, the ability to oxidize, hydrolyze, and osmotically draw out fluids. This combination allows for its use as an excellent disinfecting agent. More specifically, it dissolves organic material and acts as a broad range antimicrobial agent, effective against the following: gram-positive bacteria, gram-negative bacteria, fungi, spores, and virus (including HIV). The following properties make sodium hypochlorite an ideal irrigation solution for RCT:  the dissolving of organic tissue such as necrotic pulpal debris and its antimicrobial effectiveness on oral bacteria. Additionally, sodium hypochlorite flushes out debris and prepares dentin for instrumentation of the canal.

     Sodium hypochlorite has an advantage of being an excellent endodontic irrigant; however, it is a toxic material and should be handled with care. The disadvantages are associated with its non-specific actions. Oxidation and hydrolysis, breaking down of organic tissues occur to both necrotic, unwanted tissue as well as healthy tissue. As a result, severe inflammation, cellular destruction, and hemolysis occur, leading to necrosis of vital tissue (excluding keratinized epithelium). The damage that occurs may be temporary or permanent. The severity depends on the concentration, pH, and duration of sodium hypochlorite being exposed to vital tissues.


The subsequent exposure of sodium hypochlorite to vital tissue(s) via irrigation into the periapical region could create distressing and /or severe complications to the patient undergoing root canal therapy. In addition to necrosis of the vital tissue , sodium hypochlorite causes increased vascular permeability and the release of chemical mediators, such as histamine. Initially, the side effects manifest as physiologically as severe pain, edema, and hemorrhage.

     Depending on the concentration and duration of sodium hypochlorite exposure, further complications may arise within a period of several days. Increased edema and hematoma formation occurs due to damaged blood vessels, which can be observed clinically as intra/extra oral ecchymosis. To further complicate matters, a decrease in blood circulation can lead to the tooth becoming secondarily infected and ultimately osteonecrosis. Other complications involving sodium hypochlorite are injury to the neurovascular bundle of nerves that can lead to demyelination causing paresthesia or paralysis.  As weeks pass paresthesia and paralysis may or may not resolve as scarring occurs. Finally, the concentration, pH, and duration of sodium hypochlorite exposure, varies in each case and needs to be managed according to its severity.

Risk Assessment

In order to minimize the incidence and severity of a sodium hypochlorite accident, precautionary measures should be taken in order to assure the patient the highest quality of root canal therapy.  The techniques for root canal therapy need to be examined so this serious accident can be avoided. Sodium hypochlorite forced beyond the apex of the tooth, can be prevented by keeping the following in mind:

     •     Proper radiographic films to observe the root anatomy

     •     Adequate access preparation

     •     Good Working Length

     •     Irrigation 1 to 3mm short of working length

     •     Not locking the needle in the canal

     •     Injecting slowly

     •     The use of special endodontic needles

Another factor that can control the outcome is the use of diluted concentration of sodium hypochlorite. Currently for root canal therapy, the recommendation concentrations are 2.6% to 5.25%. A higher concentration than 5.25% may or may not increase the efficiency of debriding and disinfecting the canals; however, the damaging capabilities of vital tissues are much greater. Although the incidence of a sodium hypochlorite accident is rare, precaution must be taken to avoid serious, possibly permanent injuries to the patient.


Post-Accident Treatment

     In the unfortunate event that a sodium hypochlorite accident occurs, the most important aspect to its treatment is to quickly recognize the initial signs and symptoms. The first and immediate sign is severe pain at the tooth being treated. Edema follows as vascular permeability increases. Depending on the location of the tooth being treated, different anatomical structures are affected. Facial swelling can occur extending to the lips, cheeks, periorbital tissues, and even the floor of the mouth. The possibility of an intra-antral injection exists for root canal therapy performed on posterior maxillary teeth, where patients will complain of pain to their sinuses and taste / smell of chlorine in their nasopharynx region. As the pain continues, sodium hypochlorite will damage and break down the endothelial cells of blood vessels leading to localized hemorrhage.

     These symptoms of pain, swelling, bleeding occur immediately after sodium hypochlorite enters the periapical region. In order to properly and efficiently manage the patient, the following instructions will help the clinician in the unlikely occurance of an accident. Post accident treatment begins with copious irrigation with normal saline solution for 5 to 10 minutes. Allow the site to bleed, as this will allow the sodium hypochlorite to be ejected. The patient should be fully informed of the potential sequelae and detailed clinical notes.

     The post-operative instructions should include palliative treatment, when to return for follow-ups, and when to visit the emergency room. Palliative treatment comprises of:

     1. Instructions to minimize swelling

                - cold compresses within the first 24 hours and warm compresses afterwards


     2. Rinsing with saline water

                - 2 to 3 times a day for one week

     3. Prescribing analgesics and antibiotics

                - Analgesic of choice is Tylenol. NSAIDS are avoided to allow for hemostasis. Antibiotics are not obligatory, but in these cases the patient is at increased risk for secondary infections. Broad spectrum coverage is recommended.

     4. Steroid Therapy

                -2 to 3 days (i.e. Medrol Dose Pack)

The patient should follow-up daily for a week to control and monitor his/her recovery and to report any improvements. If severe intravascular accident occurs, informing the patient of temporary or even permanent parasthesia / paralysyis must be discussed. Subsequent follow-up visits should be scheduled to continue observation, and to complete the root canal treatment and any other planned treatment. Prior to the patient leaving, he/she should also be instructed to go to the nearest hospital emergency room if pain and swelling persists or increases. In the severe case that the patient needs to be hospitalized for surgical intervention (i.e. debridement of necrotic tissues) then all risks in volved should be discussed with the patient.



The 34 year old male patient who presented for the root canal therapy had a reaction to sodium hypochlorite after exiting the distal canal of tooth #30, penetrating the mandible. The root canal therapy was terminated and copious amounts of normal saline solution were used for 10 minutes to irrigate the canals of tooth #30. The canals were dried, cotton pellet inserted, and temporary restoration was placed. Patient was given 500mg of extra strength Tylenol immediately, was reassured with thorough post-operative instructions. The patient described the pain as radiating along the entire length of the right jaw. In a matter of minutes, the painful sensation was followed by parasthesia and swelling. Prescriptions were written for Amoxicillin (500mg) to take three times a day for 7 days, Medrol Dose Pack (for three days), and Extra Strength Tylenol (500mg). The patient was observed in the clinic for an additional 30 minutes, and determination of triage in the emergency department. Although the mild parasthesia did not resolve at that time, his pain symptoms slowly improved. The patient was instructed to return in 2 days for observation and was discharged from the clinic. He was also instructed to go to the emergency department, if pain and swelling increased. The patient did not return on the second day after the incident, a phone call was made, he stated that the symptoms of pain, parasthesia, and swelling improved. He was instructed to return the following week for the completion of his treatment plan, at this time, all of his symptoms resided.


Careful management of this accident allowed for the successful completion of this patient’s root canal therapy. Although accidents like these rarely occur, it is an important reminder of the harm certain dental materials can cause. Precautionary were taken and the procedure was not rushed, the accident still occurred. Critical factors, not discussed in this report still exist that could possibly lead to more accidental extravasations of sodium hypochlorite into the periapical region. Factors to be looked at include: How does the anatomy of the root canal increase or decrease the chance of these accidents? Are teeth with incomplete apecies affected more?

     Whether or not an accident occurs, the clinician should be properly prepared, and discussion of all risks with the patient prior to initiating treatment is prudent management for the patient.



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