Sodium Hypochlorite Accident during Canal Treatment: Report of Four Cases Documented According to New Standards

Abstract

Hypochlorite accidents are relatively rare events. Therefore, there is a lack of precise and accurate reports in the scientific literature that could help clinicians better understand the phenomenon and associated risk factors. This study reported four hypochlorite accidents attributable to 5% NaOCl extrusion in patients who had undergone treatment of the maxillary elements canal treatments. In all cases, the accidents occurred during the irrigation phase and were characterised by intracanal bleeding, ecchymosis, and swelling on the hemiface corresponding to the treated tooth. Antibiotics, paracetamol, NSAID, corticosteroids, and cold or warm compresses for oedema were prescribed to treat the symptoms of the accidents. Significant improvement of symptoms was observed in all patients after 5–6 days. Anatomic risk factors such as apical fenestration, root perforation, and large foramina were identified as possible risk factors for the accidents. After the accidents, clinicians applied endodontic procedures for which there is no scientific evidence to continue endodontic treatments, such as changing the type of irrigant or the irrigation method. Our results suggest that using a standardised approach to document each hypochlorite accident will allow researchers to collect more accurate and detailed data that can subsequently be used to identify potential risk factors and better manage the symptomatology of hypochlorite accidents.

1. Introduction

Sodium Hypochlorite (NaOCl) is the most widespread irrigant in Endodontics because of its robust antimicrobial capacity in removing biofilm and dissolving organic tissue remains [1,2]. Although NaOCl concentration, volume, contact time with canal walls, and exposed tissue area linearly and positively influence NaOCl bactericidal capacity [3], the NaOCl high proteolytic activity could cause damage to vital tissues. Haemolysis and ulceration that inhibit the neutrophils migration and damage to fibroblasts and endothelial cells have mainly been demonstrated [4], together with cell membrane disruption due to NaOCl alkaline pH (pH 11–12.5) and its hypertonic character [5,6].

Extrusion of NaOCl, known as hypochlorite accident, is a very rare accident [7], especially if compared to the high number of canal therapies executed annually using NaOCl [8], is characterised by common complications such as oedema, ecchymosis, tissue necrosis, pain, and paraesthesia, and is usually classified as a careless iatrogenic injection, extrusion of NaOCl into the maxillary sinus, infusion of NaOCl beyond the root apex into the periradicular regions [8]. According to Kleier et al., hypochlorite accidents are common in females and occur more frequently in the maxillary teeth than in mandibular because of lower bone thickness and density and thinning of the maxillary vestibular cortex [7,9,10]. Other hypotheses, such as apical fenestration and multiple visits, have also been formulated [11,12]. As reported in a recent study, the higher rate of hypochlorite accidents in certain populations or tooth positions may be related to the need for multiple visits (first visit: 0.5% vs. second or above visit: 2.4%) and the risk of disruption of apical construction during root canal filling removal [12].

The hypochlorite accident is generally characterised by an initial reaction of the patient, while the pain, with marked oedema or bruising extending over the injured side of the face, cheek, or lips, may be immediate or delayed for several minutes or hours [13]. Spontaneous and profuse bleeding from the root canal may occur, and periorbital pain, chlorine taste, or throat irritation may occur in posterior maxillary teeth [14]. More serious complications such as transient or permanent paresthesia, motor nerve dysfunction [15], or spread of irrigation fluid to the submandibular, submental, or sublingual areas may compromise the airway and require immediate hospitalisation to prevent life-threatening events [16,17].

Critical depth analysis of possible causes of hypochlorite accident, endodontic treatment prosecution, dentist’s clinical decision or procedure changes after the accident, and long-term prognosis has not been executed, mainly because of a lack of standardised and accurate procedures of data reporting [10]. Guivarch’M et al. performed a first attempt to increase standardisation in the NaOCl accident reporting, designing a valid questionnaire aimed to evaluate anamnestic data, patients’ general condition, pulp and periapex status, typology, concentration, and irrigation method of NaOCl, needle type, syringe capacity and risk factors, as anatomical or iatrogenic factors [10]. However, endodontic treatment prosecution and operators’ behaviours after hypochlorite accidents have not been specifically investigated. A modified template should help produce a narrative and iconographic material, which helps promote discussion and feedback on the subject [9].

The hypochlorite accident falls under the broader field of endodontic complications caused by apical extrusions, such as emphysema, sinusitis, and nerve damage (paresthesia and anaesthesia). Emphysema, defined as air penetration of air or other gases beneath the skin and submucosa, is due to the accumulation of gases in the tissue spaces and can result from the accidental injection of air or oxygen, e.g., released by hydrogen peroxide, which can lead to severe complications. If the filling material is injected into sensitive areas such as the maxillary sinus, inferior alveolar nerve, or mental foramen, more severe damage occurs [18], even potentially irreversible [19], including maxillary sinusitis, aspergillosis infection, paresthesias, dysesthesias, and similar neural complications. Emphysema, generally associated with compressed air delivered with an air syringe, high-speed handpiece, or a combination of both (71% of cases), presents as a soft, skin-coloured swelling without redness that occurs during or shortly after the dental appointment [20]. The swelling is accompanied by crepitus, which may not appear until after a latency period of several hours [21]. More serious complications such as dyspnea with tinny voice, chest or back pain, symptoms of pneumo-diastinum, and Hamman’s sign have also been reported [22]. Treatment is empiric and depends on the extent of emphysema. Antibiotics are usually prescribed because of the non-sterility of the air supply, and there is a possibility of necrotic debris or microorganisms invading surrounding tissues. Administration of 100% oxygen via a mask without rebreathing has been reported to accelerate the resolution of emphysema because the oxygen, which replaces the trapped air, is more readily absorbed at the site.

To date, there are no clear guidelines on causes and treatment approaches [22]: Studies on possible risk factors and treatment guidelines have been published based on case reports [16,23], and there are no standardised reporting methods [10]. Although the incidence of hypochlorite accidents is very low and, except for severe complications, recovery is rapid with little discomfort, the consequences can be significant. The practitioner may decide to change the endodontic procedure to reduce the risk, and the patient may develop a sense of mistrust toward the procedure and his or her dentist.

This case series aimed to describe four NaOCl accidents to evaluate the causes of the reported hypochlorite accidents and the endodontic treatment prosecution concerning the operator’s behaviour, applying and expanding Guivarc’h et al. questionnaire.

2. Case Series

2.1. Report A

A 59-year-old healthy woman came to the emergency department of the Dental Clinic of Brescia with evident signs of swelling and ecchymosis on her face result of a canal treatment executed on maxillary right lateral incisor (#12) with vital pulp, treated for prosthetic reasons and without using a rubber dam, by her general dental practitioner the day before. From clinical history reconstruction, it emerged that at the end of the first session. Although the patient immediately reported to her dentist the presence of moderate pain (VAS 6), the practitioner prescribed analgesic therapy, not noticing any signs on her face (ecchymosis or swelling) and reckoning the arisen algia a normal consequence of the executed treatment. The day after, the patient went to the Dental School, University of Brescia, because of swelling and purple patches appearing on her right hemiface during the night. At the extraoral inspection, swelling and ecchymosis involved the patient’s face’s right side, particularly the mouth’s angle and the periorbital region; no ophthalmologic symptoms were present (Figure 1a,b).

Furthermore, ulcerative lesions were visible on the internal mucosa of the lip (Figure 2a), especially next to dental element 12, whose access cavities had not been sealed.

The diagnosis was HA involving element 12 following an irrigating procedure with 5% NaOCl (volume 2.5 mL) performed using a bevelled needle (27 G). After that, the incisor was left open, and the root canal was not instrumented. It was recommended to put ice on the painful area to reduce oedema. The following drug therapy was prescribed: (1) Amoxicillin with Acid Clavulanic 875 + 125 mg (1 tablet every 8 h per 3 + 3 days); (2) Paracetamol 1000 mg (1 tablet every 12 h per 7 days); (3) Prednisone 25 mg (1 tablet/die per 4 days, 1/2 tablet per 2 days, 1/4 tablet per 2 days); (4) Ibuprofen 600 mg (1 tablet/die per 4 days).

In the subsequent examinations, the symptomatology and HA clinical signs appeared significantly reduced. After three days, ecchymosis, previously purple, was yellowish and in the phase of reabsorption (Figure 1c,d). Ulcers (Figure 2b) inside the right labial mucosa were full-thickness and put the muscle layers in communication with the oral cavity. After five days, the swelling was almost absent (Figure 1e,f), and the pain disappeared. The therapy with Paracetamol and Ibuprofen was suspended. Root canal treatment of the dental element 12 has been continued at the Dental School, University of Brescia. CBCT was not performed. The endodontic treatment was continued by replacing hypochlorite with chlorhexidine. The patient considered taking legal action against the first doctor. The data collection form has been completed (Supplementary Materials Table S1).

2.2. Report B

A 43-year-old woman, treated in the Endodontics department of the Dental School, University of Brescia and suffering from numerous diseases, underwent root canal treatment of the right maxillary canine (13) with vital pulp. After isolating the area with the rubber dam, establishing the working length (24 mm) through an electronic apex detector, and verifying manually the foramen apical diameter (#70), irrigation was conducted with a 10 mL syringe of 5% NaOCl, injected into the canal with a bevelled needle (25 G × 1 “; 0.5 × 25 mm) calibrated at 21 mm. The push-pull technique was performed to activate the solution. During the final rinse with 5% NaOCl, the needle blockage occurred in the apical third of the root canal, followed by intense bleeding from the canal and sudden pain.

Hypochlorite accident was immediately diagnosed and treated, injecting two syringes (10 mL) of saline solution into the canal to dilute the extruded hypochlorite. At the same time, the patient was accompanied from the supine position to the sitting one without the need for anaesthesia administration for pain management. After 30 min monitoring, given the presence of mild oedema on the patient’s face, the dentist provided a temporary sealing of the access cavity, reassured the patient, informed her about possible complications, and prescribed the following drug therapy: (1) Ciprofloxacin 250 mg (1 tablet/die per 6 days); (2) Paracetamol 500 mg (1 tablet every 12 h per 7 days); (3) Ibuprofen 600 mg (1 tablet every 12 h per 3 days); (4) Betamethasone 1 mg (2 tablet/die per 2 days, 1 tablet/die per 2 days, 1/2 tablet per 2 days).

The day after (first follow-up), oedema and ecchymosis were present on the right commissure lip, starting from the root apex of element 13 (Figure 3a,b). No mucosa lesions appeared next to the treated radicular apex. In the subsequent examinations (follow-ups at three and five days, respectively), HA symptoms appeared to be reduced: after three days (Figure 3c,d), ecchymosis, previously purple, was yellowish and in the phase of reabsorption, the pain disappeared, and the swelling was very slight. After five days, the skin lesions almost disappeared (Figure 3e,f). Therefore, root canal treatment was completed replacing hypochlorite with chlorhexidine. CBCT was non-performed. The patient evaluated no medical–legal action. The data collection form has been completed (Supplementary Materials Table S2).

2.3. Report C

A 54-year-old healthy woman received a root canal treatment of the left maxillary canine (23) with vital pulp in a private dental office. After irrigating the root canal with a 3 mL of 5% NaOCl provided with a non-bevelled and open-ended needle (27 G × 1 “; 0.5 × 25 mm) calibrated at 5 mm from WL, instrumenting apical foramen at 0.30 mm, and applying the push-pull technique to activate the solution, intense bleeding from the canal occurred during the final rinse with 5% NaOCl. After diagnosing the HA, three syringes (10 mL) of saline solution were immediately injected into the canal to dilute the extruded hypochlorite. Mild oedema was noted on the patient’s face after a few minutes. The dentist executed a temporary sealing of the access cavity, applied cold compresses on the edimegenic site, and prescribed the following drug therapy:

• Amoxicillin with Acid Clavulanic 875 mg + 125 mg (1 tablet every 8 h per 6 days);
• Prednisone 5 mg (2 tablet/die per 5 days)
• Ibuprofen 600 mg (2 tablet/die per 3 days).

The day after (first follow-up), swelling and ecchymosis involved the patient’s face’s left side, particularly the mouth’s angle and the periorbital region, without ophthalmologic symptoms or mucosa lesions next to the treated radicular apex. After five days, ecchymosis was in the reabsorption phase. Therefore, the root canal treatment was continued by replacing the needle with a side-vented needle. CBCT showed fenestration of the root apex (Figure 4). The patients took no medical–legal actions. The data collection form has been completed (Supplementary Materials Table S3).

2.4. Report D

A 50-year-old healthy man with a moderate dental fear received root canal treatment of the first maxillary premolar (#14) with vital pulp and prosthetic crown at a private dental office. After irrigating the root canal with 10 mL of 5% Sodium Hypochlorite, injected into the canal with a bevelled needle (27 G × 1 “; 0.5 × 25 mm), apical foramina 0.25 mm, severe pain (VAS 10) and intense bleeding occurred immediately during the final rinse with 5% NaOCl, followed after few minutes from mild oedema on patient’s face. After diagnosing HA, the dentist administered local anaesthesia to reduce pain and injected three syringes (10 mL) of saline into the canal to dilute the extruded hypochlorite. After performing a temporary sealing of the access cavity, the patient received cold compresses on the edemigeous site and instructions about possible complications together with the following prescribed drug therapy: (1) Amoxicillin with Acid Clavulanic 875 + 125 mg (1 tablet every 8 h per 6 days); (2) Prednisone 5 mg (2 tablet/die per 5 days); (3) Ibuprofen 600 mg (2 tablet/die per 3 days).

The day after (first follow-up), swelling and ecchymosis involved the patient’s face’s left side, particularly the mouth’s angle and the periorbital region, without any ophthalmologic symptoms. No mucosa lesions appeared next to the treated radicular apex, while paresthesia of the upper lip and dysphagia were present. In the subsequent examinations (follow-ups at two and six days, respectively), dysphagia had disappeared, and a significant reduction of other symptoms was noted. After six days, ecchymosis was in the reabsorption phase, while pain and paresthesia disappeared. CBCT revealed stripping of the third coronal canal and apical transportation (Figure 5). The patient evaluated no medical–legal actions. The patient dental fear prevented him from completing the canal treatment. The data collection form has been completed (Supplementary Materials Table S4).

3. Discussion

The NaOCl accident is a rare event, estimated at least one case in the whole dentist’s practice [7]. However, from 1975 to 2016, almost 52 cases were reported in peer-reviewed journals [10]. Nevertheless, the prevalence of such cases in clinical practice appears higher. Therefore, this work aimed to report four clinical cases of HAs that occurred in our research team over four years (2019–2022) and evaluate the causes of the reported hypochlorite accidents and the endodontic treatment prosecution in relation also to the operator’s behaviour expanding the Guivarc’h et al. template [10] adding to it the degree of severity (according to the topographical pattern of the lesions described by Zhu et al. [8] and modified by the authors), the presence of legal action against the first practitioner, and clinical information about endodontic treatment so to investigate the dentist’s behaviour. Furthermore, for better management of the accident and considering the time to onset of some symptoms, such as swelling and ecchymosis, we improved Guivarch’s template, adding a pharmacological therapy section in the post-operative extrusion management from day 1.

From applying the standardised procedure to data reporting, we noted that four reports presented similar risk factors for the occurrence of the NaOCl accident: female gender (3/4) and dental elements in the maxillary site (4/4) [7]. Furthermore, the diffusion of sodium hypochlorite in soft tissues is facilitated by the lower bone density of female subjects and by the thickness of the cortex surrounding the vestibular roots of the maxillary teeth [7,11]. In the third case, the CBCT exam, executed after the hypochlorite accident and addressed to evaluate the causes for HA, showed the apical fenestration as the probable origin of the HA. According to this, a recent quasi-experimental study [24] investigating the apical fenestration in a series of 13 HAs examined with CBCT analysis underlined the crucial role of the apical fenestration as a risk factor in the occurring of this kind of accident, so moving the attention from the use or not of NaOCl to its possible portal-of-exit. To this end, Souza et al. recommended analysing the actual reasons for the HA without renouncing a priori to use NaOCl in the following steps aimed to conclude the endodontic treatment. The prevalence of apical fenestration varies significantly among general populations and dental elements with greater maxillary involvement, especially lateral incisive, canine, and first premolar [25,26]. Specifically, analysing Kalaitzoglou et al. results and focusing only on types I, IV, and VI of root fenestration (i.e., fenestration involving apex), we determined a presence of apical fenestration in 85% of analysed elements [25].

Furthermore, the apical foramen, the stripping, the apical transportation and the lateral canals could be considered portal of exit (POE) in the irrigant extrusion. As evidenced by the conventional radiological examination and the investigation executed using an intraoperative microscope, both reports excluded any perforation except for the last. Nonetheless, in the second case, the preoperative radiological examination showed the presence of a distal lateral canal near the calibrated needle’s access, a possible POE for hypochlorite accident. Since the small diameter of the lateral canals should hamper the flow of NaOCl, involvement of the lateral canals in the occurrence of the hypochlorite accident could be possible, though rare [27]. When the aetiology of the accident is not well defined and the endodontic anatomy unclear, a CBCT exam should be performed. In cases A and B, the canal anatomy was easily interpreted by the periapical radiograph (single-rooted, straight, single-canal teeth) and the absence of suspected iatrogenic perforations did not justify performing a second-level radiologic examination according to the ESE guidelines, which recommend a CBCT examination when the additional information from reconstructed three-dimensional images can improve clinical management [28]. However, Souza et al. [24] showed how CBCT could play a crucial role in identifying the presence of 13 apical fenestration in 13 cases: the use of CBCT after HA should show a higher presence of apical fenestration as the cause of HA, so reducing the role of density bone in the occurring of HA. In other words, it could be hypothesised that the lack of apex coated is at the origin of HA. This could justify the hypochlorite accident in the absence of conceptual and technical errors on the part of the operators (lack of preoperative radiographs, iatrogenic perforations, incorrect determination of the working length) [29]. When the apical foramen is in contact with the soft tissues of the mucosa, the apical resistance of the bone tissue is absent, so even small increases in pressure during irrigation, considered irrelevant by the operator, may be sufficient to cause a hypochlorite accident.

Concerning the patients’ clinical conditions, vital pulp and normal periapex were present in all reports. Although necrotic pulps and teeth associated with periapical lesions are risk factors in HAs [7], the presence of optimal preoperative conditions was not a sufficient element to prevent this kind of accident. Examined dental elements had straight root canals but different apical diameters (Report A: #60; Report B: #70; Report C: #35; Report D: #25). Furthermore, in the second case, the positive irrigation technique and open-ended needle, although calibrated, could have favoured the occurrence of the accident: the extrusion could have occurred through the distal lateral canal, present in the middle third and visible in the preoperative radiography (Figure 6). In the third and fourth reports, the operator did not feel blockage of the needle. Still, it is likely that the extrusion, as shown by the CBCT investigation, was facilitated by an apical fenestration (C) and a stripping and apical transportation (D). In the last reported three cases, the working length of the irrigation needle was not reported, and the accident occurred during the final washing when the shaping phase was completed. Therefore, we hypothesised that an operator’s concentration reduction could have happened in the final steps of root canal treatment.

About the timely management of HA, the accident was not immediately diagnosed in the first case. As reported by the patient, swelling and ecchymosis had arisen a few hours after the endodontic session. Since pain and swelling can worsen after a few minutes/hour [30], in the presence of symptoms such as pain and intracanal bleeding during canal treatment, it is judicious to exclude all possibility of doubt waiting a few minutes before discharging the patient; however, following the clinical course is highly recommended.

All accidents reported in this study showed a low severity level: ecchymosis was limited to the face without significant neck involvement, and no permanent neurological and respiratory complications were reported, pain and swelling lasted for a short period, while signs of subcutaneous emphysema were not present. The complications described in the reports (ecchymosis, swelling and pain) belong to the first category of Spencer’s classification [31] and the second category of the classification illustrated by Zhu et al. [8].

Ecchymoses of the facial skin are a common sign of hypochlorite accidents; they may occur immediately or after a few hours and may be accompanied by tissue necrosis and sometimes by paresthesia. In cases of extensive ecchymosis, there should be damage to the blood vessels with extravasation of blood into the adjacent subcutaneous soft tissue [8]. Emphysema is also a common sign of hypochlorite accident with rapid onset. According to some authors, it is characterised by swelling and crepitus and is a consequence of the release of oxygen due to the interaction between the tissue and NaOCl [32,33,34]. However, in our cases, the observed swelling without crepitus could have resulted from an inflammatory process rather than the accumulation of air oxygen released after a chemical reaction with NaOCl.

The analgesic therapy prescribed in both cases was very efficient, confirming what was recommended by Hargreaves and Abbott [35]; steroids and antibiotics could have contributed to a quick resolution of the symptoms. Pharmacological treatment determined a high efficacy level: the reduction of side effects related to HA influenced the patients’ distress level and helped the clinician in better management of the subsequent phase. In this context, the use of antibiotics appears controversial; according to Guivarc’h et al. [10], antibiotics should be administered in case of high infection risk and for non-immunocompetent patients; on the contrary, given the low prevalence of HA, the current ESE guidelines [36] do not give any recommendation about antibiotics in case of HA. The decision about antibiotics prescription is therefore demanded to clinician’s choice, who in many cases prefer to keep a prudential approach to reduce the risk of eventual complications related to no antibiotic prescription, weighing individual best practices against perceived patient expectations. This behaviour, as well as contributing to an increase in antibiotic use [37], could expose patients to not-mandatory treatment and possible antibiotic-related side effects. In case A, a higher dose of prednisone (25 mg instead of 5 mg) was administered to effectively contain the inflammation and tissue destruction, which was more severe than in cases C and D because of the involvement of the vestibular mucosa with the appearance of ulcerative lesions that were not treated topically by the dental team.

Treatment protocols for hypochlorite accidents are empiric and based on severity, with emphasis on pain management with local anaesthetics and analgesics along with cold compresses [38]. The use of antibiotics appears controversial. According to Guivarc’h et al. [10], antibiotics should be administered in case of high infection risk, the severity of hard and soft tissue destruction and necrosis, and for non-immunocompetent patients; on the contrary, given the low prevalence of HA, the current ESE guidelines [36] do not give any recommendation about antibiotics in case of HA. The decision about antibiotics prescription is therefore demanded to clinician’s choice, who in many cases prefer to keep a prudential approach to reduce the risk of eventual complications related to no antibiotic prescription, weighing individual best practices against perceived patient expectations. This behaviour, as well as contributing to an increase in antibiotic use [37], could expose patients to not-mandatory treatment and possible antibiotic-related side effects. The choice of compresses is also controversial: Guivarc’h et al. advocate the effect of warm and cold compresses: the former to reactivate microcirculation, prevent necrosis, and promote tissue healing; the latter to reduce oedema and vasoconstriction, possibly limiting the spread of the leaked substance. Short-term administration of corticosteroids is less controversial, although questionable. Glucocorticosteroids have a positive effect on pain relief because they can inhibit or suppress inflammatory responses and thus control inflammatory mediators that are directly or indirectly involved in the development of pain [39], but their administration should be the result of a balance between the control of spreading oedema and the increased risk of infection.

Analysed the role of the operator toward HA, we observed a sense of insecurity toward dental treatment management: no diagnosis of HA, change in endodontic procedures, that is, use of a needle in the coronal third or replacement of NaOCl with chlorhexidine, or increased dental fear so to abandon of any endodontic treatment should be induced to increase attention toward HAs designing accurate recommendations and guidelines.

In the case of a hypochlorite accident, the practitioner should be capable of making a correct diagnosis and managing the patient from a therapeutic and psychological point of view. During the accident, the patient copes with an emotionally damaging, sudden, and painful situation, fearing that the event invalidates the treatment prognosis. To reduce medical–legal actions deriving from a deterioration of the relationship of trust between the doctor and the patient, the clinician should reassure the patient and direct his efforts toward a favourable prognosis. In this study, despite the same complications [31] and similar severity classifications (Zhu’s classification [8]), the four accidents reported different medical–legal consequences. The undiagnosed and thus not correctly managed accident (report A) could cause medical–legal action (at the moment patient required her case sheet for some legal evaluation). In contrast, in the other cases, the timely diagnosis and the proper management of HA allowed patients to maintain trust in the endodontic team.

Hypochlorite accident is undoubtedly rare, but the lack of standardised procedures to analyse its causes and endodontic treatment to adopt after it makes the accident even few documented. Therefore, the rarity of the accidents, the impossibility of designing large retrospective studies, and the lack of systematic data reporting [10] prevent researchers from deepening current literature. In Endodontics, sodium hypochlorite is still the widest irrigant despite its well-known cytotoxic effects, especially in extrusion outside the root canal [40].

4. Conclusions

Hypochlorite accidents represent a rare occurrence in dental activity. Early diagnosis, timely treatment and symptomatology monitoring are as necessary as risk prevention. After the accident and the recovery of patients, endodontic therapies should be performed as soon as possible and with a high grade of safety, without compromising root canal disinfection. The case reports, together with the systematic reviews, illustrate to clinicians the numerous patterns that the hypochlorite accident can take, suggest preventive and therapeutic measures to be adopted in these cases, and indicate clinical and extra-clinical risk factors such as those inherent to the medical–legal field. Documenting NaOCl accidents following standardised indications is necessary to create a homogeneous dataset for future revisions. Endodontic scientific societies worldwide should distribute the material required to record this event to their members to stimulate more accurate data collection.