Management of root perforation and sodium hypochlorite extrusion injury

History and examination

A 33-year-old female presented to the A&E department, accompanied by her general dental practitioner (GDP) with a large, painful swelling on the right side of her mandible. Medically, the patient was fit and well, took no regular medication and had no known allergies. She gave consent to the taking of clinical photographs and the use of her radiographs in writing up this case report.

The patient had been undergoing the first stage of root canal treatment on her LR4. Root canal treatment was indicated for LR4 as the patient had persistent discomfort from the tooth and tenderness to percussion. A diagnosis of symptomatic apical periodontitis associated with a non-vital LR4 was made. During irrigation of the root canal system with NaOCl solution, the patient complained of severe pain. The GDP suspected an iatrogenic perforation had occurred and removed the rubber dam to examine the tissues surrounding LR4. He attempted to manage the situation by irrigating the access cavity of LR4 with saline and applying cold compression to the patient's face. The tooth was not temporized before bringing the patient to hospital.

On examination, extra-orally there was a facial swelling localized around LR4, extending to the angle of the mandible on the right side. In addition, the right submandibular lymph node was tender to palpation. There was normal mouth opening. Intra-orally, there was a large ulcer forming adjacent to LR4 and a dark-coloured area of necrotic tissue in the buccal sulcus. There was no sinus tract visible. The endodontic access cavity in LR4 was open and the tooth was otherwise restored with the remains of an occlusal amalgam. Clinical photographs were taken (Figures 1 and 2).

The patient was reviewed the following day, where it was found that the extra-oral swelling had increased in size. Pain was still present but the patient reported it as ‘manageable'. The patient was reviewed again 48 hours after the original injury. This time she reported the pain had gone but instead, she now had paraesthesia in of the right side of her lower lip and chin (distribution of the right mental nerve) (Figure 3).

Special investigations

The special investigations are summarized in Table 1. Neurosensory testing was conducted to assess the nature, severity and extent of the paraesthesia. A Boley gauge was used to test for two-point discrimination. On the unaffected left side of the lower lip and chin, the patient could discriminate between points 3 mm apart, which is considered normal. On the right, the value was 14 mm. Light touch sensation was tested using a cotton tip applicator and a sterile needle was used to test nociception. Both were found to be reduced (hypo-aesthesia) in the distribution of the right mental nerve (Figure 3).

A cone beam computed tomography (CBCT) scan with a limited field of view was taken to show LR4 (Figures 4-6). It confirmed the presence of a perforation exiting LR4 at the level of the crestal bone distobuccally. It demonstrated that the access cavity did not communicate with the pulp chamber, which was located centrally. The pulp chamber was entirely below the level of the alveolar bone, indicating some level of sclerosis, which may explain why this tooth was at higher risk of perforation. Only one, central root canal was present.

The CBCT showed bone loss at the point where the perforation exited the tooth and another radiolucent area in the soft tissue buccal to LR4 where NaOCl had entered the buccal sulcus. The radiolucency resulted from a fluid-filled space within the soft tissue.

Immediate management

The focus in immediate management of the injury was to limit the caustic effects of the NaOCl and to prevent an excessive immune response in the damaged tissues. It began when the patient's GDP irrigated the suspected perforation with saline and applied cold compression to the patient's face. The objective of saline irrigation was to dilute the strength of the NaOCl as it has been demonstrated in vitro that cytotoxicity of NaOCl is greater at higher concentrations.⁷ Dilution also neutralizes the highly alkaline pH, which contributes to its penetrating capabilities and thus its damaging effects on vital tissues.^8,9,10 Cold compression is a commonly employed method to reduce tissue swelling and pain because it promotes vasoconstriction and therefore limits the accumulation of tissue fluid and the influx of pro-inflammatory cells and cytokines.

After assessment at hospital, the patient was prescribed a 5-day course of amoxicillin and metronidazole to prevent infection in the necrotic tissue. She was also prescribed dexamethasone (10 mg once/day) for 1 week, followed by a gradual decrease in strength. The purpose of the steroid prescription was to reduce the patient's inflammatory response to the NaOCl because excessive inflammation leads to greater pain and swelling.⁶

Monitoring of healing

Review appointments were arranged at 24 hours, 48 hours, 1 week, 2 weeks, 6 weeks and 4 months. Follow-up is vital in cases of NaOCl injury to monitor symptoms and sequelae. In some cases, it is necessary to arrange surgical debridement of the necrotic tissue¹¹ but, fortunately, in this instance, this was not required.

At the 24 hour review, the swelling was found to have increased in size, but the patient reported their pain as manageable. At 48 hours, the swelling was still present and patient complained of altered sensation in the distribution of the right mental nerve. At the 1 week review, the patient complained that the right cheek was getting bigger and the paraesthesia persisted. By 2 weeks, the swelling was starting to reduce, the ulcer in the buccal sulcus was showing signs of healing and there had been some sensory recovery in the right side of the lower lip. By 6 weeks, the swelling had resolved, and the ulcer had healed. However, the mucosa adjacent to LR4 retained a dark, pigmented colour. There was no pain on palpation of the sulcus, but there was reduced sulcal depth owing to thick, underlying submucosal fibrous tissue. The paraesthesia took approximately 2 months to resolve.

Restorative management

Restorative treatment of LR4 was planned to take place over two appointments, under local anaesthesia, isolated with a rubber dam, and with an endodontic microscope to aid perforation repair and intracanal visualization.

Perforation repair in LR4 commenced approximately 6 weeks after the injury. According to the literature, perforations should ideally be repaired immediately, and a delay results in a poorer prognosis.^12,13,14,15 Immediate repair prevents infection from establishing, which results in less periodontal destruction, a better peri-radicular environment and more favourable healing.¹⁶ However, in this case, it was impractical to do so owing to the patient's level of distress.

A rubber dam was placed on LR4 and the access cavity was re-opened. The tooth was examined under a dental operating microscope, and it was found that the original access had deviated and access had not been gained to the root canal system. The level at which the perforation exits the tooth is the most significant prognostic factor in treatment success and crestal perforations carry the worst prognosis.^16,17,18 The histological reaction to perforation in this critical zone is periodontal inflammation and downward migration of epithelial tissue, resulting in periodontal pocketing and a higher chance of contamination from the oral environment, which in turn maintains irritation of the periodontium.¹⁹

The perforation was repaired non-surgically before accessing the pulp chamber to avoid cross contamination. No NaOCl was used to clean the perforation. Under the microscope, it could be seen that gingival tissue had grown into the opening of the perforation but the cavity was dry and there was no bleeding. Mineral trioxide aggregate (MTA) cement was carefully packed into the perforation using a micro-apical placement needle so that it pushed out the in-growing epithelium. Then, a layer of glass ionomer cement (GIC) was placed to shield the setting MTA cement during pulp chamber access. MTA is antibacterial to facultative bacteria²⁰ without being cytotoxic to the periodontal tissues. It is biocompatible and promotes tissue repair and regeneration.^18,21 Furthermore, it has been shown to exhibit better healing results than calcium hydroxide based materials.²² This non-surgical approach to repair was adopted rather than surgically exposing the perforation site because calcium silicate-based cements exhibit reduced bond strength and antibmicrobial activity when set in contact with blood.^23,24

The pulp chamber was accessed and a single, large, central canal was found. Shaping was achieved using nickeltitanium rotary files in conjunction with an ethylenediaminetetraacetic acid (EDTA)-based lubricant. NaOCl (5.25%) and EDTA (17%) solutions were used to irrigate and disinfect the root systems and were agitated using an ultrasonic ‘activator'. EDTA functions to remove the smear layer and allow better NaOCl penetration into the dentinal tubules,²⁵ while agitation of irrigants improves the tissue-dissolving properties of NaOCl solutions.²⁶

Between appointments, the canals were dressed using a non-setting calcium hydroxide (CaOH) medicament, which has a pH of 12.5 and has been shown experimentally to penetrate dentinal tubules and eliminate bacteria within 24 hours.²⁷ Strong antimicrobial activity has also been demonstrated by CaOH dressings left for 7 days.²⁸

A gutta-percha (GP) master cone was tried in the canal and a radiograph was taken to check its position. Obturation was achieved with warm vertical condensation and a zinc oxide-eugenol sealer. The thermoplasticized GP was deposited in small increments and packed down using pluggers to minimize shrinkage of the material and risk of air bubbles. The GP filling extended to just above the level of the alveolar bone and a thin layer of GIC was placed on top to seal it over. The tooth was definitively restored with a composite core build-up.

The post-operative radiographic result (Figure 7) is significant in determining the tooth's prognosis. In this case, it showed the length of the root filling was within 2 mm of the radiographic apex without extruding beyond it, there were no voids visible within the root filling and there was a good coronal seal. A review of the literature on the influence of clinical factors on endodontic outcomes concluded these features are the best predictors for treatment success.²⁹

Treatment outcomes

The post-operative radiograph reveals that there was approximately 3 mm of bone loss in the distal aspect of the tooth. Bone loss is a likely outcome when perforation has occurred at the level of the crestal bone. The likelihood was increased because 6 weeks had passed before the perforation was repaired, meaning that apical migration of gingival epithelium was inevitable. Fortunately, the bone loss did not result in any pathological mobility and there has been no persistent pocketing. The patient was happy to report the painful symptoms settled within 4 days following the first stage of root canal treatment, and at all follow-up appointments the tooth remained asymptomatic.

At the 4 month review, the ulcer had completely healed and a normal colour was restored to the mucosa. All swelling had resolved and normal sensation had returned to the lower lip. LR4 had been prepared for an onlay, and the patient was delighted with the outcome of her treatment.

Conclusions

NaOCl is an essential irrigant in root canal treatment. However, it is vital that practitioners are aware of the caustic effects it can have. It is recommended that an electronic apex locator, or a working length radiograph, should always be used to check for perforations before irrigating with NaOCl.

In the event of an NaOCl injury, the patient should be informed, a full clinical assessment should be conducted and appropriate treatment and monitoring planned. In severe cases, an urgent referral to a maxillofacial unit will be required.

Perforations may be restorable with specialist equipment, and a referral should be discussed as one of the possible treatment options with the patient.

CBCT scans are a useful assessment tool in treatment planning perforation repairs.