Eucalyptus Extrusion Injury: not such an Essential Oil?

Case report

A 44-year-old male was referred to the Oral and Maxillofacial department on an acute basis with a history of a sudden onset of facial swelling. The swelling of the lower right cheek had appeared during root canal re-treatment of the lower right second premolar (LR5) by his general dental practitioner (GDP) earlier that morning. It had worsened over the following few hours. His medical history was unremarkable except for a penicillin allergy.

On discussion with the dentist, it was reported that, during the re-treatment, eucalyptus oil (EO) was used to help dissolve the gutta-percha (GP) root canal filling material, and that this was delivered using an irrigation syringe. Irrigation of the canal with EO had elicited immediate severe pain around the jaw, shortly followed by onset of swelling. It was concluded that this was due to an extrusion injury involving the EO. It was reported that no other irrigants were used. Treatment was discontinued and the tooth was temporized appropriately.

Examination revealed tender right-sided facial swelling involving the lower lip, right periorbital region, buccal and submandibular spaces, and early necrosis of the buccal mucosa adjacent to the LR5 (Figures 1 and 2). The LR5 was tender to percussion. There were no airway concerns and the patient was systemically well, with normal observations. There was no sensory deficit.

The patient was admitted to hospital and given analgesia, intravenous (IV) dexamethasone and IV antibiotics (clarithromycin and metronidazole). On discussion, the patient decided against further endodontic treatment, and the LR5 was extracted the following day under general anaesthesia with copious saline irrigation and limited debridement of the adjacent necrotic buccal mucosa. The patient was discharged 48 hours after admission on oral antibiotics, following improvement in his pain and swelling. He was reviewed 3 weeks post-discharge and all presenting features had resolved.

Discussion

Extrusion injuries in dentistry are relatively rare, and are more commonly associated with the use of sodium hypochlorite (NaOCl) during endodontic treatments when forceable pressure on an engaging and non side-venting irrigation needle is used. This arises from inadvertent application of NaOCl into the peri-radicular tissues, typically through the apical foramen, accessory canals or via perforations of the pulp floor or canal wall. The risk of injury is increased in teeth with immature or over-instrumented apices.^1,2

The presence of NaOCl in the tissues results in an intense inflammatory response, causing significant tissue necrosis, and can cause widespread oedematous swelling and contusion.³ Whilst the injury can be localized to the periodontium and surrounding mucosa, it is also frequently reported as more widespread, involving periorbital tissues, neck, and even mediastinum, with airway compromise reported.⁴ The injury pattern of ecchymosis follows the superficial venous vasculature draining from the teeth and bone into the surrounding veins. In the maxilla, this may be the anterior or posterior superior alveolar veins and, in the mandible, this can include the inferior alveolar vein.¹ Interestingly, the above case demonstrated no ecchymosis of the overlying skin.

To the authors' knowledge, this is the first reported extrusion injury involving EO, although it has previously been reported involving chloroform, resulting in localized tissue necrosis⁵. EO is reported to be a safe and biocompatible material,⁶ yet is known to cause mucosal irritation,⁷ a burning sensation within the oral cavity,⁸ and has been shown to be cytotoxic.⁹

Eucalyptus oil is an essential oil distilled from the leaf of ‘Eucalyptus’, a plant from the family of Myrtaceae. The main constituent of the oil is the chemical 1,8-cineol, also known as ‘Eucalyptol’. Within dentistry, EO is most commonly used as a solvent in the re-treatment of root canal systems previously obturated with GP, and is considered a safer alternative to chloroform^10,11 which, while highly effective,¹² remains controversial due to its carcinogenic potential.^13,14,15 During re-treatment, it is advised to use a chemo-mechanical approach as root filling materials often resist mechanical instrumentation.¹⁶ Various solvents can be used for this purpose, including xylene, halothane, orange oil, rectified turpentine, Endosolv (Septodont) and Ethyl Benzene and ether.⁶ Orange oil has been demonstrated to be significantly less cytotoxic than EO¹⁵ and has comparative effectiveness in removing GP and endodontic sealant.^6,17,18

Other uses vary widely. In alternative medicine, it is used as an antibacterial agent, and can also be used in low doses as flavouring in foods and as a fragrant in soaps and perfumes. Documented incidents involving EO are mainly from ingestion, resulting in vomiting, coma, lethargy and seizures, and can be potentially fatal.^8,19 Skin reactions have been noted to involve contact dermatitis.²⁰

Endodontic re-treatment can be a complex procedure, and is recognized as such within the Restorative Index of Treatment Need.²¹ However, each case should be carefully assessed with respect to anticipated complexity, and many are within the scope of practice of appropriately experienced GDPs. The quality of the existing obturation may give an indication as to the complexity of GP removal; for example, poorly-condensed GP with numerous voids will likely allow instruments to pass into the canal more easily, whereas well-condensed GP is likely to be more challenging.²²

In re-treatment, solvents should be used sparingly with careful introduction into the root canal system. Virdee details how Gates Glidden burs can be used initially to remove the GP mechanically from the coronal one to two thirds of the canal, alongside copious irrigation to remove the debris.²² The apical GP is then removed using a combination of ISO K files and Hedström files carefully measured to length. Finally, the authors advocate the use of a solvent to retrieve any GP remnants, especially in curved canals. They recommend flushing the canals and aspirating repeatedly and using paper points to absorb the dissolved root filling material. In the context of this case, inappropriate irrigation technique may introduce unnecessary risk.

An alternative technique described in the literature is to remove the first 2−3 mm of GP below the cementoenamel junction thus creating a reservoir for the solvent. This is followed by mechanical instrumentation of the canal to the working length using either Hedström files, rotary files or ultrasonic retreatment tips.²³

When irrigants are used within the root canal system, the operator should exercise caution in order to prevent extrusion into the peri-radicular tissues:

Given the absence of previously reported cases of extrusion injury involving EO, the case discussed involved management based upon that of hypochlorite injuries, given the clinical similarity on presentation. Removal of the causative agent is the first key step, and typically will involve cessation of endodontic treatment, and dilution of the agent within the root canal system using a neutral and inert irrigant, such as saline. Antibiotics are advised to prevent secondary infection following tissue necrosis, and steroids can reduce swelling. Management is, of course, subjective and dependent on the severity of the injury.

Conclusion

This case highlights the importance of careful use with all chemicals within endodontics, and not just with sodium hypochlorite. Whilst EO is an effective solvent and can be used safely within re-treatment procedures, care must be taken to ensure that delivery techniques complement this. It is unclear if other solvents may produce similar tissue damage, and further research is recommended to highlight the safest options. However, orange oil may be preferable to EO owing to its lower cytotoxicity. All cases must be assessed on an individual basis, and consideration should be given as to whether solvents are necessary at all.