Subcutaneous emphysema during root canal treatment

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Subcutaneous emphysema is caused by the introduction of air beneath the skin and submucosa leading to swelling and crepitus. It is an uncommon complication of root canal treatment and resolution is usually uncomplicated, but it can lead to pneumomediastinum and air way compromise or infection of deeper spaces. Cases linked to root canal treatment have been reported since 1927 but the aetiology is not fully understood and there is no consensus on management.

The aim of this review was to assess the factors affecting the development of subcutaneous emphysema during root canal treatment and its management.


Searches were conducted in the Embase, LILACS, PubMed, SciELO, Scopus, Web of Science, Grey Literature Report ( and OpenGrey ( databases. This was supplemented by hand searches in the journals  (International Endodontic Journal, Journal of Endodontics, Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology and Endodontology, Dental Traumatology and Endodontics, Australian Endodontic Journal (1982, ENDO – Endodontic Practice Today, British Dental Journal, Journal of the American Dental Association and Journal of Dentistry) and 4 endodontic textbooks. There were no restrictions on language or data of publication. Clinical studies, case reports or case series describing subcutaneous emphysema that developed during or immediately after root canal treatment in adult patients were considered.

Two reviewers independently selected studies assessed study quality and extracted data. Study quality was assesses using criteria based on the Case Report (CARE) guideline and a suggested tool for evaluating care reports and series. A narrative synthesis of the data was conducted.


  • 51 papers (15 case series, 36 case reports) describing 65 cases of subcutaneous emphysema were included.
  • More cases were reported in females (39/65) than in males (20/65).
  • 51 cases occurred during initial root canal treatment, 9 during non-surgical root canal retreatment and 3 during endodontic surgery and 2 during incision and drainage of an acute abscess.
  • 71% of cases involved maxillary teeth.
  • Drying tooth canals with pressurised air in three-way syringe was most common intervention related to subcutaneous emphysema (31/65)
  • 10 cases were linked to irrigation of the root canals with hydrogen per-oxide (concentrations varying between 3% and 10%0.
  • 8 cases were linked to access cavity preparation using an air rotor.
  • 2 cases were linked to use of ozone gas
  • 4 cases were associated with more than one potential cause with no potential cause being reported in 3 other cases.
  • In 11 cases air reached the thorax causing a pneumomediastinum in 9.
  • Management was mainly by antibiotics (40/65) with 15 patients being hospitalised.
  • Time to resolution ranged from 1- 17 days (median 6 days)


The authors concluded: –

Subcutaneous emphysema can develop during both nonsurgical and surgical root canal treatment. Pressurized air streams or air-water sprays should not be directed towards the root canals or areas with mucosal discontinuity. None of the management approaches were clearly related to expedited recovery. Guidelines should be developed in order to avoid unnecessary or potentially harmful interventions.


The authors have conducted an extensive search of databases and the grey literature to identify cases of this uncommon adverse effect of root canal treatment.  The included studies spanned the years from 1919 to 2015 and were published in 12 different languages. The authors highlight a significant degree of heterogeneity in the amount of information provided in the included papers and better adherence to reporting guidelines such as those outlined by the CARE group would be helpful. Interestingly more than 70% of the cases were published more than 20 years ago and there is some suggestion that increased use of rubber dam may have reduced the number of cases.  However, the evidence seems circumstantial and may relate to better knowledge of the potential risks and improved techniques.  While there may have been a reduction in the number of cases of subcutaneous emphysema there is also the potential for under reporting of the actual number of episodes in general practice unless other reporting mechanisms available as journal publication is a potential barrier.


Primary Paper

Fasoulas A, Boutsioukis C, Lambrianidis T. Subcutaneous emphysema in patients undergoing root canal treatment: a systematic review of the factors affecting its development and management. Int Endod J. 2019 Jul 4. doi: 10.1111/iej.13183.[Epub ahead of print] Review. PubMed PMID: 31271657.

Other references

Gagnier JJ, Kienle G, Altman DG, Moher D, Sox H, Riley D; CARE Group*. The CARE Guidelines: Consensus-based Clinical Case Reporting Guideline Development. Glob Adv Health Med. 2013 Sep;2(5):38-43. doi: 10.7453/gahmj.2013.008. PubMed PMID: 24416692; PubMed Central PMCID: PMC3833570.

 Murad MH, Sultan S, Haffar S, Bazerbachi F. Methodological quality and synthesis of case series and case reports. BMJ Evid Based Med. 2018 Apr;23(2):60-63. doi: 10.1136/bmjebm-2017-110853. Epub 2018 Feb 2. PubMed PMID:29420178; PubMed Central PMCID: PMC6234235.




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