Subcutaneous emphysema in patients undergoing root canal treatment: a systematic review of the factors affecting its development and management

Background: Subcutaneous emphysema is an infrequent mishap during root canal treatment which, in rare cases, can lead to severe complications. Aim: To systematically review the literature on the factors affecting the development of subcutaneous emphysema during root canal treatment, and on its management. Data sources: An electronic search was conducted in EMBASE (1947–2018), LILACS (1982–2018), PubMed (1950–2018), SciELO (1997–2018), Scopus (1970–2018), Web of Science (1900–2018) and two grey literature databases. Moreover, all issues of nine journals and four endodontic textbooks were hand-searched. Study eligibility criteria, participants, interventions: The retrieved studies were screened by two reviewers to select clinical studies, case reports or case series describing subcutaneous emphysema that developed during or immediately after root canal treatment in adult patients. Study appraisal and synthesis methods: Included studies were critically appraised according to a custom list of quality requirements. The extracted data were arranged in tables, and combined through a narrative synthesis. Results: The search retrieved 99 unique articles. Thirty six case reports and 15 case series describing a total of 65 cases of subcutaneous emphysema were included in this review. The methodological quality was medium. Reported cases of emphysema more often involved females and maxillary teeth. Drying of the root canal system with air under pressure, inadvertent extrusion of hydrogen peroxide through the apical foramen, the air-water spray produced by handpieces or laser devices, and the use of ozone gas were the most commonly suspected causes. Its management involved prescription of antibiotics and NSAIDs/analgesics, local application of ice packs or compresses and hospitalization. The signs and symptoms resolved completely within 1-17 days. Limitations: Case reports and case series are a low level of evidence. Conclusions and implications of key findings: 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