Systematic review of lingual nerve retraction during surgical mandibular third molar extractions

The lingual nerve is at risk of damage during mandibular third molar (M3M) surgery. Current trends to avoid lingual retraction and prevent injury to the nerve run counter to the surgical principles of locating and protecting important structures. To our knowledge, the last review of this subject only considered repurposed lingual retractors such as the Howarth. Other studies have reported the use of purpose-built retractors with improved outcomes for lingual nerve injuries. This systematic review aims to assess the current view regarding lingual nerve retraction in M3M surgery. A search of PubMed and Web of Science using the key words "lingual", "nerve", "retractor", and "retraction" returned 118 results, 10 of which were selected for inclusion (nine original research papers and one systematic review). The data comprised 16,133 M3M extractions using no lingual retractor, repurposed, and purpose-built retractors. No lingual retraction showed a 0.60% risk of temporary and a 0.08% risk of permanent injury to the nerve. Repurposed retractors showed a 7.9% risk of temporary and 0.41% risk of permanent injury, and purpose-built retractors a 0.56% risk of temporary injury. No reported cases of permanent injury were associated with the use of purpose-built instruments. The evidence suggests that whilst the use of repurposed retractors increases the risk of injury to the nerve, there is no such risk with purpose-built retractors. Current data sets are confounded by the limitations of non-randomised, non-blinded studies, but trends show that lingual nerve retraction with purpose-built retractors may help to prevent permanent injury to the lingual nerve.