Etiology of Lingual Nerve Injuries in the Third Molar Region: A Cadaver and Histologic Study

Purpose

It has been suggested that different etiologies of lingual nerve damage in the third molar area will produce a different clinical and histologic appearance in the nerve. If the clinical and histologic pictures were different, it could result in different treatments being recommended.

Materials and Methods

Eight preserved cadavers (16 lingual nerves) were used for this study. As far as possible, the nerves were left in situ and damaged in a way that could be envisaged during third molar surgery. In each case, the damaged sections of nerve were photographed, resected, embedded in paraffin wax, sectioned in 5 μm sections, stained with hematoxylin-eosin, and examined histologically.

Results

The scalpel clinically produced a clean wound with sharply defined edges; this was confirmed histologically with minimal disruption to the fascicles. The 702 fissure bur produced a ragged stretch-type injury clinically, and histologically this was confirmed with an irregular-edged border to the lesion and stretching and internal damage to the fascicles immediately adjacent to the wound. The crush injury clinically caused considerable apparent damage to the nerve, which was confirmed histologically with crushing and disruption of the fascicles and reduction to approximately 25% of their preinjury thickness. The stretch injury clinically showed no damage, but histologically showed irregular internal disruption of the fascicles over the whole area subject to stretching movements.

Conclusion

It does appear that different modalities in nerve injury produce a different type of injury both clinically and histologically. This information has implications for both natural clinical recovery and the indications for surgical intervention. Clinical recovery may occur best with close approximation of a sharp scalpel-type wound or excision of a crushed area of nerve with reapproximation of the nerve endings, but a ragged wound caused by a fissure bur may require excision back to healthy nerve with subsequent reapproximation, whereas with the stretching injury it may be difficult to ascertain the edges and limits of the wound, and difficult to repair, and it may be most appropriate to rely on a natural healing process for the best results.