An air-turbine handpiece is used for bone cutting and tooth dissection during extraction of an impacted lower third molar. However, subcutaneous emphysema and mediastinal emphysema may develop as advanced complications. Six patients had emphysema caused by the use of an air-turbine handpiece in our department during the last 10 years. Mediastinal emphysema developed in 3 patients. The route of the air was examined by CT scanning. The findings suggested that the air extended from a lingual sparse part of the extraction cavity to the sublingual space, submandibular space, masticator space, pterygomandibular space, lateral parapharyngeal space, carotid sheath, retropharyngeal space, and finally to the mediastinum. Since the pterygomandibular space communicates with the contralateral side, air easily invades this region.
