Anatomical relationship between mandibular third molar roots and mandibular canal in panoramic radiography and CT scans

Background: Inferior alveolar nerve (IAN) injuries are the third common complication after
infections and alveolar osteitis during third molars (M3s) extraction. The most common cause of
IAN injuries, is the proximity of M3 apices with mandibular canals, so the pre-operative
radiographic views (such as common or advanced techniques) are outmost important to detect the
proximity, number and position of M3s roots, and mandibular canal branches. the aim of this study
was to assay the exact detection of relationship between M3s and mandibular canals in panoramic
views and CT-Scans
Method and Material: 165 panoramic radiographs were assessed to detect the proximity signs
between M3 and mandibular canals. 9 patients (with 18 teeth) were detected and CT scan was
obtained.
Results: In panoramic views of 18 teeth, we could see root darkening in 11 cases, interruption of
white lines in 11 teeth, deflected root in 6 of them and canal divergence in 4 cases. In CT scan
views 12 teeth (%66/6) showed the association with mandibular canals and the 6 other teeth, in
spite of significant proximity signs in panoramic views, did not have any relation with the canal.
The associated teeth were mostly seen in women, left side and mesioangular and most of the canals
placed in lingual side to root apices.
Conclusion: Admittedly, the IAN injuries are complication during M3s extraction. So we have to
use the pre-operative radiographs for exact detection of anatomical proximities. If the proximity
signs between M3s and mandibular canals are seen in panoramic radiographs, it is highly
suggested to use advanced radiographic views such as tomography and CT scans.