ABSTRACT
Extraction of mandibular third molar is one of the routine surgical procedures in dentistry. Disestesia because of damage to sensory bundles of inferior-alveolar nerve is one of the complications which may happen following this surgery. Panoramic radiograph is the method which, most of the dentists commonly apply for the assessment of the relationship between the tooth and canal. However, this technique can show a two dimensional view of the site. In this study we compared tomography which showed the third dimension with, panoramic in determining the position of the tooth relative to canal. Sixty tomographs and panoramic radiographs of 60 impacted mandibular 3rd molar of patients being 25 years old or more were evaluated. The mean of the vertical distance of the tooth apex to superior border of mandibular canal was measured in both radiographs and then means were compared together. The mean of horizontal distance was measured in tomographs compared with zero in panoramic. Buccolingual location of the canal relative to the tooth was determined in tomographs. The mean of vertical distance in tomographys and panoramic views was 2.7 mm and 1.1 mm respectively. Both of the differences were significant. About 39% of canals were buccal, 19.5% were lingual and 41.5% were inferior to the tooth. The difference between panoramic radiography and tomography in determining the vertical distance of the tooth apex to superior border of mandibular canal was significant. Tomography can show buccolingual relationship of the canal relative to the tooth and distinguish the roots superimposed on canal that seem tangent from real tangent roots