Evaluation of different relationships between inferior alveolar nerve canal and impacted mandibular third molars on panoramic radiographs

Introduction: Dentists use panoramic radiographs to assess the relationship between impacted wisdom teeth and inferior alveolar canal before their surgical removal to avoid injuries to inferior alveolar nerve. The aim of this study was to evaluate inferior alveolar canal configuration and position adjacent to the impacted mandibular third molar by panoramic radiography. Materials and Methods: In this descriptive study, standard panoramic radiographs with 384 impacted lower third molars were selected. The relationship between inferior alveolar canal and the roots of impacted mandibular third molars was evaluated by two experienced experts. Data were analyzed by SPSS 11.5 using descriptive statistics. Results: Evaluation of panoramic radiographs showed superimposition of the canal on third molar roots (85.4%), periapical radiolucency (28.4%), a decrease in the density of tooth roots (19.8%), deviation of mandibular canal (11.5%), narrowing of mandibular canal (3.4%), interruption of radiopaque border of mandibular canal (2.9%), and external root resorption (2.1%). In some cases more than one abnormality were observed in tooth roots. Conclusion: In the present study, superimposition of the roots of third molars on the superior border of the inferior alveolar nerve canal and external root resorption of third molars were the most and least common anomalies on radiographs, respectively. In addition, mesial angulation, class I and type B were the most common types of impaction of mandibular third molars.   Key words: Mandible, Radiography, Third Molar