Comparison of the inclination of unerupted mandibular third molars on panoramic radiography and casts made after surgical incision

Background and aims. Panoramic radiographs are used for surgical planning of unerupted third molars. The major problems associated with panoramic radiography include unequal magnification and geometric distortion of the image. The purpose of this study was the clinical evaluation of the effect of radiographic distortion on the position and classification of unerpted mandibular third molars. Materials and methods. Panoramic radiographs of 20 patients with indication for extraction of lower third molars were included in this study. On the day of surgery, a silicon impression was taken from the second and third molar region and poured with type IV gypsum to provide a study cast. The inclination of the lower third molar to the second molar on panoramic radiography was compared with this angulation on the study casts. Results. There was a mean difference of 5.75° ± 1.65 between the position of the lower third molar on panoramic radiographs and on study casts. Student’s t-test indicated a statistically significant difference (P < 0.05). Conclusion. Panoramic radiography tends to exhibit a more mesial position of the third molars; however, panoramic radiography can still be used as the main tool for surgical planning of lower third molars.