The CEJ, as it appears on PA film is commonly used as a landmark in order to quantify root resorption amount following orthodontic treatment. Usually 2 lines depict the CEJ on the film. Since the crown length during orthodontic treatment does not change, the CEJ identification in the calculation is obsolete. Misidentification of the CEJ will lead to root resorption miscalculations. The objective of this study is to examine the identification of the CEJ on PA films of upper central incisor by 6 examiners, at different times in 4 different angles (10, 20, 30 and 40 degrees).
Results: There is a significant difference between the examiners in identifying the CEJ in the same angle. No difference was found when the time was the variable. ANOVA results demonstrate that the CEJ location was affected by the examiner and the angle between the tooth and the film. In all, but the 10 degree PA film, the mean point marked by the examiners was significantly different from either, the true buccal or palatal anatomic point, marked with a contrast material. CEJ identification is dependent by both, the angle between the tooth and the film, and the examiner. This may affect the accuracy of the assessment of the amount of root resorption as measured on PA film following orthodontic treatment.