Amount of root resorption - Is it a myth or real?

The risk of orthodontically induced inflammatory root resorption (OIIRR) is related, according to several publications, to the amount of resorption seen on PA film before treatment or 6-9 months in treatment. Objectives: to find the presence of an agreement in the definition of root resorption among different examiners. Materials and Methods: Nine examiners analyzed ninety one pairs of upper incisors PA film, taken prior to and following orthodontic treatment. Each examiner was asked to mark on a special image one of 5 different root resorption degrees, namely: no resorption, irregular root contour, less than 2 mm of root shortening, from 2 mm to a third of the root missing, and shortening exceeding more than one third of the original root length. Results: the Kappa values for the amount of OIIRR definitions of the same examiner as well as the Kappa values between the examiners were under the acceptable statistical value to confirm agreement on the amount of OIIRR. Conclusion: According to this study estimation of the amount of root resorption with statistical significance from a PA film is not reliable.