Apical root resorption is a common adverse
effect during orthodontic treatment, specially the intrusion forces. Apical
photographs by using the parallel technique and with the help of some
formulas were the most common approaches to investigate th
e root
resorption. The aim of this study was to study the reliability of periapical
photographs in evaluating of root length shortening during orthodontic
intrusion forces, by comparing with that diagnosed by using the CT-scan
images.