ASSESSMENT OF APICAL ROOT RESORPTION USING DIGITAL RECONSTRUCTION

Objectives: To assess the in vitro and in vivo accuracy of a mathemati cal computer-based reconstruction of two images that are not taken wit h the same recording geometry for the measurement of apical root resor ption following orthodontic treatment. Methods: A gold standard for ro ot resorption in vitro was developed from 10 extracted upper central i ncisors using calipers. Radiographs made with five different projectio n angles were reconstructed mathematically by two observers. The calcu lated loss of length was compared with the gold standard. Eighty-two u pper central incisors from 61 patients were radiographically evaluated for the prevalence and degree of apical root resorption after orthodo ntic fixed appliance therapy. The relative amount of reduction was cal culated after mathematical reconstruction. Results: The inter-observer error in vitro was 1.8%. The 95% confidence intervals for the differe nce with the gold standard are small. The duplicate measurement in viv o error was 2.2% and the correlation between duplicate measurements wa s 0.94. The mean loss of tooth length was 7.8% (s.d. 6.9). Conclusions : The prevalence of root resorption corresponds well with that in the literature. Digital reconstruction is a reliable method to correct for different projection angles and to monitor the effects of orthodontic movement in serial dental radiographs.