Assessment of apical root resorption using digital reconstruction.

OBJECTIVES

To assess the in vitro and in vivo accuracy of a mathematical computer-based reconstruction of two images that are not taken with the same recording geometry for the measurement of apical root resorption following orthodontic treatment.

METHODS

A gold standard for root resorption in vitro was developed from 10 extracted upper central incisors using calipers. Radiographs made with five different projection angles were reconstructed mathematically by two observers. The calculated loss of length was compared with the gold standard. Eighty-two upper central incisors from 61 patients were radiographically evaluated for the prevalence and degree of apical root resorption after orthodontic fixed appliance therapy. The relative amount of reduction was calculated after mathematical reconstruction.

RESULTS

The inter-observer error in vitro was 1.8%. The 95% confidence intervals for the difference with the gold standard are small. The duplicate measurement in vivo error was 2.2% and the correlation between duplicate measurements was 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.