Characteristics of patients with severe root resorption

The purpose of this study was to compare a group of patients in whom all four maxillary incisors were resorbed at least 20% with a matched group.

Retrospective, case-control. Root resorption was measured on pre- and post-treatment periapical radiographs collected from 868 patients treated in private practices in southern California. Diagnostic and treatment factors were recorded, and vertical and horizontal apical movement calculated from cephalometric films. Root shape was assessed with a six-object non-parametric rating system. From this patient population, 25 patients were found who had >20% root resorption on all four maxillary incisors. A case control group without severe root resorption matched by sex, treating office, age at start, ethnicity, and duration of treatment was created with two controls for each severe case.

There were no statistically significant differences found for extractions, use of Class II and finishing elastics, transverse treatments, overjet, overbite, vertical, tooth length, habits, and root shape. Higher estimated risk was found for abnormal root shape for both maxillary incisors, and tongue thrust. Horizontal apical displacement was not significantly different (p = 0.07) but severely resorbed incisors were retracted an average of one millimeter further.

Twenty-five of 868 patients were found to have over 20% of all four of their maxillary incisors resorbed. This is <3% of the total patients. Matching this group by sex, ethnicity, office, treatment time, and age greatly reduced the number of factors that would differentiate these patients from 50 who did not get severe root resorption. We conclude that horizontal root displacement, tongue thrust, and abnormal root shape may have higher estimated risk but interoffice variability and treatment time cannot be underestimated.