External Apical Resorption in Orthodontic Movement: Register a Posteriori.

Objective: To quantify the external apical root resorption in individuals submitted to orthodontic treatment and to correlate the root resorption with possible predisposing factors. Method: The sample comprised 79 individuals (mean age 13.7 years) divided into two groups: individuals treated with and without extractions of the maxillary first premolars. Periapical radiographs of maxillary central incisors obtained in the beginning and in the end of the orthodontic treatment were selected, digitized and imported to Regeemy® – Image Registration and Mosaicking v.0.2.43-RCB (DPI-INPE, São José dos Campos, SP, Brazil) for image registration a posteriori (correction of geometric, density and contrast differences between two images). The maxillary central incisors were measured in the reference (pre-treatment) and registered (post treatment) images using UTHSCSA Image Tool® (University of Texas Health Science Center at San Antonio). The measurements were obtained in pixels and converted to percentage. Result: Statistically significant root resorption was found for both groups, but it was greater for the extraction group (p<0.05). The comparison of pre and post-treatment differences of variables between the groups demonstrated statistically significant differences for cephalometric measurements 1.NA (inclination of the maxillary incisors) and 1-NA (horizontal position of the maxillary incisors) (p<0.05). These differences were greater for the extraction group. The treatment duration was found to be statistically higher for the extraction group as well as the root resorptions (p<0,05), although the later was statistically significant only for tooth 11. Statistically significant correlation was found only between root resorption and the difference between 1-NA pre and post-treatment for the extraction group (Rho=0.45; p<0.05). Conclusion: Based on the results, we concluded that orthodontic treatment with extractions is associated with greater external root resorption, greater treatment duration and greater alterations of 1.NA and 1-NA at the end of the treatment.