Morphometric evaluation of changes in the alveolar bone and roots of the maxillary anterior teeth before and after en masse retraction using cone-beam computed tomography

Objective: To evaluate the morphometric changes in the alveolar bone and roots of the maxillary anterior teeth (MXAT) after en masse retraction with maximum anchorage (EMR-MA). Materials and Methods: The samples consisted of 37 female adult patients who had Class I dentoalveolar protrusion (CI-DAP) and were treated by extraction of the first premolars and EMR-MA. Using three-dimensional cone-beam computed tomography taken before treatment and after space closure, the maxillary central incisors (MXCI, N = 66), lateral incisors (MXLI, N = 69), and canines (MXC, N = 69) were superimposed using individual reference planes. After alveolar bone area (ABA), vertical bone level (VBL), root length (RL), root area (RA), and prevalence of dehiscence (PD) were measured at the cervical, middle, and apical levels, statistical analyses were performed. Results: On the palatal side, ABA significantly decreased in all levels of MXAT (P<.001; middle of MXC, P<.01). MXCI and MXLI exhibited a greater decrease in the ratio of change in palatal ABA than did MXC (cervical, P<.01; middle and apical, P<.05; total, P<.001). Palatal/labial ABA ratios decreased in MXCI (cervical, middle, total, P<.001; apical, P<.05) and MXLI (cervical, P<.001; apical, P<.05). They showed greater amounts and ratios of change in VBL on the palatal side compared to the labial side (all P<.001). The palatal side showed more PD in the cervical area than did the labial side (MXCI and MXLI, P<.001; MXC, P<.01). Significant root resorption occurred in MXAT (RL and RA, all P<.001). Conclusions: During EMR-MA in cases with CI-DAP, ABA and VBL on the palatal side and RL and RA of MXCI and MXLI were significantly decreased. (Angle Orthod. 2013;83:212-221.)