Cone-beam computed tomography assessment of maxillary anterior alveolar bone remodelling in extraction and non-extraction orthodontic cases using stable extra-alveolar reference

Objective To explore alveolar cortical positional change in response to tooth movement in extraction and non-extraction orthodontic cases, using cone-beam computed tomography (CBCT) and stable extra-alveolar references. Materials and Methods The pre-treatment (T1) and post-treatment (T2) CBCT scans of 25 extraction (EXT) and matched 25 non-extraction (Non-EXT) orthodontic cases were imported into Dolphin Imaging 3D, and oriented uniformly. Sagittal and axial CBCT cross-sections were traced using customized software-generated guides. The displacement of teeth and alveolar bone cortices were automatically measured using the palatal plane (PP) and the line perpendicular to PP and passing Sella as reference. Intra- and inter-group differences between T1 and T2 were analysed. Subjects were also superimposed three-dimensionally using Geomagic Control X for qualitative analysis of cortical remodelling. Results The EXT group showed incisor retraction, while the Non-EXT group exhibited statistically significant incisor anterior tipping (P < .05). In EXT, both the labial and palatal cortices are resorbed. Non-EXT showed labial cortex anterior modelling, and statistically significant palatal cortex resorption (P < .05). In both groups, statistically significant decrease in total and palatal alveolar widths, increase in labial widths, and palatal dehiscence were observed. Comparatively, EXT showed significantly more incisal total and palatal width decrease and palatal vertical bone loss. Conclusion Labial cortical remodelling was shown to follow anterior tooth movement, but the palatal cortical response to incisor retraction and labial cortical remodelling in general remained inconclusive. Narrowing of the alveolar housing and palatal dehiscence were observed regardless of extraction following orthodontic treatment.