Characterization of Mandibular Tooth Movement in Corticotomy-Facilitated, Non-Extraction Orthodontics

Objectives: To characterize how mandibular teeth move following non-extraction orthodontics facilitated by alveolar corticotomy. Methods: CT scans at pre-treatment (T1), post treatment (T2) and retention (T3) were evaluated on 12 patients who underwent corticotomy-facilitated, non-extraction orthodontics plus alveolar augmentation grafting in order to resolve lower incisor crowding. SimPlant 3-dimensional software (version 8) was utilized to measure transverse dental arch widths from root tip to root tip and from cusp tip to cusp tip on all posterior contralateral teeth. Dental arch depth was measured from each lower incisor to a reference line constructed from 1st and 2nd lower molar interproximal contact points bilaterally. Results: Paired t-testing demonstrated that during treatment (T1-T2), lower second molar roots constricted 1.3mm, second crowns expanded 1.2mm and lower second premolar crowns expanded 1.8mm (p<.05); these variables were stable (p>.05) during retention (T2-T3). Arch depth, as measured from incisal edges to reference line, increased about 3mm during orthodontic treatment for each incisor (p<.001) and decreased approximately 1.5mm during retention for each incisor (p<.05). Conclusions: Root movements were clearly delineated using the SimPlant 3-D software for mandibular CT scan images. Non-extraction, corticotomy-facilitated orthodontics resulted in incisor crown flaring with incisor crown up-righting during retention.