Morphometric Evaluation of Changes in Alveolar Bone and Root Length During Mandibular Incisor Retraction in Class I Bimaxillary Protrusion: A Prospective Study.

Introduction Orthodontic treatment often involves first premolar extraction and anterior tooth retraction to achieve aesthetic and functional harmony in bimaxillary protrusion cases. However, excessive retraction may cause complications such as root resorption and bone loss. This study aimed to evaluate morphometric changes in anterior mandibular alveolar bone and root length during retraction of the mandibular incisors in patients with class I bimaxillary protrusion using cone-beam computed tomography (CBCT). The objective of this study was to assess changes in alveolar bone width, height, and root length before and after retraction. Materials and methods This prospective observational study included 32 systemically healthy patients aged 18-30 years with class I bimaxillary protrusion requiring first premolar extractions. CBCT scans (pre- and post-retraction) were analyzed using standardized imaging parameters. Patients underwent orthodontic treatment with pre-adjusted edgewise appliances and temporary anchorage devices for maximum anchorage. The alveolar bone width, height, and root length were measured in the mandibular incisors. Intra- and inter-observer reliabilities were assessed, and the data were analyzed using paired t-tests and one-way analysis of variance (ANOVA), with a significance threshold of p < 0.05. Results Labial alveolar bone height, as determined by the vertical distance between the cementoenamel junction and alveolar crest, decreased significantly across all mandibular incisors post-retraction, whereas lingual bone height increased in all teeth, suggesting crestal bone apposition and resorption on the labial and lingual sides, respectively. The labial bone width decreased significantly, whereas the lingual bone width increased in all incisors, suggesting labial root movement with retraction. The root length was significantly reduced in all incisors, indicating the risk of root resorption. No significant intragroup differences were found among the incisors (p > 0.05); however, intergroup comparisons confirmed significant pre- and post-retraction changes (p < 0.05), indicating dynamic bone remodeling. Conclusion The retraction of the mandibular incisors in bimaxillary protrusion significantly altered alveolar bone dimensions and reduced root length with site-specific variations. CBCT proved essential for precise assessment, emphasizing the need for controlled retraction to balance aesthetic and functional outcomes while minimizing complications. Future research should explore long-term stability and strategies to mitigate root resorption.