Three-Dimensional Evaluation of Root and Alveolar Ridge Width of Maxillary Lateral Incisors in Patients with Unilateral Agenesis

Introduction: The objective of this study was to measure the maxillary lateral incisor root dimensions and quantify the labial and palatal bone in patients with unilateral maxillary lateral incisor agenesis (MLIA) and compare them to non-agenesis controls using cone beam computed tomography. Methods: The labiopalatal and mesiodistal root dimension and labiopalatal bone width of maxillary lateral incisors were assessed on pre-treatment and post-treatment cone beam computed tomography scans of 23 subjects (mean age 14.5 years, 17 females and 6 males) with maxillary lateral incisor agenesis and 23 gender-matched subjects (mean age 13.5 years, 17 females and 6 males) with no dental agenesis or anterior Bolton discrepancy. The Mann-Whitney Test was used to distinguish any differences in root width, crown width or changes in labial or palatal bone between the two groups. The Wilcoxon Signed Rank Test was used to compare the pre-treatment and post-treatment findings within each group. Results: The mean labiopalatal root width was narrower in the maxillary lateral incisor agenesis group than controls by 1.25mm (P≤0.000) at the level of the CEJ. The mesiodistal root width did not differ significantly between the groups. Both groups had thin labial bone with a mean post-treatment labial bone of 0.4mm and 0.8 mm at 4mm apical to CEJ for the maxillary lateral agenesis group and the control group, respectively. At the end of orthodontic treatment the MLIA group lost about 60% of labiopalatal bone width. The mesiodistal crown width was significantly smaller in the maxillary lateral agenesis group at both the incisal edge and at crown midpoint by an average of 1.5mm and 1.4mm, respectively. Conclusion: The buccolingual root, the mesiodistal crown widths, and the labial bone width at 10mm apical to the CEJ of the maxillary lateral incisor in patients with unilateral agenesis were significantly smaller than normal controls.