The differences of root morphology and root length between different types of impacted maxillary central incisors: A retrospective cone-beam computed tomography study.

INTRODUCTION: The purpose of this trial was to use 3-dimensional data to analyze the differences of root morphology and root length between 3 different types of impacted maxillary central incisors. METHODS: Cone-beam computed tomography images of 126 patients with impacted maxillary central incisors were included in this retrospective study. On the basis of the angle of the impacted incisor to the palatal plane, we categorized the tooth as labial inversely impacted, labially positioned, or palatal impacted incisor. In each category, the early and late dental age groups were classified according to the method of Nolla. The total root length of both impacted and homonym teeth, length of the nondilacerated part of the root, length of the dilacerated part of the root, the angle between the crown and root, and root direction, were measured in the sagittal-view sections using Dolphin Imaging software (version 11.9; Dolphin Imaging and Management Solutions, Chatsworth, Calif). RESULTS: Compared with the early dental age groups, the length of the dilacerated portion of the root and rate of dilaceration for inverse labial and labially positioned impactions increases, and crown-root angle decreases (P <0.05). The dilacerated part of the root bent labially, and the root morphology shows an obvious L-shaped curve. The length of the nondilacerated part of the root for palatal impactions is greater(P <0.05). The dilacerated part of the root bends palatally, and the root morphology shows a continuous C-shaped curve. CONCLUSIONS: Obstruction from the alveolar bone will cause different root morphology. Root morphology of labial impactions shows an obvious L-shaped curve; palatal impactions show a continuous C-shaped curve.