Positional and morphological characteristics of palatally impacted maxillary central incisors

Palatally impacted maxillary central incisors are commonly caused by obstructive phenomena and trauma, predisposing them to root dilaceration and subsequent aesthetic and functional complications. The three-dimensional intraosseous position of maxillary central incisors dictates the complexity of orthodontic traction, while root morphology is a critical determinant of treatment prognosis. This study aimed to characterize the positional and morphological features of these impacted teeth using pretreatment cone-beam computed tomography images. Pretreatment CBCT scans of 53 patients with unilateral palatally impacted maxillary central incisors were included in this retrospective study. Patients were classified into early and late dental age groups according to Nolla’s method. Three-dimensional distribution of impacted incisors was observed. Measurements of the impacted and contralateral teeth were obtained using Dolphin software, and included the following variables: crown angle to the palatal plane, crown angle to the midline, crown distance to the palatal plane, crown rotation angle, root length, length of nondilacerated part of the root, length of dilacerated part of root, crown-root angle. Most impacted incisors were distally inclined (71.70%), palatally inclined (96.23%), and located at a low axial level (50.94%). Compared to contralateral teeth, impacted incisors were 83.88° more palatally inclined, 47.18° more rotated, 2.64 mm shorter in root length, and 35.01° smaller in crown-root angle (all P < 0.001). Patients in the late dental age group had longer roots but a significantly higher incidence of dilaceration ( P = 0.011), which predominantly affected the cervical third in a labiopalatal direction. Palatally impacted maxillary central incisors feature a low, palatally tipped, distogingivally rotated crown, with cervical-third labiopalatal root dilaceration. A positive association was observed between dental age and the probability of root dilaceration.