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.

Association between palatally displaced maxillary central incisors and lateral incisors: A retrospective cone-beam computed tomographic study.

INTRODUCTION: The objective of this study was to investigate the location, orientation and root development of maxillary lateral incisors in patients with palatally impacted central incisors. Comparison was made between the lateral incisor on the affected side and that on the normally erupted side. METHODS: Cone-beam computed tomographic images from 20 patients (10 boys, 10 girls, mean age (9.01 ± 1.52 years old) with unilateral palatally impacted maxillary central incisors were imported into Dolphin imaging software 11.8 for 3-dimensional reconstruction and reorientation. Software measurement tools were used to measure the root length, crown distance, angle to palatal plane, distance to midline, and angle to midsagittal plane of the maxillary lateral incisors on both the impacted and unaffected sides. RESULTS: The Wilcoxon signed rank test indicated that lateral incisors on the impacted side were more proclined, at a mean angle difference of 29.47° in the sagittal plane (P < 0.001). The mean length of the roots of the lateral incisors was 1.21 mm shorter (P < 0.05) on the affected side compared with the normal side, and the lateral incisor crowns on the impacted side were located at an average of 4.57 mm closer to the palatal plane than on the normally erupted side (P < 0.001). The angle of long axis of the lateral incisors on the affected side had a greater angulation to the midsagittal plane compared with the unaffected side, with a mean difference of 30.27° (P < 0.001). CONCLUSIONS: Maxillary lateral incisors adjacent to palatally impacted maxillary central incisors side had abnormal root development and demonstrated angulation and position change compared with those adjacent to normally erupted central incisors.