New clues for early management of maxillary impacted central incisors based on 3-dimensional reconstructed models

The objective of this study was to provide new clues for the prevention and early management of root dilacerations in impacted maxillary central incisors.

Cone-beam computed tomography images of 108 patients with unilateral impacted maxillary central incisors were obtained and reconstructed into 3-dimensional models. Crown direction, crown height, root length, bone thickness, and position and angle of root dilaceration were measured in the sagittal-view sections. K-value, defined as the ratio between the available length of the direct root and the ideal length of the direct root, was proposed, and the relationships between K-values with root dilacerations were studied. Root development of the contralateral erupted maxillary incisor was also assessed. Independent t test, chi-square test, and 1-way analysis of variance were used for data analysis.

Root dilacerations occurred when the K-values were 0.16 to 0.19 (palatal impaction), 0.25 to 0.53 (labial impaction), and 0.69 to 0.75 (nasal impaction). The position and angle of root dilacerations were different among nasal, labial, and palatal impactions (P <0.01). K-values and positions of root dilacerations among nasally, labially, and palatally impacted incisors were in descending order, respectively. Retarded root formation was noted in the impacted incisors compared with the contralateral incisors (P <0.001).

Nasal, labial, and palatal impacted incisors had different patterns of root dilacerations. Analyses of crown direction and K-value may aid in evaluating root dilacerations at early dental ages and facilitating early intervention of impacted incisors.