Root Development and Morphology of Impacted Maxillary Central Incisors due to Obstruction: A CBCT Study

A developing maxillary central erupts at the age of 7 years and the apical third of its root apexifies 3 years later, at age 10 years. During this period, an impacted incisor root develops its root in a restricted area, above the alveolar bone, high up in the cortex of the floor of the nose. The aim of this study was to radiographically assess whether the root development of the unerupted incisor is affected by its lack of eruption. A cross-sectional retrospective split mouth study was designed. The sample consisted of 30 consecutive patients (20 males, 9 females) aged 8–30 years (mean 11.6 years), who attended the Orthodontic Department between 2016 and 2019 for treatment of a unilateral impacted maxillary central incisor due to obstruction. Root length, volume and morphology (presence and angle of dilaceration) were evaluated on CBCT scans by 2 calibrated observers using OnDemand3DTM application software to compare the impacted and normally erupted incisors. The effects of dental age at diagnosis, type and location of obstruction and 3D position of the impacted tooth were evaluated. The impacted central incisors had significantly shorter roots (mean 3.1 mm, p < 0.001) and significantly more dilacerations (40%), while their root volume was only slightly reduced. Advanced dental age closed apex and buccally located obstruction were each found to be associated with more root dilacerations. Closed apex was also associated with an increased angle of dilaceration. Odontomas affected root volume more than supernumerary teeth. A more angulated horizontal position of the impacted tooth in sagittal and transverse dimensions resulted in less dilacerations. Non-eruption of a maxillary central incisor due to obstruction prevents normal root development and causes malformation of the apex, due to its proximity to anatomical borders. These findings suggest that interventional procedures aimed at encouraging timely eruption should be initiated early before development of the apical third of the root.