Epidemiological and imaging characteristics of impacted maxillary incisors and effect on root development

Despite extensive research on maxillary impacted canines, studies specifically investigating maxillary impacted incisors remain limited. This retrospective study aimed to determine the prevalence of impacted teeth among adolescent orthodontic patients, analyze the imaging characteristics of maxillary impacted incisors, and evaluate factors influencing root development. From a cohort of 2163 underage patients who attended the children malocclusion special clinic between August 2022 and July 2024, individuals with impacted teeth were identified and their clinical data were collected. Subsequently, detailed analyses were conducted on impacted maxillary incisors using high-quality Cone-beam computed tomography (CBCT). There were 157 patients with 205 impacted teeth observed, presenting a prevalence rate of 7.26%. Maxillary canines were the most popular impacted teeth (39.51%), followed by maxillary incisors (30.24%). The tooth dilaceration demonstrated a significant relationship with the three-dimensional (3D) locations of tooth. Impacted teeth situated in low impacted depth (P < 0.05) and those with buccal-lingual (P < 0.05) or vertical (P < 0.01) orientations showed reduced susceptibility to root dilaceration. A positive correlation was observed between the Upper Incisor to Palatal Plane Angle (UI-PP) and both the probability (P < 0.05) and earlier occurrence (P < 0.01) of root dilaceration. The root length of impacted tooth was positively correlated with age (P < 0.05). Besides, the average root length of the impacted central incisors was 1.84 mm shorter than the contralateral. The prevalence of impacted teeth in our orthodontic specialist clinics was 7.26%, and 69.76% of impacted teeth were maxillary anteriors. The development of tooth roots was mainly influenced by age and 3D location. These findings enhance clinicians' understanding of impacted maxillary incisor characteristics and factors affecting the root development. The UI-PP proves to be an effective 3D location evaluation indicator. Early intervention is recommended for impacted teeth lacking sufficient space for root development, which could facilitate root development and minimize the risk of root dilaceration.