Three-dimensional analysis of root changes after orthodontic treatment for patients at different stages of root development

Abstract

We investigated changes in the roots of maxillary incisors at different stages of root development after fixed-appliance treatment using cone-beam computed tomography. Data from 52 subjects receiving fixed-appliance treatment were collected retrospectively. The subjects were divided into 3 groups: mixed dentition group (aged 7-10 years; root development stage: Nolla eighth-10th; n= 16), early permanent dentition group (aged 12-18 years; root development stage: Nolla 10th; n= 20), and adult group (aged 18-35 years; root development stage: Nolla 10th; n= 16). Changes in root lengths and volume of the maxillary central incisors were measured using pretreatment and posttreatment cone-beam computed tomography. The root lengths and volumes of maxillary central incisors in the mixed dentition group significantly increased after orthodontic treatment (P>0.05). No significant differences were found when comparing the final root length and volume of the mixed dentition group with the pretreatment maxillary incisor values of the early permanent dentition group (P>0.05). The early permanent dentition group showed a significant decrease in root length (P<0.05), and both the root length and volume of the adult group significantly decreased after treatment (P<0.05). The differences in root length and volume reduction between the 2 groups were not significant (P>0.05). Orthodontic treatment had no significant negative impact on the continued root development of incomplete roots with two-thirds root formation. Both the early permanent dentition and adult groups exhibited root resorption after orthodontic treatment. It seemed age was not a factor that resulted in significant root resorption during routine orthodontic leveling and alignment treatment once the roots were fully developed.