Evolution of root length throughout orthodontic treatment in maxillary incisors with previous history of dental trauma: a longitudinal controlled trial

Objectives To compare changes in root length of maxillary incisors with and without dental trauma throughout orthodontic treatment. Materials and method Patients younger than 18 years, with trauma on at least one maxillary incisor, undergoing orthodontic treatment between 2017 and 2021 were included, using the contralateral side as control without trauma when available. Periapical radiographs were taken pre-treatment and at 6 months intervals, and root/crown ratio was calculated. Linear mixed models were used to describe the evolution of root length at the different time points and to compare trauma and control values. Differences between central and lateral incisors and between treatment modalities were additionally explored. Results A total of 1768 measurements were performed on 499 teeth (201 with trauma) in 135 patients. Incisor root length significantly decreased during orthodontic treatment in teeth with and without trauma. Lateral incisors with trauma were more susceptible to root resorption than those without trauma and central incisors. No significant decrease in root length was observed with removable appliances, which never exceeded 15 months of treatment. Treatment with fixed appliances led to gradually increasing, significant root length shortening in teeth with and without trauma. Conclusion Treatment duration directly correlated with root length shortening both in teeth with and without trauma history. Teeth with trauma showed significantly more root resorption after treatment with fixed appliances while removable appliances had no significant influence on root length. Clinical relevance Previous history of dental trauma is no absolute contra-indication to start orthodontic treatment, as long as treatment duration is kept as short as possible.