# Comparison of Orthodontically Induced External Apical Root Resorption in Endodontically Treated and Vital Teeth: A Retrospective Split-Mouth Study

## TL;DR

This study found that teeth that have had root canals experience less root damage during orthodontic treatment compared to healthy teeth.

## Contribution

The study provides new evidence comparing root resorption in endodontically treated versus vital teeth during orthodontics.

## Key findings

- Endodontically treated teeth showed significantly less root resorption than vital teeth.
- Treatment duration was a key predictor of resorption in both tooth types.
- Vital teeth were more likely to experience moderate or severe resorption.

## Abstract

Background: Orthodontic tooth movement can induce biological responses in dental and periodontal tissues, most notably external apical root resorption (EARR). The behavior of endodontically treated teeth (ETT) during orthodontic therapy remains a subject of clinical interest, with conflicting evidence regarding their susceptibility to root resorption compared with vital teeth. This study aimed to compare the incidence and severity of orthodontically induced EARR in ETT and adjacent vital teeth and to identify factors associated with root resorption in both groups.

Materials and methods: This retrospective split-mouth cohort study evaluated the records of patients aged 18-30 years who underwent comprehensive fixed orthodontic treatment and had at least one endodontically treated tooth. ETT were compared with the adjacent vital teeth in the same patient. Pre- and post-treatment radiographs were analyzed to measure root length changes, and the resorption severity was categorized as none, mild, moderate, or severe. Demographic variables, tooth type, treatment duration, and pre-treatment root length were also recorded. Paired sample t-tests and chi-square tests were used for intergroup comparisons, and multivariable linear regression analysis was performed separately for endodontically treated and vital teeth to identify predictors of root resorption. Statistical significance was set at p < 0.05.

Results: Fifty patients were included, with a mean age of 25.66 ± 2.99 years and a mean treatment duration of 18.62 ± 4.72 months. The mean root resorption was significantly lower in ETT (0.34 ± 0.48 mm) than in vital teeth (1.15 ± 0.65 mm). Vital teeth exhibited a higher frequency of moderate and severe resorption, whereas most ETT showed no or mild resorption. Regression analysis revealed that treatment duration was the only significant predictor of root resorption in ETT, whereas both the treatment duration and pre-treatment root length were significant predictors in vital teeth.

Conclusion: ETT demonstrated significantly less orthodontically induced EARR than vital teeth. Treatment duration plays a key role in root resorption for both tooth types, suggesting that careful force control and treatment timing are essential to minimize adverse effects.