External apical root resorption in non-extraction cases after clear aligner therapy or fixed orthodontic treatment

BACKGROUND/PURPOSE: The application of removable aligner in orthodontic treatment has increased rapidly in recent years, while its effects on root resorption remains unclear. The aim of this study was to comparatively evaluate the amount of external apical root resorption (EARR) in non-extraction patients receiving clear aligner therapy (CAT) or fixed orthodontic treatment (FOT). MATERIALS AND METHODS: Eighty non-extraction patients treated with CAT or FOT exclusively were evaluated retrospectively. Panoramic radiographs were used to measure the length of crowns and roots of the incisors before and after treatment. The amount of EARR was determined by the relative change of root-crown ratio and compared between the two groups. The potential predictive factors of EARR were investigated using spearman correlation analysis. RESULTS: The overall EARR in the CAT patients was significantly less than the FOT. Similar results were observed in maxillary central incisors, maxillary lateral incisors, mandibular central incisors and mandibular lateral incisors. The duration of treatment positively correlated with the amount of EARR in both modalities. Gender, age, skeletal pattern or degree of malocclusion did not affect the occurrence of EARR. CONCLUSION: Clear aligner therapy may have a superiority of reducing external apical root resorption compared to fixed orthodontic treatment in non-extraction patients.