Three-dimensional comparative analysis of upper central incisors external apical root resorption/ incisive canal changes in first premolar extraction cases: clear aligners Versus passive self-ligating fixed braces.

Abstract

Objective: To assess the upper central incisor's (U1) external apical root resorption (EARR) and incisive canal (IC) changes and their influencing factors under clear aligners and passive self-ligating fixed braces in first premolar extraction cases using CBCT.

Materials and methods: This retrospective study included 60 participants (120 teeth) with similar baseline characteristics based on the American Board of Orthodontics discrepancy index scores. Participants were divided into clear aligner (CA) and passive self-ligating fixed appliance (FA) groups, with 30 participants per group. Pre- and post-treatment EARR, IC dimensional changes, U1-IC proximity, and orthodontic movements were analyzed through CBCT using Invivo 6.0.3 software. Descriptive and analytical statistics are performed, and a P-value < 0.05 is considered statistically significant.

Results: The CA group exhibited statistically significantly lower U1-EARR compared to FA group. However, there were no significant differences in overall IC dimensions (P < 0.05). In FA, contact or invasion of U1 with IC are associated with a significant increase in EARR, but not in CA. The invasion also reveals significant reductions in IC dimensions in FA, whereas CA exhibited more limited changes (P < 0.05). Retraction and intrusion were significantly positively correlated with U1-EARR in FA, whereas intrusion only was correlated positively with U1-EARR in CA (P < 0.05). In both FA and CA, there was no significant correlation between the torque and U1 EARR (P > 0.05). Retraction, intrusion, and torque movements had differential impacts on IC dimensions in FA and CA treatments.

Conclusion: In this study, our findings indicate that in cases involving the extraction of first premolars, Invisalign® clear aligners may have less U1-EARR than passive self-ligating fixed braces but no significant differences in the overall IC dimensions between both appliances. Clear aligners may reveal better outcomes in U1 EARR/IC changes concerning U1-IC proximity and different orthodontic movements. These findings may be necessary for orthodontists to consider during treatment planning.

Clinical relevance: Clear aligners may be an appropriate choice in first premolar extraction cases, especially when the U1 is closer to IC or when there is a need for more retraction, intrusion, and torque. Their potential to reduce root resorption while preserving IC dimensions may make them more advantageous over passive self-ligating fixed braces in these scenarios.