Root resorption during maxillary molar intrusion with clear aligners: a randomized controlled trial

Area of Science:

• Orthodontics
• Dental Biomaterials
• Biomechanical Engineering

Background:

• Molar intrusion is a critical step in correcting anterior open bite.
• Both clear aligners (CA) and fixed appliances with miniscrews (FM) are used for orthodontic treatment.
• Understanding the comparative efficacy and side effects of these modalities is essential for clinical decision-making.

Purpose of the Study:

• To compare maxillary molar root resorption, intrusion amount, dentoskeletal changes, and maximum bite force (MBF) between CA and FM during molar intrusion.
• To evaluate the efficiency and safety of clear aligners versus fixed appliances with miniscrews for molar intrusion in adults with anterior open bite.

Main Methods:

• Forty adults with anterior open bite were randomized into CA or FM groups.
• Data including lateral cephalograms, cone-beam computed tomography (CBCT), and MBF were collected at pretreatment and 6 months.
• Maxillary molar intrusion was achieved using NiTi closed-coil springs in FM and clear aligners with a squeezing exercise in CA.

Main Results:

• After 6 months, FM showed significantly more root resorption (0.38-0.47 mm) and molar intrusion (1.49 mm) than CA (0.21-0.24 mm root resorption, 0.68 mm intrusion).
• CA exhibited less overbite increase and bite closing but a greater MBF increase compared to FM.
• MBF in the CA group was positively correlated with the amount of maxillary molar intrusion (r = 0.736, P < .05).

Conclusions:

• Maxillary molar intrusion and root resorption were approximately half with CA compared to FM over 6 months.
• Root resorption was about one-third of the intrusion distance in CA.
• Clear aligners offer a potentially favorable alternative for molar intrusion, demonstrating reduced root resorption and enhanced bite force recovery.