Tip, torque and rotation of maxillary molars during distalization using Invisalign: a CBCT study

Area of Science:

• Orthodontics
• Dental Biomechanics

Background:

• Achieving bodily molar distalization is a complex orthodontic challenge.
• Clear aligner therapy (CAT) is increasingly used for complex tooth movements.

Purpose of the Study:

• To investigate changes in molar angulation, inclination, and rotation during clear aligner therapy-assisted molar distalization.
• To evaluate the efficacy of CAT in achieving controlled molar movement.

Main Methods:

• Retrospective analysis of 38 cone-beam computed tomographic scans from 19 adult patients treated with Invisalign® for maxillary molar distalization (≥2 mm).
• Pre- and post-treatment CBCTs were used to measure changes in molar tip, torque, and rotation for 61 molars.
• Statistical analysis included paired t-tests and intraclass correlation coefficient for reproducibility.

Main Results:

• No significant changes in molar angulation (mesiodistal tipping) were observed after distalization (p=0.158).
• A significant increase in buccal molar inclination (buccolingual torque) was noted (p=0.034).
• Significant mesiobuccal rotation of molars occurred during distalization (p<0.001).

Conclusions:

• Clear aligner therapy for 2 mm of molar distalization does not result in significant molar tipping.
• Significant buccal inclination and mesiobuccal rotation are observed in maxillary molars following clear aligner therapy-assisted distalization.