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Efficiency of upper arch expansion with the Invisalign system
The Angle Orthodontist
|August 2, 2019
Summary
Invisalign aligners expand arches primarily through tipping, not bodily movement, with lower efficiency than designed. Initial molar torque and expansion amount negatively correlate with bodily expansion efficiency.
Area of Science:
- Orthodontics
- Dental Biomaterials
- Biomechanical Engineering
Background:
- Clear aligners like Invisalign are increasingly used for orthodontic treatments.
- Understanding the biomechanical efficiency of clear aligner systems is crucial for predictable treatment outcomes.
Purpose of the Study:
- To evaluate the efficiency and movement patterns of upper arch expansion using Invisalign aligners.
- To assess the correlation between planned expansion and actual bodily expansion.
- To determine the influence of initial molar torque on expansion efficiency.
Main Methods:
- Twenty adult patients undergoing Invisalign treatment for arch expansion were studied.
- Pre- and post-expansion digital models and cone-beam computed tomography scans were analyzed.
- Specialized software was used to measure and compare planned versus achieved expansion and tooth movement.
Main Results:
- Significant discrepancies were found between intended and actual arch expansion.
- Average crown expansion efficiencies ranged from 68.31% (first molar) to 79.75% (canine).
- Bodily expansion efficiency for the maxillary first molar was only 36.35%, with negative correlations to planned expansion and initial molar torque.
Conclusions:
- Invisalign aligners achieve arch expansion mainly through tooth tipping rather than bodily movement.
- Lower-than-expected bodily buccal expansion efficiency necessitates careful evaluation of initial tooth position and adequate root-buccal torque.
- Optimizing torque prescription is essential for improving the predictability of bodily expansion with clear aligners.
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