Title & Authors

Effects of Attachment of Plastic Aligner in Closing of Diastema of Maxillary Dentition by Finite Element Method
Yukiko Yokoi, Atsushi Arai, Jun Kawamura, Tomoko Uozumi, Yohei Usui, and Norimasa Okafuji

Key Findings

1. Initial Movement (Tipping Phase):
   Both with and without attachments, teeth initially exhibit tipping and rotation.
   Example:
   Without attachment: θ1=0.30∘θ1​=0.30∘, displacement U=0.11 mmU=0.11mm.
   With attachment: Similar initial tipping (θ1=0.25∘θ1​=0.25∘, U=0.11 mmU=0.11mm).
   Conclusion: Attachments do not prevent initial tipping.

2. Long-Term Movement (Bodily Movement):
   After sufficient time (e.g., 500 iterations), teeth with attachments achieve bodily movement (uprighting).
   Without attachments, tipping persists (θ1=0.25∘θ1​=0.25∘).
   Mechanism: Attachments increase the moment-to-force ratio, generating a counter-moment to upright the tooth.

3. Stress Distribution (FEM Analysis):
   Equivalent stress (σeσe​) in aligners differs with/without attachments (Figure 7).

Clinical Implications

• Diastema Closure: Simulated for a 0.2 mm gap (typical aligner movement per stage: 0.2–0.25 mm).
  Target: Mesial translation by 0.1 mm per step.

• Attachments are critical for long-term control but do not eliminate initial tipping.

References & Context

• Yokoi et al. (2019) used Finite Element Method (FEM) to study attachment effects.

• Figure 7: Shows stress distribution in aligners (higher stress with attachments).

Additional Notes

• Clear Aligner Academy: For more insights, visit www.caadeducation.com.

• Email: caadeducation@gmail.com

Summary

• Without Attachments: Tipping dominates.

• With Attachments: Initial tipping → Bodily movement over time.

• Practical Tip: Allow sufficient time for attachments to facilitate uprighting.