Incisor Extrusion with Clear Aligners: Finite Element Analysis Insights

Study: Appl. Sci. 2021, 11(3), 1167.
Authors: Rossini G, Modica S, Parrini S, Deregibus A, Castroflorio T (University of Turin, Italy*)

Key Findings

1. Challenges in Pure Extrusion:
   Lateral incisor extrusion is particularly difficult with aligners alone.
   Pure extrusion requires auxiliary techniques (e.g., bootstrap, procline-retract protocol).

2. Optimal Attachment Strategies:
   Best Results:
   ATT3-7 (attachments from second molar to canine) + horizontal attachments on incisors (buccal/palatal).
   Stress Distribution: This combination improved force application and reduced uneven pressure.

3. Anchorage Preservation:
   Posterior attachments are critical to prevent anchorage loss during incisor extrusion.

Author Recommendations

• For Effective Extrusion:
  Always use horizontal attachments on all four incisors.
  Add posterior attachments (molars/canines) to maintain anchorage.

• Clinical Note:
  Relative extrusion (e.g., intruding adjacent teeth) is easier than pure extrusion.

Study Methodology (FEA Simulations)

Tested 6 configurations:

1. No attachments.

2. Horizontal attachments (incisors only).

3. ATT3-7 (molar to canine).

4. ATT3-7 + optimized extrusion attachments (incisors).

5. ATT3-7 + buccal horizontal attachments (incisors).

6. ATT3-7 + palatal horizontal attachments (incisors).

Result: Configurations 5/6 (horizontal incisor attachments + posterior anchorage) performed best.

Clear Aligner Academy Tips

• For Complex Extrusion: Combine aligners with auxiliary techniques (e.g., elastics, temporary anchorage devices).

• Follow for More: www.caadeducation.com | ✉️ caadeducation@gmail.com

Takeaway

• Attachments are non-negotiable for predictable incisor extrusion.

• Posterior anchorage is key to avoid unwanted tooth movement.

• Hybrid approaches (aligners + auxiliaries) may be needed for pure extrusion cases.