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Applying Science to Aligner Mechanics and Design Brent Larson. AAO June 2021. Episode 89

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Hosted by
Farooq Ahmed

Applying Science to Aligner Mechanics and Design  Dr. Brent Larson

 

Torque expression and aligners

·      2 ideas

1.     Trim level – scalloped or straight trim

2.     Stiffness – greater stiffness greater torque control

 

Movement of teeth with aligners Jiang 2021

·      CBCT used to superimpose tooth STL and tooth movement

·      Conclusion – biomechanics of clear aligners are still not fully understood

·      Not enough evidence on forces delivered by CAT Lliadi 2019 systematic review

 

Accuracy in non-extraction cases Grunheld 2017

·      Overall good outcomes

·      Consistently poor Ppredictability for transverse, torque, 2nd molars

o   Allows planning of over compensation

o    

Gingival margin design study of aligner and force delivery  and strain of material, ex vivo Brook thesis

·      Essix and Zendura 0.030”

·      3 margin designs, scalloped, straight 0.75mm, straight 1.5mm

 

Results

·      AP crown movement

o   Straight delivered 2-3 x greater force than scalloped

·      Moment of crown

o   Straight delivered 2-3 x greater force than scalloped

·      Strain measurements

o   Straight delivered 2-3 x greater force than scalloped

 

Passive aligner

·      Areas of high strain on facial 1/3 , incisal lingual aspect

 

CBCT assessment of aligner tooth interaction

·      Gaps between tooth and aligner with any activation

 

Conclusion further research into

·      Material, PUR, PET

·      Shape, trim, thickness, relief cuts

 

Improve efficiency and understanding

 

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