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
