TAD mechanics for fixed appliances and aligner: Chris Chan. AAO Episode 2. May 3rd 2020

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Farooq Ahmed

Summary of Chris Chan’s lecture at the AAO, looking at TADs and their use.



Aligners are a push appliance

TADs usage

o   For distalisation

o   Maxilla: infrazygomatic region (6-7 buccally)

o   Mandible: buccal shelf region (vertically lateral to 6-7 region)


o   Anterior intrusion

o   Labially placed U1-U2 region

o   Elastic from palatal aspect over the incisal edge to labial TADs


Extraction cases: Aligners lose anchorage and extrude upper incisors


Aligners tip teeth, to achieve bodily movement require counter vector


When in doubt mini screw





·      Grünheid, T., Loh, C. and Larson, B.E., 2017. How accurate is Invisalign in nonextraction cases? Are predicted tooth positions achieved?. The Angle Orthodontist87(6), pp.809-815.


·      Zhou, N. and Guo, J., 2020. Efficiency of upper arch expansion with the Invisalign system. The Angle Orthodontist90(1), pp.23-30.

Extraction cases

o   Dai, F.F., Xu, T.M. and Shu, G., 2019. Comparison of achieved and predicted tooth movement of maxillary first molars and central incisors: First premolar extraction treatment with Invisalign. The Angle Orthodontist89(5), pp.679-687.

Cases from Journal of Digital Orthodontics (freely available)


#Orthodontics #farooqahmed #orthodonticsinsummary




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