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Clear aligner therapy. Empty promises or wishful thinking. Ki Beom Kim Episode 66 December 17th 2020

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Hosted by
Farooq Ahmed

 

Clear aligner therapy. Empty promises or wishful thinking. Ki Beom Kim

 

 

 

Does it work well?

·      Clincheck does not represent the patients final occlusal outcome Bruschang 2015

·      Accuracy

o   Horizontal: Predictable Charalampakis 2018

o   Rotation and vertical movements: Unpredictable Charalampakis 2018

o   Deep bite reduction:

§  1.6mm Khosravi 2017

§  Lower incisor proclination 2.4 degrees

§  Overcorrection Vs no overcorrection = no differences

o   Anterior openbite:

§  3.27mm Harris 2020

§  Mostly through retroclined by 11 degrees, 1mm of posterior intrusion

§  AOB cases showed no molar intrusion Garnett

 

 

Biomechanics

·      Torque

o   To torque with aligner – greater force required at the cervical aspect

o   Aligner does not seat with torque at cervical aspect, therefore no effective force for torque Hahn 2010

o   Root discrepancy of planned and delivered = 2mm for root change = little root change

o   Aligner strength

§  Strongest aspect of aligner – Incisal aspect

§  Weakest aspect of aligner – gingival aspect

§  = Invisalign tend to not adapt well to gingival margin and therefore torque movements not achieved

 

·      Intrusion

o   Proclination of teeth

o   Buccal attachment = further proclination

o   Lingual attachment – little counter moment

o   Retrocline incisors during rotation – helps to achieve pure intrusion resultant force

 

Antagonistic and synergistic movement

·      Incisors:

o   Buccal tipping and extrusion Vs Buccal tipping and intrusion

o   Lingual tipping and intrusion Vs  Lingual tipping and extrusion

 

Attachments

·      Rotations added to typodont, different attachments buccal, lingual and adjacent teeth Momtaz 2017

o   60% with no attachments

o   more Attachments on adjacent teeth, reduce accuracy down to 27%

·      We don’t truly know how attachments work

o   What size, direction, active surface shape

 

Accuracy of aligner outcomes

·      77% accurate for tipping Wheeler 2017

o   However tipping most accurate movement

·      50% overall movements 1ST set of aligner Haouili 2020

o   1st refinement 75% accuracy

·      ABO 80% fail, fixed 50% fail Djeu 2005

 

Extraction of upper 1st premolars

o   Finite model analysis, showed uncontrolled tipping upper incisors Jiang 2020

o   Patients molar anchorage loss 2.3mm, mesial rotation 5 degrees,  reduced retraction of incisors, only 2mm of retraction, Retroclination of upper incisors 5 degrees, Dai 2019

 

Ki study

o   Observed adjacent teeth to moving teeth:

o   Unpredictable movement of adjacent teeth = biomechanics more complex

o   Occlusal forces change resultant forces?

 

Development

o   Scrapy East Asia material – currently experimental

o   Direct to printing, save costs

o   No polishing

o   Alter aligner thickness

 

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