Search

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

Play episode
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

 

Author

Join the discussion

1 comment

More from this show