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Aligner orthodontics. from basic research to clinical application. Tommaso Castroflorio. Episode 70 December 17th 2020

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Hosted by
Farooq Ahmed

Aligner orthodontics. from basic research to clinical application. Tommaso Castroflorio

 

Join me for Tommaso’s lecture looking at basic reseach of aligners:

He describes the changes to aligners which help to optimally manage periodontal patients, distalisation cases, anterior openbite and rotated teeth.

Advantages of aligners and periodontal outcomes

o   Periodontal health outcomes better, GI, BoP during treatment S/R Rossini 2015

o   Robertson S/R

§  Pros:

·      Effective anterior alignment

·      Comparable to fixed for anterior alignment bucco-lingual changes

§  Cons

·      Most movements not predictable, except minor horizontal movement

·      Additional refinement likely most cases

·      Periodontally compromised patient

o   Reduce velocity of tooth movement

§  More gentle movement. Linear movement 0.12, angular 1 degree

·      Aligners ideal for periodontal patients – mostly tipping movements of anterior region

·      Limitations of biology

·      Biochemical markers of bone metabolism of OTM RankL Osteoprotegarin (OPG)  biological responses the same  as fixed

Distalisation

·      Sequential distalisation

·      Class 2 elastics

What movements take place when distalise teeth with aligners Rossini 2020

·      Observed movements with sequential distalisation:

·      Distalisation of 7: 

o   Proclination of incisors

o   Plastic is like a compressed coil between 6-7

·      Distalisation of 6

o   Proclination of incisors

o   Like compressed coil between 6-5

·      Distalisation of 5:

o   Most likely lose anchorage in distalisation sequence

o   Like compressed coil between 4-

o   BUT ALSO like elastometic chain from 7-5 = mesialisation of 6s and 7s

o   Why = aligner squeezes arch to close space

·      How to provide premolar anchorage when distalising

o   Distal crown tipping of molars 5-10 degrees when distalise 5s

Cut out Vs buttons for class 2 elastics and distalisation:

·      Cut outs

o   Deformation to distalise anterior teeth and intrude

o   Resultant movement to distalise

·      Button bonded

o   Canine buttons

o   Aligner deforms to procline incisors and upper incisors

o   Resultant anterior movement of teeth

·      3/16th – 6oz

Biomechanics protocols for class 2 distalisation cases

·      Ext 8s

·      50% distalisation sequence

·      Attachments 7-3s

·      Class 2 elastics from U4s until end of U4s movement, then cut outs on U3s

·      Aesthetic start – small alignment of anterior teeth for patients

·      Change aligners 1/52

AOB

·      Relative extrusion with Retroclination

·      Attachment design = no difference for anterior attachment design, any design increases Retroclination.

·      Posterior attachments  = reinforce anchorage

·      Periodontal stress = 76g/cm, ideal tooth movement force

·      AOB correction due to anterior extrusion, posterior intrusion and mandibular autorotation Harris 2020

Rotation of rounded teeth Cortona 2019

·      Difficult movement

·      Accuracy 40% Simon 2014

·      Mathematical model shows attachment design:

o   Rectangular and vertical attachment 1.2 degrees activation (3 degrees was not as predictable)

o   Anterior teeth act as anchorage

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