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
