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2nd Saudi Orthodontic Clear Aligner meeting: December Day 1

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Hosted by
Farooq Ahmed

 

Join me as I summarise Maz Moshari’s masterclass at this years 2nd Saudi Orthodontic Clear Aligner Meeting

 

Conclusions:

·      Attachment design: perpendicular to resultant force

·      Rotations: Place oblique attachment to counter intrusive force of aligner

·      Overcorrect torque, add mesial crown tip due to wagon wheel effect

·      Deep bite: synergistic movements: proclinatiion and extrusion

·      AOB: synergistic movements: retroclination and extrusion

 

Concepts

 

Intrusion attachment

1.     Intrusion on aligners

a.     No intrusion attachment

o   Require attachments on adjacent teeth

o   If loss of tracking = occurs on adjacent teeth, with the aligner extruded off the teeth

 

Rotation and intrusion

·      Force labial face and palatal face to create rotation moment.

·      ‘Squeeze force’ occurs =  vertical force = intrusion force.

·      Solution

o   Optimised attachment = Extrusive vector, usually gingival bevel and oblique

o   Resolve resultant force, horizontal and vertical = oblique attachment

 

Torque

·      Wagon wheel effect, for every 4 degrees of lingual crown torque there is distal crown tipping / mesial root tipping.

o   Solution: OFFSET with 1 degree of mesial crown tip

·      Torque lags behind, takes longer , like rectangular NiTi archwire

·      Buccal root torque: Upper molar buccal attachment to provide extrusive buccal force to create moment.

 

 

Design of attachment

 

·      KEY CONCENT: Attachment perpendicular to the force

·      Perpendicular force to rotation = Long vertical attachment

·      But rotational force has intrusive force the ‘squeeze force’

o   Therefore horizontal and vertical force = attachment perpendicular to the force = oblique attachment

Root tip

·      Open space 0.2mm interproximal =  so more plastic wrap around tooth

·      Then start root movement in staged way.

 

 

Deep bite

 

Concept:

Synergistic movements, procline = relative intrusion

 

Staging AP movements

o   Proclination 1st to open the bite

o   Then IPR

§  Not at the same time as IPR = retroclination, therefore should not procline and iPR at the same time as bite will  not open

§  Does round trip – procline and intrude, then IPR and align

 

Staging deep bite

·      Staging of OB, canines intrude 1st, then 2-2

·      Likely loose tracking on lower incisors or 4s – anchorage horizontal G5/G7 attachments

 

Curve of Spee

·      If COS not corrected, then AP also difficult to correct

·      If not correct COS:

o   Posterior openbite – caused by anterior interferences

§  Caused by inadequate attachment

§  Lack of over correction

 

OGN case deep bite

·      Order 10 passive aligners near end stage pre surgery = minimum 2 months to make up for ‘lag’ or vivera retainer / essix – thicker, greater expression of torque

·      TAD – intermaxillary elastics x 2

o   TAD maxilla:

§  Buttons lower premolars

§  Intermaxillary elastics to guide lower premolar teeth into the tray

 

Openbites

 

Concept

Synergistic movement: Retrocline and extrude

·      Aligners do not extrude along the long access

·      Aligner pushes tooth lingually and extrudes in the process, retroclines

 

Tips

·      Dental more predictable than skeletal

·      Extrusion anterior teeth

·      Retraction of anterior teeth

·      Large IPR anterior – can result in deeping of openbite on 3-3 and premature contact

o   Causing mandible  to be distally trapped / counterclockwise

·      Solution

o   Intrusion / elimination of occlusal interferences

 

Case class 3, retromolar TAD AOB

·      Extrusion anterior teeth with lower IPR and retroclination – extrusion greater clinically then planned

·      Retromolar TADs orthobone screws SS 12mm for Buccal shelf.

·      Class 3 elastic and retromolar tad with class 1 eastic.

 

 

Posterior intrusion

·      For expansion – prevent palatal cusps hanging down

o   Add posterior intrusion = reduce palatal cusp hanging down

·      For true intrusion

o   Reciprocal anterior extrusion

o   Attachments on occlusal surface – to aid intrusion

o   Class 2 elastic short 3-4 to force intrusion of 6/7s

·      TADs

o   8s removed

o   TADs – buccal and palatal – boot strapping: buccal – palatal over occlusal surface

 

Posterior intrusion is unpredictable, anterior extrusion is more likely

 

Thank you to the Saudi Orthodontic Society for facilitating this podcast

 

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