Simplified Mechanics for Aligners in Treating Complex Cases Dr. Chris Chang
Focus of lecture: pre aligner treatment, extrusion, space closure, crossbite, rotation
Chris spends 5-6 months prior to aligner treatment
TADs = pulling mechanics
Aligner = pushing mechanics
Papers on predictability of aligner movement: poorly delivered movements
· Extraction cases: Incisors torque loss and extrusion, molar anchorage loss and intrusion Dai 2019
· Expansion: Bodily movement for expansion 36% Zhou 2019
· Incisor intrusion Charalampakis 2018
· Second molar movement Grunheld 2017
· Rotation of canines / round teeth Charalampakis 2018, Grunheld 2017
Solutions
· TADs
· Power ridges
· Attachment design
· Over-correction
· Pre aligner orthodontics
Pre aligner orthodontic scenarios
· Extrusion
o Fixed appliances to upright a molar
· Large space closure
o Sectional mechanics with bucco-lingual space closure
· Deep bite cases
o Class 3 with deep bite
o Anterior bite turbo with flowable composite lower 3-3
· Class 3
o Anterior bite turbo lower arch
o Early light short elastics 2 Oz, L2-U4
o Open coil posteriorly to advance incisors
· Scissor bite posterior with over eruption
o Posterior bite block on unaffected side
o Buccal shelf TAD on effected side
§ Intrusion and labial movement
§ Failure rate 7% Chang 2015
· Ramus TAD
o Rotated 7
o 14 mm
o Horizontal insertion
o Failure rate 5% Chang 2016
o Nerve is lingual
Impacted canine
· 3d lever arm, 19×25 ss auxillary arm
o U -loop to attach to elastic
o Flowable composite to lock to
· Infrazygmatic TAD
· Extrude, retract and buccal movement
