Invisalign Flashcards
Desired properties of aligners
- constant f delivery
- correct stiffness
- low material stress relaxation
Why are attachments imp
Design and placement imp for controlled 2 point force application -> control moment - force ratio
Conventional vs optimised attachments
Conventional: passive, increase engagement of aligner to tooth
Optimised: placed when certain thresholds of OTM detected
Karras et al., 2021: NO. sig. diff. in mean accuracies of OTM
M/F ratio in Invislign
Uncontrolled tipping: tooth rotates around center of R
M/F: 1-7: controlled tipping, center of R displaced by attachment design
M/F: 8-10: translation e.g molar distalisation
- conventional attachments used for backward mvm, rotation and root tip
M/F >10: torque mvm
- power ridges when >3 deg Lirtq
- force applied on crown cervically to create couple
Attachment of extrusion
Bevelled attachment on gingival side
- exert more force on active surface
Intrusion attachment
NO need - light f
- KIV passive attachment on anchor tth for anchorate and relative extrusion
Rotation attachment
Optimised rotation attachments (U/L3s,L4s,L5s)
Aux
What is staging
the sequence and speed of OTM with aligner
Velocity of OTM in aligners
Up to
Rotation - 2deg/aligner
Torque - 1 deg
AP - 0.25mm
considerations for staging plan
- biologically possible
- clinically predictable
- anchorage demand
- attachment design
- auxillary technique
- stage linear and rotational velocities separately
- slow down OTM for better predictability
esp difficult mvm: extrusion, derotation of premolars/canines
Space closure CAT mechanics
torque 2-3 trays before incisor retraction
- reduce bowing effect
Migitating poor rotational correction
overcorrection
Staging pattern for anchorgage
Max: G6, posterior mesialisation <2mm
Canine retraction 1st into 1/3 of exo space + Cl. II elastics
Mod: 2-5mm anchorage loss
- reciprocal SC -> simultaneous staging where tth are moving
Molar distalization:
- sequential
- attachments on premolars and canines for bodily translation
- Cl. II
What is leap frog staging pattern
early OJ reduction -> longer tx time
Non-exo + IPR Case
avoid round tripping
post IPR first -> sequential distalisation
- special instructions to maintain position of most labially displaced Li
Adv of CAT
- better perio with less PI,GI,PD (Jiant et al., 2018)
- sig. shorter time in mild-moderate malocclusion (Zheng et al., 2017)
- molar distalisation
- better vert.control
- predetermine torque/tip
- avoid proclination of incisors
- better aesthetics
- less pain
- less emergency visits
Compliance rate
36% wore recommended amt of time >75% of aligners
25.7% wore as recommended for <50% aligners
(Timm et al., 2021)
- dyed indications not accurate
- subjected to oral cavity, dishwashing process, soft drinks, fruits
Disadv of CAT
- compliance
- no diff. in root resorption
same changes in pulpal blow flow no prem. pulp damage as FA (Alhaija et al., 2019)
Less predictable OTM with CAT
- rotations of canine and premolars >10-15deg
- extrusion
- OB control
Predictable OTM in CAT
- intrusion of post tth
- distalization
- M-D crown tip
Case selection (AP)
< 4mm in buccal rs: elastics, IPR, distalisation
>4mm: exo
Case selection (exo)
If pretx root angulation divergent from exo site
OR >6mm root mvm
- use FA (better torque and root control)
Case selection (vert)
Avg-high MPA cases: Invisalign can resolve deep bite
Low MPA: FA more post. extrusion, more sk. change
Resolve AOB via incisor mvm: min change to MPA
Case selection (transverse)
Invisalign expansion: largely tipp, good for lingually tipped molars
If bodily mvm and torque req.: FA + RME/MARPE
DTC aligners
- more value on cost and convenience than tx outcome
- no attachments
- unsatisfied pt on NDA for refunds
Zenyum: no liability for any advice/consultationa nd service furnished , not dr-pt rs
AAO:
- lack of industry standards
- lack of pt follow up
Behrents 2016:
serious health risk w/o supervision
