Defect in material
- Not 3D printed
- Membrane material same for all patients – different malocclusions, aligners provide same force
Defect in efficiency Kravitz 2009, Simon
- Anterior intrusion and extrusion
- Canine and premolar rotation
- incisor torque
- Anchorage
Efficiency of aligners
- Distalisation
- Alignment
- Anterior expanded
Defect in mechanics
- Force placed at a distance from the CoR = tipping in space closure = roller coster effect
Gate Spring – single tooth torque auxillary crimped onto the wire
Overbite correction Zhao 2019
- Aligner efficiency in OB correction = 50%
- Aim for openbite
- Additional 100% anterior intrusion
- Anchorage for overbite – premolar extrusion efficiency poor
- As lower anterior intrude the lower premolars extrude
- To ensure the lower premolars extrude – horizontal attachments are placed on the premolars
- Bite ramps
- On upper 3-3
- Maintains occlusal contact of upper incisors – preventing over eruption
- Staging of intrusion for deepbite – anchorage efficiency is poor
- Intrude lower 2-2 first
- 2nd stage lower canine intrusion
- Anterior tooth torque efficiency poor 15% Zhao 2019
- For 1mm of retraction 2.50 of anterior torque loss
- Overcorrect anterior torque loss
- Power ridge
- Produce counter moment effectively – to aid bodily movement.
- Power ridge force closer to the CoR
- Can lose tracking with power ridge
- Attachment placement tips
- Extrusion of teeth = attachment on tooth to be moved
- Intrusion of teeth = attachments on anchorage teeth (not teeth to be intruded)
- Attachment to match movement type
- Horizontal rectangular for vertical movement / molar uprighting
- Not cause occlusal interference
- If they will – place lingually
- Prevent undesired mesial tip
- Use class 2 elastics
- First molar cut out placed on the mesial side
Clinical case of space closure
- Distalisation of posterior teeth
- Reactionary proclination of upper incisors
- Resolved by use of class 2 elastics
- Retraction of anterior teeth
- Reactionary torque loss of the upper incisors
- Resolved by over correcting upper anterior torque with power ridges
- Reactionary extrusion of upper and lower molars
- Due to upper molar distalisation
- Due to lower molar class 2 elastics
- Resolved by intrusion upper and lower molars
- Reactionary torque loss of the upper incisors
- Reactionary proclination of upper incisors
