Join me as I summarise Willy Dayan’s lecture looking at biomechanics in AOB, class 2 and extraction cases
Introduction
Question is not if we can do Invisalign, like asking a sports star do they do Nike, it may be the best equipment but it comes down to our skill as clinicians
- Don’t think of clincheck as video, think of the clincheck as delivering force to teeth
Case selection
- Do all fixed cases have the same number of wires / aligners
- Biological limitations – software cannot plan, clinical decision
Cases where we shouldn’t idealise occlusion
- Severe skeletal 3, bilateral crossbite, hypoplastic maxilla, accept discrepancy
- Spacing cases: open up for 5th lower incisor, prevents over retraction
- Avoid over expansion upper arch, exaggerate lower lingual crown torque
Vertical control
- AOB: with aligners can close without elastics through staging:
- Molar intrusion with premolars anchorage
- Premolars intrusion, anterior teeth anchorage
= Lateral openbite in treatment but corrected when premolars intrude and autorotate
Sagittal correction
2 methods
- Sequential distalisation, utilising anterior anchorage for individual distalisation
- Bite jump
- What is it: overjet increases in the clincheck, posterior teeth don’t move
- However with class elastics the maxillary teeth distalised
Bicuspid / premolar extraction cases
Can have the following effects
- Loss of anterior torque
- Reverse curve of spee in the upper, and curve of spee lower
- Roots not parallel Gable
Biomechanics FOR CORRECTION
- Increase anterior torque,
- Lingual vertical attachments to achieve parallel roots
- Excessive gable bends to compensate for unwanted tipping
- Curve of spee upper, reverse curve of spee lower arch
