Join me for part 2, where Jae Park describes how to plan either extrusion or intrusion movements, the key evidence around AOB closure and TADs, aligners and orthognathic surgery.
Conclusion
- Resting tongue position is the main soft tissue factor.
- For increased LAFH, posterior intrusion with tads is indicated.
- Invisalign for mild AOBs, correction is achieved with incisor extrusion mainly.
- TADs for intrusion should be placed in the palate should be as distal as possible.
- If intruding upper molars with TADs, lower molars will erupt unless an appliance is used.
- 80% of vertical relapse with posterior intrusion occurs in 1st year after debond.
How to plan intrusion posterior teeth Vs extrusion of anterior teeth
- Extrusion:
- No autorotation
- Increase incisal show
- Effects of intrusion:
- Autorotation of mandible
- Reduction in LAFH
- Reduced posterior tooth show
CONSIDER EFFECTS ON OCCLUSAL PLANE WITH POSTERIOR INTRUSION
- If too steep = occlusal interference
- If too flat = reverse smile
How to plan extrusion / intrusion:
- Upper incisor tip positioned 4mm from the upper lip tip
Evidence of AOB closure with TADs
- Posterior intrusion of 2mm in the upper and 1mm in the lower 1mm, with 3mm of autorotation. Deguchi 2011
- TADs and intrusion less stable, 1mm or 30% relapse Sugawara 2002
- If intrude upper posterior teeth, use lower fixed or VFR to prevent lower posterior over eruption.
Aligners
- Correct AOBs through 1.5mm incisor extrusion, minimal posterior changes. Khosravi 2017
Orthognathic surgery
Reduced stability due to Stylomandibular and medial pterygoid muscles.
Solution
- Strips muscles in surgery
- Short split
