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Indications and application of minimum anchorage mechanics Vishnu Raj

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Indications and application of minimum anchorage mechanics Vishnu Raj


Join me for a summary of Vishnu Raj’s lecture looking at minimum anchorage mechanics, with a focus on utilising Burstone’s Geometries for a simple and effective way to manage anchorage, a well explained lecture with useful tips.
· Group C minimum anchorage
o 75% or greater posterior movement into the extraction space
o Incisor movement minimal
· Mild anterior crowding
· Posterior crowding, ectopic 2n molars
· Missing 5s
Aetiology of crowding
· Compared to pre-historic man = 30% increase = greater likelihood of impaction of 8s and 7s
2nd molar eruption – posterior crowding associated with Hwang 2017
· Wider teeth and crowding
· Maintenance of E space
Premolar extraction and posterior crowding Turkos 2013
· Increase space for 3rd molars
· Mesial movement of 1st and 2nd molars
· Mesial movement molars = 3.2-4.6mm
Biology and mechanical considerations
Anchorage considerations
· Upper molars move more mesial then mandibular molars due to :
o Growth of mandible
o Bone type and density
§ Cortical bone more resistance to tooth movement Devlin 1998
· Posterior maxilla = 0.31gcm2
· Anterior maxilla 0.55 gcm2
· Mandible 1.11gcm2
· Upper incisors tend t retract less then lower incisors Gu 2017
o Large root surface area upper 2-2
o Prescription torque upper high – anchorage loss
Preparing anterior anchorage
· Allow working archwires to be passive for 4-6 weeks
· Start space closure 1-2 weeks after extractions
· Curve in archwire to accentuate inclination to resist over retraction
· Increase 2nd order 2-2
· Increase 3rd order 2-2
· Elastics
2nd order bend what is it
· Gable bend or V bend 15-25 degrees
· Bend closer to anterior segment
· 6 geometries between slots Burstone 1988
· Effects:
o Increases anterior anchorage
o Root parallelism
Increase 3rd order
· Increase stiffness SS,
· Torsional stiffness SS:TMA:NitI 10:3:1
· increase cross section 21x25
Decrease wire slot engagement angle
3rd order bend
· Posterior crowding to be considered
· Mesial movement 1st molre more predicable to resolve posterior crowding
· Anterior anchorage
· Control of incisor and lip position