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Indications and application of minimum anchorage mechanics Vishnu Raj. Episode 142. November 23rd 2021

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Farooq Ahmed

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.

 

 

Indications

 

Classification

  • Group C minimum anchorage
    • 75% or greater posterior movement into the extraction space
    • Incisor movement minimal

 

Indications

  • 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 :
    • Growth of mandible
    • 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
        • Large root surface area upper 2-2
        • 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:
    • Increases anterior anchorage
    • Root parallelism

 

 

Increase 3rd order

  • Increase stiffness SS,
  • Torsional stiffness SS:TMA:NitI 10:3:1
  • increase cross section 21×25

Decrease wire slot engagement angle

3rd order bend

 

Conclusion

  • Posterior crowding to be considered
  • Mesial movement 1st molre more predicable to resolve posterior crowding
  • Anterior anchorage
  • Control of incisor and lip position

 

 

Conclusion

Posterior crowding to be considered

Mesial movement 1st more more predicable to resolve posterior crowding

Anterior anchorage

Control of incisor and lip position

 

 

 

        

 

 

 

 

 

 

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1 comment
  • Very interesting and informative from a historical perspective and vital to understand at the initial stages of ones career.
    However ,in my view,long superceded by more other techniques that better lend themselves to a busy practice.
    EG.Damon style mechanics,NOT necessarily Damon brackets.
    Full disclosure,I have absolutely no ties ,of any kind,with Ormco or any other dentl/ortho .company.

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