Managing Complex Cases in Orthodontics. Kleber Meireles and Andre Machado. Episode 149. June 1st 2022

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Farooq Ahmed

Managing Complex Cases in Orthodontics. Kleber Meireles and Andre Machado

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Join me for a summary of a dynamic conversation between Kleber and Andre, It was a lecture full of biomechanics and the podcast will focus on specific examples with fixed appliances and aligners.

Fixed appliance mechanics

1.     Canine retraction in extraction case with buccal canine: sectional mechanics

o   Conventional sliding mechanics retract canine but also distally tip and rotate distal in

o   Loop mechanics

§  Mechanics = canine retraction – line of force buccal

§  Side effects = no distal in rotation due to line of the force buccal

§  Mechanics = sectional mechanics allows counter moment to increase as canine retracts = bodily retraction

§  Side effect = no distal tipping of the canine


2.     Retraction of upper anterior teeth in extraction cases

o   Loss of anterior torque on retraction,

o   Torque mechanics:

§  Stop active space closure

§  Apply anterior buccal crown torque

§  When recovered, continue final space closure


Aligner biomechanics

Comment:  Physics is physics & there is nothing magical appliance

Distalisation with aligners

·       Not effective with aligners

·       Mechanics: Distal tip

·       Side effects: No root movement


·       Attachments for molar distalisation:

o   6mm:  horizontal requires 120g, 10mm from the CoR = 1200gm force required for counter moment, however no aligner material can deliver this force or provide retention to the force, therefore not effective tooth movement

o   4mm attachment requires greater force, 1200/4 = 300g


Issues with aligners

·       Rely more on companies to do the treatment planning

o   AI does not have knowledge of the roots and its angulation – which is difficult to correct even with conventional braces

·       Lack of stiffness in the aligners make it difficult to apply counter moment

o   For example incisor retraction in extraction cases


Thank you to our sponsors for supporting this episode

I hope to see you Porto for the Simply Ortho congress on the 9-11 of June


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