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Expansion In The Early Mixed Dentition Is It Worth The Effort James A. Mcnamara. Episode 32 IOC 2020

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Hosted by
Farooq Ahmed

Common occurrence:

  • Posterior / anterior crossbite
  • Tooth-size discrepancy

 

Correction devices

  • Expansion maxilla: RME – bonded appliance – skeletal change
  • Expansion mandible: Schwarz appliance in 40% of cases – dentoalveolar change

 

Decision making for expansion

  1. Transpalatal arch-width – measured from narrowest point
    • Average dimensions: Howe 1983 & Riolo 1974
      • Adult 35-39mm
      • Child 32-35mm
    • If -31mm require expansion

 

  1. Mesial-distal width of the central incisor
    • Average dimensions: Riolo 1974
      • Male 8.9mm +/- 0.6
      • Female 8.7mm +/- 0.6
    • If 2 SD greater than average = 10mm – consider delay treatment as likely require extraction therapy as tooth size discrepancy significant.
  2. Arch-length discrepancy:
    • +6mm delay as likely extractions
    • 3-6mm borderline – ideal for expansion

 

Timing of treatment

  • Eruption of all 1st molars, lower 2-2 and upper centrals

 

Treatment protocol

  1. Maxillary expansion
    • 1 x activation per day
    • 28 days of activation
    • Over-expansion

 

  1. Mandibular expansion
    • Activated 1 x week Schwarz appliance
    • 4mm of expansion
    • Wear: full time, including meals
    • Dento-alveolar = upright posterior teeth and expansion of arch
    • Active expansion 5 months
    • No retention – as intercuspation retainers – require only upper retainer

 

Long term effects?

  • RME Vs no MRE 8 year follow up 12-20 years of age MnNamara 2003
    • Control = Reduction of maxillary arch perimeter 6mm
    • RME = Reduction of maxillary arch perimeter 1.5mm
  • = overall RME 4.5mm longer arch perimeter
  • Passive expansion of mandibular arch 2.5mm Geran 2006

 

Class 2 correction with RME?

  • Bite plane effect from bonded RME
  • Following removal patient postures forward = growth at condyle
  • Guest 2010 = 90% improved, of which 50% 2mm molar correction
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