Principles of Orthodontic Management

• The scope of orthodontics:

  • Align teeth within available alveolar bone
  • Limited "growth modification" leaves a lot of problems difficult to treat
• Aetiology of orthodontic problems:

  • Skeletal
  • Class I/II/III
  • Maxilla/mandible
  • Soft tissue/habits
  • Lip trap
  • Active lower lip
  • Digit sucking habit
  • Large tongue
  • Dental
  • Crowding/spacing
  • Early loss of deciduous teeth
  • Hypodontia/supernumerary
  • Trauma/extractions
  • Tooth size discrepancy
  • Incisor inclination

  
• Fixed appliances are appliances which are attached to the teeth and so are capable of a greater range of tooth movements than a removable appliance.

  
• Removable appliances are orthodontic appliances that can be removed by the patient.

  
• Orthodontic treatment for crowding = extractions and fixed appliance treatment

  
• Orthodontic treatment for trauma (loss of UL1) = trial fixed appliance (as there may be ankylosis). Then extractions and full fixed appliance treatment.

  
• Orthodontic treatment for impacted tooth = surgical exposure, gold chain & fixed appliance treatment.

  
• Orthodontic treatment for mild hypodontia = fixed appliances - open/close spaces depending on preference

  
• Orthodontic treatment for severe hypodontia = fixed appliances, mutidisciplinary involvement, liaise with restorative team/GDP about restoration of spaces

  
• Functional appliances are removeable or fixed orthodontic appliances which use forces generated by the stretching of muscles, fascia and/or periodontium to alter skeletal and dental relationships.

  
• Orthodontic anchorage = resistance to unwanted tooth movement.
• Anchorage - Newton's Third Law

  • For every action (a force) there is an equal (same magnitude) and opposite reaction
  • Therefore, if an object exerts a force on a second object, the second exerts an equal oppositely directed force on the first one

  
• Overjet reduction:

  • AP (antero-posterior movement)
  • Change in inclination

  
• Extraction decision considerations:

  • Position of tooth
  • Prognosis of tooth
  • Amount of space required
  • Where space is required
  • Incisor/molar relationship
  • Anchorage requirements
  • Appliances to be used
  • Patient profile
  • Aims of treatment
• Extraction decision - incisors:

  • Rarely first choice; incisors should 'fit'
  • Lower incisors - poor prognosis/PDL support
  • Upper incisors - rarely (sometimes peg laterals or teeth that have experienced trauma/resorption)
• Extraction decision - canines:

  • Rare; guidance
  • Occasionally - if severely displaced/ectopic; treatment may be faster/not required

  
• Extraction decision - first premolars:

  • Common
  • Moderate-severe anterior crowding
  • Overjet reduction
  • 40-60% tooth width -> space
• Extraction decision - second premolars:

  • Mild-moderate crowding
  • Severely displaced upper 5s - common with early loss of deciduous teeth
  • 25-50% tooth width -> space
• Extraction decision - first molars:

  • Poor prognosis
  • Limited space anteriorly
  • Anchorage reinforcement
  • Enforced extraction
  • Consider compensating
  • Class I molar - loss of lower 6 may result in overeruption of upper 6
  • Class II molar - loss of upper 6 may result in overeruption of lower 6
• Extraction decision - second molars:

  • Facilitate distal movement 6s (headgear)
  • Mild lower premolar crowding
  • Poor prognosis - facilitate 8s eruption
• Extraction decision - lower molars:

  • Loss of lower 6 -> lower 7 eruption
  • Loss of lower 7 -> lower 8 eruption
  • Angle 10-30°
  • Crypt overlaps adjacent tooth
  • Erupting tooth developed to bifurcation
• Extraction decision - third molars:

  • Previously thought to cause lower incisor crowding
  • No link proven - not justified
  • Extraction of lower 8 may be required for orthognathic surgery
• Indications for primary tooth extractions:

  • Anteriors are generally ok
  • Try to avoid posteriors though; risk of centreline shift and overeruptions and drifting

  
• GDP's guide to orthodontic management:

  • Communicate with orthodontist
  • Extractions should be 1-2 weeks prior to appliance
  • Root remnants may prevent space closure
  • Teeth of poor prognosis (especially upper 6s) communicate if crowding - timing of XLA important
  • Anxiety management for pt