8 Extractions and Anchorage

Reasons for Extractions

  • Creating Space

    • Relieve crowding through:

      • Appliance therapy (removable or fixed)

      • Interceptive (spontaneous tooth movement)

    • Reduce increased overjet

    • Correct centrelines

    • Open space for missing teeth

    • Correct anterior open bite (AOB)

Crowding

  • Definition: total tooth size - total arch length

  • Horizontal relationship: upper vs. lower incisors

    • Normal: 2-4 mm; >4 mm may indicate extractions

Anchorage in Orthodontics

  • Definition: The source of resistance to reaction from active components

  • Importance of anchorage to achieve desired treatment results

    • Inadequate anchorage can result in:

      • Residual crowding

      • Residual overjet

      • Centreline discrepancies

    • Extraction spaces may close due to forward movement of anchor teeth

Types of Anchorage

  • Removable Appliances

    • Minimal anchorage loss

    • Maximum tooth movement

    • Specific designs such as base plate clasps

  • Orthodontic Mini-Implants

    • Reinforces anchorage

  • Extraoral Appliances

    • Conventional headgear

    • Facemask/reverse pull headgear

Extraction Patterns

  • Most common extractions: upper 1st premolars and sometimes upper 2nd premolars

  • Choices depend on anchorage considerations

  • Example: Extraction of upper 1st premolars can provide 7 mm of space per side, ideal for Class II/I cases.

Classifications of Cases

  • Class II Div 1

    • Typically results in increased overjet requiring extraction

  • Class III Malocclusions

    • Extraction decisions based on anchorage considerations

Anatomical Considerations

  • Identify teeth for extraction:

    • Upper 1st premolars and lower premolars chosen based on anchorage

  • Impact of Extractions

    • Upper 7s can over-erupt without proper anchorage

Surgical Considerations for Wisdom Teeth

  • Surgical removal should be limited to cases with pathology such as caries or cysts.

Conclusion

  • Extraction decisions are critical for optimal orthodontic outcomes and depend on evaluating individual cases for crowding, anchorage needs, and relevant anatomical features.