Safety Placement Of Orthodontic Anchoring Screws Mitsuru Motoyoshi. Episode 41. IOC 2020

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Farooq Ahmed

TAD failure

  • TAD failure rate 5%
  • Main cause due to root contact 80%


Which teeth to TADs contact and fail? Hee-Moon 2006

  • Maxilla: contact is usually with the distal tooth:
  • Mandible: RHS contact with distal teeth
  • Mandible: LHS contact with mesial teeth


How to avoid root contact?

  • Increase oblique path – 30 o
    • TAD further apical – greater root divergence
    • Greater cortical plate engagement = more stable


Root proximity from radiograph

  • TADs appearing to contact the roots were likely to be successful – 83%
  • If TADs did not appear to contact root surface, success rate higher 98%


Greater failure in mandible

  • Potential microcrack due to insertion torque
  • Torque 15Nm = crack in bone, 10Nm no crack


Sinus perforation

  • In 10% of cases


Root fracture

  • Possible with self drilling TADs

Increase midpalatal TAD success suggestions

  • Avoid mid-palatal suture
  • Place anterior to 1st molar
  • Embedded depth should be 4.5mm +
  • 2mm screw with pre drilling
  • Larger torque improves stability up to 30Nm
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