Orthodontics - Important

Question 1

Ectopic canines

Answer 1

• canines start to develop palatally and very high, but migrate labially and distal to lateral permanents
• should palpate between 9-11, if cant when 11 then x-ray
• should erupt 10-11yo
• treatment = extract c’s (if distal to half way point of lateral long axis of root then 90% success, if past this then 60%) (ALSO if <55 degrees to midsaggital plane) (consider space maintainer and reassess in 1 year) WHEN = 10-13yo
• risks of no tx (more ectopic, impacted, root resorption, angle/mobile laterals, cyst formation, ankylosis of 3)
• surgery open or closed and gold chain or spontaneous

Question 2

theories of tooth movement

Answer 2

1. differential pressure theory (PDL compression and tension)
2. mechanochemical theory (cellular level)
   * controlled by osteoblasts as they secrete RANKL and OPG (osteoprotegrin)
   * RANKL and OPG balance regualtes bone remodeling
   * compression = osteoblasts compressed allowing osteoclasts access to ostioid layer AND cytokines (RANKL) released (activates osteoclasts and causes monocytes in blood to fuse forming osteoclasts)
   * tension = flattens osteoblasts blocking osteoclasts from osioid layer AND causes release of collagen / other proteins (organic mix) then secrete hydroxiapitie crystals AND rleases OPG (supress osteoclast activity and differentiaion of monocytes)
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3. piezoelectric theory

Question 3

• what age does a fucntional appliance become useless
• how long worn for

Answer 3

• after the age of 14 yo
• 6-12 months