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BDS3 ORTHODONTICS > PHYSIOLOGY OF TOOTH MOVEMENT & APPLIANCE OVERVIEW > Flashcards

PHYSIOLOGY OF TOOTH MOVEMENT & APPLIANCE OVERVIEW Flashcards

1
Q

What are the different types of tooth movement?

A
  • physiological (tooth eruption & mesial drift)
  • orthodontic (from externally generated forces)
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2
Q

what is the physiological basis of orthodontic appliances?

A

if an external force is applied to a tooth (ortho appliance), the tooth will move as the bone around it remodels

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3
Q

what is bone remodelling around a tooth mediated by?

A

The PDL
- if a tooth has no PDL or is ankylosed the tooth will NOT move

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4
Q

what is meant by ankylosed?

A

tooth fused to bone

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5
Q

what are the different theories for orthodontic tooth movement?

A
  • piezo-electric theory
  • differentials pressure theory
  • mechano-chemical theory
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6
Q

what is the differential pressure theory?

A

In areas of compression bone is resorbed and in areas of tension bone is deposited

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7
Q

what is the mechano-chemical theory?

A

Cell mediated interactions take place.
- cell shape changes in the PDL & adjacent alveolar bone
- initiates signalling between cells (production of cytokines)
- cytokines activate osteoblasts
- osteoblasts produce prostaglandins & leukotriene which initiates production of RANKL
- RANKL & CSF cause formation of osteoclasts (which resorbs bone)

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8
Q

how do osteoblasts act in areas of compression?

A
  • osteoblasts bunch up together & expose the osteoid layer giving osteoclasts access to resorb bone
  • osteoblasts send RANKL signals to osteoclasts to activate resorption of bone
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9
Q

how do osteoblasts act in areas of tension?

A
  • osteoblasts are flattened covering the osteoid layer and prevent osteoclasts from gaining access to the bone
  • osteoblasts secrete collagen and other proteins forming the organic matrix into which they secrete hydroxyapatite crystals which forms new bone
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10
Q

the balance between which two proteins mediates the bone remodelling?

A

balance between RANKL & OPG regulates bone remodelling

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11
Q

what are the different types of orthodontic appliances?

A
  • removable (URA)
  • functionals
  • fixed
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12
Q

in order for a functional appliance to work, what must the patient be?

A

patient must be growing!

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13
Q

what are the different types of tooth movement?

A
  • tipping
  • bodily movement
  • intrusion
  • extrusion
  • rotation
  • torque
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14
Q

what occurs when a tooth undergoes bodily movement?

A

crown and root move together

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15
Q

how do functional appliances work?

A
  • the mandible is postured away from its normal rest position
  • the facial musculature is stretched which generates forces transmitted to the teeth and alveolus
  • may be an effect on facial growth
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16
Q

what is the mode of action of functionals?

A

Skeletal change (30%) = growth of mandible restraint of maxilla

Dentoalveolar change (70%) = retroclination of upper teeth & proclination of lower teeth

17
Q

what is the optimal force applied to cause tipping of tooth?

A

35-60g

18
Q

what is the optimal force applied to cause bodily movement of tooth?

A

150-200g

19
Q

what is the optimal force applied to cause intrusion of tooth?

A

10-20g

20
Q

what is the optimal force applied to cause extrusion of tooth?

A

35-60g

21
Q

what is the optimal force applied to cause rotation of tooth?

A

35-60g

22
Q

what is the optimal force applied to cause torque of tooth?

A

50-100g

23
Q

what histological changes occur in orthodontics when a light force is applied?

A
  • hyperaemia within the PDL
  • appearance of osteoclasts & osteoblasts
  • resorption of lamina dura from pressure side
  • apposition of osteoid on tension side
  • remodelling of socket
  • PDL fibres reorganise
  • gingival fibres appear not to become reorganised but remain distorted
24
Q

what is frontal resorption of a tooth?

A

remodelling of socket

25
Q

what are some unwanted side effects of excessive forces applied to a tooth?

A
  • pain
  • root resorption
  • anchorage loss
  • possible loss of tooth vitality
26
Q

what are some factors that affect the response to orthodontic force?

A
  • magnitude of force applied
  • duration force is applied
  • age of patient
  • anatomy of patient
27
Q

what anatomical factors can effect the response of a tooth to force?

A
  • no bone (wasting/cleft)
  • soft tissues
  • mid-palatal suture
28
Q

how much movement of tooth should occur per month when using orthodontics?

A

1mm of tooth movement per month

29
Q

What is the usual treatment time for fixed appliances?

A

24 months

BDS3 ORTHODONTICS (8 decks)

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