Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BDS3 Orthodontics > Physiology of tooth movement and appliances overview > Flashcards

Physiology of tooth movement and appliances overview Flashcards

1
Q

What is the Physiological basis of orthodontics?

A
  • If external force applied to tooth, tooth will move as bone around it remodels
  • Bony remodelling is mediated by periodontal ligament
  • If tooth has no PDL or is ankylosed will not move
  • Cementum more resistant to resorption than bone
  • Some degree of root resorption after orthodontics should be expected
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the 3 theories for orthodontic tooth movement?

A
  • Piezo-electric theory
  • Differential pressure theory
  • Mechano-chemical theory
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the differential pressure theory?

A
  • Coronal part of tooth undergoes a force
  • Root undergoes compression and tension
  • In areas of compression bone is resorbed
  • In areas of tension bone is deposited
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the mechano-chemical theory?

A
  • Occurs at cellular level
  • Cell shape changes occur within periodontal ligament and adjacent alveolar bone
  • Inititiates signalling interactions between cells e.g. Production and release of cytokines
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are cytokines?

A
  • Low molecular weight proteins
  • Regulate action of target cells
  • May cause target cells to secrete mediators
  • Lots of cytokines within PDL
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the mechano-chemical theory?

A
  • Occurs at cellular level
  • Cell shape changes occur within periodontal ligament and adjacent alveolar bone
  • Initiates signalling interactions between cells e.g. Production and release of cytokines
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Histologically how is the periodontal space maintained?

A
  • On root surface the cementum covered by cementoblasts
  • Sharpey’s fibres (collagen fibres) penetrate cementoblasts and attach to cementum
  • In PDL epithelial cells islands form 3D network around root (called Epithelial Rests of Malassez)
  • Epithelial Rests of Malassez constantly release Epithelial Growth Factor (EGF)
  • EGF diffuse through cells in extracellular matrix and stimulate osteoclasia on periodontal bone surface
  • Promotes maintenance of periodontal space
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the mechanism for bone resorption in the mechano-chemical theory?

A
  • Mechanical loading
  • Fluid movement, stretching and compression of fibres within PDL ; lead to 1,2,3,4
    • Adjacent bone distorted
      - Fluid flow within bone canaliculi is altered
      - Osteocytes within bone detect distortion
      - Osteocytes produce cytokines
      - Cytokines activate osteoblasts to recruit osteoclasts
      - Bone resorption
  2. Macrophages increase production of IL-1
    - Bone resorption
  3. Osteoblasts produce prostaglandins and leukotrienes
    - Bones resorption
  4. Fibroblasts produce Matrix metalloproteinases
    - Bone resorption
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the cascade of cytokines within the periodontal ligament leads to bone resoprtion?

A
  • Cytokines activate osteoblasts to produce Prostaglandins (PGE-2) and leukotrienes
  • PGE-2 and leukotrienes causes osteoblasts to produce intracellular messenger (secondary messenger)
  • Intracellular secondary messengers initiate production of Receptor Activator of Nuclear factor Kappa-B-Ligand (RANKL) and CSF and IL-1
  • IL-1 increases production of RANKL
  • RANKL and CSF cause blood monocytes to fuse and form multinucleated osteoclasts
  • RANKL stimulates osteoclast to become active and resorb the bone
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How are osteoblasts involved in areas of compression?

A
  • Osteoblasts bunch together
  • They expose the osteoid layer giving osteoclasts access to resorb the bone
  • Osteoblasts send signals to osteoclasts (e.g. RANKL) to recruit and activate osteoclasts to resorb bone
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How are osteoblasts involved in areas of tension?

A
  • Osteoblasts are flattened covering the osteoid layer
  • Prevents osteoclasts from gaining access to the bone
  • Osteoblasts secrete collagen and other proteins forming the organic matrix
  • Secrete Hydroxyapatite crystals which form new bone into the organic matrix
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What two components are viral in regulating bone remodelling?

A
  • Osteoblasts release another protein called Osteoprotegerin (OPG) which prevents osteoclastic differentiation and suppresses their activity
  • Balance between RANKL and OPG produced regulates bone remodelling
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How do orthodontists use this knowledge to their advantage?

A
  • Utilise the inflammatory response which occurs in PDL when a force is placed on teeth
  • Use appliances to transmit force to PDL and bone
  • Manages patients carefully through periods of resorption and repair of their alveolar bone
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the types of orthodontic appliances?

A
  • Removable (URA)
  • Functionals
  • Fixed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the types of tooth movement?

A
  • Tipping
  • Bodily movement
  • Intrusion
  • Extrusion
  • Rotation
  • Torque
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the effects of functional applicance on Class II case?

A
  • Restrict maxillary growth
  • Promote mandibular growth
  • Remodel the glenoid fossa
17
Q

What are the dental changes that occur in functional applicance Class II case?

A
  • Lower incisors procline
  • Upper incisors retrocline
  • Twin block therapy for 6-12 months
  • Reduce overjet
18
Q

What are the mode of actions of functional appliances? (Twin blocks)

A
  • Skeletal change (30%) lead to growth of mandible, restraint of mandible
  • Dentoalevolar change (70%) lead to retroclination of upper teeth, proclination of lower teeth
  • Mesial migration of lower teeth
  • Distal migration of upper teeth
  • Combo of above achieve class I
19
Q

How is bodily movement acheived?

A
  • Fixed appliance
  • Frontal resorption
  • Bony deposition on opposiute side so bone remodels around tooth
  • Need 150-200grams of force
  • In order for PDL to retain normal width and stability then secondary remodelling occurs
20
Q

What occurs histologically during frontal resorption?

A
  • Occurs on side of pressure
  • Hyperaemia of blood vessels
  • Increased osteoclastic activity, resorption of lamina dura
  • Slow tooth movement which is why it takes years
  • PDL reorganises
21
Q

What occurs histologically during deposition?

A
  • Occurs on tension side
  • Hyperaemia of blood vessels
  • Increased osteoblastic activity
  • Deposition of osteoid
22
Q

What are Matrix Metalloproteinases?

A
  • Enzymes that break down the extracellular matrix
23
Q

What is apical root torque?

A
  • Rotation of root at apex
  • Uses force couple in opposite directions
  • Need 50-100grams
24
Q

What is the optimum force for tipping movement?

A

35-60g

25
Q

What is the optimum force for bodily movement?

A

150-200g

26
Q

What is the optimum force for intrusion?

A

10-20g

27
Q

What is the optimum force for extrusion?

A

35-60g

28
Q

What is the optimum force for rotation?

A

35-60g

29
Q

What is the optimum force for torque?

A

50-100g

30
Q

What are the histological events that occur during light forces applied to tooth?

A
  • Hyperaemia or increase in blood flow throughout PDL
  • Osteoclasts appear on pressure side
  • Osteoblasts on tension side
  • Osteoclasts resorb the lamina dura on pressure side
  • Osteoblasts lay down osteoid in increased PDL space on tension side
  • AKA frontal resorption
  • Over time PD fibres reorganise
  • Supracrestal gingival fibres don’t
  • Shows why rotations and spacing most likely to relapse following correction
31
Q

What are the histological events that occurs in moderate forces?

A
  • Increased forces lead to occlusion of blood vessels on pressure side
  • Hyperaemia of vessels on tension side
  • Due to increased pressure on pressure side there are cell free areas, process called hyalinsation
  • Tooth does not move (stasis)
  • Anchor units or teeth can still move leading to loss of space
  • Increased vascularity on underside of bone supporting tooth, with increase in osteoclasts lead to undermining resorption
  • Resorption continues until tooth moves in desired direction
  • Healing of PDL occurs and process repeats
32
Q

What are the histological events that occur in heavy forces?

A
  • Excessive forces associated with occlusion of blood vessels, areas of hyalinisation, undermining resorption, areas of necrosis of bone and areas of resorption of root surface
  • Pt may experience pain and loss of vitality of tooth
  • ## Adjacent alveolar bone also undergoes extensive remodelling
33
Q

What are some unwanted side effects of excessive forces?

A
  • Pain
  • Necrosis of bone
  • Anchorage loss
  • Root resorption
  • Possible loss of tooth vitality
34
Q

What are some factors that affect the response to orthodontic forces?

A
  • Magnitude
  • Duration
  • Age
  • Anatomy
35
Q

What are some anatological features that affect response to ortho appliances?

A
  • No bone perhaps if wasting or cleft pt
  • Soft tissues like anterior open bite
  • Mid-palatal suture
  • Teeth that have been root treated
  • Thin bone (has lots of dense cortical plate)
36
Q

What are some negative effects of orthodontic forces?

A
  • Pain and mobility
  • Pulpal changes
  • Root resorption
  • Loss of alveolar bone support
  • Relapse
37
Q

What is the ideal tooth movement per month for ortho appliances?

A
  • 1mm per month
38
Q

What is the treatment time for fixed appliances?

A

24 months

BDS3 Orthodontics (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions