Physiology of Tooth Movement Flashcards
1
Q
What are the different types of tooth movement?
A
- physiological
- tooth eruption
- mesial drift
- orthodontic
- externally generated forces
2
Q
What is the physiological basis of orthodontics?
A
- if external force is applied, tooth will move
- bone around tooth remodels
- mediated by PDL
3
Q
Why does root resorption occur after orthodontics?
A
- only 1-2mm
- severe resorption not common
- cementum more resistant to resorption than bone
4
Q
What is the differential pressure theory?
A
- in areas of compression bone is resorbed
- in areas of tension bone is deposited
5
Q
What is the mechano-chemical theory?
A
- cell shape changes in PDL and adjacent alveolar bone
- fluid flow in bone canaliculi altered
- osteocytes detect distortion and produce cytokines
- signalling interactions between cells
- production and release of cytokines
- regulate action of target cells
- production and release of cytokines
- macrophages increase production of IL-1
- increases RANKL production
- osteoblasts produce prostaglandins and leukotrienes
- activated by cytokines
- PGE2 and leukotrienes act on osteoblasts
- production of secondary intracellular messengers - production of RANKL and CSF initiated
- cause blood monocytes to fuse and form osteoclasts - RANKL stimulates osteoclast activity
- fibroblasts produce MMPs
- breakdown extracellular matrix - in areas of compression osteoblasts bunch together
- exposure of osteoid layer
- osteoclasts allowed access to bone
- in areas of tension osteoblasts are flattened
- covering of osteoid layer
- osteoclasts cannot gain access to bone
- secretion of collagen and OPG to form organic matrix
6
Q
What are the different ways in which teeth can move?
A
- tipping
- bodily movement
- crown and root move at same time
- intrusion
- extrusion
- rotation
- torque
- tipping movement of root within bone
- usually used in buccal-lingual fixed appliances
7
Q
What is tipping movement?
A
- movement around a centre of rotation
- requires 35-60g force
8
Q
What kind of tooth movement to upper removable appliances facilitate?
A
tipping
9
Q
How do functional appliances work?
A
- mandible postures away from rest position
- occlusion corrected
- facial muscles stretched
- forces transmitted to teeth and alveolus
- facial growth altered
- restrained maxillary growth
- promoted mandibular growth
- remodel of the glenoid fossa
- appliance created with blocks
10
Q
What are the clinical effects of a twinblock appliance?
A
- reduced overjet
- posterior open bite created
- appliance worn at night to allow continued eruption
- may require fixed appliance to restore buccal occlusion
11
Q
What is bodily movement?
A
- movement of both the crown and root simultaneously
- resorption on one aspect
- deposition on the other
- 150-200g force required
- secondary remodelling
- allows tooth to retain normal PDL width and stability
12
Q
What is intrusion in terms of tooth movement?
A
- movement of a tooth further into the alveolar bone
- pressure on supporting structs evenly distributed
- bone resorption occurs
- apical area
- alveolar crest
- 10-20g force required
- reduce risk of root resorption with light force
13
Q
What is extrusion in terms of tooth movement?
A
- movement of a tooth further out of the alveolar bone
- tension induced in supporting structures
- bony deposition to maintain tooth support
- tension induced in supporting structures
- 35-60g required
14
Q
What is rotation?
A
- rotation of a tooth in its socket
- wire bracket exerts force
- palatal or lingual surface attached to elastic chain
- 35-60g force required
15
Q
What is torque?
A
- root uprighting
- force couple around bracket
- results in apical torque
- 50-100g force required
