Biomechanics and Tooth Movement

Question 1

Physiological

Answer 1

Pre-Eruptive
Eruptive
Post-eruptive

Question 2

Pre-eruptive movements

Answer 2

Early eruption generally occurs on lingual surface when there is a lack of space

Question 3

Eruptive movements

Answer 3

~ 1mm per month

Question 4

Post eruptive movements

Answer 4

Accomodate for growing jaws
Compensate for occlusal wear
Compensate for inter proximal wear e.g mesial drift

Question 5

Growing jaws

Answer 5

Teeth move to adapt to growth

Question 6

Occlusal wear seen as

Answer 6

Not as much nowadays due to change in diet

Thickened cementum

Question 7

Mesial drift

Answer 7

May be responsible for late incisal crowding e.g from unerupted 3rd molars

Question 8

PDL involvement

Answer 8

Needs to be vital

Vital nerve not required - root filled teeth can be moved

Question 9

Cells of PDL

Answer 9

Osteoclasts - remove bone
Osteoblasts - create new bone where teeth have been moved
Other cells important in bringing about biochemical changes e.g ectomesenchymal cells, ECRM

Question 10

Extracellular compartment

Answer 10

Fibres - fibrotomy

Ground substance

Question 11

PDL fibres

Answer 11

Collagen

Question 12

Ground substance

Answer 12

Glycosaminoglycans
Glycolipids
Glycoproteins

Question 13

Bone resorption

Answer 13

Spring e.g applied to mesial aspect means pressure on mesial side and tension on distal

Question 14

Pressure side - what occurs here

Answer 14

Pressure on opposite sides leads to differentiation of osteoclasts at these sites

Question 15

Tension side - what occurs here

Answer 15

Tension side is where bone deposition occurs

Question 16

Initial compression

Answer 16

tooth moves within PDL

Question 17

Delay phase occurs due to

Answer 17

recruitment of osteoclasts

Question 18

tooth movement

Answer 18

PDL is populated by new cells
osteoclasts derived from vascular system
Vascular system compressed slightly –> biochemical response
Bone resorption
Collagen fibre remodelling

Question 19

Duration of force

Answer 19

Effectiveness becomes more every time force is applied

Question 20

Force levels are either

Answer 20

Optimum

Excessive

Question 21

Optimum forces 1

Answer 21

Electrical signal where alveolar bone bends
PDL fluid expressed, tooth moves into PDL space
Vessels compressed to distort fibres and cells
Chemical mediators released
Metabolic changes
Tooth movements as osteoclasts and blasts enter space

Question 22

Optimum force - where should oblasts and oclasts ideally be derived from and why?

Answer 22

Ideally want osteoblasts and clasts to be derived from vessels within PDL as still patent

Question 23

Excessive Force 1
Some areas always exist where there is no blood flowing through
Complete loss of blood vessels in PDL
Osteoclasts recruited from endosteal surface of bone

Process of loss of blood flow?

Answer 23

PDL incompressible, AB bends
Tooth moves
Blood vessels occluded
Blood flow cut off to compressed PDL area
Cell death in this area
Cell differentiation cannot occur here therefore resorption is undermined
Undermining resorption removes lamina dura adjacent to compressed PDL

Question 24

Light force involves

Answer 24

Resorption from PDL side

Question 25

Heavy force involves

Answer 25

Resorption from endosteal side

Question 26

Excessive force can result in

Answer 26

Delay in movement
Pain 
loss of vitality 
mobility 
root resorption 
loss of anchorage

Question 27

Optimum force depends on

Answer 27

Size of root
type of movement
continuous or intermittent force

Question 28

Force generally applied onto

Answer 28

One tooth to the other
Anchor tooth - teeth respond to pressure
Moving tooth

Question 29

Types of tooth movement

Answer 29

Tipping R F
bodily movement F
rotation F
torque F
VERTICAL IE extrusion+ INTRUSION F

Question 30

Fully controlled movement needs

Answer 30

Needs attachment to tooth