Tooth movement

Question 1

What is centre of resistance?

Answer 1

The point in the body where the resistance to movement is concentrated. When moving a tooth, the force that is applied must hit its centre of resistance to enable it to move.

Question 2

Where is the centre of rotation found?

Answer 2

Single rooted tooth - halfway down the root surface

Multi-rooted teeth -found in the area of the root furcation.

Question 3

What is furcation?

Answer 3

Furcation is the area found at the dip of the root on multi-rooted teeth.

Question 4

What is force moment?

Answer 4

Causes rotational movement, the moment of a force is the component found within the force.

Question 5

What is force couple?

Answer 5

In fixed appliances when the archwire connects into a bracket slot, a force couple is created. A force couple will achieve the following movements:

Rotation
Inclination of teeth
Torque

Two equal and opposite forces produce a force couple which acts to cause rotation.

Question 6

What produces bodily movement?

Answer 6

Force couple and moment working together

Question 7

What are the types of tooth movement?

Answer 7

Tipping 30-60 g
Bodily 60 - 120g
Torque 50 - 100 g
Rotation 30- 60 g
Extrusion 30-60 g
Intrusion 10-20 g

Question 8

What are the two types of forces that can be applied to a tooth?

Answer 8

Optimum

Excessive

Question 9

What is the pressure tension theory?

Answer 9

When a force is applied to a tooth, it results in areas of compression (pressure) and tension within the PDL.
Bone is resorbed on the compression side and bone deposited on the tension side. This is the pressure/tension theory

Question 10

What are osteoblasts?

Answer 10

Found on tension side - 48 hours after force is applied
Deposit bone
Cells stretched and flattened
Recruit and activate osteoclasts

Question 11

What are Osteoclasts?

Answer 11

Found on pressure side - 48 hours after force is applied

Resorb bone in front of the root

Question 12

What are Osteocytes?

Answer 12

Used to be osteoblasts, turn into osteocytes in mineralised bone
Detect mechanical load on the bone

Question 13

What happens to the alveolar bone?

Answer 13

Allow physiological tooth movement (good)

Results in frontal resorption

Question 14

What are the chemicals which trigger cellular reactions?

Answer 14

Prostaglandins, cytokines and nitric oxide

Question 15

What are fibroblasts?

Answer 15

Cells that help remodel the PDL. They produce and destroy collagen fibres.

Question 16

What do cementoblasts do?

Answer 16

Form the cementum and deposit bone around it?

Question 17

What do cementoclats do?

Answer 17

Resorb the necrotic tissue and the cementum.

Question 18

What are the factors to consider for the rate of tooth movement?

Answer 18

Light ideal forces applied to teeth 24 hours a day
Continuous force is applied for at least 6 hours a day
1mm a month should be acheived
Every individual responds differently
Adult treatment is known to be slower

Question 19

What are the 3 different types of tooth germination?

Answer 19

Concresant
Fusion
Germination

Question 20

What is tooth germination?

Answer 20

When tooth teeth develop together and form one tooth

Question 21

What is tooth fusion?

Answer 21

Two individual teeth are fused together, each tooth has an individual pulp chamber and root canal

Question 22

What are the options for germinated teeth?

Answer 22

Extraction is the usual approach

If not very wide - may be considered to keep and use the tooth within the orthodontic treatment plan

Good OH must be adhered too as there is more risk of caries due to the joining of the enamel