Orthodontics - Physiology of Tooth Movement

Question 1

name the types of tooth movements. (2)

Answer 1

physiological:
eruption
mesial drift

orthodontic

Question 2

name the 2 subgroups of physiological tooth movement.

Answer 2

tooth eruption

mesial drift

Question 3

list the types of physiological tooth eruption movements. (4)

Answer 3

pre-eruptive

intra-osseous

mucosal

post occlusal

Question 4

describe when pre-eruptive movement occurs.

Answer 4

Starts when crown is forming, ends when crown is complete and root starts to form

Question 5

describe how quickly intraosseous movement occurs.

Answer 5

As soon as roots start to develop the tooth moves 1mm every 3 months

Question 6

describe how quickly mucosal movement occurs.

Answer 6

just reaches the mucosa and it come through really fast 1-2mm per month

Question 7

describe when post occlusal movement occurs, how fast is this?

Answer 7

Once tooth hits something hard i.e. the opposing tooth, the PDL becomes establish and there are very slow movements

Question 8

describe the suggested mechanism of tooth eruption. (3)

Answer 8

• Root elongation and pressure around the apex from secretions
• Alveolar bone remodelling and the action of the dental follicle
• Reorganisation of the PDL membrane fibres and the role of fibroblasts

Question 9

name the important factors in the eruption process. (3)

Answer 9

the dental follicle

apical blood flow

genetic factors i.e parathyroid receptor gene

Question 10

how do you analyse ectopic canines on a radiograph?

Answer 10

• Height
• Closeness to the midline/how much is it overlapping the adjacent tooth
• Angle : bad prognosis = > 30 degrees or horizontal

Question 11

what angle of an ectopic canine has poor prognosis?

Answer 11

> 30 degrees

horizontal

Question 12

what structure allows a tooth to move? (1)

Answer 12

a PDL

Question 13

name the mechanism responsible for orthodontic tooth movement?

Answer 13

Mechano-chemical pressure

Question 14

describe the Mechano-chemical pressure mechanism of orthodontic tooth movement. (5)

Answer 14

• Mechanical stress applied to the tooth there are areas compression and tension on the tooth
• Neuropeptides are released from nerve endings
• Neuropeptides stimulate fibroblasts, endothelial cells and alveolar bone.
• Fibroblasts communicate with osteoclasts and osteoblasts
• The activation of the osteoblasts and osteoclasts = alveolar bone and PDL remodelling

Question 15

where does resorption take place in tooth movement?

Answer 15

in areas of compression - in front of the tooth

Question 16

where does deposition take place in tooth movement?

Answer 16

in areas of tension - distal aspect of a tooth moving forward

Question 17

name the types of tooth movements that we can achieve. (6)

Answer 17

1. Tipping - URAS = 35-60g
2. Bodily movements – root moved with the crown 150-200g
3. Intrusion = 10-20g
4. Extrusion = 35-60g
5. Rotation = 35-60g
6. Torque = 50-100g

Question 18

what movement do URA’s use?

Answer 18

tipping

Question 19

how much pressure is required for tipping movements?

Answer 19

35 – 60g

Question 20

how much pressure is required for bodily movements?

Answer 20

150 - 200g

Question 21

describe bodily movements.

Answer 21

• Coordinated bone modelling and remodelling: allows resorption on one side and deposition on the other

Question 22

how much pressure is required for intrusion?

Answer 22

10-20g

Question 23

how much pressure is required for extrusion?

Answer 23

35-60g

Question 24

how much pressure is required for rotation?

Answer 24

35-60g

Question 25

how much pressure is required for apical torque?

Answer 25

50 – 100g

Question 26

name the histological changes occur in the application of light orthodontic forces?

Answer 26

Frontal Resorption

Question 27

name the histological change that occurs in the application of moderate orthodontic forces? (1)

Answer 27

undermining resorbtion

Question 28

what happens if excessive orthodontic force is applied? (5)

Answer 28

• Necrosis
• Undermining resorption
• Resorption of root surfaces
• Pain
• Permanent change

Question 29

what factors affect the response to orthodontic forces?

Answer 29

1. Magnitude (the force applied)
2. Duration of wear
3. Age
4. Anatomy

Question 30

what anatomical features influence the response to orthodontic treatment? (3)

Answer 30

• Volume of bone
- Alveolar neck (from lost teeth) composed of 2 dense cortical plates: takes a long time to move tooth through this bone.

• Effects of the tongue – acts against the appliances
• Digit habits

Question 31

what are the deleterious effects of orthodontics? (5)

Answer 31

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