Overview of Appliances & Physiology of Tooth Movement

Question 1

what are the 2 general types of tooth movement?

Answer 1

• physiological (tooth eruption, mesial drift, natural etc)
• orthodontic (applied external forces)

Question 2

what happens to a tooth when an external force is applied and how does the process occur?

Answer 2

tooth will move as the bone around it remodels

the remodelling is MEDIATED by the PDL

Question 3

what happens to orthodontic treatment if a tooth has NO PDL or is ankylosed?

Answer 3

tooth will NOT move

Question 4

what is the function of an osteoblast during bone remodelling?

Answer 4

areas where compression occurs (where the tooth wants to move), osteoblasts exposure the area so osteoclasts can resorb the bone. Use signals like RANKL which are for bone resorption

areas where theres tension (where tooth is being moved away from). The osteoblasts are flattened covering the osteoid layer so that osteoclasts CANNOT gain access to the bone. Osteoblasts also secrete proteins and hydroxyapatite forming new bone

Question 5

what is OPG and RANKL in bone remodelling?

Answer 5

RANKL - signals osteoclasts to breakdown bone
OPG - binds onto RANKL to PREVENT signalling from RANKL [similar to an inhibitor]

Question 6

what are the 3 types of orthodontic appliances?

Answer 6

• Removables (URA)
• Functionals
• Fixed

Question 7

what are the TYPES of tooth movement?

Answer 7

• tipping
• bodily movement
• intrusion
• extrusion
• rotation
• torque

Question 8

what is a functional appliances and how do they work?

Answer 8

removable brace which works on both upper & lower teeth to help correct protrusion of anteriors

facial muscles are stretched transmitting forces to the teeth and alveolus promoting growth.

[usually restricts maxilla from growing, and promoted mandible to balance occlusion]

[also retroclines uppers, proclines lowers]

Combined - achieving Class 1 occlusion

Question 9

how is entire bodily movement achieved of teeth?

Answer 9

through FIXED APPLIANCES (like braces etc)

Question 10

what are the biological effects of light forces on teeth?

Answer 10

• apposition of osteoid on tension side (blasts)
• resproption from pressure side (clasts)
• remodelling of socket
• PDL fibres reorganise
• hyperaemia within the PDL

Question 11

what are the biological effects of moderate forces on teeth?

Answer 11

• occlusion of vessels of PDL on pressure side
• hyperaemia on tension side
• period of stasis (inactivity)
• relatively rapid movement of tooth with deposition, tooth may be slightly loose
• Healing of PDL

Question 12

what are the biological effects of excessive forces on teeth?

Answer 12

• pain
• necrosis of tooth & pulp (vitality)
• root resorption
• loss of anchorage

Question 13

what are factors that affect the response to orthodontic force?

Answer 13

• magnitude (of force)
• duration
• age (older)
• anatomy (soft tissues, poor bone)