Physiology of Tooth Movement and Appliances Flashcards
what is bone remodelling mediated by
PDL
what happens if a tooth has no PDL or is ankylosed
will not move
what is the mechano-chemical theory
cell shape changes within the PDL and adjacent alveolar bone which initiates signalling interactions between cells
what happens in the mechano-chemical theory
mechanical loading
stretching and compression of PDL fibres
osteocytes detect bone distortion and produce cytokines to recruit osteoblasts and clasts for bone resorption
macrophages produce IL1
osteoblasts produce prostaglandins and leukotrienes
fibroblasts produce MMPs
on a cellular level what happens in areas of compression
osteoblasts bunch up together and expose the osteoid layer giving osteoclasts access to resorb the bone
osteoblasts send signals to osteoclasts to recruit and activate osteoclasts
on a cellular level what happens in areas of tension
osteoblasts are flattened covering the osteoid layer and prevents osteoclasts from gaining access to the bone
osteoblasts secrete collagen and other proteins which secrete hydroxyapatite crystals which forms new bone
what does osteoprotegerin do
prevents osteoclastic differentiation and suppresses their activity
what regulates bone remodelling
amount of RANKL produced and amount of OPG produced
what is the role of orthodontists
utilise inflammatory response which occurs in PDL
use appliances to transmit force to PDL and bone
manage patient carefully through periods of resorption and repair of bone
what are the types of orthodontic appliances
removable
functional
fixed
what are the types of tooth movement
tipping
bodily movement
intrusion
extrusion
rotation
torque
how do functional appliances work
mandible postured away from normal rest position
facial musculature stretched which generates forces to teeth and alveolus
what effect can functional appliances have on facial growth
restrict maxillary growth
promote mandibular growth
remodel glenoid fossa
what is the skeletal change with functionals
30% change - growth of mandible and restraint of maxilla
what is the dentoalveolar change with funtionals
70% change - retroclination of upper teeth, proclination of lower teeth
what is the mode of action with functionals
skeletal change
dentoalveolar change
mesial migration of lowers
distal migration of uppers
achieving class 1
what does secondary remodelling allow
tooth to retain PDL width and stability
what is bodily movement
moving the tooth as a whole
what happens with intrusion
pressure on supporting structures evenly distributed and bone resorption necessary at apical area and alveolar crest
what happens with extrusion
tension induced in the supporting structures and bone deposition necessary to maintain tooth support
what is the force needed for tipping a tooth
35-60g
what is the force needed for bodily movement
150-200g
what is the force needed for intrusion
10-20g
what is the force needed for extrusion
35-60g
what is the force needed for rotation
35-60g
what is the force needed for torque
50-100g
what type of resorption does light force movement result in
frontal resorption
when applying light force to a tooth what happens to the PDL
hyperaemia (increased blood flow)
what happens on the pressure side when applying light force
resorption of lamina dura
what happens on tension side when applying light force
apposition of osteoid on tension side
what is the remodelling of the socket in light force movement driven by
frontal resorption
what happens to periodontal fibres during light force
reorganise
when applying a moderate force what happens to the blood vessels
occlusion of vessels of PDL on pressure side
hyperaemia of vessels of PDL on tension side
what is hylinisation
cell free areas
when does hylinisation occur
during moderate forces
what type of resorption happens with moderate forces
undermining resorption
what is undermining resorption
increased endosteal vascularity
what is the movement of the tooth during moderate force movement
rapid movement with bone deposition on tension side - tooth can loosen
what does light force movement allow for
slow continuous tooth movement
what does moderate force movement mean for tooth movement overall
rapid movement initially then 10-14 days with little movement while undermining resorption occurs
what are the unwanted side effects of excessive forces
pain
necrosis and undermining resorption
root resorption
anchorage loss
possible loss of tooth vitality
what factors affect the response to orthodontic force
magnitude
duration
age
anatomy
what anatomical structures affect response to force
no bone
soft tissues
mid palatal suture
what are the deleterious effects of orthodontic force
pain and mobility
pulpal changes
root resorption
loss of alveolar bone support
relapse
how much movement do we want to see per month
one mm
how long is treatment for fixed appliances
24 months
