Appliances and Physiology of Tooth Movement Flashcards
what are the types of tooth movement
physiological (eruption of teeth and mesial drift)
orthodontic tooth movement
what is the physiological basis of orthodontics
if an external force is applied to a tooth the tooth will move as the bone around it remodels
what two situations can you not move teeth
if a tooth has no PDL or if it is ankylosed
what happens to every tooth you move orthodontically
there will be some degree of root resorption (root loss length of like 1-2mm)
what are the two theories for orthodontic tooth movement
differential pressure theory
mechano-chemical theory
what is the differential pressure theory
in area s of compression bone is resorbed and in areas of tension bone is deposited
what is the mechano-chemical theory
a description of what is happening at cell level
cells changing shape in PDL and adjacent alveolar bone which causes release of cytokines
cytokines cause target cells to secrete other mediators
what are cytokines
low molecular weight proteins that regulate the actions of target cells
what occurs after a force is applied to the tooth in the mechano-chemical theory
mechanical loading causes fluid movement in periodontal ligament membrane and osteocytes detect this and produce cytokines
the cytokines recruit osteoblasts to produce more cytokines which upregulate osteoblasts or RANKL
what two molecules act on the blood vessels to cause blood monocytes to fuse and form multinucleated osteoclasts in an area of compression
RANKL and CSF
what happens in areas of compression
osteoblasts bunch up together and expose the osteoid layer giving osteoclasts access to absorb the bone
what happens in areas of tension
the osteoblasts are flattened covering the osteoid layer and preventing osteoclasts from gaining access to the bone
what protein do osteoblasts also release
OPG
what is the action of OPG
prevents osteoclastic differentiation and prevents the activity
what are the types of orthodontic appliances
removable
fixed
functional
what type of tooth movement are removable appliances used for only
tipping or tilting
what tooth movement do functional appliances use
tipping
what are functional appliances used for and indications
skeletal problems
used while the patient is still growing
what type of tooth movement do fixed appliances cause
bodily movement
intrusion
extrusion
rotation
torque
what is bodily movement
crown and root moving at the same time
what is torque
almost like a tipping movement but the crown doesn’t move - looking for the root to move
what is the force you would want to use to tip a tooth
35 -60 grams
how do functional appliances work
using blocks to posture the jaws into a better occlusion which stretches facial muscles and transmits force to the teeth and alveolus
what changes occur when wearing a twin block
retroclination of upper incisors and proclinaiton of lowers
how long do patients need to wear a twin block
6-12 months continuously
what do twin blocks cause posteriorly
open bite
how would you fix a posterior open bite caused by twin block wear
ask patient to wear twin block only at night for 6 months and hope for continuous eruption
sometimes fixed appliances are needed
what occurs during bodily movement of a tooth
when fixed appliances are applied there is frontal resorption and then bony deposition on the opposite side
how much forces is needed for bodily movement
100-120 grams
what is intrusion of the teeth
pressure on the supporting structures evenly and bone resorption apically at alveolar crest
what does a high force when trying to intrude teeth cause
root resorption
use 10-20 grams
what is extrusion
tension is induced in supporting structures and bone deposition is necessary to maintain tooth support
how do you generate torque
engage rectangular wire in rectangular bracket
what occurs on pressure side of the tooth when moving teeth
hyperaemia of blood vessels
osteoclasts increase activity to resorb bone
why is there time left between applying force on the teeth
so there is time for PDL to remodel
what occurs in light forces
hyperaemia with PDL
appearance of osteoclasts and osteoblasts
resorption and deposition
remodelling of socket
PDL fibres reorganise
what occurs to gingival fibres when moving teeth
they remain distorted - this is why teeth try to relapse after ortho treatment
what are moderate forces
occlusion of vessels on the pressure side - no cells due to this so there is no deposition or resorption - period of stasis
what do you have to wait for in moderate forces
osteoclasts coming in to resorb bone - this can take a number of days
what are excessive forces
causes pain
necrosis and undermining resorption takes place resulting in permanent changes
causes root resorption
anchorage loss
what is anchorage
resistance to unwanted tooth movement
what are the factors that affect response to orthodontic force
magnitude of force
duration
age
anatomy
when should appliances be worn ideally
24/7
when can we not move teeth
if there is no bone
what is alveolar necking
when there is not a tooth in that aspect of the bone and the cortical plates of the bone are much closer together in this area
can we orthodontically treat RCT teeth
yes if there is an intact PDL
what are side effects of ortho treatment
pain and mobility
pulpal changes
root resorption
loss of alveolar bone support
relapse
how much should teeth move between visits
1mm per month
