Physiology of Tooth Movement Flashcards
What are the types of tooth movement
physiological
orthodontic
What are the physiological tooth movements
tooth eruption
mesial drift
How is orthodontic movement done
through externally generated forces
What are the different movements in tooth eruption
pre-eruptive tooth movement intra-osseous eruption mucosal penetration pre-occlusal eruption post-occlusal eruption
What is the speed of pre-eruptive tooth movement
small and random
What is the speed of intra-osseous eruption
occurs after crown forms
slow
1mm takes around 3-24 months
What is the speed of mucosal penetration
fast
1mm takes about 2 weeks
What is the speed of pre occlusal eruption
slow
What is the speed of post occlusal eruption
very slow
What are the different tooth eruption theories
pulpal pressure
pulpal growth
fibroblast traction
blood vessel thrust
main 3:
root elongation
alveolar bone remodel
PDL formation
What is the process of tooth eruption
the dental follicle is the mediator for bone resorption
the bone and the deciduous root has to be resorbed for the tooth to come through
apical blood flow is important
collagen fibre cross linking is only important after eruption
parathyroid hormone receptor gene (PTHR1 and PPE)
How can orthodontics utilize tooth eruption
to minimize impact of a developing malocclusion
How can an ectopic upper permanent canine be treated
by interceptive extraction of the deciduous canine (10-13yrs)
How can permanent teeth be encouraged to erupt
if deciduous tooth is extracted at correct stage
1/3-2/3 of root development
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
if a tooth has no PLD or it is ankylosed it will not move
What is the bony remodeling seen in orthodontics mediated by
periodontal ligament
Why does bone resorb and cementum not in tooth movement
cementum is more resistant to resorption than bone
although some degree of root resorption after ortho should be expected
What does an orthodontist do
manages the growth and development of the teeth face and jaws
What are the 3 theories for orthodontic tooth movement
differential pressure theory
piezo electric theory
mechano-chemical theory
What is the differential pressure theory
The side of pressure’s PDL is under tension while the other is compressed
on the tension side there is bone deposition and the compression side there is bone resorption
What is the piezoelectric pressure theory
Piezoelectric currents are generated when crystalline structures, such as bone, are deformed
these currents have been suggested as the prime mechanism by which tooth movement is modulated
What is the mechano-chemical pressure theory
mechanical stress –> release of neuropeptides from nerve endings –> stimulate fibroblasts, endothelial cells and alveolar bone –> fibroblasts also communicate with osteoblasts and osteoclasts –> alveolar bone and PDL remodeling –> tooth movement
What are the types of ortho appliances
URA (removable)
functionals
fixed
What are upper removable appliances
made of acrylic and wire
can tip teeth
What is a functional appliance
growth modification device
twin block
good for class 2 division 1
What are the types of tooth movement
tipping bodily movement intrusion extrusion rotation torque
What is the ideal force for tipping
35-60 grams
What is tipping
the centre of rotation is around the middle of the tooth and as it tips it moves up
How do functional appliances work
mandible is postured away from usual rest position
facial musculature is stretched which generates forces transmitted to the teeth and alveolus
may be effect on facial growth
What is the mode of action of functionals
skeletal change (30%), growth of mandible, restraint of maxilla
dent-alveolar change (70%) retroclination of upper teeth, proclamation of lower teeth
mesial migration of the lower teeth
distal migration of the upper teeth
combination of the above achieves class I
What is the ideal force of bodily movement
150-200 grams
What is bodily movement
there is coordinated bone remodeling response leading and trailing the moving tooth
this mechanism allows a tooth to move relative to basilar bone while maintaining a normal functional relationship with its periodontist
What is the ideal force for intrusion
10-20 grams
What is intrusion
pressure on supporting structures is evenly distributed and bone resorption is necessary, particularly at the apical area and at the alveolar crest
What is the ideal force for extrusion
35-60
What is extrusion
tension is induced in the supporting structures and bone deposition is necessary to maintain tooth support
What is the ideal force of rotation
35–60 g
How is rotation achieved
two forces going in opposite directions
have stretched elastic module
stretched elastic chain on other side
What is apical root torque
root uprighting
What is the ideal force for apical root torque
50-100g
What happens with light force
hyperemia within the PDl
appearance of osteoclasts and osteoblasts
resorption of lamina dura from the pressure side via osteoclasts
apposition of osteoid on tension side via osteoblasts
remodeling of socket in frontal resorption
periodontal fibres reorganise
gingival fibres appear not to become reorganized but remain distorted
What happens with moderate force
occlusion of vessels of PDL on pressure side
hyperemia of vessels of PDL on tension side
cell free areas on pressure side (called hyalinization)
period of stasis
increased endosteal vascularity (undermining resorption)
relatively rapid movement of tooth with bone deposition on tension side - tooth may become slightly loose
healing of PDL - reorganization and remodeling
What happens with excessive force
necrsos undermining resorption resorption of root surfaces pain permanent change
What is the histological effects of excessive force
extensive lateral root resorption (RR) and undermining resorption (UR), just to the left of an area of PDL necrosis (N) is associated with the lag phase of tooth movement
What are factors affecting the respone to ortho force
magnitude
duration
age
anatomy
What anatomy can effect response to force
no bone - wasting/cleft
soft tissue mid palatal suture
What is the deleterious effects of ortho force
pain and mobility pulpal changes root resoprtion loss of alveolar bone support relapse
How much tooth movement per month is ideal
1mm
What is the treatment time for fixed appliances
24m
