Tooth Movements & Types of Orthodontic Appliances Flashcards
What are the two types of tooth movement ?
Physiological and orthodontic.
What are two types of physiological tooth movement ?
Tooth eruption.
Mesial drift.
What mediates bone remodelling ?
PDL compression and tension.
What are the two theories of tooth movement ?
Differential pressure theory.
Mechano-chemical theory.
Explain differential pressure theory.
Areas of compression are resorbed by osteoclasts.
Areas of tension, bone deposition occurs via osteoblasts.
Explain mechano-chemical theory.
Fluid movement in bony caniculi occurs as a result of tension and compression in PDL - osteocytes detect this and recruit osteoblasts and osteoclasts via cytokines and fibroblasts in bone produce MMPs which breakdown ECM.
The ratio between what two enzymes regulates bone remodelling ?
RANKL : OPG.
What is the function of OPG ?
Prevents osteoclast differentiation and so lowers osteoclastic activity.
What type of tooth movement can be achieved using functional or upper removable appliance ?
Tipping tooth movement.
What are the 6 types of tooth movement a orthodontic appliance can generate ?
Tipping.
Bodily tooth movement.
Intrusion.
Extrusion.
Torque.
Rotation.
What types of tooth movement can only be resolved by fixed appliances ?
Intrusion.
Extrusion.
Torque.
Rotation.
Bodily tooth movement.
How does a functional appliance work ?
Mandible postured away from normal rest position causing stretch of facial musculature, stretch is transmitted onto teeth and alveolus.
What skeletal class should twin block appliance be used for ?
Correction of Class 2 malocclusion.
How long does a twin block appliance have to be worn for to see results ?
6-12 months.
What does a twin block appliance aim to do in terms of bone growth i.e. skeletal change ?
- Decrease maxilla growth.
- Increase mandibular growth and mandibular length.
- Remodel glenoid fossa allowing mandible to sit more anteriorly in skull base.
What does a twin block appliance aim to do in terms of tooth movement i.e. dentoalveolar change ?
- Retroclination of upper teeth.
- Proclination of lower teeth.
- Create posterior open bite.
- Posterior open bite fixed with fixed appliances or naturally by continued eruption of maxillary molars.
In terms of change seen after use of twin block appliance, what percentage is deemed to be skeletal changes ?
30%.
In terms of change seen after use of twin block appliance, what percentage is deemed to be dentoalveolar changes ?
70%.
When does secondary bone remodelling occur ? Why does it happen ?
During bodily tooth movement.
Maintains PDL and stability of tooth.
What is the optimum tipping force for teeth during orthodontic treatment ?
35-60g.
What is the optimum bodily movement force for teeth during orthodontic treatment ?
150-200g.
What is the optimum intrusion force for teeth during orthodontic treatment ?
10-20g - to prevent root resorption.
What is the optimum extrusion force for teeth during orthodontic treatment ?
35-60g.
What is the optimum rotation force for teeth during orthodontic treatment ?
35-60g.
What is the optimum torque force for teeth during orthodontic treatment ?
50-100g.
What magnitude of force is desirable for orthodontic tooth movement ?
Light forces.
What are the side effects of moderate-excessive orthodontic tooth forces ?
Pain.
Loss of tooth vitality,
Root resorption.
Anchorage loss.
What is the length of stasis period seen in orthodontic tooth movement where moderate-excessive forces have been transmitted ?
10-14 days.
What factors affect response to orthodontic tooth movement ?
Age.
Magnitude of forces.
Anatomy.
Duration of treatment.
What is the main cause of orthodontic relapse ?
Poor reorganisation of supracrestal fibres.
What are the risks of orthodontic force ?
Pain.
Mobility.
Pulpal changes.
Root resorption.
Loss of alveolar bone support.
Relapse.
How many mm of tooth movement is desirable within one month ?
1mm.
What is the expected treatment time for fixed appliance orthodontic treatment ?
24 months.
What histological effects can be seen as a result of excessive orthodontic force ?
Extensive lateral root resorption.
Undermining resorption.
PDL necrosis.
