Biomechanics of Tooth Movement Flashcards
When can physiological tooth movement occur?
Pre-eruptive, eruptive, post-eruptive
Types of tooth movement?
Physiological, orthodontic
What is pre-eruptive tooth movement?
Lingual or palatal direction
What rate does eruptive tooth movement occur at?
1mm per month
Why does post-eruptive tooth movement occur?
Accomodate growing jaws (teeth move to adapt to growth)
Compensate occlusal wear
Compensate for interproximal wear
What are resting forces?
Teeth are usually in position of stability between soft tissues - forces applied but balanced and light
Definition of orthodontic movement?
Pathological process from which tooth usually recovers
What is PDL?
Periodontal ligament
Made of cells and extracellular component
Need vital PDL to move teeth (can move root filled)
If ankylosed virtually impossible
What cells make up PDL?
Osteoblast - make new bone
Osteoclast - remove bone
Osetoblast, osetoclast, cementoblasts, epithelial cell rests of Malassez, macrophages, undifferentiated mesenchymal cells
EMU COO
What makes up ligament fibres in PDL?
Collagen fibres bundles
Oxytalan fibres
What makes up extracellular matrix in PDL?
Fibres - type I collagen
Ground substance: glycosaminoglycans, glycoproteins, glycolipids
What forces placed on moving tooth?
Pressure side and tension side
Pressure side
- Differentiation of osteoclast = bone resorption
- Collagen fibre remodelling
Tension side
- Bone deposition
- Collagen fibre remodelling
3 stages in rate of tooth movement?
- Initial compression
- Delay phase (2-14 days)
- Tooth movement
What happens during initial compression?
Tooth move through PDL
What happens during delay phase?
Loss of cells from area - no movement possible
New cells move into area
What happens during tooth movement?
PDL populated by new cells
Bone resorption and collagen fibre remodelling
What does mechanical stress, compression and tension cause?
Mechanical stress= intracellular response
Compression = bone resorption
Tension = bone deposition
What affects does force have from initial force to 2 days?
<1 sec = PDL fluid incompressible, alveolar bone bend, piezoelectrical signal generated
1-2 sec = PDL fluid expressed, tooth move in PDL space
3-5 sec = Blood vessel compressed pressure side and dilated on tension side, PDL fibres and cells distorted
Minutes = blood flow altered, oxygen tension changes, chemicals released
Hours = metabolic changes, cell diff begins
2 days = tooth movement begin as osteoblast/clast within PDL remodelling bony socket
What happens if excessive force is placed?
Complete loss of blood vessels in PDL - eventually osteoclast recruited from endosteal surface of bone
What happens if excessive forces placed from initial to 2 days?
> 1 sec = PDL fluid incompressible, alveolar bone bend, piezoelectric signal generate
1-2 sec = PDL fluid expressed, tooth move in space
3-5 sec= blood vessel in PDL occluded on pressure side
Minutes = blood flow cut off compressed side
Hours = cell death compressed area
3-5 days = cell differentiation in adjacent space = undermining resoprtion
7-14 days = undermining resorption removed lamina dura adjacent compressed PDL - tooth movement
What does excessive force cause - clinically?
Delay tooth movement Pain Loss vitality Mobility Root resorption Loss anchorage
What is the ideal optimum force?
20-25/cm2
table of optimum force for each tooth movement in notes
Which 2 types of tooth movement require more force?
Bodily movement
Root uprighting
Definition of pressure?
Force per unit root area
What is orthodontic anchorage?
Control unwanted tooth movement
Teeth respond to pressure
Types of tooth movement?
Tipping Bodily Rotation Torque Vertical - extrusion/ intrusion
