Biomechanics and Tooth Movement Flashcards
Physiological
Pre-Eruptive
Eruptive
Post-eruptive
Pre-eruptive movements
Early eruption generally occurs on lingual surface when there is a lack of space
Eruptive movements
~ 1mm per month
Post eruptive movements
Accomodate for growing jaws
Compensate for occlusal wear
Compensate for inter proximal wear e.g mesial drift
Growing jaws
Teeth move to adapt to growth
Occlusal wear seen as
Not as much nowadays due to change in diet
Thickened cementum
Mesial drift
May be responsible for late incisal crowding e.g from unerupted 3rd molars
PDL involvement
Needs to be vital
Vital nerve not required - root filled teeth can be moved
Cells of PDL
Osteoclasts - remove bone
Osteoblasts - create new bone where teeth have been moved
Other cells important in bringing about biochemical changes e.g ectomesenchymal cells, ECRM
Extracellular compartment
Fibres - fibrotomy
Ground substance
PDL fibres
Collagen
Ground substance
Glycosaminoglycans
Glycolipids
Glycoproteins
Bone resorption
Spring e.g applied to mesial aspect means pressure on mesial side and tension on distal
Pressure side - what occurs here
Pressure on opposite sides leads to differentiation of osteoclasts at these sites
Tension side - what occurs here
Tension side is where bone deposition occurs
Initial compression
tooth moves within PDL
Delay phase occurs due to
recruitment of osteoclasts
tooth movement
PDL is populated by new cells
osteoclasts derived from vascular system
Vascular system compressed slightly –> biochemical response
Bone resorption
Collagen fibre remodelling
Duration of force
Effectiveness becomes more every time force is applied
Force levels are either
Optimum
Excessive
Optimum forces 1
Electrical signal where alveolar bone bends
PDL fluid expressed, tooth moves into PDL space
Vessels compressed to distort fibres and cells
Chemical mediators released
Metabolic changes
Tooth movements as osteoclasts and blasts enter space
Optimum force - where should oblasts and oclasts ideally be derived from and why?
Ideally want osteoblasts and clasts to be derived from vessels within PDL as still patent
Excessive Force 1
Some areas always exist where there is no blood flowing through
Complete loss of blood vessels in PDL
Osteoclasts recruited from endosteal surface of bone
Process of loss of blood flow?
PDL incompressible, AB bends
Tooth moves
Blood vessels occluded
Blood flow cut off to compressed PDL area
Cell death in this area
Cell differentiation cannot occur here therefore resorption is undermined
Undermining resorption removes lamina dura adjacent to compressed PDL
Light force involves
Resorption from PDL side
Heavy force involves
Resorption from endosteal side
Excessive force can result in
Delay in movement Pain loss of vitality mobility root resorption loss of anchorage
Optimum force depends on
Size of root
type of movement
continuous or intermittent force
Force generally applied onto
One tooth to the other
Anchor tooth - teeth respond to pressure
Moving tooth
Types of tooth movement
Tipping R F bodily movement F rotation F torque F VERTICAL IE extrusion+ INTRUSION F
Fully controlled movement needs
Needs attachment to tooth
