Biology of Tooth Movement
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define active stabilization
maturational shortening of collagen fibers which can cause teeth to move
how does the fluid in the PDL react to short/long duration loads
- Shock Absorber
- Heavy for <1 sec: alveolar bone bends. Piezo electric currents stimulate skeletal regen/repair
- Constant pressure: fluid rapidly leaves (after 3-5 sec w/ pain). causes remodeling of bone.
which theory of orthodontic tooth movement is used currently and define it
- Pressure-Tension theory: chemical signals act as a stimulus for tooth movement.
- 3 stages
- 1. alteration in blood flow associated with pressure w/i the PDL
- 2. release of chemical messengers
- 3. activation of cells
define undermining resorption
heavy forces causing necrosis of cellular elements of PDL. minimal tooth movement during a lag phase.
define front resorption
light pressures to move teeth used in ortho where the cells of the PDL survive. osteoclasts remove bone in pressure area and build bone on tension side.
define tipping movement
one point of force applied at the crown of the tooth, tooth rotates around center of resistance. pdl is compressed near apex and opposite side of the force. force shouldn't exceed 60g
define bodily movement
2 forces applied simultaneously so the PDL is loaded uniformly. twice as much force is required as tipping (120g).
list 3 predisposing factors for root resorption
- 1. abnormal tooth morphology
- 2. prolonged ortho forces
- 3. genetic predisposition
resistance to unwanted tooth movement.
define reciprocal and differential anchorage
reciprocal: forces applied to teeth are equal and so is force distribution in the PDL. larger tooth has larger area for force distribution
differential: tooth movement increases as pressure increases up to a point and may actually decline with extreme heavy pressure. more teeth in the anchor unit = more pressure.
explain reinforcing anchorage
adding more resistance units is effective bc more teeth are in anchorage with distributes the force over a larger PDL area.
where is the Crot during controlled tipping?
at the apex
where is the Crot during uncontrolled tipping?
slightly apical to Cres
where is the Crot during bodily tooth movement?
where is the Crot during root movement?
define a Moment
force acting at a distance from the Cres. produced when a force will cause some rotation. potential for rotation is measured as a moment.
two forces equal in magnitude and opposite in direction that are parallel and non-colinear. only a couple can produce pure rotation, no single force can produce a pure rotation
if a force is applied through the Cres, what type of movement results?
Translation/Bodily Movement. no rotation.
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