mech principles in controlling ortho force Flashcards
why change ruber bands each day
Lose eleasticity
how is a crozat appliance activated
Each time you go to the dentist
is gold a good spring
No
what do we use as ortho appliances today
Ni-Ti
Beta- ti
what is the future of ortho appliances
plastics
what are the properties of materials for ortho
strength
stiff/spring
range
what is the proportional limit
the point at which the wire begins to deviate from elastic behavior
what is yield strength
point at which a measurable deviation is observed
what measurment is often shown as the strength of anortho wire
yield strngth
what is the goal of an ortho springs mech properties
high strength
best springiness
best range
what is resilinece
the area under the curve up to the proportional limit
what is formability
area under curve betwen ultimate tensile strenth and failure
what is a cantilever beam
attached at one end
what is a supported beam
attached at both ends
how does doubling a cantilever beam thickness change its physical properties
(2d/d)^3 in stregth
(d/2d)^4 in spring
(d/2d) in rnage
how does doubling a supported beam change physical properites
puts the coefficient in front of the eq
how does doubling length for a cantilever beam affect it
1/2 strength
springiness 8 times
range in creased 4 times
how does one increase springiness and increase change in an ortho wire
lengthening via loop in wire
how can you increase strngth and sprininess
long wire with loops to increase betwwn individual teth
what does a superelasticity mean
violates hoos law
Why is superelasticit possible
materials undergo phase transition witha change in temp or internal stress
how can superelasticity exist in the mouth
Due to the material phase change being close in temp to the mouth
what material is used in ortho
NiTi with a temp transition like that in mouth
how can one reactivate superelastic wire
releasing it then putting it back
what the problem with super elastic wire
zero formability
what is superelastic wire super useful for
Tipping
rotation
extrusion
crowded/irregular teeth
what is a moment
a force delivered at a distance from the objects center of resistance
what creates a pure moment
2 equal forces in opposite directions
how can you cancel the moment to get bodily movement
Provide force in the oposite direction to the moment in equal magnitude as the moment force
what happens as the Mc/Mf ratio becomes more possitive
center of rotation is displaced from center of center of resistance
what does it mean when the Mc/Mf=1
tooth moves bodily
center of of rotation is infinately away from center of reistance
how do you do anything but tip a tooth
use a fixed attachment
2 points of contact
how does one create Facio-lingo torque
use a rotated wire within a rectangle slot
how must wire change when you wnat to slide a tooth
must have a smaller wire to allow for less friction and a wider braket
what is the major source of resistance to sliding
corner of the bracket touching, not friide the gowth of jawsction
what are the types of removable appliance
Functional for growth mod
Activate plates with finger springs and screws for minor toothmovemnt
clear aligners for types of malocclusion in adult
what is the goal of functional appliances
Guided growth
what are the spring properties of screws
Almost zero, so must be screwed every couple days
how far does one turn of skrew open plate
.25mm
when to use an active plate
produce more physiologic force overa range with tipping force being the main concern
should you use invisiline if you need to extract teeth
No
what tooth movements does invisiline not work well with
rotation
extrusion
what is the basis for all fixed appliances
Angle’s edgewise appliance witha bracket in a rectangular slot
how is ortho bonding different than restorative
Ortho needs to me removed
what is the benifit of bonded breaks
vary thickness vary inclination vary torque - reduced wire bending - increased efficiency
what is the main feature of active-clip braket
springiness of clip adds to the springiness of the wire
what is the most common bracket
active-passive clip
what is an active passive clip
active when teeth are initially aligned, but create no more force when complete
what does a passive-clip bracket need for force
uses only the springiness of the wire to create forces
