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ortho > mech principles in controlling ortho force > Flashcards

mech principles in controlling ortho force Flashcards

1
Q

why change ruber bands each day

A

Lose eleasticity

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2
Q

how is a crozat appliance activated

A

Each time you go to the dentist

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3
Q

is gold a good spring

A

No

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4
Q

what do we use as ortho appliances today

A

Ni-Ti

Beta- ti

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5
Q

what is the future of ortho appliances

A

plastics

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6
Q

what are the properties of materials for ortho

A

strength
stiff/spring
range

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7
Q

what is the proportional limit

A

the point at which the wire begins to deviate from elastic behavior

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8
Q

what is yield strength

A

point at which a measurable deviation is observed

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9
Q

what measurment is often shown as the strength of anortho wire

A

yield strngth

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10
Q

what is the goal of an ortho springs mech properties

A

high strength
best springiness
best range

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11
Q

what is resilinece

A

the area under the curve up to the proportional limit

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12
Q

what is formability

A

area under curve betwen ultimate tensile strenth and failure

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13
Q

what is a cantilever beam

A

attached at one end

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14
Q

what is a supported beam

A

attached at both ends

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15
Q

how does doubling a cantilever beam thickness change its physical properties

A

(2d/d)^3 in stregth
(d/2d)^4 in spring
(d/2d) in rnage

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16
Q

how does doubling a supported beam change physical properites

A

puts the coefficient in front of the eq

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17
Q

how does doubling length for a cantilever beam affect it

A

1/2 strength
springiness 8 times
range in creased 4 times

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18
Q

how does one increase springiness and increase change in an ortho wire

A

lengthening via loop in wire

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19
Q

how can you increase strngth and sprininess

A

long wire with loops to increase betwwn individual teth

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20
Q

what does a superelasticity mean

A

violates hoos law

21
Q

Why is superelasticit possible

A

materials undergo phase transition witha change in temp or internal stress

22
Q

how can superelasticity exist in the mouth

A

Due to the material phase change being close in temp to the mouth

23
Q

what material is used in ortho

A

NiTi with a temp transition like that in mouth

24
Q

how can one reactivate superelastic wire

A

releasing it then putting it back

25
Q

what the problem with super elastic wire

A

zero formability

26
Q

what is superelastic wire super useful for

A

Tipping
rotation
extrusion
crowded/irregular teeth

27
Q

what is a moment

A

a force delivered at a distance from the objects center of resistance

28
Q

what creates a pure moment

A

2 equal forces in opposite directions

29
Q

how can you cancel the moment to get bodily movement

A

Provide force in the oposite direction to the moment in equal magnitude as the moment force

30
Q

what happens as the Mc/Mf ratio becomes more possitive

A

center of rotation is displaced from center of center of resistance

31
Q

what does it mean when the Mc/Mf=1

A

tooth moves bodily

center of of rotation is infinately away from center of reistance

32
Q

how do you do anything but tip a tooth

A

use a fixed attachment

2 points of contact

33
Q

how does one create Facio-lingo torque

A

use a rotated wire within a rectangle slot

34
Q

how must wire change when you wnat to slide a tooth

A

must have a smaller wire to allow for less friction and a wider braket

35
Q

what is the major source of resistance to sliding

A

corner of the bracket touching, not friide the gowth of jawsction

36
Q

what are the types of removable appliance

A

Functional for growth mod
Activate plates with finger springs and screws for minor toothmovemnt
clear aligners for types of malocclusion in adult

37
Q

what is the goal of functional appliances

A

Guided growth

38
Q

what are the spring properties of screws

A

Almost zero, so must be screwed every couple days

39
Q

how far does one turn of skrew open plate

A

.25mm

40
Q

when to use an active plate

A

produce more physiologic force overa range with tipping force being the main concern

41
Q

should you use invisiline if you need to extract teeth

A

No

42
Q

what tooth movements does invisiline not work well with

A

rotation

extrusion

43
Q

what is the basis for all fixed appliances

A

Angle’s edgewise appliance witha bracket in a rectangular slot

44
Q

how is ortho bonding different than restorative

A

Ortho needs to me removed

45
Q

what is the benifit of bonded breaks

A 
vary thickness
vary inclination
vary torque
 - reduced wire bending
 - increased efficiency
46
Q

what is the main feature of active-clip braket

A

springiness of clip adds to the springiness of the wire

47
Q

what is the most common bracket

A

active-passive clip

48
Q

what is an active passive clip

A

active when teeth are initially aligned, but create no more force when complete

49
Q

what does a passive-clip bracket need for force

A

uses only the springiness of the wire to create forces

ortho (22 decks)

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