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Ortho II > Biomechanics > Flashcards

Biomechanics Flashcards

1
Q

Define mechanics

A

The branch of physics that is concerned with the analysis of the action of forces on matter or material systems

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2
Q

Define biomechanics

A
  • Application of mechanical principles on living organisms
  • Includes research and analysis of the mechanics of living organisms and the application of engineering principles to and from biological systems
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3
Q

Define wire

A

Metallic strand stretched by tensile forces

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4
Q

Active use of orthodontic wires? (2)

A
  • Archwires

- Coils or springs

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5
Q

Passive use of orthodontic wires? (3)

A
  • Retention: adams clasp, ball clasp, arrowhead clasp
  • Stabilization: labial wire spring (labial bow)
  • Ligatures
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6
Q

What is an archwire?

A

Metallic strand shaped according to a diagram that reproduces ideal dental arch
form

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7
Q

What is Hooke’s law?

A

The displacement or size of the deformation is directly proportional to the deforming force or load. Under these conditions the object returns to its original shape and size upon removal of the load

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8
Q

What are the physical properties described in biomechanics? (6)

A
  • Hooke’s law
  • Springiness
  • Stiffness
  • Resilience
  • Formability
  • Range
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9
Q

Formula for Hooke’s law?

A

K=stress/strain

K- elastic modulus/young’s modulus
stress = force
strain = deflection

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10
Q

What is hooke’s law measured in?

A

Megapascals (MPa)

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11
Q

Formula for force?

A

F=K*Deflection

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12
Q

What happens if force is greater than deflection?

A

stiffness

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13
Q

What happens if deflection is greater than force?

A

Springiness

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14
Q

Define stiffness

A

The extent to which it resists deformation in response to an applied force

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15
Q

Define springiness (2)

A
  • aka elasticity

- Property of materials which return to their original shape after they are deformed.

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16
Q

Define resilience

A

Energy storage capacity of the wire, which is a combination of strength and springiness

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17
Q

Define formability

A

Amount of permanent deformation that a wire can withstand before failing

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18
Q

Define deflection

A

If the wire is deflected beyond its yield strength, it will not return to its original
shape, but clinically useful springback will occur unless the failure point is reached.

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19
Q

Define range

A

Distance that the wire will bend elastically before permanent deformation occurs

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20
Q

Biocompatibility properties of an ideal wire? (3)

A
  • Corrosion resistant
  • Dental plaque
  • Environmental stability
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21
Q

What are the types of forces? (3)

A
  • Tensile (traction and compression)
  • Torsion
  • Bending
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22
Q

How can you classify wires? (3)

A
  • cross-sectional shape
  • size (cross sectional diameter)
  • alloys
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23
Q

What are the cross-sectional wire shapes? (5)

A
  • Round
  • Multistrand
  • Square
  • Rectangular
  • Others: Semicircular, oval
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24
Q

Convert mm to inches

A

multiply by 4 and divide by 100

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25
Q

Convert inches to mm

A

multiply by 100 divide by 4

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26
Q

What are the types of wire alloys? (4)

A
  • Gold and precious metal
  • Stainless steel
  • Cobalt Chromium alloy
  • Titanium alloys
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27
Q

What is the composition of stainless steel alloy wire? (4)

A
  • iron and carbon alloy
  • 18% chromium
  • 8% nickel
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28
Q

Stainless steel martensitic? (3)

A

Body centered cubic

  • stronger and more resistant
  • instruments
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29
Q

Stainless steel austenitic A-300? (5)

A

Face centered cubic

  • Springiness (Depends on diameter)
  • formability
  • good properties
  • most used
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30
Q

Advantages of stainless steel wires? (6)

A
  • Formability
  • Reasonable degree of stiffness/springiness
  • Low cost
  • Low superficial friction
  • Can be soldered and welded
  • Corrosion resistant
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31
Q

Disadvantages of stainless steel wires? (4)

A
  • High Young’s modulus
  • Intense deactivation curve
  • Nickel release
  • Difficult clinical management
32
Q

What is the composition of cobalt chromium alloy wires?

A
  • 40% Co
  • 20% Cr
  • 15 % Ni
  • Iron
  • Mo (Molybdenum)
33
Q

What is another name for cobalt chromium alloy wires?

A

Elgiloy

34
Q

Cobalt chromium alloy wires are ______ stiff than stainless steel

A

less

35
Q

Which wire type has the greatest formability?

A

cobalt chromium alloy wires

36
Q

How many different grades with different properties do cobalt chromium alloy wires have?

A

4

37
Q

Which cobalt chromium alloy wire can be soldered?

A

Blue eligiloy

38
Q

How much are cobalt chromium alloy wires used?

A

little use

39
Q

What are the different generations of titanium alloy wires? (4)

A
  1. Nitinol or M - NiTi
  2. Beta Titanium. TMA (Titanium Molybdenum alloy)
  3. A – NiTi
  4. Copper NiTi
40
Q

What is NiTi composed of?

A
  • 54% titanium

- 44% Nickel

41
Q

What is the structure of NiTi? (3)

A

Two criystallographic structures
• Austenitic. Cubic crystal. Stable. “High temperatures”
• Martensitic. Monoclinic crystal,, hexagonal. Unstable. Low temp.

42
Q

Austenitic of Ni Ti?

A
  • Cubic crystal.
  • Stable.
  • “High temperatures”
43
Q

Martensitic of Ni Ti?

A
  • Monoclinic crystal
  • Hexagonal
  • Unstable
  • Low temp
44
Q

Phase transitions of NiTi in response to… ? (2)

A
  • reasonable temperature
    changes
  • applied force
45
Q

NiTi elasticity? (2)

A
  • Superelasticity

- Thermoelasticity

46
Q

NiTi memory?

A

Shape

47
Q

NiTi hookes law? (2)

A

Non-elastic force-defelction curve

don´t obey Hooke’s law

48
Q

What happens when there is a phase transition from austenitic to martensitic? (5)

A

changes crystal’s structure, volume, shape and

properties WITHOUT atomic strain

49
Q

How do wires change from austenitic to martensitic? (2)

A

In response to applied forces or cooling

50
Q

How do wires change from martensitic to austenitic?

A

Martensitic phase is unstable so it returns to austenitic structure with the ideal dental arch form

51
Q

What is shape memory?

A

Ability of the material to “remember” its original shape after being plastically deformed while in the martensitic form

52
Q

What is superelasticity or pseudoelasticity?

A

Elastic (reversible) response to an applied stress, caused by a phase transformation between the austenitic and martensitic phases of a
crystal (fails Hooke’s law)

53
Q

What is thermoelasticity?

A

Great “elastic” deflection that reverts in response to temperature changes

54
Q

Look at slide 51/61

A

and figure out what its for

55
Q

M-NiTi general characteristics? (5)

A
  • Stabilized martensitic form
  • No phase transition effects
  • Great shape memory
  • Much more springiness than stainless steel
  • No formability
56
Q

TMA general characterisitcs? (4)

A
  • Titanium-molybdenum alloy
  • Nickel free
  • Formability-elasticity
    (More springiness than stainless steel
    Less formability than stainless steel)
  • Little use: Springs of some appliances (pendulum)
57
Q

A-NiTi characterisitcs? (4)

A
  • Not stabilized
  • Phase transition in response to applied force
  • Superelasticity
  • Light, continuous, predictable forces
58
Q

Copper NiTi (5)

A
  • Thermoelasticity
  • Copper allows control of transition temperature.
  • From austenitic form to martensitic by cooling, without atomic strain.
  • Rising temperature makes the wire return to austenite and ideal arch form.
  • Austenite transition temperatures: 27, 35 y 40ºC
59
Q

Deactivtation graphs

A

slide 56/57

60
Q

Clinical characterisitcs of A-NiTi, Niti-Cu? (5)

A
  • Light, continuous, constant, predictable forces
  • Easy clinical management
  • Shorter chair time
  • More time between appointments
  • Easy to get out of control. Iatrogenic
61
Q

Formability of the types of titanium wires in order? (5)

A
  • 1º Cr -Co
  • 2º Acero
  • 3º TMA
  • 4º M- NiTi
  • 5º A-NiTi
62
Q

Springiness of the types of titanium wires in order? (5)

A
  • 1º NiTi - Cu
  • A-NiTi
  • 2º M-NiTi
  • 3ºTMA
  • 4º Cr -Co
  • 5º Acero
63
Q

Effects of length and diameter on elastic properties?

A

The force needed to deflect a wire (stiffness) is directly proportional to the fourth power of diameter and inversely proportional to the third power of length

64
Q

Formula for stiffness?

A

Stiffness = d^4
or
Stiffness = 1/(L^3)

65
Q

Formula for springiness

A 
Springiness = 1/(d^4)
Springiness = L^3
66
Q

Round wire? (2)

A
  • Initial stages of treatment

- Crown alignment and leveling

67
Q

Multistrand wire? (2)

A
  • Initial stages of treatment

- Crown alignment and leveling

68
Q

Square wire?

A

Harder to bend because there is more volume

69
Q

Rectangular wire? (5)

A
  • Used in final stages of orthodontic treatment
  • Causes very small teeth movements
  • ex. changes in inclination of roots
  • Torque control
  • Radicular movements
70
Q

Rounded wire size 0.008-0.012

A

Ligatures (fragility)

71
Q

Rounded wire size 0.012-0.020

A

Archs (springiness)

72
Q

Rounded wire size 0.020-0.045

A

Auxiliary appliances (formability)

73
Q

Rounded wire size 0.045-0.060

A

Intra/extra oral appliances (stiffness)

74
Q

Multistrand wire size 0.015-0.021

A

Archs

75
Q

Square wire size 0.016-0.018 x 0.016-0.018

A

Archs

76
Q

Rectangular wire size 0.016-0.018 x 0.022

A

Archs - Bracket slot (0.018”)

77
Q

Rectangular wire size 0.017-0.022 x 0.025

A

Archs - Bracket slot (0.018”)

Ortho II (6 decks)

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