1. Introduction to DMS Flashcards

1
Q

Mechanical properties of materials (3)

A

Forces
Stress
Strain

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2
Q

Types of forces (3)

A

Compressive
Tensile
Shear

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3
Q

What do forces cause when applied

A

Change in material shape (stretch/compress, deform, fracture)

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4
Q

Stress calculation

A

Stress (Pa/Nm2) = force (F) / unit area (A)

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5
Q

YM and rigidity relationship

A

Greater value of elastic modulus/YM, greater the rigidity (stiffness)

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6
Q

YM calculation

A

YM (MPa) = stress / strain

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7
Q

Typical biting forces

A

500-700N (50-70kg)

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8
Q

Definition of tensile force (2)

A

Grinding/chewing involves the tooth sliding along the surface of the other
Frictional forces are experienced - this is tensile force
(Abrasion involves the tooth grinding/sliding along the opposing tooth surface. The tooth is abraded (loss of material surface layers –> roughened surface))

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9
Q

Why does material need to adhere to enamel

A

If not, it will be removed by masticatory (shear) forces

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10
Q

Gradual increases in biting forces can cause

A

Fractures

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11
Q

Reason for most fatigues (2)

A

Most fatigues are not due to the application of a single load (force)
When repeated loads are applied, small flaws (cracks) in the material grow (propagate), allowing fracture when only a relatively small force is applied

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12
Q

Chemical properties of materials (3)

A

Setting time
Setting mechanism
Corrosive potential

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13
Q

Physical properties of materials (5)

A
Viscosity
Thermal conductivity
Thermal expansion
Density
Radiodensity
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14
Q

Definition of ideal material properties

A

Perfect or maximum characteristics of a material

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15
Q

Material failure mechanisms (9)

A
Fracture
Hardness
Abrasion
Abrasion resistance
Fatigue
Creep
Deformation
De-bond
Impact
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16
Q

Definition of fracture

A

When a large force causes catastrophic destruction of material’s surface

17
Q

Definition of hardness

A

Ability of surface to resist indentation (KHN)

18
Q

Definition of abrasion

A

Material surface removal due to grinding

19
Q

Definition of abrasion resistance

A

Ability to withstand surface layers being removed, so compromising surface integrity

20
Q

Definition of fatigue

A

When repetitive ‘small’ stresses cause material fracture

21
Q

Definition of creep

A

Gradual dimensional changes due to repetitive small forces

22
Q

Definition of deformation

A

An applied force may cause permanent change in material’s dimensions (but not fracture it)

23
Q

Definition of de-bond

A

Applied forces sufficient to break material-tooth bond

24
Q

Definition of impact

A

Large, sudden force that causes fracture