Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Stage 2 Cheat sheets > DMT > Flashcards

DMT Flashcards

1
Q

Elastic, plastic and viscoelastic, explain using models and graphs what these mean

A

Elastic
Model = spring
When load applied - deforms quickly
If load held it stays deformed and when removed return to original dimensions

Plastic
Model = dashpot
When load applied deforms quickly
If load is held it stays deformed and when removed it stays deformed

Viscoelasticity
Model = dashpot and spring (in series = Maxwell model) (in parallel = Voigt model)
Maxwell = only some deformation returns
Voigt = all deformation returns but slowly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What effect does adding plasticiser to a polymer have on Tg?

A

Reduces Tg
Acts as a lubricant between chains so they cannot get as close together
Residual monger can act as a plasticiser

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Force?

Equation?

A

Results from an outside agency acting upon a body to change its momentum
load x acceleration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Define stress

A

Internal forces set up inside a body to oppose and externally applied force

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Define strain

A

The amount of deformation that occurs due to an applied stress

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Define tensile strength

A

Maximum stress a material can withstand before breaking

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Define stiffness

A

The mount of resistance against deformation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Define ductility

A

How much a material can be pulled

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Define proportional limit

A

The point where stress is not proportional to strain (switch from elastic to plastic)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Define Young’s modulus

A

Measures stiffness - defining relationship between stress and strain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Define resilience

A

How much energy something can take before it deforms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Define toughness

A

How much energy something can take before it breaks

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Define malleability

A

How much something can be compressed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Define yield strength

A

Point on Young’s modulus graph (stress and strain) where plastic deformation occurs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

3 methods to shape metals and alloys

A

Casting
Working
Amalgamation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Soluble vs insoluble alloys

A

Soluble - atoms form into planes

Insoluble - atoms don’t form into planes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Working time

A

Time from start of mix until the material can no longer be effectively used (should be in the mouth by this point)
At RT

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Setting time

A

Time from start of mix until the material has minimum properties for function
At suitable temp e.g. mouth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is quenching?

A

Rapid cooling of a solid in a cooler liquid

20
Q

Effect of quenching?

A

Increases speed of cooling - atoms closer together - more grains per volume, more grain boundary per unit of volume
More grain boundaries = higher yield strength (atoms cannot move as much)

21
Q

What is glass transition temperature?

A

The temperature at which the material switches from being rubbery to glassy

22
Q

What type of material does glass transition temperature affect?

A

Thermoplastic polymers

23
Q

Thermoplastic

A

Type of polymer that hardens on cooling and softens on heating

24
Q

Thermosetting

A

Type of polymer that hardens on setting and does not soften on heating
All cross-linked polymers are thermosets

25
Q

Gaseous porosity

A

Increased temperature leads to vaporised monomer causing weakness and failure

26
Q

Where does porosity occur?

A

Thickest part of the denture (most volume)

27
Q

Contraction porosity

A

Polymers are denser than monomers so polymerisation causes shrinkage = contraction porosity = weakness and failure

28
Q

Interstitial alloy

A

When the atoms forming the alloy are very different in size the smaller element sits int he interstitial gaps between the larger ones = solid solution

29
Q

The type of molecule is the molecule forming free radicals?

A

An initiator molecule - weak bond e.g. BPO

30
Q

Through what step does an initiator molecule become a free radical?

A

Activation (heat or light)

31
Q

What increases working time?

A

Retarder by delaying setting

32
Q

How to reduce polymerisation contraction?

A

Use larger monomers or add a filler that will not polymerise

33
Q

Composition of orthodontic wire

A

18/8 austentitic stainless steel

18% Cr 8% Ni added to steel

34
Q

What is steel?

A

An alloy of carbon and iron (carbon much smaller = so in interstitial sites)

35
Q

Why is steel so useful?

A

Number of phases with different properties
Austentite = stable at useful temperatures
Ferrite
Cementite = ionic solution (hard but brittle)
Pearlite = ferrite and cementite (depends on concentration of carbon)

36
Q

How does C concentration affect mechanical properties of perlite?

A

Increase C = increased hardness, yield strength, ductility

37
Q

Purpose of light cures

A

Protect the eyes of the dentist because high intensity visible light can cause retinal damage

38
Q

What increase Tg?

A 
Increased polymerisation (lower residual monomer)
Change monomer = C=C bond is more rigid than Si-o
39
Q

What decreases Tg?

A

Plasticiser

Large pendant groups

40
Q

Order hardening

A

Heat treatment on a solid to increase hardens and yield strength by making the atoms form ordered solid solution

41
Q

Precipitation hardening

A

Heat treatment on a solid to increase yield strength and hardens in partially soluble alloys
Must be below RcT

42
Q

Eutectic point

A

Point at which homogenous mixture of substances has a single melting point

43
Q

Why does steel have no more than 2% carbon?

A

2% carbon is its solubility limit

unstable above this

44
Q

Rheology?

A

Study of deformation and flow of material, measurement of how viscosity changes

45
Q

Newtonian
Pseudoplastic
Dilatant

A

Viscosity does not change as shear rate increases/decreases

Viscosity decreases as shear rate increases (ketchup)

Viscosity increases as shear rate increases (bullet proof vest)

46
Q

Thixotropy

A

No flow until sufficient pressure is applied

Stage 2 Cheat sheets (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions