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Flashcards in Dental Materials Deck (293)
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31

What are 3 areas in why temp. is important in dentistry?

1. Use of drill
2. Exothermic setting reactions: can't do in mouth
3. Effect of hot/cold on restoration

32

Why is knowing temp. important?

Temp change may alter properties of material

33

What is heat of fusion?

Energy required to convert 1g of material from solid to liquid at melting temp.

34

What is thermal conductivity?

Quantity heat/second passing through a 1cm thick substance w/ cross section of 1cm2 w/ temp. inc. of 1 degrees

I.e. ease with which heat is transferred through a material

35

What is the clinical significance of thermal conductivity?

Large amalgam filling close to pulp may be sensitive to hot/cold thus use a non-mental cement between tooth and filling to insulate

Metal denture base material will more closely follow temp. of oral mucosa

36

What is specific heat?

Quantity of heat required to heat 1g material by 1 degrees

37

What is thermal diffusivity?

Measure of transient heat flow: how long does cold end of material take to heat up?
Rate of transfer of heat from hot side to cold side of material

38

What is the clinical relevance of thermal diffusivity?

Good inlay, crown, amalgam have low specific heat but high thermal conductivity thus if close to pulp may get thermal shock

39

What is thermal expansion coefficient?

Change in length of material for a 1 degree change in temp.

40

What is the clinical significance of thermal expansion?

Tooth and material will expand and contract due to hot/cold
Could result in breaking of marginal seal of inlay/filling

41

What electrical conductivity and resistivity?

Ability of material to conduct electrical current

42

Why is electrical conductivity and resistivity important?

Correlation between electrical conductivity and change in physical and mechanical properties of material
E.g. gold alloys: change in resistivity changes internal crystal structure

43

What is electromotive force?

Difference in electrical potential that gives rise to current

44

What is the electromotive series?

List of metals ordered in dec. tendency to oxidise in solution

45

What is galvanism?

Induction of current due to chemical reaction

46

Why is galvanism important in dentistry?

If 2 fillings of different electronegativities touch will cause short circuit which if near the pulp will cause pain

47

Why does amalgam have a high copper content?

Copper-tin complex much harder and less corrodible than tin-mercury

48

How do GICs bond to enamel?

Bind to Ca2+ in enamel
Carboxyl group plays role in setting reaction and bonding mechanisms

49

What is solubility?

Of inorganic salt: number moles of pure solid that will dissolve in 1L solvent at given temp

50

Compare solubility of hydroxyapatite and fluoroapatite

FA less soluble than HA: remains supersaturated for longer than HA even at lower pH

51

What are the 6 optical factors important in DMs?

1. Colour
2. Opacity
3. Fluorescence
4. Surface finish
5. Refractive index
6. Metanerism

52

What are the 6 thermal factors important in DMs?

1. Heat of fusion
2. Thermal conductivity
3. Thermal diffusivity
4. Specific heat
5. Temp
6. Thermal expansion

53

What are the 3 electrical factors important in DMs?

1. Conductivity and resistivity
2. Electromotive force
3. Galvanism

54

What are the 3 chemical factors important in DMs?

1. Reactions
2. pH and solubility
3. Bonding

55

Define biomaterial

Natural or synthetic material that interfaces w/ living or biological tissue

56

Define biocompatible

Ability of material to elicit an appropriate biological response, in given application, in body/mouth

57

What is biocompatibility dependent on?

Physical function
Biological response required
Location
Composition
Interaction w/ OC

58

What are the 4 main reasons for restorations?

1. Trauma
2. Decay/caries
3. Tooth loss
4. Revisions: repair failed restoration

59

Define safe in terms of DMs

Must not cause any local or systemic adverse reactions

60

What are the 2 categories of research?

1. Basic: lab research; pre-market
2. Clinical: post-market surveillance