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BDS2.5 Dental Materials - operative dentistry > Abrasives and Polishing > Flashcards

Abrasives and Polishing Flashcards

1
Q

Why is it important that all intra-oral surfaces are smooth?

A

food debris and dental plaque accumulation is reduced

corrosion of metals is prevented

no damage done to oral soft tissues

more comfortable for patient

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2
Q

What factors effects the abrasiveness?

A

hardness of abrasive

shape of abrasive particles

size of the abrasive particles

mechanical properties of abrasive

speed and movement of abrasive over surface

direct of movement

amount of load applied to substrate

properties of substrate

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3
Q

What is the sequence of using abrasives?

A

start with the most coarse and them go down onto the small/fine

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4
Q

What is the effect of heat generation during finishing?

A

surface substrate may melt

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5
Q

What can happen with thermoplastic polymers?

A

changes to properties of surface produced as it flows to fill in any scratches

excessive heat can cause stress relief and warping

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6
Q

What cab occur due to heat with resin-based materials?

A

smearing can occur as polymer approaches its glass transition temperature

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7
Q

What are common abrasives used in dentistry?

A

alumina and silica

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8
Q

What is the most popular method of finishing restorations?

A

finishing discs

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9
Q

What handpiece is used for the finishing discs?

A

slow speed

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10
Q

What do the finishing discs clip onto?

A

mandrel

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11
Q

Where would you use the finishing strips?

A

interproximally

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12
Q

Is there griot in the centre of the finishing strips?

A

no grit in the middle to facilitate insertion into area to be smoothed

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13
Q

What is the active ingredient of the rubber wheels?

A

silicon carbide or alumina bonded with rubber

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14
Q

What colour of rubber wheels tends to be coarser?

A

darker colour

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15
Q

What are rubber wheels used for?

A

polishing

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16
Q

What are the abrasives bonded with to produce various types of finishing instruments?

A

a binder

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17
Q

What are types of polishing instruments?

A

sintering

vitreous bonding

resinous bonding

rubber binding

18
Q

What is sintering?

A

abrasive is heated so that it softens and particles bind together

strongest type

19
Q

What is vitreous bonding?

A

using either glass or ceramic

glass acts as a binder holding abrasive particles together

20
Q

What is resinous bonding?

A

binder is usually a phenolic resin

softer than abrasive and wears quickly

21
Q

What is rubber bonding?

A

achieved using a silicone rubber

wear very quickly is used on a hard surface

22
Q

What do resinous and rubber bonding require?

A

rely on cold or hot pressing to mould instrument

23
Q

What are the features of hot pressing?

A

produces a more durable material which frequently has low porosity

24
Q

What occurs if the polishing instrument wears too slowly?

A

will become clogged with swarf and debris which they have removed

25
Q

What is the risk of swarf and debris build up?

A

heat generation leading to damage to substrate

26
Q

What are polishing stones made from?

A

alumina that has been sintered

27
Q

What handpiece do you use polishing stones in?

A

slow speed

28
Q

What are the colours of polishing stones in order of most to least abrasive?

A

pink
blue
green
white

29
Q

What colour of polishing stones do you use intra-orally?

A

green
white

30
Q

Do you use a polishing stone with or without water?

A

can be both but probs use with to reduce friction and heat generation

31
Q

What are brushes simiar to?

A

extra hard toothbrush

32
Q

What speed do you use brushes at?

A

600-1000rpm

33
Q

What is the recent movement of brushes?

A

impregnated bristles with an abrasive rather than using a separate slurry

34
Q

What are the polishing materials?

A

lustre paste

35
Q

What is lustre paste used on?

A

resin composite

36
Q

What are polishing materials - lustre paste composed of?

A

diamond or aluminium oxide in glycerin

37
Q

What colours are lustre paste available in?

A

pink and white

white is less abrasive

38
Q

What is a pumice slurry?

A

crushed porous volcanic stone that is a highly siliceous volcanic glass

39
Q

What is used to remove stains?

A

prophylaxis paste

40
Q

What composes prophylaxis paste?

A

abrasive usually pumice or chalk (calcium carbonate) within a solution of oils

  • oils act as binder
41
Q

What is electrolytic polishing?

A

used when only a minimum amount of material is to be polished

BDS2.5 Dental Materials - operative dentistry (22 decks)

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