Abrasives and Polishing

Question 1

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

Answer 1

food debris and dental plaque accumulation is reduced

corrosion of metals is prevented

no damage done to oral soft tissues

more comfortable for patient

Question 2

What factors effects the abrasiveness?

Answer 2

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

Question 3

What is the sequence of using abrasives?

Answer 3

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

Question 4

What is the effect of heat generation during finishing?

Answer 4

surface substrate may melt

Question 5

What can happen with thermoplastic polymers?

Answer 5

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

excessive heat can cause stress relief and warping

Question 6

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

Answer 6

smearing can occur as polymer approaches its glass transition temperature

Question 7

What are common abrasives used in dentistry?

Answer 7

alumina and silica

Question 8

What is the most popular method of finishing restorations?

Answer 8

finishing discs

Question 9

What handpiece is used for the finishing discs?

Answer 9

slow speed

Question 10

What do the finishing discs clip onto?

Answer 10

mandrel

Question 11

Where would you use the finishing strips?

Answer 11

interproximally

Question 12

Is there griot in the centre of the finishing strips?

Answer 12

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

Question 13

What is the active ingredient of the rubber wheels?

Answer 13

silicon carbide or alumina bonded with rubber

Question 14

What colour of rubber wheels tends to be coarser?

Answer 14

darker colour

Question 15

What are rubber wheels used for?

Answer 15

polishing

Question 16

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

Answer 16

a binder

Question 17

What are types of polishing instruments?

Answer 17

sintering

vitreous bonding

resinous bonding

rubber binding

Question 18

What is sintering?

Answer 18

abrasive is heated so that it softens and particles bind together

strongest type

Question 19

What is vitreous bonding?

Answer 19

using either glass or ceramic

glass acts as a binder holding abrasive particles together

Question 20

What is resinous bonding?

Answer 20

binder is usually a phenolic resin

softer than abrasive and wears quickly

Question 21

What is rubber bonding?

Answer 21

achieved using a silicone rubber

wear very quickly is used on a hard surface

Question 22

What do resinous and rubber bonding require?

Answer 22

rely on cold or hot pressing to mould instrument

Question 23

What are the features of hot pressing?

Answer 23

produces a more durable material which frequently has low porosity

Question 24

What occurs if the polishing instrument wears too slowly?

Answer 24

will become clogged with swarf and debris which they have removed

Question 25

What is the risk of swarf and debris build up?

Answer 25

heat generation leading to damage to substrate

Question 26

What are polishing stones made from?

Answer 26

alumina that has been sintered

Question 27

What handpiece do you use polishing stones in?

Answer 27

slow speed

Question 28

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

Answer 28

pink blue green white

Question 29

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

Answer 29

green white

Question 30

Do you use a polishing stone with or without water?

Answer 30

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

Question 31

What are brushes simiar to?

Answer 31

extra hard toothbrush

Question 32

What speed do you use brushes at?

Answer 32

600-1000rpm

Question 33

What is the recent movement of brushes?

Answer 33

impregnated bristles with an abrasive rather than using a separate slurry

Question 34

What are the polishing materials?

Answer 34

lustre paste

Question 35

What is lustre paste used on?

Answer 35

resin composite

Question 36

What are polishing materials - lustre paste composed of?

Answer 36

diamond or aluminium oxide in glycerin

Question 37

What colours are lustre paste available in?

Answer 37

pink and white white is less abrasive

Question 38

What is a pumice slurry?

Answer 38

crushed porous volcanic stone that is a highly siliceous volcanic glass

Question 39

What is used to remove stains?

Answer 39

prophylaxis paste

Question 40

What composes prophylaxis paste?

Answer 40

abrasive usually pumice or chalk (calcium carbonate) within a solution of oils - oils act as binder

Question 41

What is electrolytic polishing?

Answer 41

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