dental materials

Question 1

what is the medical devices directive changes?

Answer 1

• statement of manufacture offered to all patients recieving dental appliance
• GDC often invite patients to ask for this certificate

Question 2

what is an alloy?

Answer 2

-a mixture of two or more metals

Question 3

what is a grain boundary?

Answer 3

• where the crystals meet

- a source of tension

Question 4

how are grain boundaries visualised?

Answer 4

-light reflecting microscope

Question 5

what are the 3 different types of solid solution?

Answer 5

1. ordered solid solution
2. random solid solution
3. interstitual solid solution

Question 6

what are the two compositions of amalgam?

Answer 6

1. conventional

2. copper enriched ( high copper)

Question 7

what is to composition of conventional amalgam?

Answer 7

65% Ag, 29% Sn, 6% Cu, 2% Zn, 3% Hg

Question 8

what is the composition of high copper amalgam?

Answer 8

40% Ag, 32% Sn, 30% Cu, 2% Zn, 3% Hg

Question 9

what is the ISO limits of expansion/contraction??

Answer 9

+/- 0.1%

Question 10

what does Zn act as in amalgam?

Answer 10

-Zn acts as a scavenger for Oxygen

Question 11

when is amalgam fully set?

Answer 11

24hrs after placement

Question 12

what is creep?

Answer 12

• protrusions at restoration margins

- gamma 2 phase is largerly, not exclusively responsible

Question 13

what does corrosion provide?

Answer 13

-corrosion provides marginal seal

Question 14

Mercury compounds in amalgam are known to be toxic to what?

Answer 14

-CNS

Question 15

what are silicates?

Answer 15

• earliest tooth coloured restorative material
• releases flouride
• prone to eriosion
• brittle

Question 16

what are the 4 stages of free radical polymerisation of methyl methacrolate?

Answer 16

1. activation
2. initiation
3. propogation
4. termination

Question 17

what is a resin composite?

Answer 17

-a combination of two chemically different materials with a distinct interface seperating the components and having properties which could not be achieved by any of the components alone

Question 18

what are the 3 kinds of resin composites?

Answer 18

1. microfilled
2. hybrid
3. macrofilled

Question 19

for a product to be on the market, what must they confirm with?

Answer 19

-ISO 4049

Question 20

what is an ormocer?

Answer 20

-monomer free nano-hybrid composite

Question 21

can you place an amalgam in a pt that is pregnant?

Answer 21

-No. Department of health banned amalgam placing in pts that are pregnant

Question 22

what are the two classifications of impression material?

Answer 22

• elastic

- non-elastic

Question 23

what are the two types of hydrocolloid?

Answer 23

-reversible and irreversible

Question 24

give an example of a reversible hydrocolloid?

Answer 24

-agar

Question 25

give an example of irreversible hydrocolloid?

Answer 25

-alginate

Question 26

what features do reversible and irreversible hydrocolloids both have in common?

Answer 26

-both colloidal suspensions of polysaccharides in water

Question 27

what is agar?

Answer 27

-complex polysaccharide derived from seaweed

Question 28

give examples of mucostatic materials?

Answer 28

• plaster

- alginate

Question 29

what are some alternatives to impressions?

Answer 29

• CAD CAM

- Intra oral scanner

Question 30

what are 4 types of elastomeric impression material?

Answer 30

1. polysulphides
2. silicon rubbers(condensation curing)
3. silicon rubbers(addition curing)
4. polyether

Question 31

what is the byproduct of silicon rubbers (condensation curing)?

Answer 31

-alcohol (ethyl)

Question 32

what is the by product of silicone rubber (addition curing)?

Answer 32

-there is no by product

Question 33

what are the 3 products of gypsum?

Answer 33

1. dental plaster
2. dental stone
3. densite

Question 34

what does borax act as in gypsum?

Answer 34

-borax acts as the retarder and slows down the reaction