Resin composite!

Question 1

what were the earliest tooth coloured restorative materials? and when were they used?

Answer 1

silicate cements - 1950-1960s

Question 2

what is the reaction to give silicate cements?

Answer 2

aluminosilicate glass + phosphoric acid = salt and water

Question 3

give 4 properties of silicate cements

Answer 3

• releases fluoride
• moisture sensitive
• erosion prone (due to acid)
• brittle

Question 4

what causes the silicate cement to be brittle?

Answer 4

the glass

Question 5

where would you use silicate cements?

Answer 5

only on anterior teeth

Question 6

what was used between 1960-1980s?

Answer 6

acrylic resin

Question 7

what type of product is acrylic resin made from?

Answer 7

the same product used to fabricate dentures

Question 8

what is vital in avoiding inferior properties for acrylic resin restorations?

Answer 8

a correct powder:liquid mixing ratio

Question 9

how is acrylic resin set and what is the disadvantage to this

Answer 9

chemically set which decreases working timeq

Question 10

what is contained within the powder for acrylic resin? 3 things

Answer 10

• pmma beads
• chemical indicator
• pigment

Question 11

what is contained within the liquid for acrylic resin? 2 things

Answer 11

• mma monomer

- chemical activator

Question 12

what type of chemical activator is contained in the liquid for acrylic resin?

Answer 12

tertiary amine

Question 13

what is the function of the tertiary amine?

Answer 13

starts off the setting reaction

Question 14

what is the setting reaction for acrylic resin?

Answer 14

free-radical addition polymerisation of methyl methacrylate

Question 15

what are the 4 stages in free radical addition polymerisation of methyl methacrylate?

Answer 15

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

Question 16

what happens in the initiation phase? in free radical addition polymerisation of methymethacrylate

Answer 16

the tertiary amine is in liquid and it cleaves the molecule at o-o

Question 17

at which stage does the joining up occur? in free radical addition polymerisation of methymethacrylate

Answer 17

the propagation stage

Question 18

what occurs at the initiation stage? in free radical addition polymerisation of methymethacrylate

Answer 18

the double bond breaks up

Question 19

what happens at activation phase? in free radical addition polymerisation of methymethacrylate

Answer 19

o - o bond is cleaved due to the tertiary amine in the liquid of the acrylic resin

Question 20

what does the material do on polymerisation?

Answer 20

shrinks (6% by volume)

Question 21

what occurs at termination? in free radical addition polymerisation of methymethacrylate

Answer 21

• when a chain attaches to free radicals or further growing chain

Question 22

When does the process stop all together? in free radical addition polymerisation of methymethacrylate

Answer 22

when there is a lack of properties

Question 23

what type of reaction is free radical polymerisation of methylmetacrylate? (endothermic or exothermic)

Answer 23

exothermic - releases heat

Question 24

what happens if the tertiary amine is not all used up??

Answer 24

poor colour stability occurs (clear to brown)

Question 25

what are 5 benefits to acrylics compared to silicates?

Answer 25

1. less brittle
2. less prone to erosion
3. less acidic
4. less soluble
5. exhibits lower thermal diffusivity

Question 26

if there is amine still present in the acrylic then what may happen to the tooth shade and how is this avoided?

Answer 26

it may loose its shade and you can avoid by getting a perfect powder to liquid ratio

Question 27

what type of lining can acrylic resin react with?

Answer 27

zinc oxide eugenol

Question 28

what makes acrylic resin irritant to the pulp? 2 reasons

Answer 28

residual mma monomer in the liquid and exothermic (only irritant in deep cavity

Question 29

who investigated acrylic in 1951? what did they conclude?

Answer 29

knock and glenn discovered