resin based materials and fissure sealants e lec

Question 1

what is the ideal material to replace teeth

Answer 1

a material like itself

Question 2

what are some metallic materials

Answer 2

amalgam

and gold

Question 3

what are the disadvantages of amalgam or gold

Answer 3

they are not aesthetic

Question 4

give examples of ceramic materials

Answer 4

feldspatic ceramic( dental porcelain)

Question 5

what is the disadvantage of dental porcelain

Answer 5

have to damage natural tooth

Question 6

example of the polymer based systems

Answer 6

resin based materials

Question 7

how are fissure sealants activated

Answer 7

light/chemical activation

Question 8

how are dental composites activated

Answer 8

light/chemical activation

Question 9

how are polyacid modified resins activated

Answer 9

light/chemical activation

Question 10

how is resin modified polyalkenoate activated

Answer 10

light/chemical activation

Question 11

how is glass polyalkenoate activated

Answer 11

chemical activation

Question 12

what else are glass polyalkeontes also called

Answer 12

glass ionomers

or glass ionomer cements GIC

Question 13

what are the three phases of reacted set material

Answer 13

silica gel
polymer
ionomer glass

Question 14

how does the setting reaction occur

Answer 14

the starting materials are poly acid and an ionomer glass- a powder and a liquid

Question 15

what is the liquid

Answer 15

usually water

Question 16

what is the chemical reaction

Answer 16

acid + base = salt + water

Question 17

what are acidic polymers called

Answer 17

poly acids

Question 18

what is it called when poly acids react with poly bases

Answer 18

poly salts

Question 19

poly salts can be used to make

Answer 19

cohesive solid material called glass polyalkeonates cements (GPAC)

Question 20

what are the specifics of the GPAC reaction

Answer 20

initially the acid dissolves forming a vicious aqueous liquid with the glass dispersed into it
Hydrogen ions which have dissassociate from the polyacid are available to displace cations on the surface of the glass these then migrate away with some ion species reacting with the negatively charged polymer ions( fluoride) crosslinking them to become long polymer chains or polysalts.

Question 21

what happens to the modified glass surface

Answer 21

silica gel

Question 22

when will the material reach full strength

Answer 22

one week

Question 23

how long do we have to wait to polish the restoration

Answer 23

a week

Question 24

during the period where the material is strengthening what can it cause

Answer 24

CRACKS IN the surface of the material

Question 25

how can we stop cracks in the surface of the material

Answer 25

applying varnish or petroleum jelly

Question 26

what does the reaction also release

Answer 26

fluoride which forms fluoroapatite crystals which is greater acid resistance

Question 27

how was secondary caries prevented

Answer 27

by fluoride being released by poly alkeonates

Question 28

what are other schools of thought about fluorine being released from polyalkenoate

Answer 28

However, some now doubt whether there is enough fluoride release to be of statistical benefit. Other schools of thought are that the glass polyalkenoate can act as a fluorine “sponge” absorbing fluoride during treatments, say with tooth paste or mouth wash, then releasing it over a prolonged period afterwards

Question 29

what do polyalkenoates also react with

Answer 29

calcium ions on the tooth surface and therefore has a direct link with the tooth

Question 30

what is the disadvantage of polyalkenoates

Answer 30

their wear resistance is poor - do not make good materials if used alone they are too opaque where excellent aesthetics are required eg incisal edges

Question 31

what class restorations are poly alkenoates used for

Answer 31

class III and V restorations

Question 32

what are the advantages of poly alkenoates

Answer 32

sometimes can be used on the tooth without any preparation The material can also be used a luting cement (adhesive) for fixed prosthetics. also can be used as an intermediate under amalgam or composite

Question 33

what attempts have been used to strengthen poly alienates

Answer 33

by binding silver to the poly alkenoates which strengthens it but also castes a grey shadow also a copolymer of polyvinylphosphonic acid and polyacrylic acid, these form an improved matrix.

Question 34

what two copolymers can strengthen the poly alkenoate glass

Answer 34

polyvinylphosphonic acid and polyacrylic acid

Question 35

what is special about the filler

Answer 35

it is inert

Question 36

why is a filler used if its not a primary ingredient in the reaction

Answer 36

because the polymers used shrink by a large margin It reduces swelling due to water absorption, the polymers are highly crosslinked leading to the formation of voids into which water can ingress.

Question 37

what could the shrinkage of the polymer lead to

Answer 37

cracking of the teeth and also tooth/cusp failure

Question 38

if we add glass to the poly alkenoate what will happen

Answer 38

it will reduce the thermal expansion and stop fracturing the tooth in extreme cases - could reduce sensitivity due to the fact the fluid in the dentinal tubules stopped moving

Question 39

what things increase by adding fillers

Answer 39

strength aesthetics \ youngs modulus wear resistance

Question 40

what is the conventional filler size

Answer 40

5-10 micrometers in diameter,

Question 41

what is the size of the microfilled composite

Answer 41

0.04micrometres

Question 42

hybrid materials have around % volume of filler

Answer 42

78-85%

Question 43

what does bis-GMA mean

Answer 43

bisphenol glycidyl methacrylate

Question 44

what does UDMA mean

Answer 44

urethane dimethacrylate

Question 45

what materials are used to dental composite

Answer 45

bis-GMA and UDMA

Question 46

what does bis-GMA and UDMA commonly mixed with

Answer 46

triethyleneglycol dimethacrylate (TEGMA)

Question 47

why is bis-GMA and UDMA controversial

Answer 47

skin sensitivity and linked to carcinogenic

Question 48

why can bis-GMA and UDMA still be used in dental composites

Answer 48

they are used in small amounts and polymerised in to a highly crosslinked polymer chain which is quite different.

Question 49

what is the polymer matrix cured with

Answer 49

the blue light activation

Question 50

what is the issue if the cavity is overfilled with the polymer matrix

Answer 50

the blue light will only travel a few mm so it will lead to a soggy bottom formation in the bottom of the cavity

Question 51

what are the benefits of the blue light

Answer 51

Not only that blue light sources age and there may be a need to increase exposure at the end of the bulbs life. will build up your Dental composite restoration incrementally to avoid the problems; this will also help reduce the over all effect of shrinkage which potentially could fracture a tooth

Question 52

what are the issues with dental composites

Answer 52

hydrophobic meaning you need to dry the tooth | it doesn't bond to teeth as well- series of bonding systems that aim to interface tooth and composite

Question 53

what do bonding agents rely on

Answer 53

a pre treatment

Question 54

what is the smear layer

Answer 54

when you cut into dentine and causes debris to spread over the surface blocking the dentinal tubules

Question 55

what is used to remove the smear layer

Answer 55

phosphoric acid

Question 56

what forms if the bonding material is successful

Answer 56

the formation of tags which can enter the dentinal tubules

Question 57

what binds the filler and the matrix

Answer 57

silaine coupling agent

Question 58

what does silaine coupling agent bind

Answer 58

the filler and the matrix

Question 59

what range is the blue light wavelength

Answer 59

420-450 nm

Question 60

what's special about resin modified polyalkenoate

Answer 60

it has carbon carbon double bond which can be broken meaning that addition polymerisation

Question 61

what are poly acid modified resins called

Answer 61

compomers

Question 62

how does poly acid modified resins work

Answer 62

once the material is placed, small amounts of water will be absorbed from the patients saliva causing disassociation at the acid groups. This in turn starts a reaction with the glass which has been replaced with an ionomer glass thus there is a small background acid base reaction which is very much secondary.

Question 63

is there a need for a bonding system in poly acid modified resins

Answer 63

no - as no initial chemical reaction with the tooth

Question 64

what are fissure sealants

Answer 64

preventative materials

Question 65

what are fissure sealants used for

Answer 65

to protect vulnerable tissues in the occlusal surfaces from acid producing bacteria

Question 66

what age group will fissure sealants be applied to

Answer 66

paediatric patients