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Dental Materials Y2 > Comparison of Restorative Materials > Flashcards

Comparison of Restorative Materials Flashcards

1
Q

What ways can resin composites be cured

A

Chemically Cured

Light Cured

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2
Q

How are chemically cured resin composites often mixed

A

two paste ting

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3
Q

Why might mixing be difficult for two paste resin composites

A

The pastes are very viscous

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4
Q

What might the incorporation of bubbles into the mixing pastes cause

A

You will compromise the mechanical properties as the bubbles act as a point where the stresses will concentrate and can cause cracks

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5
Q

What are some disadvantages of using a two paste resin composite system

A
  • Mixing is difficult
  • May incorporate air bubbles
  • Discolouration with time
  • Homogenous mix is not easy to get - due to viscosity
  • Degree and time of polymerisation varies throughout the mass
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6
Q

What will be affected by the disadvantages of two paste resin composites

A

Youngs modulus and strength

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7
Q

What are the advantages of using one paste light cured resin composites

A
  • Minimal porosity
  • Less discolouration
  • Virtually command set
  • Rapid polymerisation
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8
Q

What are some of the disadvantages of one paste light cured resin composites

A
  • Light sensitive during application
  • Thin inhibited layer -due to oxygen in air
  • Limited depth of cure
  • Cure in increments
  • Retina damage from curing light
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9
Q

What can be used to prevent the thin inhibited top layer on resin composites

A

Cellulose strip on top

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10
Q

What is the machine called to mix amalgams

A

Amalgamators

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11
Q

Why are manual mixing methods for amalgams not often used anymore

A

A lot more exposure to mercury vapour, but in capsules the mercury and alloy are less exposed and you also get a better mix off

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12
Q

What are the oil based acid base cements also called and give examples

A

Phenolate bonded cements

e.g. Zinc Oxide Eugenol (ZOE) and Calcium Hydroxide

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13
Q

Describe the features of the mixing for phenolate bonded acid base cements

A

Easy to mix,
Long working tie
Quick set in the mouth due to temperature and presence of moisture in oral cavity

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14
Q

Why are phenolate bonded acid base cements quick to set in the mouth

A

Due to temperature and presence of moisture in oral cavity

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15
Q

What are some types of the polycarboxylate bonded acid base cements

A

Zinc Polycarboxylate cements

Glass Ionomer cements

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16
Q

How do zinc phosphate acid base cements need to be mixed

A

On a cooled slab
Small increments
Over a large area

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17
Q

Why do zinc phosphate acid base cements need to be mixed on a cooled slab and over a large area

A

The reaction is very exothermic so you can slow the setting and prolong the working time

Large area to allow better mixing and dissipate any heat into the cool slab

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18
Q

How would decreasing powder/liquid ratio of zinc phosphate acid base cements affect the properties of the cement

A

Decreased compressive strength
Increased solubility
Increased initial acidity
Increased setting time

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19
Q

How would increasing the rate of powder incorporation of zinc phosphate acid base cements affect the properties of the cement

A

Decreased compressive strength
Increased solubility
Increased initial acidity
Decreased Setting time

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20
Q

How would increasing the mixing temperature of zinc phosphate acid base cements affect the properties of the cement

A

Decreased compressive strength
Increased solubility
Increased Initial acidity
Decreased setting time

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21
Q

How would water contamination of zinc phosphate acid base cements affect the properties of the cement

A

Decreased compressive strength
Increased solubility
Increased initial acidity
Setting time can go up or down depending on when water is added

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22
Q

List the acid base cements from most acidic to least acidic

A 
Zinc phosphate cement
Glass ionomer cement
Zinc polycarboxylate cement
ZOE cement
Calcium hydroxide cement
23
Q

AY BAWS CAN I HABE DE NOTE PLZ

A

Over the first few minutes of setting the cements their pH will increase

24
Q

In terms of thermal conductivity which cement is similar to dentin

A

Zinc oxide eugenol

25
Q

In terms of thermal diffusivity what cement is similar to dentin

A

Glass ionomer cements

26
Q

List Amalgam, zinc phosphate, ZOE, GIC and composite from most to least thermally conductive

A 
Amalgam
Composite
Zinc phosphate
GIC
ZOE
27
Q

List Amalgam, zinc phosphate, ZOE, GIC and composite from most to least thermally diffusive

A 
Amalgam
Composite
ZOE
Zinc phosphate
GIC
28
Q

What cement has similar thermal expansion properties to the tooth

A

GICs

29
Q

List Amalgam, composites, GICs and ZOE from highest thermal expansion to lowest

A

Composites
ZOE
Amalgam
GIC

30
Q

List Calcium hydroxide, composite, zinc phosphate, amalgam, ZOE, zinc polycarboxylate and glass ionomer from highest to lowest compressive strength

A

Amalgam (stronger than enamel and dentin)
Composite (sometimes stronger than enamel and dentin)
Glass Ionomer
Zinc Phosphate
Zinc Polycarboxylate
ZOE
Calcium hydroxide

31
Q

What is the compressive strength of enamel and dentin

A

Enamel - 350 MPa

Dentin - 270 MPa

32
Q

List Calcium hydroxide, composite, zinc phosphate, amalgam, ZOE, zinc polycarboxylate and glass ionomer from highest to lowest tensile strength

A 
Amalgam
Composite
Zinc polycarboxylate
Zinc phosphate
Glass ionomer
Zinc oxide eugenol
Calcium hydroxide
33
Q

What are the tensile strengths of enamel and dentin

A

enamel - 10MPa

dentin - 40 MPa

34
Q

How do composites and amalgams compare in terms of aesthetics

A

Composites are much better but the colour matched shades can discolour

Amalgams are grey and metallic and can turn black if tarnished as sulphides form

35
Q

How long to amalgam and composite fillings last

A 
Amalgam = 12 years
Composites = 5-7 years
36
Q

What are the biocompatibility issues of amalgams

A

They contain mercury and are potentially toxic

Rare cases of allergy

37
Q

What are the biocompatibility issues of composites

A

Composites can leach components that are potential carcinogens

38
Q

How do amalgams and composites compare in terms of wear

A

Composites wear more than amalgam

39
Q

What types of wear are there

A

Abrasive
Fatigue
Corrosive

40
Q

Where does wear occur to the highest extent

A

at the cusp contact points

41
Q

How do amalgams and composites compare in terms of shrinkage

A

Amalgams shrink less - 0.02-0.2%

Composites undergo polymerisation shrinkage - 2-3% leads to marginal leakage

42
Q

Which direction does shrinkage occur in self cure composites

A

Towards the cavity walls

43
Q

Which direction does shrinkage occur in bulk light cure composites

A

Towards the lateral walls but away from the base of the cavity so yeh not good

44
Q

How can be minimise the shrinkage problems of bulk light cure composites

A

Incremental light curing

45
Q

Why are composites more likely to form secondary caries

A

Due to the shrinkage factor and bruh composites have quite a large risk of these.

46
Q

How do composites and amalgams compare in terms of cavity preparation

A

Composites require less removal of tooth structure

Amalgam requires more removal to give adequate retention (undercuts)

47
Q

What should be the size of the increments of composites

A

2mm.

48
Q

How long does it take to place composite fillings compared to amalgams

A

20 mins for amalgam

30 for composite due to increments, etching, bonding etc

49
Q

How do composites and amalgams compare in terms of pulp protection

A
  • Composites are thermal insulators but can cause chemical irritation due to leakage
  • Amalgams conduct heat so can cause reversible pulp damage without clinical symptoms
50
Q

Compare ZOE and CH as cavity liners

A
  • Both long working time, sharp set in mouth
  • Water accelerates set of both cements
  • ZOE stronger and less soluble than CH
  • ZOE has a calming effect on inflamed tissue
  • CH is alkaline - antibacterial
  • CH stimulates secondary dentin formation
  • The eugenol in ZOE inhibits curing of composites
51
Q

List these filling materials from highest to lowest in terms of fluoride release : Resin-modified glass ionomer, Compomers, Glass ionomers and Composites

A

Glass ionomer
Resin-modified glass ionomer
Compomers
Composites

52
Q

List these filling materials from highest to lowest in terms of strength of mechanical properties

A

Composites
Compomers
Resin-modified glass ionomers
Glass ionomers

53
Q

The table on the last page of this lecture is quality if you want to see some comparisons

A

Honestly should probably have a look at it

Dental Materials Y2 (13 decks)

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