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3rd Yr- CSB- Extra-coronal restorations > LUTING CEMENTS > Flashcards

LUTING CEMENTS Flashcards

1
Q

Define cement

A

A cement is a solid from a paste

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2
Q

What do dental luting cements do?

A

They provide a link between fixed prosthesis and the supporting prepared tooth structure

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3
Q

What are dental luting cements are used to bond what to what?

A

Bond tooth tissue to restoration

enamel to metal, dentine to compost etc

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4
Q

What must dental cement be able to do?

A
  1. Seal the interface between the tooth and the restoration
  2. Act as a barrier against bacterial micro leakage
  3. Hold the tooth and the restoration together through some form of surface attachments
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5
Q

Give examples of surface attachment

A

1, Mechanical

  1. Chemical
  2. Mechanical + chemical
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6
Q

Talk through the steps of how we cement something onto the tooth

A
  1. Isolate and dry the preparation
  2. Clean and dry the restoration
  3. Mix cement
  4. Place a layer I’m the restoration
  5. Seat restoration firmly, apply pressure
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7
Q

Name some different cement types

A
  1. Calcium hydroxide
  2. Zinc oxide/eugenol
  3. Zinc phosphate
  4. Zinc polycarboxylate
  5. Glass ionomer
  6. Composite resin
  7. Resin modifed GIC
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8
Q

What are the properties of an ideal dental luting cement

A
  1. Biological
  2. Mechanical
  3. Aesthetic
  4. Working
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9
Q

What are the ideal biological properties of dental luting cement

A
  1. Biocompatible: little/ no interaction with oral fluids/ tissues
  2. Non toxic
  3. Low allergic potential
  4. Inhibits the formation of caries of plaque
  5. Prevents micro leakage
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10
Q

What are the ideal aesthetic properties of dental luting cement

A
  1. Colour stability

2. Radiopacity

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11
Q

What are the ideal working properties of dental luting cement

A
  1. Low film thickness

2. Low Viscosity

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12
Q

Which is better thick film or thin film?

A

Thinner film

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13
Q

What is the ideal thickness of dental luting cement

A

25 micrometres (Rare in practice)

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14
Q

Why is lower film thickness better than higher?

A
  1. Improves retention
  2. Gives the closest relationship between restoration and the tooth surface
  3. Can more easily take up the space created by the dye
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15
Q

Is it more favourable to have bigger particles or smaller?

A

Smaller

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16
Q

Why has smaller particles more favourable

A
  1. Smaller particles improve flow of cement

2. They reduce aggregation of particles (lower viscosity)

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17
Q

Do we want a dental luting cement that has a high or low viscosity ?

A

Low

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18
Q

Name the ideal dental luting cement

A

There is no available product that satisfies all the requirements

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19
Q

How do dental luting cements often fail?

A
  1. Micro fractures form in the cement
    2, This leads to micro leakage
  2. Bacteria ingress and cause bacterial disease
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20
Q

How does zinc phosphate set?

A

Sets by acid base reaction

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21
Q

What is zinc phosphate cement made up of?

A

Powder (90% ZnO, 10% MgO)

Liquid (67% phosphoric acid with buffer(

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22
Q

How is the ionisation of the acid and rate of setting reaction controlled?

A

The water content (33%) controls the ionisation of the acid

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23
Q

How thick is zinc phosphate?

A

Less than 25 micro metres

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24
Q

What is the strength of zinc phosphate cement dependent on?

A

Linearly dependent on powder to liquid ratio (more powder the better)

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25
Q

If you want a stronger cement of zin phosphate would you use more liquid or powder?

A

Powder

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26
Q

What is the compressive and tensile strength of zinc phosphate?

A

Compressive strength: 80-110MPa

Tensile straight: 5-7MPa

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27
Q

State the modulus of elasticity of set zinc phosphate cement

A

13 GPa

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28
Q

What are the problems with zinc phosphate cement

A

It does no chemical bond to the tooth structure

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29
Q

Give some of the indications fo zinc phosphate cement

A
  1. Metal inlays and onlays
  2. Crowns
  3. Fixed bridges
  4. Aluminous all ceramic crowns
  5. Amalgam
  6. Composite
  7. GIC cores
30
Q

How do glass ionomer cements set?

A

Acid base reaction between aluminium fluorosilicate glass particles and and a polyalkenoic acids liquid consisting of copolymers

31
Q

What is the compressive strength of glass ionomer cements

A

90-230 MPa

32
Q

What are the benefits of glass ionomer cements

A
  1. They adhere directly onto the tooth surface
  2. Studies have shown they have a reduced micro leakage ver non adhesive type cements
  3. Adequately low film thickness
  4. Releases fluoride
  5. Less soluble than GIC so more resistant to water attack during setting
33
Q

What does the setting of resin modified glass ionomer cement lead to?

A

Leads to formation of a merl polyacrylate salt and a polymer

34
Q

How do resin modified glass ionomers harden?

A
  1. Acid base reaction

2. Photo/chemcially imitated freer radical polymerisation of methacrylate units

35
Q 
Out of:
Zinc phosphate
GIC 
Polycarboxylate 
Resin modified GIC 
which has the highest compressive strength
A

Resin modified GIC

36
Q

What are the disadvantages of resin modified GIC

A
  1. Hydrophilic nature of polyHEMA results in increased water sorption and plasticity
  2. Potential for dimensional change means use with all ceramic feldspathic type restoration is a contra indication
  3. Questions about how biocompatible it is due to free monomers and HEMA being present
37
Q

Give an example go a resin moodier GIC

A

Rely X

FujiCEM

38
Q

How is rely X set

A

In 2 setting reactions:

  1. An acid base reaction
  2. a free radical polymerisation
39
Q

What free radical polymerisation reaction occurs when RelyX is setting

A

Free radical; polymerisation of the pendant methacrylate groups of the polymer and HEMA

40
Q

Does the free radical reaction in RelyX need to be light activated?

A

no can be dark cured

41
Q

How is RelyX sold?

A

As a paste/paste dispensed from a clicker

42
Q

What do the 2 pastes that make up RelyX have in them

A

Paste A: Fluoraluminosilicate glass, HEMA and reducing agent

Paste B: methacrylate polycarboxylic acid

43
Q

How do resin composite cements work?

A

Via a BIS GMA resin+ methacrylates rection

44
Q

How are resin composite cements polymerised?

A

Through photo/chemically imitated mechanisms

45
Q

Do resin composite cements bond straight to the tooth?

A

Yes they micro mechanically adhere to enamel land dentine

46
Q

What is a disadvantage of resin composite cements

A

Polymerisation shrinkage can occur

47
Q

What is the polymerise shrinkage of resin composite cements dependent on?

A

Cement type and thickness

48
Q

What are resin composite cements filled by?

A

50-70% filled by weight with glass/ silica

49
Q

What are the advantages of using resin composite cements

A
  1. High compressive strength
  2. Resistant to tensile fatigue
  3. Virtually insoluble in oral environment
  4. They give an improved marginal wear resistance
50
Q

What happens If you increase the filler content in resin composite cements?

A

High filler content:

  1. increases viscosity
  2. Reduces flow
  3. Increases film thickness
51
Q

When do we use resin compote cements?

A

Aesthetic restorations ie:
Resin onlays/ inlays
All ceramic restorations
Fibre reinforced composites

52
Q

What can polymerisation stress lead to in resin composite cements

A

Polymerisation stresses may form gaps between the cement and the tooth

53
Q

How do resin composite cements bond?

A

They bond chemically to resin composite restorative materials and silanated porcelain

54
Q

How can resin composite cements improve ceramic materials

A

Can be used to increase the fracture resistance of ceramic materials that can be etched and silanated

55
Q

How can resin composite cements improve base metal alloys

A

Good bond strengths to sandblasted use metal alloys (micro mechanical)

56
Q

What happens when 4 META cements are combined with resin?

A

4 META cements show strong adhesion due to chemical interaction of resin with oxide layer

57
Q

What are the products with MDP called?

A

Panavia

58
Q

What is a Panavia ?

A

It is a cement that has MDP

59
Q

Name the active monomer in Panavia

A

MDP

60
Q

Give some of the advantages of Panavia

A
  1. It bonds well to sandblasted non precious and tin plated surfaces
  2. Good physical properties
  3. Bonding is water resistant
61
Q

Give some of the disadvantages of panavia

A
  1. Bonds weakly to dentine
  2. Highly technique sensitive
  3. Highly air inhibited
62
Q

How does RelyX adhere to teeth?

A

It is formulates to be self adherent and moisture tolerant

63
Q

What are the benefits of RelyX being self adherent

A

Elimates the need for a separate priming, etching or bonding step

64
Q

Name the 2 mechanisms for the cements ability to bond to tooth surfaces

A
  1. Self etching

2. Secondary reaction

65
Q

How does self etching allow materials to bond to the tooth surface

A

Implies a lot of competing process until the methacrylate polymerise via light or self curing action to form a strong micro mechanical bond to the dentin and enamel

66
Q

How do cements that work by secondary reactions bond to the tooth surface

A

The basic filler reacts with the acid in the presence of some water that is formed to produce a glass ionomer type chemical bond

67
Q

Name some potential bonds that we may need to achieve

A
  1. Enamel/dentine to resin
  2. Resin to composite
  3. Composite to resin
  4. Resin to silane
  5. Silane to porcelain
  6. Resin to metal
68
Q

List the ideal properties of a cementing material

A
  1. Low film thickness
  2. Long working time
  3. Short setting time
  4. High compressive strength
  5. Low pulp irritation
  6. Very low solubility
  7. Very low micro leakage
  8. Easy to remove excess
  9. High retention
69
Q 
Out of the 3 cement options:
Zin phosphate
RMGIC
Composite resin
Which has the lowest film thickness?
A 
Zinc phosphate (<25)
RMGIC and Composite resin with >25
70
Q 
Out of the 3 cement options:
Zin phosphate
RMGIC
Composite resin
Has the longest working time
A

Longest: Composite resin (3-10mins)

Zinc phosphate (1.5-5mins)

Shortest: RMGIC (2-4MINS)

71
Q 
Out of the 3 cement options:
Zin phosphate
RMGIC
Composite resin
Has the shortest setting time
A

Shortest: RMGIC (2mins)

Composite resin (3-7mins)

Zinc phosphate (5-14mins)

72
Q 
Out of the 3 cement options:
Zin phosphate
RMGIC
Composite resin
Has the highest compressive strength
A

Strongest: Composite resin (194-200MPa)

RMGIC: (40-141)

Weakest: Zinc phosphate (62-101MPa)

3rd Yr- CSB- Extra-coronal restorations (11 decks)

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