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5th yr- Finals- CSB revision > 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 prove a link between fixed prosthesis and the supporting prepared tooth structure

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3
Q

Why are dental luting cements used

A

To bond tooth tissue to restorations eg enamel to metal

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4
Q

What must dental cement be able to do

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

Give examples of surface attachment

A
  1. Mechanical
  2. Chemical
  3. Mechanical and chemical
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6
Q

give example fo different dental luting cements

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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7
Q

What are the properties of an ideal dental luting cement

A
  1. Biological
  2. Mechanical
  3. Aesthetic
  4. Suitable working time
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8
Q

What are the ideal biological properties of dental luting cement

A
  1. Biocompatible
  2. Non toxic
  3. Low allergic potential
  4. Inhibits the formation of caries or plaque
  5. Prevents micro leakage
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9
Q

What are the ideal aesthetic properties of dental luting cement

A
  1. Colour stability
  2. Radio opacity
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10
Q

What are the ideal working properties of dental luting cement

A
  1. Low film thickness
  2. Low Viscosity
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11
Q

Why is low film thickness better than thick

A
  1. Improves retention
  2. Gives the closest relationship between restoration and tooth surface
  3. can more easily take up space crated by dye
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12
Q

Do we want dental luting cement with a low high viscosity

A

Low

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13
Q

Name the ideal dental luting cement

A

There is no available product that satisfies all the requirements

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14
Q

How do dental luting cements often fail?

A
  1. Micro fractures form in the cement leading to micro leakage
  2. Bacteria ingress and cause bacterial disease
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15
Q

How does zinc phosphate set

A

Acid base reaction

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16
Q

What is zinc phosphate cement made up of

A

Powder: 90% ZnO, 10% MgO
Liquid: Liquid 67% phosphoric acid with buffer

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17
Q

How thick is zinc phosphate

A

less than 25 micro metres

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18
Q

What is the strength of zinc phosphate cement depend on

A

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

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19
Q

What is the compressive and tensile strength of zinc phosphate

A

Compressive strength: 80-110MPa
Tensile straight: 5-7MPa

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20
Q

State the modulus of elasticity of set zinc phosphate cement

A

13 GaP

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21
Q

What are the problems associated with zinc phosphate cement

A

It does not chemical bond to the Tooth

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22
Q

Give some indication 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
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23
Q

How do glass ionomer cements

A

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

24
Q

What is the compressive strength of GIC

A

90-230 MPa

25
Q

What are the benefits of GIC

A
  1. They adhere directly onto the tooth surface
  2. Reduced micro leakage
  3. Adequately low thickness
  4. Releases fluoride
  5. Less soluble than GIC so more resistant to water attack during setting
26
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

27
Q

How do resin modified glass ionomers harden

A

Acid base reaction
Photo/chemcially imitated freer radical polymerisation of methacrylate units

28
Q

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

A

RMGIC

29
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
30
Q

Give examples of RMGIC

A

Rely X
FujiCEM

31
Q

How is rely x set

A

In 2 setting reactions:

  1. An acid base reaction
  2. a free radical polymerisation
32
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

33
Q

How do resin composite cements work

A

Via a BIS GMA resin+ methacrylates rection
(Add Clarifier)

34
Q

How are resin composure cements polymerised

A

Through photo chemically initiated mechanisms

35
Q

Do resin composite cements bond straight to the tooth

A

YEs

36
Q

What is the disadvantage of resin composite cements

A

polymerisation shrinkage can occur

37
Q

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

A

Cement type and thickness

38
Q

What are resin composite cements filled by?

A

50-70% filled by weight with glass/ silica

39
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
40
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
41
Q

When do we use resin compsoite cements

A

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

42
Q

What can polymerisation stress lead to in resin composite cements

A

Polymerisation stresses may form gaps between the cement and the tooth

43
Q

How do resin composite cements bond

A

Chemically

44
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

45
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

46
Q

What are the products with MDP called?

A

Panavia

47
Q

What is panavia

A

A cement that has MDP

48
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
49
Q

Give some of the disadvantages of panavia

A
  1. Bonds weakly to dentine
  2. Highly technique sensitive
  3. Highly air inhibited
50
Q

How does rely x adhere to teeth

A

It is formulates to be self adherent and moisture tolerant

51
Q

What are the benefits of RelyX being self adherent

A

Eliminates the need for separate priming, etching or bonding steps

52
Q

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

A
  1. Self etching
  2. Secondary reaction
53
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

54
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

55
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

5th yr- Finals- CSB revision (17 decks)

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