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

LUTING CEMENTS Flashcards

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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
If you want a stronger cement of zin phosphate would you use more liquid or powder?
Powder
26
What is the compressive and tensile strength of zinc phosphate?
Compressive strength: 80-110MPa | Tensile straight: 5-7MPa
27
State the modulus of elasticity of set zinc phosphate cement
13 GPa
28
What are the problems with zinc phosphate cement
It does no chemical bond to the tooth structure
29
Give some of the indications fo zinc phosphate cement
1. Metal inlays and onlays 2. Crowns 3. Fixed bridges 4. Aluminous all ceramic crowns 5. Amalgam 6. Composite 7. GIC cores
30
How do glass ionomer cements set?
Acid base reaction between aluminium fluorosilicate glass particles and and a polyalkenoic acids liquid consisting of copolymers
31
What is the compressive strength of glass ionomer cements
90-230 MPa
32
What are the benefits of glass ionomer cements
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
What does the setting of resin modified glass ionomer cement lead to?
Leads to formation of a merl polyacrylate salt and a polymer
34
How do resin modified glass ionomers harden?
1. Acid base reaction | 2. Photo/chemcially imitated freer radical polymerisation of methacrylate units
35
``` Out of: Zinc phosphate GIC Polycarboxylate Resin modified GIC which has the highest compressive strength ```
Resin modified GIC
36
What are the disadvantages of resin modified GIC
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
Give an example go a resin moodier GIC
Rely X | FujiCEM
38
How is rely X set
In 2 setting reactions: 1. An acid base reaction 2. a free radical polymerisation
39
What free radical polymerisation reaction occurs when RelyX is setting
Free radical; polymerisation of the pendant methacrylate groups of the polymer and HEMA
40
Does the free radical reaction in RelyX need to be light activated?
no can be dark cured
41
How is RelyX sold?
As a paste/paste dispensed from a clicker
42
What do the 2 pastes that make up RelyX have in them
Paste A: Fluoraluminosilicate glass, HEMA and reducing agent Paste B: methacrylate polycarboxylic acid
43
How do resin composite cements work?
Via a BIS GMA resin+ methacrylates rection
44
How are resin composite cements polymerised?
Through photo/chemically imitated mechanisms
45
Do resin composite cements bond straight to the tooth?
Yes they micro mechanically adhere to enamel land dentine
46
What is a disadvantage of resin composite cements
Polymerisation shrinkage can occur
47
What is the polymerise shrinkage of resin composite cements dependent on?
Cement type and thickness
48
What are resin composite cements filled by?
50-70% filled by weight with glass/ silica
49
What are the advantages of using resin composite cements
1. High compressive strength 2. Resistant to tensile fatigue 3. Virtually insoluble in oral environment 4. They give an improved marginal wear resistance
50
What happens If you increase the filler content in resin composite cements?
High filler content: 1. increases viscosity 2. Reduces flow 3. Increases film thickness
51
When do we use resin compote cements?
Aesthetic restorations ie: Resin onlays/ inlays All ceramic restorations Fibre reinforced composites
52
What can polymerisation stress lead to in resin composite cements
Polymerisation stresses may form gaps between the cement and the tooth
53
How do resin composite cements bond?
They bond chemically to resin composite restorative materials and silanated porcelain
54
How can resin composite cements improve ceramic materials
Can be used to increase the fracture resistance of ceramic materials that can be etched and silanated
55
How can resin composite cements improve base metal alloys
Good bond strengths to sandblasted use metal alloys (micro mechanical)
56
What happens when 4 META cements are combined with resin?
4 META cements show strong adhesion due to chemical interaction of resin with oxide layer
57
What are the products with MDP called?
Panavia
58
What is a Panavia ?
It is a cement that has MDP
59
Name the active monomer in Panavia
MDP
60
Give some of the advantages of Panavia
1. It bonds well to sandblasted non precious and tin plated surfaces 2. Good physical properties 3. Bonding is water resistant
61
Give some of the disadvantages of panavia
1. Bonds weakly to dentine 2. Highly technique sensitive 3. Highly air inhibited
62
How does RelyX adhere to teeth?
It is formulates to be self adherent and moisture tolerant
63
What are the benefits of RelyX being self adherent
Elimates the need for a separate priming, etching or bonding step
64
Name the 2 mechanisms for the cements ability to bond to tooth surfaces
1. Self etching | 2. Secondary reaction
65
How does self etching allow materials to bond to the tooth surface
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
How do cements that work by secondary reactions bond to the tooth surface
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
Name some potential bonds that we may need to achieve
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
List the ideal properties of a cementing material
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
``` Out of the 3 cement options: Zin phosphate RMGIC Composite resin Which has the lowest film thickness? ```
``` Zinc phosphate (<25) RMGIC and Composite resin with >25 ```
70
``` Out of the 3 cement options: Zin phosphate RMGIC Composite resin Has the longest working time ```
Longest: Composite resin (3-10mins) Zinc phosphate (1.5-5mins) Shortest: RMGIC (2-4MINS)
71
``` Out of the 3 cement options: Zin phosphate RMGIC Composite resin Has the shortest setting time ```
Shortest: RMGIC (2mins) Composite resin (3-7mins) Zinc phosphate (5-14mins)
72
``` Out of the 3 cement options: Zin phosphate RMGIC Composite resin Has the highest compressive strength ```
Strongest: Composite resin (194-200MPa) RMGIC: (40-141) Weakest: Zinc phosphate (62-101MPa)
3rd Yr- CSB- Extra-coronal restorations
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