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DMS > Luting Agents > Flashcards

Luting Agents Flashcards

1
Q

What properties are advantageous for luting agents?

A

Low viscosity and film thickness
Easy to mix
Long working time
Short setting time
Radipaque
Bond chemically to tooth
Tooth coloured
Low solubility
Cariostatic
Non-toxic
High compressive strength, tensile strength, hardness.
YM similar to tooth

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2
Q

Why do you want a luting agent with a low viscosity?

A

Must be low to allow seating of the restoration without interference.

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3
Q

Why do you want a luting agent that is radiopaque?

A

Some ceramic crowns are radiolucent, so it is important that the cement is radiopaque to see marginal breakdown.

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4
Q

Why do you want a luting agent that has a low solubility?

A

So that the cement does not wash away with fluid in the mouth, otherwise, the restoration will fall out.

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5
Q

Why is Zinc Phosphate not a good luting agent?

A

It does not bond directly to teeth, takes 24 hours for final set, brittle.

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6
Q

What type of reaction is involved in zinc phosphate cement?

A

Acid-base reaction between zinc oxide and phosphoric acid.

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7
Q

Name a use for zinc phosphate cement.

A

Cement in a temporary only where there are not lots of retentive surfaces.
It doesn’t bond to tooth, so will come out easily when you remove the temporary and not damage the tooth.

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8
Q

What type of reaction occurs in glass ionomer cement?

A

Acid-base reaction between glass- SiO2, Al2O3 and CaF2, poly acid- poly acrylic acid.

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9
Q

What are the three stages of the reaction?

A

Dissolution
Gelation
Hardening

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10
Q

What occurs during the dissolution phase?

A

Dissolving of the glass in the acid.
Causes release of polyions.

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11
Q

What occurs during the gelation reaction?

A

Initial set- calcium ions cross link with he poly acid by chelation with the carboxyl groups.
- makes calcium polyacrylate.

Takes several minutes.

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12
Q

What occurs during the hardening reaction?

A

Trivalent aluminium ions crosslink with the calcium polyacrylate to make aluminium polyacrylate.

Starts after 30 minutes and can take a week or longer to complete.

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13
Q

How does GI cement bond to the tooth surface?

A

Ion exchange with calcium in female and dentine
Hydrogen bonding with the collagen in dentine.

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14
Q

What must be done to the surface of the restoration before bonding with GI cement?

A

Surface of restoration should be sandblasted to allow mechanical adhesion.

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15
Q

What is the difference between GI as a filling material and GI as a cement?

A

GI cement has smaller particle size to allow for suitable film thickness.

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16
Q

Advantages of GI cement

A

Insoluble once set
Self adhesive to tooth substance
Fluoride release
Cheap
Long term stability

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17
Q

What is the extra component in RMGI cement that is not in GI cement?

A

HEMA- hydrophilic monomer.

18
Q

What type of reaction occurs in RMGI cement?

A

Acid-base reaction
Light activation causes polymerisation of the HEMA.
Also redox reaction which cures the resin where light has not reached.

19
Q

Advantages of RMGI

A

Shorter setting time
Longer working time
Higher compressive and tensile strengths
Higher bond strength to tooth
Decreased solubility

20
Q

Why can RMGI not be used to cement in porcelain crowns or posts?

A

HEMA swells in a wet environment.
Porcelain crowns may crack under this pressure.

21
Q

Why do you need a DBA. when using a composite cement?

A

Need to turn the tooth from hydrophilic to hydrophobic, so that the composite cement will bond.

22
Q

What is a disadvantage of composite cements?

A

Very technique sensitive
- needs to be very dry, light penetration is poor for light cured.

23
Q

What bond is present between the composite cement and the surface of the inlay?

A

Micromechanical through the roughened surface of the inlay and also chemical through the C=C bonds on the fitting surface of the inlay.

24
Q

Why is it better to use a dual-cured composite cement than light cured?

A

Light penetration through the inlay is poor.

25
Q

What substance is used to etch the surface of porcelain?

A

Hydrofluoric acid- roughens the surface to make it more retentive.

26
Q

Why is a silane coupling agent needed when bonding to porcelain?

A

After the porcelain surface is etched with HF, it is still hydrophilic.
The Silane part binds to oxide groups on the porcelain surface and the other end has a C=C bond, which binds to the composite resin luting agent.

27
Q

What must be done to the surface of metal before bonding to composite luting cement?

A

Sandblasted to roughen the surface.

28
Q

What components are found in a metal bonding agent?

A

MDP and 4-META
- acidic end and C=C bond.

29
Q

Why must you use dual-cured material for metal restorations?

A

Light will not penetrate the metal.

30
Q

What is a self adhesive composite resin?

A

Metal bonding agent is already incorporated into the resin.

31
Q

Name an example of a self adhesive composite resin.

A

Panavia.

32
Q

What is a self etching composite resin cement?

A

Combination of composite resin cement and a self etching dentine bonding agent.

33
Q

What is the mechanism of action of s self-etching composite resin luting cement?

A

Acidic group binds with the calcium in hydroxyapatite- attaches tooth to resin.

34
Q

How do self-etching composite resin luting cements compare to conventional resin luting agents?

A

Slightly lower strength in all categories
- compressive strength
- Tensile strength
- Hardness
- Wear resistance

35
Q

What is an example of a self-etching composite resin luting cement?

A

RelyX.

36
Q

What restorations should be cemented with GIC?

A

MCC, metal post, zirconia crown, gold restoration.

37
Q

What cement should be used to cement in a veneer?

A

Light cure composite plus DBA.

38
Q

What restorations should be cemented in with dual cure composite?

A

Fibre post, composite inlay and porcelain inlay.

39
Q

What cement should be used for an adhesive bridge?

A

Anaerobic core composite (self etching).

40
Q

What is the purpose of a temporary cement?

A

Cement in a temporary restoration while the permanent restoration is fabricated.

41
Q

What is the reaction of a temporary cement?

A

Base and catalyst.
Carnauba wax weakens the bond, making it easier to remove.

42
Q

Why must you not use a temporary cement with eugenol if you are going to use resin cement for the permanent restoration?

A

Eugenol will interfere with the setting of the resin luting cement.

DMS (13 decks)

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