7 - Luting agents Flashcards
1
Q
What are examples of luting agents?
A
- dental cements
- composite resin
- self adhesive composite resin
- surface modifying chemicals
2
Q
Describe the ideal film thickness of a luting agent.
A
- film thickness is dependant on the filler particle size
- film thickness must be low to allow seating of the restoration without interference
- ideally 25um or less
3
Q
Describe the ideal viscosity of a luting agent.
A
- low viscosity prevents interference with the seating o the restoration
- the viscosity increases as the material sets, so restoration should be placed quickly and pressure maintained during set
4
Q
Describe the ideal working time of a luting agent.
A
Long, to allow for seating of restoration
5
Q
Describe the ideal setting time of a luting agent.
A
Short
6
Q
How are luting agents mixed?
A
- some are encapsulated
- some use a clicker system
7
Q
Describe the ideal radiopacity of a luting agent.
A
- ideally radiopaque
- some ceramic crowns are radiolucent so it make it easier to see the margin and any breakdown
8
Q
Describe the ideal bond of a luting agent.
A
- marginal seal ideally chemically bonds to both the tooth and the restoration
- should be permanent and impenetrable
9
Q
Describe the ideal aesthetics of a luting agent.
A
- tooth coloured (prevents metal restoration shining through)
- non staining (may shine through tooth)
10
Q
Describe the ideal solubility of a luting agent.
A
LOW
11
Q
Describe the cariostatic properties of a luting agent.
A
- fluoride releasing
- antibacterial
- helps to prevent secondary caries in crown margins
12
Q
Describe the ideal biocompatibility of a luting agent.
A
- non toxic
- not damaging to pulp, ie neutral pH and low heat release on setting
- low thermal conductivity
13
Q
Describe the ideal mechanical properties of a luting agent. (4)
A
- high compressive strength
- high tensile strength
- high hardness value
- similar Youngs modulus to tooth (15GPa)
14
Q
Name a dental cement.
A
- zinc phosphate
- zinc polycarboxylate
15
Q
What are the different types of GI cement?
A
- conventional
- resin modified
16
Q
What are the different types of composite resin luting agent?
A
- total etch for use with DBA
- self etch
- requires etch but has own bonding agent incorporated
17
Q
Describe zinc phosphate cement.
A
- dental cement
- acid base reaction
- powder and liquid
- easy to use
- cheap
18
Q
What are the components of zinc phosphate? (3+3)
A
POWDER
- zinc oxide
- magnesium dioxide
- alumina and silica oxides
LIQUID
- phosphoric acid
- aluminium oxide
- zinc oxide
19
Q
What are the components of zinc polycarboxylate?
A
POWDER
- zinc oxide
- magnesium dioxide
- alumina and silica oxides
LIQUID
- polyacrylic acid
- aluminium oxide
- zinc oxide
20
Q
What are the negatives associated with zinc phosphate cement?
A
- low pH (2) which can cause pulpal irritation
- exothermic setting reaction
- not adhesive to tooth or restoration (acts like grout)
- not cariostatic
- final set 24hrs
- brittle
21
Q
Describe zinc polycarboxylate cement.
A
- dental cement
- similar to zinc phosphate, phosphoric acid replaced by polyacrylic acid
- bonds to tooth surfaces
- less exothermic reaction
- low pH is for less time, therefore less pulpal irritation
- cheap
22
Q
What are the negatives associated with zinc polycarboxylate cement?
A
- difficult to mix
- difficult to manipulate (jelly like consistency)
- soluble in oral environment
- lower modulus and compressive strength than zinc phosphate
23
Q
Describe GI cement.
A
- particle size smaller than that of the filling material
- acid base reaction between glass and acid
- same dissolution, gelation and hardening reaction
- bonds to tooth via ion exchange from calcium and hydrogen bonding with collagen
- no chemical bond to restoration
- cheap
24
Q
Describe the physical properties of GI cement. (6)
A
- low shrinkage
- long term stability
- relatively insoluble after set
- aesthetic
- self adhesive to tooth
- fluoride release
25
Describe RMGIC.
- same acid base reaction as GIC
- HEMA added to cause polymerisation resulting in rapid set
26
How does RMGIC properties differ from GIC?
RMGIC has
- shorter setting time
- longer working time
- higher compressive and tensile strength
- higher bond strength to tooth
- decreased solubility
27
What are the negatives associated with RMGIC?
- HEMA is cytotoxic and can damage pulp
- HEMA swells in a damp environment, can crack crowns or tooth (do not use to cement posts as may split root)
- no bond to restoration
28
Describe composite luting agents.
- variant on filling material, with smaller filler particles
- used in conjunction with DBA
- light or dual cured
- better physical properties but technique sensitive
- can chemically bond to indirect composite restorations
29
How do composite luting agents bond to porcelain restorations?
- hydrofluoric acid (lab use) etches the surface of porcelain to allow for micro-mechanical bonds to form
- wetting agent is required as composite luting agent and porcelain are not compatible (porcelain is hydrophilic and composite is hydrophobic)
30
What is silane coupling agent?
- applied to etched porcelain surface as a monolayer
- very strong bond between oxide groups on porcelain surface and silane
- other end of silane has C=C bond which bonds with composite
31
How do you bond to an indirect metal restoration?
- surface needs to be roughened by sandblasting for mechanical bond
- bond strengthened by chemical bonding
- requires dual curing as light does not penetrate metal
- can be used to cement most indirect restoration including posts
32
What material can be used to bond to a non-precious metal?
Materials with carboxylic or phosphoric acid derived resin monomers
33
How do you bond to a precious metal?
- change the alloy composition to allow oxide formation (eg increase copper)
- tin plate
- very technique sensitive
34
Describe self adhesive composite resin.
- metal coupling agent is incorporated
- anaerobic self cured material
- good film thickness
- opaque (prevents shine through of metal)
- moisture sensitive
35
What type of dental cement should you use for a metal ceramic crown?
GIC
36
What type of dental cement should you use for a metal post?
GIC
37
What type of dental cement should you use for a fibre post?
Dual cure composite and DBA
38
What type of dental cement should you use for a veneer?
Light cure composite and DBA
39
What type of dental cement should you use for an adhesive bridge?
Anaerobic cure composite
40
What type of dental cement should you use for a zirconia crown?
GIC
41
What type of dental cement should you use for a composite inlay?
Dual cure composite and DBA
42
What type of dental cement should you use for a porcelain inlay?
Dual cure composite and DBA
43
What type of dental cement should you use for a gold restoration?
GIC
44
What are temporary cements?
- used to hold temporary restorations in place whilst a permanent one if constructed
- soft for easy removal
- prep must be physically retentive
45
What are the components of temporary cement? (3+3)
BASE
- ZnO
- Starch
- mineral oil
ACCELERATOR
- resin
- eugenol
- carnauba wax (prevent set)
45
When are eugenol temporary cements contraindicated?
When the permanent restoration contains resin
