dental luting agents Flashcards
1
Q
what are they used for?
A
to cement indirect restorations
2
Q
properties of a luting agent
A
radiopaque viscosity and film thickness ease of use mechanical properties biocompatible cariostatic solubility aesthetics marginal seal
3
Q
what does the viscosity depend on?
A
size of powder or filler particles
4
Q
viscosity requirements
A
must be low - 20um or less
to allow seating of restoration without interference
5
Q
how does viscosity change as agent sets?
A
increases
- so must seat Rx quickly and maintain pressure
6
Q
film thickness requirements
A
as thin as possible
ideally 25um or less
7
Q
how are many made easy to use?
A
encapsulated
clicker system
8
Q
what should the working time be long enough to allow for?
A
seating
9
Q
why is it preferable for agents to be radiopaque?
A
makes it easier to see marginal breakdown or secondary caries
10
Q
ideal marginal seal
A
ideally chemical bond to tooth and indirect restoration
- permanent and impenetrable
11
Q
ideal aesthetics
A
tooth coloured - variation in shade and translucency
non-staining - problem with some of the resin materials
12
Q
ideal solubility
A
low
13
Q
biocompatibility
A
not toxic
not damaging to pulp (pH, heat on setting)
low thermal conductivity
- as many Rxs metal - want the cement to be insulating
14
Q
cariostatic
A
F releasing (GI) - bacteria don't like high F antibacterial important in preventing secondary caries around crown margins some redox reaction materials bactericidal - but tend to be bad for pulp
15
Q
ideal mechanical properties
A
high compressive strength
high tensile strength
high hardness value
YM similar to tooth
16
Q
types of materials
A
dental cement - zinc phosphate - zinc polycarboxylate GI cement - conventional - resin-modified composite resin luting agents - total etch for use with DBA - self-etch - requires etch but has own bonding agent incorporated
17
Q
zinc phosphate 2 basic components
A
powder
liquid
18
Q
zinc phosphate powder
A
ZnO >90% - main reactive ingredient MgO2 <10% - white colour - increases compressive strength other oxides (alumina and silica) - improve physical properties - alter shade of set material
19
Q
zinc phosphate liquid
A
H3PO4 (aq) 50%
oxides which buffer - Al2O3, ZnO
20
Q
zinc phosphate advantages
A
easy to use
cheap
21
Q
zinc phosphate liquid - oxides which buffer - Al2O3
A
ensures even consistency of set material
22
Q
zinc phosphate liquid - oxides which buffer - ZnO
A
slows reaction, better working time
23
Q
zinc phosphate reactions
A
initial - acid base
then hydration reaction
formation of crystallised phosphate matrix (around unreacted ZnO particles)
Al2O3 prevents crystallisation - amorphous glassy matrix of the zinc phosphate salt surrounding unreacted ZnO powder
matrix almost insoluble, but porous and contains free water from the setting reaction
cement subsequently matures (larger hydration reaction) binding this water - stronger, less porous material
24
Q
zinc phosphate problems
A
low initial pH2 exothermic setting reaction not adhesive to tooth or restoration not cariostatic final set takes 24hrs brittle opaque
25
zinc phosphate problems - low initial pH
can cause pulpal irritation as pH can take 24hrs to return to normal
26
zinc phosphate problems - not adhesive to tooth or restoration
works like grout on tiles just filling in any spaces
retention may be slightly micro mechanical due to surface irregularities on prep and restoration
advantage for temporary cement
- can use cavitron to remove instead of drill
- good for poorly retentive temps - quite rigid
27
zinc polycarboxylate cement chemistry
phosphoric acid replaced by poly acrylic acid
28
zinc polycarboxylate cement advantages
bonds to tooth in similar way to GIC (not as good)
less heat of reaction
pH low to begin with but returns to neutral more quickly and longer chain acids don't penetrate dentine as easily
cheap
29
zinc polycarboxylate cement disadvantages
difficult to mix and manipulate
soluble in oral env at lower pH
opaque
lower modulus and compressive strength than zinc phosphate
30
why are the dental cements mainly historic?
all of the more modern materials utilise chemical bonding to the tooth surface (some also bond to indirect restoration)
31
what is the main difference between GI filling material and cement?
particle size of glass
| <20um to allow for a suitable film thickness
32
AquaCem
GIC
33
GIC reaction chemistry
acid base reaction between glass and polyacid
dissolution, gelation, hardening
34
GIC bonding
cement bonds to tooth
- ion exchange with Ca in E and D
- H-bonding with collagen in the dentine
=fairly strong durable and possibly dynamic bond to tooth
no chemical bond to restoration surface
- sandblast to allow mechanical adhesion
35
advantages of GIC
```
easy to use
durable
low shrinkage
long term stability
relatively insoluble once fully set (Al)
- first week a bit soluble
aesthetically better than zinc phosphate
self-adhesive to tooth substance
fluoride release
cheap
```
36
RMGIC difference with filling material
glass particle size smaller so it has an acceptable film thickness
37
RMGIC chemistry
cGIC liquid and powder but liquid also contains a hydrophilic monomer
- HEMA (hydroxyethylmethacrylate)
38
in RMGIC why does the monomer need to be hydrophilic?
GIC is a water-based material so it needs to be water-soluble
39
RMGIC reactions
same acid base reaction as cGIC
- continues for some time
light activation - polymerisation of the HEMA and any co-polymers in the material - rapid initial set
GI setting within resin matrix
some materials have a secondary cure via a redox reaction - allows 'dark curing' - where material not exposed to light will cure
40
RMGIC advantages of having resin
```
shorter setting time
longer working time
higher compressive and tensile strengths
higher bond strength to tooth
decreased solubility
```
41
RMGIC problems
HEMA cytotoxic - v important that no monomer remains as it can damage the pulp
HEMA swells over time - expands in a wet env
- can't use to cement conventional porcelain crowns as they may crack
- don't use to cement posts - may split root
no bond to indirect restoration
42
how do composite luting agents vary form the filling material?
viscosity and filler particle size
43
what do composite luting agents need to be used with and why?
DBA
| no bond to tooth without
44
what can a light cure composite luting agent be used for?
veneers
45
advantages of composite luting agents
better physical properties
lower solubility
better aesthetics
46
disadvantages of composite luting agents
technique sensitive - need dry env
| physical properties reduced by 25% if not light cured
47
bonding to indirect composite
composite bonds to composite
- both hydrophobic so don't need anything between
bond strength lower to inlay fitting surface than to new composite
bond micro mechanical to rough internal surface of inlay
chemical to remaining C=C bonds on fitting surface of the inlay
48
what should be used to cement indirect composites?
dual cure composite resin cement and DBA
| - light penetration through an inlay poor
49
bonding to indirect composite diagram
resin inlay - hydrophobic
composite luting resin - hydrophobic
DBA - make tooth surface hydrophobic
tooth - hydrophilic
50
why does porcelain need to be bonded to the tooth?
it is brittle so needs to be bonded to tooth to prevent fracture (relying on tooth for strength)
51
etching the surface of porcelain
HF acid (v toxic)
52
why does the porcelain surface need to be etched?
untreated porcelain smooth and non-retentive
| etch to make rough retentive surface
53
why does porcelain require a surface wetting agent?
as it is not hydrophobic and compatible with composite resin luting agents
54
what is silane coupling agent applied to?
etched porcelain surface, ideally as a monolayer
55
what does the silane coupling agent bond to?
oxide groups on porcelain
| resin groups in composite resin luting agent
56
how does a silane coupling agent work?
in the same way as DBA to tooth
hydrophobic end - resin groups
hydrophilic end - to oxide on porcelain
57
components of bonding to porcelain
```
tooth - hydrophillic
DBA - makes tooth surface hydrophobic
composite luting resin - hydrophobic
silane - makes it hydrophillic
porcelain - hydrophilic
```
58
when is the only time you should use light cured?
if porcelain thin and use increased curing time
| if thick use dual cured
59
what should you do with composite luting resin before curing?
remove as much excess as possible
60
composite cements staining
long-term dual curing materials stain more whereas light-cured won't
61
do metals bond directly to composite?
no
62
what should be done to the metal surface before cementing?
sandblasting
roughens surface but doesn't give undercut surface of etching
- need chemical bonding to strengthen bond
63
etching metals - electrolytic etching
metal in acid, pass electric current through it
removes the different phases of the alloy at different rates
gives v retentive surface
BUT
- technique sensitive
- beryllium containing alloys work best - carcinogenic to lab worker
- cant etch precious metals at all
rarely used
64
bonding to non-precious metal components
```
tooth - hydrophillic
DBA - makes surface hydrophobic
composite luting resin - hydrophobic
metal bond agent - makes it hydrophilic
non-precious metal - hydrophilic
```
65
metal bonding agent
materials with carboxylic and phosphoric acid derived resin monomers
MDP and 4-META
have acidic end - reacts with the metal oxide and makes the surface hydrophobic
has C=C end
66
what luting agent should be used for bonding to non-precious metal?
dual cure as light won't penetrate metal
67
bonding to precious metal
change precious alloy composition to allow oxide formation
- increase copper content and heat 400 degrees in air
tin plate
sulphur based chemistry of bonding agent
all complicated and technique sensitive
68
self-adhesive composite resin
```
metal coupling agent incorporated into the composite resin
simplifies bonding process
MDP used in panavia
consistent results
good film thickness
opaque
moisture sensitive
expensive
```
69
Panavia
anaerobic self-curing composite resin which contains MDP
anaerobic - will only set with no air
- put special gel on - to ensure the edges are all set
70
bonding to non-precious metal with panavia ex components
tooth
(own) DBA
panavia ex
non-precious metal
71
RelyX Unicem
self-etching composite resin luting agent
72
self-etching composite resin luting agents
combination of a composite resin cement and a self-etching DBA
has self-etching and self-bonding
has MDP - will stick to oxide groups to metal and porcelain
73
chemistry of self-etching composite resin luting agents
attaches like a self-etching primer (sort of)
acid groups in the resin bind to Ca of HA in tooth
- bind stabilising attachment
ions from dissolution of filler neutralise remaining acidic groups - chelate reinforced methacrylate network
has acid groups attached to long chain polymers, act on E and D surface so more chemical can attach in that area
74
self-etching composite resin luting agents problems
requires good moisture control
? bond strength to enamel due to inadequate etching
pH of carboxylic monomer doesn't stay low for long enough to give a good etch
limited removal of smear layer/significant infiltration into tooth surface (only a couple of microns)
v expensive
75
self-etching composite resin luting agents advantages
good bond strength to dentine
micro mechanical adhesion
mechanical strength and wear resistance slightly lower than conventional resin luting agents but better than 'cements'
easy to use
76
self-adhesive composite resin
```
metal coupling agent incorporated into the composite resin
simplifies bonding process
MDP used in panavia
consistent results
good film thickness
opaque
moisture sensitive
expensive
```
77
Panavia
anaerobic self-curing composite resin which contains MDP
anaerobic - will only set with no air
- put special gel on - to ensure the edges are all set
78
bonding to non-precious metal with panavia ex components
tooth
(own) DBA
panavia ex
non-precious metal
79
RelyX Unicem
self-etching composite resin luting agent
80
self-etching composite resin luting agents
combination of a composite resin cement and a self-etching DBA
has self-etching and self-bonding
has MDP - will stick to oxide groups to metal and porcelain
81
chemistry of self-etching composite resin luting agents
attaches like a self-etching primer (sort of)
acid groups in the resin bind to Ca of HA in tooth
- bind stabilising attachment
ions from dissolution of filler neutralise remaining acidic groups - chelate reinforced methacrylate network
has acid groups attached to long chain polymers, act on E and D surface so more chemical can attach in that area
82
self-etching composite resin luting agents problems
requires good moisture control
? bond strength to enamel due to inadequate etching
pH of carboxylic monomer doesn't stay low for long enough to give a good etch
limited removal of smear layer/significant infiltration into tooth surface (only a couple of microns)
83
self-etching composite resin luting agents advantages
good bond strength to dentine
micro mechanical adhesion
mechanical strength and wear resistance slightly lower than conventional resin luting agents but better than 'cements'
84
self-etching composite resin luting agents bonding to E
lower strength than to dentine (less acid)
| etch with phosphoric acid
85
self-etching composite resin luting agents bonding to D
better than to enamel
| don't need to etch
86
self-etching composite resin luting agents bonding to ceramics
brand specific
| RelyXUnicem seem to bond quite well to sandblasted Zi
87
self-etching composite resin luting agents bonding to metal
better to non-precious
| not good enough to cement ortho brackets
88
self-etching composite resin luting agents research
v few clinical studies - nothing long term enough
89
self-etching composite resin luting agents vs traditional uses
if you can't use a DBA and conventional resin cement you cant use these
90
self-etching composite resin luting agents components
tooth
self-etching composite resin luting agent
indirect Rx
91
MCC
GIC
92
metal post
GIC
93
fibre post
dual cure composite and DBA
94
veneer
light cure composite and DBA
95
adhesive bridge
anaerobic cure composite
96
Zi crown
GIC
97
composite inlay
dual cure composite and DBA
98
carnauba wax
weakens structure of set cement - easier to remove
99
gold restoration
GIC
100
general rules of what to use
if you can break it with your fingers use a resin cement
if you can throw it off a wall you can stick it in with a cement
exception adhesive bridge
101
cementing temporary restorations requirements
soft for easy removal
prep needs to be physically retentive
can be used for trial lute of permanent
102
what won't temporary cements work with?
veneer or round onlay - not retentive
103
temporary cements 2 paste systems
base and catalyst/accelerator
104
temporary cements 2 paste systems - base
ZnO, starch and mineral oil
105
temporary cements 2 paste systems - accelerator
resins, eugenol or ortho-EBA and carnauba wax
106
carnauba wax
weakens structure of set cement - easier to remove
107
how can you make temp cement weaker?
incorporate petroleum jelly into the mixture
108
2 main types of temporary cement
with eugenol
| without eugenol
109
when shouldn't you use temp cements containing eugenol?
where permanent will be cemented with a resin cement
| eugenol plasticiser for composite - any residual eugenol may interfere with the setting
110
why should you ensure complete removal of the temporary cement?
may stop you seating restoration
| will stop you bonding to tooth surface
