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BDS3 CLINICAL DMS > Dental Luting Agents > Flashcards

Dental Luting Agents Flashcards

1
Q

What comes under luting agents

A

dental cements
composite resins
self adhesive composite resins
surface modifying chemicals

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2
Q

What are properties of a luting agent

A 
viscosity and film thickness
ease of use
radiopaque
marginal seal
aesthetics
solubility
cariostatic
biocompatible
mechanical properties
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3
Q

What is viscosity and film thickness dependent on

A

size of powder or filler particles in the material

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4
Q

Should a luting agent be viscous

A

no

must be low to allow seating of the restoration without interference

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5
Q

What happens to the viscosity once the material sets

A

increases

need to seat the restoration quickly and maintain pressure

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6
Q

What is the ideal film thickness

A

should be as thin as possible ideally

25 um or less

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7
Q

What is required for ease of use

A

easy to mix
working time should be long to allow for seating of the restoration
setting time should be short

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8
Q

What are systems that allow for something to be easy to mix

A

encapsulated

clicker system

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9
Q

What is the ideal way of setting

A

command set

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10
Q

Why is radiopacity important

A

some ceramic crowns are radiolucent

makes it easier to see marginal breakdown

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11
Q

What is the ideal way for a marginal seal to be made

A

ideally the luting agent should bond chemically to the tooth and the indirect restoration with a permanent and impenetrable bond

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12
Q

What is the ideal aesthetics

A

tooth colored and a variation in shade and translucency

non staining as long term if there is luting agent at the surface of the restoration we don’t want it to stain

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13
Q

What is the ideal solubility

A

LOW

don’t want it to wash away under influence of saliva

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14
Q

What is the ideal cariostatic properties

A

fluoride releasing
antibacterial
to prevent secondary caries around margins and prevent leakage

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15
Q

What is ideal biocompatible properties

A

non toxic
not damaging to the pulp whether it be that on setting or an inappropriate pH
low thermal conductivity

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16
Q

Why is low thermal conductivity significant

A

many restorations that we fit are metal based and it would be good for low thermal conductivity to have similar to a lining under a metal filling to protect from hot and cold

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17
Q

What are important mechanical properties

A

high compressive strength
high tensile strength
high hardness value
young’s modulus similar to tooth

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18
Q

What are the types of materials

A

dental cements
GIC cements
composite resin luting agents

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19
Q

What are the dental cements

A

zinc phosphate

zinc polycarboxylate

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20
Q

What are the GIC

A

conventional

RMGI

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21
Q

What are the composite resin luting agents

A

total etch for use with DBA
self etch
requires etch but has own bonding agent incorporated

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22
Q

Describe zinc phosphate as a dental cement

A 
acid base reaction
powder and liquid
excellent clinical service
easy to use
cheap
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23
Q

What is the powder composition of zinc phosphate cement

A 
zinc oxide (main reactive ingredient)
magnesium oxide
other oxides (alumina and silica)
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24
Q

What is the function of magnesium in the ZPC

A

gives white colour

increases the compressive strength

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25
Q

What is the function of the other oxides in ZPC

A

improves physical properties

alters shade of set material

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26
Q

What is the liquid part of ZPC

A

aqueous solution of phosphoric acid

oxides which buffer the solution (aluminum and zinc oxides)

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27
Q

What is the function of aluminum oxide in the liquid portion of zinc phosphate cement

A

ensures even consistency of set material

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28
Q

What is the function of zinc oxide in the liquid component of zinc phosphate cement

A

slows the reaction giving better working time

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29
Q

What is the initial reaction of ZPC

A

acid base

zinc oxide + phosphoric acid –> zinc phosphate + water

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30
Q

What is the second reaction in ZPC

A

hydration reaction resulting in the formation of a crystallized phosphate matrix

results in matrix of zinc phosphate surrounded by unreacted zinc oxide particles

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31
Q

What does the aluminum oxide prevent in zinc phosphate setting reaction

A

crystallization

leads to an amorphous glassy matrix of the acid salt surrounding unreacted ZnO powder

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32
Q

What is the resultant matrix of zinc phosphate cement like

A

almost insoluble, but it is porous and contains free water from the setting reaction

cement subsequently matures binding this water leading to a stronger less porous material

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33
Q

What are problems with zinc phosphate cement

A

low initial pH (approx. 2) and can take 24h to return to neutral

exothermic reaction
not adhesive to tooth or restoration

not cariostatic

final set takes 24h

brittle

opaque

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34
Q

What does the zinc phosphate cement do in relation to the tooth or restoration

A

works like grout on tiles filling any spaces

retention may be slightly micro mechanical due to surface irregularities on prep restoration

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35
Q

What is zinc polycarboxylate cement

A

similar material but phosphoric acid replaced by poly acrylic acid

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36
Q

What are advantages of zinc polycarbonate cement

A

this material had the advantage of bonding to tooth surfaces in a similar way to GIC

there is less heat reaction

the pH is low to begin with but returns to neutral more quickly and longer chain acids do not penetrate dentine as easily

cheap

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37
Q

What are disadvantages of zinc polycarboxylate cement

A 
difficult to mix
difficult to manipulate
soluble in oral environment at lower pH
opaque 
lower modulus and compressive strength than zinc phosphate
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38
Q

Why are dental cements rarely used now

A

modern materials utilize chemical bonding to tooth surface and can also bond to indirect restoration too

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39
Q

What is main difference between GI and GIC

A

GIC has a particle size of glass which is less than 20um to allow for suitable film thickness

if they were bigger they would interfere with the ability of the restoration to seat hence why you can’t use the GI filling material as a luting agent

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40
Q

What is the reaction of GIC

A

acid base

between glass and acid

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41
Q

What is the glass in GI made up of

A

silicone oxide
aluminum oxide
calcium fluoride

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42
Q

What is the poly acid mixture of GIC

A

mixture of acrylic, malice and itaconic acid and their copolymers

43
Q

How does GIC bond to the tooth surface

A

ion exchange with calcium in enamel and dentine

hydrogen bonding with the collagen in the dentine

44
Q

What does the GIC bond result in

A

fairly strong durable and possibly diamond bond to tooth

no chemical bond to restoration surface

surface of the restoration should be sandblasted to allow mechanical adhesion

45
Q

What makes GIC clinically easy to use

A

it is easy to use and a durable cement

low shrinkage
low term stability
relative insoluble once fully set
aesthetically better than zincphosphate
self adhesive to tooth substance
fluoride release
cheap
46
Q

What is the chemistry of RMGI

A

same as filling material

glass particle smaller to allow acceptable film thickness

47
Q

What does RMGI contain that the conventional GI doesn’t

A

hydrophilic monomer

48
Q

Why must the RMGI monomer be hydrophilic

A

as GIC is water based material

49
Q

What is the hydrophilic monomer in RMGI

A

HEMA

50
Q

What is the reaction of RMGI

A

same acid base reaction

light activation causes polymerization of the HEMA and any copolymers in the material leading to a rapid initial set

acid base reaction then continues for some time

some materials have a secondary cure via a REDOX reaction which allows for dark curing where material is not exposed to light will cure

51
Q

What are the improved problems due to incorporation of resin in GI

A 
shorter setting time
longer working time
higher compressive strength and tensile strengths
higher bond strength to tooth
decreased solubility
52
Q

What are potential problems with RMGI

A

HEMA is cytotoxic
HEMA swells and expands in a wet environment
no bond to indirect restoration

53
Q

What is the consequence of HEMA swelling in wet environment

A

cannot be used to cement conventional porcelain crowns as they may crack

shouldn’t be used to cement posts as they may split the root

54
Q

What are temporary cements

A

made to cement temporary restorations in place while permanent is fabricated

55
Q

What are features of temporary cements

A

soft for easy removal, some do not set at all

prep must be physically retentive or they will not work

can be used for trail lute of permanent restorations to allow assessments by patient or clinical

56
Q

How are temp cements supplied

A

two paste systems - base and catalyst or accelerator

57
Q

What does the base of temp cements contain

A

ZNO, starch and mineral oil

58
Q

What does the accelerator of temp cements contain

A

resins, eugenol or ortho-EBA and carnauba wax

59
Q

What is the role of wax in temp cements

A

weakens the structures of set cement and makes it easier to remove

60
Q

How can temp cements be modified

A

make it weaker by incorporating petroleum jelly into mixture

61
Q

What are the two types of temp cements

A

eugenol containing and without eugenol containing

62
Q

Where should eugenol temp cements not be used

A

to cement the provisional restoration where the permanent restoration will be cemented with a resin cement

63
Q

What may residual eugenol interfere with

A

the setting of this type of resin luting agent

64
Q

What are the 3 phases of GI setting reaction

A

dissolution
gelation
hardening

65
Q

What is the dissolution phase

A
  1. Acid goes into solution and reacts with outer layer of glass
    1. Layer becomes depleted in aluminium, calcium and fluorine ions so that only a silica gel remains
    2. Hydrogen ions that are released from the carboxyl group of the acid diffuse to the glass and makeup for the loss of other ions
      LEAVES AN UNREACTED GLASS CORE WITH SILICA GEL ON THE OUTSIDE
66
Q

What is the gelation phase

A

Initial set is due to calcium ion crosslinking with the carboxyl group of the polyacid (chelation) but the cross linking is not ideal as the calcium can chelate with the two carboxyl groups on the same molecule

Initial set is caused by formation CALCIUM POLYACRYLATE

67
Q

What is the hardening phase

A

w Aluminium is what provides the final strength to cement
w Aluminium is trivalent so ensures a high degree of cross linking on the polymer molecule
Once cement has fully reacted the final structure consists of glass particles, each which is surrounded by a silica gel in a matrix of cross linked polyacrylic acid

68
Q

What is the bond to indirect composite restorations

A

the bond strength is lower to inlay fitting surfaces than to new composite
the bond is micromechanical
bond is also chemical
we use a dual curing cement

69
Q

What is the micro mechanical bond to in indirect composite restorations

A

rough internal surface of the inlay

70
Q

What is the chemical bond to in indirect composite restorations

A

remaining C=C bonds on the fitting surface of the inlay

71
Q

What is used to bond the composite inlay

A

tooth –> DBA –> composite luting resin –> resin inlay

72
Q

Why should porcelain be bonded to tooth

A

to prevent fracture

untreated porcelain to is smooth and non retentive

73
Q

How is porcelain treated for boding to tooth

A

hydrofluoric acid

74
Q

What does hydrofluoric acid do to the porcelain

A

produced a rough retentive surface but it is still not hydrophobic and compatible with composite resin luting agents

75
Q

What is required to bond the hydrophilic porcelain to the composite resin luting agent

A

a surface wetting agent - silane coupling agent

76
Q

What is the silane coupling agent applied to

A

etched porcelain surface in a monolayer

77
Q

How does the silane bonding agent work

A

Has a hydrophilic end (hydroxyls on it) that can bond to the oxide groups on the porcelain surface

Has a hydrophobic (C=C) double bond which reacts with the composite resin luting agent

78
Q

What are the components of bonding porcelain to tooth

A

tooth > DBA > comp luting agent > silane > porcelain

79
Q

Why is a dual curing cement needed for indirect composite

A

as light penetration through the inlay will be poor

80
Q

What kind of luting agent do we use for bonding to porcelain

A

light cured if restoration is thin

if thick use a dual cured composite

81
Q

How do we bond tooth to metal

A

does not bond to metal directly
metal surface needs roughened
can be done by etching but more usually done by sandblasting

82
Q

What did etching the metal do

A

was called electrolytic etching

removes diff phases of alloy at diff rates giving a retentive surface

83
Q

What were the issues with etching metal

A

technique sensitive

cannot etch precious metals

84
Q

What does sandblasting the e-mail do

A

roughens surface but does not give the undercut surface of etching
chemical bond required to strengthen bond

85
Q

How do we bond the composite luting agent to the non precious metal

A

materials with carboxylic and phosphoric acid derived resin monomers
MDP and 4-META

86
Q

How do the metal bonding agents work

A

have a acidic end of the molecule that reacts with the metal oxide and renders the surface hydrophobic

87
Q

What type of cure does the luting agent need to be when bonding to metal

A

dual

light will not penetrate

88
Q

What is the issues with the materials used to bond the non precious metal

A

technique sensitive
will not work unless moisture control is adequate
we don’t use it for everything
will not bond to precious metal

89
Q

What is the components of bonding non precious metal to tooth

A

tooth > DBA > composite luting resin > metal bond agent > non precious metal

90
Q

How do we bond to precious metal

A

change precious alloy composite to allow oxide formation
tin plate
sulphur based chemistry of bonding agent
all complicated and technique sensitive

91
Q

How do we change the precious alloy composition to allow oxide formation

A

increase copper content and heat 400 degrees in the air

92
Q

What are self adhesive composite resins

A

metal and coupling agent is incorporated into the composite resin
this simplifies the bonding process

93
Q

What are the adv and disadv of self adhesive composite resin (panavea)

A 
anaerobic self cured material 
consistent results over many years
good film thickness
opaque
moisture sensitive
expensive
94
Q

So what is required in bonding non precious material to tooth using panavia

A

tooth > DBA > panacea ex > non precious metal

95
Q

What is self etching composite resin cements

A

combo of comp resin cement and self etching DBA

96
Q

What are the issues with self etching composite resin cements

A

Dentine bonding requires good moisture control
there is doubt about the bond strength to enamel due to inadequate etching
pH of carboxylic monomer doesn’t stay low for long to give good etch

97
Q

How does the self etching composite resin luting agents work

A

acidic groups bind with calcium in hydroxyapatite forming a stabilizing attachment between tooth and resin

ions form dissolution of filler neutralize the remaining acid groups forming a chelate reinforced methacrylate network

limited removal of smear layer or significant infiltration into tooth surface

good bond strength to dentine

98
Q

What are the mechanical properties for self etching composite resin luting agent

A

compressive strength
tensile strength
hardness
wear resistant

all slightly lower than conventional resin luting agents but better than ‘cements’

99
Q

How does self etching composite resin luting agent compare in bonding to enamel

A

lower than dentine

should be etched with acid prior to application

100
Q

How does self etching composite resin luting agent compare in bonding to dentine

A

better than enamel

should not be etched with acid prior to application

101
Q

How does self etching composite resin luting agent bonding to ceramic

A

brand specific

102
Q

How does self etching composite resin luting agent compare in bonding to metal

A

better to non precious

not good enough to cement ortho brackets

103
Q

When can you not use a self etching composite resin luting agent

A

if you can’t use a DBA or conventional resin cement can’t use this as still have issue of moisture control

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