all about glass ionomer cement

1. All about
Glass Ionomer Cements
by
dr.anoop.v.nair

2. • Introduction
• Definitions & terminologies
• Scientific & clinical development
• Classification
• Composition
• Setting reaction
• Water balance
• Adhesion
• Properties
• Clinical implications
• Instructions to dental assistants
• Review of literature
• References
• Summary & conclusion

3. DEFINITIONS &
TERMINOLOGIES

4. • The word “ionomer” was coined by Dupont company
• Describe its range of polymers containing a small proportion of
ionized or ionizable groups generally of the order of 5% to 10%.
• Does not properly apply to components of GI dental cement
• Therefore the term Glass polyalkenoate cement was devised.
• Systematic name in Chemical Abstracts ; Official ISO terminology
• Does not apply to recently developed poly(vinyl phosphonic acid)
cements ---- Glass Polyphosphonates.
• Therefore the term “Glass - ionomer cement” is a generic one for
all glass polyacid cements.

5. • Glass : Acid-decomposable glass
• Acidic polymer :Typically poly(acrylic acid)
• Successful acids are – water soluble &
polyelectrolytes.
 Acid-base reaction :The cement forming reaction is defined
as the conversion of initially viscous paste to a hard solid, & in
a true glass-ionomer cement this reaction takes place within a
clinically acceptable time i.e, a few minutes.
Definition of glass ionomer cement
A cement that consists of a basic glass & an acidic polymer
which sets by an acid-base reaction between these
components. (Mclean & Wilson 1994)

6. The essential elements of a true glass ionomer :
• Acid-base setting reaction
• Ion-exchange adhesion with underlying tooth structure
• Continuing ion activity, with mobility of fluoride, calcium and
phosphate ions

7. • Definition (Akinmade & nicholson, 1993) water based
cement where-in following mixing, the glass powder &
polyalkenoic acid undergo an acid/base setting reaction.
The acid attacks the surface of powder particles,
releasing calcium & aluminium ions, thus developing a
diffusion-based adhesion between powder & liquid

8. Types of glass ionomer cements
1. Based on chemical composition
2 types of glass ionomer :
• Glass-ionomer cement
• Glass polyalkenoates
• Glass polyphosphonates
• Glass-ionomer hybrid materials
• Resin modified glass-ionomer
2. Based on types of cure :
• Autocure : Chemical cure – acid-base reaction
• Dualcure : Light initiation followed by acid-base reaction
• Tricure : Autocure resin reaction in remaining uncured resin

9. Glass-ionomer hybrid materials
• The term “Resin-modified glass-ionomer” originally
used by Antonucci et al, is the trivial name.
• Systematic name, for precise chemical nomenclature
as in ISO standards is “Resin-modified glass-
polyalkenoate”
• Consists of components of glass ionomer, modified
by inclusion of a small quantity of additional resin,
mostly HEMA.
• They set partly by acid-base reaction & partly by
photochemical polymerization.

10. Other polymerizable restorative materials :
Polyacid modified composite resins (Compomers)
• Donot belong to glass-ionomer category.
• The correct ingredients are present (acid decomposable glass
& possibly some polymeric acid) but in an insufficient amount
to promote acid-base cure in dark
• Donot set without light activation.
• Donot bond to tooth structure through ion-exchange
mechanism.
• Fluoride reservoir effect of glass ionomer is not available.

11. Diagram showing theoritical composition of various resin-modified materials &
the potentialeffect of modifying the relative percentage of the contents
As resin component increases – acid-base reaction reduces ; benefits of
glass ionomer are lost & the material becomes light activated only
Compomers would belong in one of the middle 2 bars (acid-base component
is negated & therefore belong to composite resin end of table)

12. Compomer -
– anhydrous resin-based material
– not possible to have ion
transport within it.
Fluoride release is minimal
At 20 min ; compomer does not
show signs of set if not light
activated
Resin modified glass ionomers
-By 7-10min show signs of
chemical set
-Over the next 15020min becomes
quite hard
Mix under a light proof cover

13. SCIENTIFIC & CLINICAL
DEVELOPMENT
• INVENTION :
• Resulted directly from basic studies on dental silicate
cements & studies where the phosphoric acid in dental
silicate cements were replaced by organic chelating acids.

14. EARLY DEVELOPMENT
• 1966 : A.D.Wilson – examined cements prepared by mixing
dental silicate glass powder with aqueous solutions of various
organic acids (including poly(acrylic acid)
- unworkable, set slowly, sluggish, not hydrolytically
stable.Silica glass :
Highly cross linked
network of connected
silicon & oxygen
atoms; does not carry
an electric charge
Impervious to acid
attack
Ionomer glass :
ionic polymer ;
contains negative
sites which are
vulnerable to attack
by positive hydrogen
ions of acid

15. • 1968,1969 : A.D.Wilson + Kent & Lewis – found that
hydrolytically stable cements could be produced by
employing novel glass formulations.
• 1968 : Kent – found that setting of these cements was
controlled by Al2O3/ SiO2 ratio in the glass.
• 1973,1979 : Kent et al – found a glass that was high in
fluoride that gave a usable cementASPA 1
(aluminosilicate polycrylates).

16. • 1972 (reported in 1976):Wilson & Crisp – key discovery –
tartaric acid – modified the cement-forming reaction, thus
improving manipulation, extending working time & greatly
sharpening setting rate.
• This refinement of ASPA I was termed ASPA II & constituted
the first practical GIC.
• 1975 : Crisp et al – the disadvantage for general practice was
that its liquid tended to gel.
• 1975,1977 : Crisp &Wilson – developed copolymer of acrylic &
itaconic acid that did not gel at high (50%) concentration in
aqueous solution
• ASPA IV. But this was inferior in other properties to ASPA II

17. • 1974 : McLean &Wilson – used it for fissure sealing & filling
• 1977c : McLean &Wilson – ideal for restoration of classV erosion lesions.
• 1979 : Crisp et al – ASPA X – with excellent translucency.
• 1977 :Wilson et al – ASPA IVa – fine grained version for luting.
• With less viscous polyacid, lacked the mobility of traditional zinc
phosphate cement.
• 1977 : Mclean &Wilson – in a review article suggested use in pediatric
dentistry & as a liner in composite – resin / ionomer laminate.

18. LATER DEVELOPMENT
• 1973 :Wilson & Kent – reported use of poly(acrylic acid) in dry
powder form blended with glass powder.
• The cement was formed by mixing this powder with water or
tartaric acid solutions.
• 1984 : Prosser et al – re-examined the above & resulted in
development of ASPAV
• ASPAVa – a water-hardening luting agent – proved to have the
mixing qualities & mobility of zinc phosphate cement.
• 1985 : McLean et al – the original 1977 idea of using composite resin
/ ionomer laminate was revived in a modified form.
• GIC & enamel was etched – double etch technique (composite resin
was attached micromechanically to enamel & GIC bonded
indirectly to dentin).

19. • 1984 : Hunt & Knight – tunnel preparation for Class II
• The reasoning behind the technique – GIC core bonds enamel
shell together, preventing fracture (described by Hunt 1984, &
Mclean 1987)
• 1980 : Sced & Wilson & 1983 : Simmons – incorporated metallic
oxides & metal alloy fillers, to improve strength of GIC.
• 1985 : McLean & Gasser – fused silver particles onto ionomer glass,
giving cement radioopacity, burnishability, smoother surface,
increased wear resistance (reported by Moore et al 1985)
• 1986 : McLean – Developed new Cermet cements for clinical use.

20. • 1988 :Wilson & McLean – Highly viscous glass ionomer
cements
• Late 1980’s : Resin-modified glass ionomer cements

21. COMPOSITION

22. Glass ionomer cement is defined as an acid-base
reaction cement (Wilson 1978, Wygant 1958)
Basic component Acid component
Calcium aluminosilicate
glass containing fluoride
Polyelectrolyte which is a
homopolymer or copolymer of
unsaturated carboxylic acids
known scientifically as
alkenoic acids.

23. Types of Calcium fluoroaluminosilicate glass:
SiO2 - Al2O3 - CaF2 (Simple 3-component system)
SiO2 - Al2O3 - CaF2 - AlPO4
SiO2 - Al2O3 - CaF2 - AlPO4 – Na3AlF6
Components are fused between 1100°C - 1500°C
Melt poured onto metal plate / into water
Glass then ground to fine powder
(Maximum particle size: 50µm for restorative & 20µm for luting)
Chemical composition of original ionomer glass (G-200)
(Modified from Barry et al 1979)
SiO2 30.1%
Al2O3 19.9%
AlF3 2.6%
CaF2 34.5%
NaF 3.7%
AlPO4 10.0%

24. Fluoride – Lowers temperature of fusion
Improves working characteristics of cement paste
Increases markedly strength of set cement
Enhances translucency
Contributes to cements therapeutic value
Cryolite (Na3AlF6) - Supplements fluxing action of CaF2
Reduces temperature at which glass will fuse
Increases translucency of set cement
AlPO4 - Increases translucency
Adds body to set cement

25. Visual appearance of glass – clear /
opal / opaque
Glasses high in SiO2 (>40%) -
transparent
Glasses high in Al2O3 -
opaque
Al2O3 / SiO2 ratio :
Crucial , required to be 1:2
Increase in ratio
• Decreases setting time
• Clear to opaque
• Compressive strength increases
• Determines the rate at which
breakdown of glass matrix occurs Negative sites are vulnerable to acid
attack ; if enough Al atoms, all the
connecting links in network will be
completely decomposed ; such a glass
has cement forming potential

26. VARIATION ON BASIC GLASS COMPOSITION
1. Calcium may be replaced by strontium / barium /
lanthanum
2. Disperse phase glasses
Flexural strength
3. Fibre re-inforcement (eg. Alumina fibres )
Flexural strength
4. Metallic inclusions
Radioopaque glass

27. POLYELECTROLYTES
• Are both electrolytes and polymers
• includes copolymers of unsaturated mono-, di-, and tri-
carboxylic acids, particularly those of acrylic acids.
• The more important carboxylic acids in ionomer include
acrylic acid, maleic acid and itaconic acid.
• The polyacids may be
• in the form of concentrated aqueous solution (40-50% by mass)
• Blended dry with glass powder

28. COMPOSITION OF ASPA CEMENTS
• ASPA I – G-200 + 50% polyacrylic acid
• ASPA II – G-200 + 47.5% polyacrylic acid + 5% tartaric acid
• ASPA III – G-200 + 45% polyacrylic acid + 5% tartaric acid +
5% methyl alcohol
• ASPA IV – G-200 + 47.5% copolymer of acrylic & itaconic
acid 2:1 ratio + 5% tartaric acid

29. Different configurations affect adhesion ??
• Polyacrylic acid cements – bond more strongly to enamel &
dentin (Aboush & Jenkins, 1986)
• Copolymer cements – less resistant to acid attack than
Polyacrylic acid cements (Setchell et al, 1985)
• Copolymer cements – harder than polyacrylic acid aids early
finishing (Mount & Makinson 1982, Matis & Philips 1986)

30. Effect of molecular weight and concentration of polyacrylic
acid
• Increase in molecular weight and concentration
• Shortens setting time
• Increases strength
• Increased viscosity of mix

31. Water
• Reaction medium
• Plays role in hydrating reaction products i.e metal
polyalkenoate salts and silica gel

32. Tartaric acid
• The principal obstacle in developing practical GIC was
• Sluggish nature of set
• Working time was minimal
• Slow hardening
• In 1976Wilson et al reported addition of tartaric acid made
glass ionomer cement a practical one
• It enabled reduction of fluoride
• Delayed onset of viscosity

33. Other additives
Working time Setting time
Polyphosphates
Metals
Stannous
fluoride

34. SETTING REACTION

35. Cement forming reaction of glass ionomer cement
Showing extraction of ions from the glass, migration into aqueous
phase, & subsequent precipitation as polyanion hydrogels

36. There are 4 overlapping
stages that can be identified
but not clearly separated out
Unattacked
glass
particles
dispersed
in polyacid
liquid
Outer layer of glass
particles is depleted
of metal ions &
degraded to silica gel.
Metal ions migrate to
liquid, where they
remian in soluble form
(red dots)
Initial gelation
Soluble metal
ions remain ..
The cement is
still vulnerable
to moisture
Fully hardened glass
ionomer in an
insoluble form
Cement is no longer
vulnerable to attack
by moisture
Decomposition
Migration
Gelation
Further slow maturation
Post-set hardening

37. Glass structure
unattacked
(electrically charged
network)
H ions attack
network dwelling
ions, Ca 2+ & Na+
H ions attack the
charged aluminosilicate
network, destroying the
glass network &
liberating Al ions
1
st
s
t
a
g
e
2
n
d
s
t
a
g
e
3
r
d
s
t
a
g
e
Silicic acid formed condenses
to form silica gel

38. Setting reaction of auto cure cements
Only the surface of each particle is
atacked by the acid
Releasing Ca & Al ions, & F ions which
remain free & are not part of the matrix
The calcium polyacrylate chains form
first then the aluminium polyacrylate
chains follow immediately
By stage 3, there is a degree of maturity,
with more calcium & aluminium chains
Also a halo of siliceous hydrogel
surrounding each glass particle, which
increases resistance to acid attack
Note : these chains can break & reform
throughout the life of the restoration

39. Stage 1 : Decomposition of glass & migration of metal ions
(Dissolution)
• 20-30% of glass is attacked by polyacid
• Surface of the glass particles decompose
• Releasing metal ions (Al 3+ , Ca 2+ )
• Glass network breaks down into silicic acid which polymerises at surface of the
glass powder
• As pH of aqueous phase increases, polyacrylic acid will ionize & create
electrostatic field that will aid the migration of liberated cations into the
aqueous phase
• The ions thus migrate into the aqueous phase
• As the negative charge increases, polymer chains unwind, viscosity increases

40. Stage 2 : Precipitation of salts; gelation & hardening
• At a critical pH & ionic concentration, precipitation of insoluble
polyacrylates begins
• Ca 2+ &Al 3+ bind to polyanions via carboxylate groups
• The initial set is achieved by the cross-linking of the more readily available
Ca 2+ (forming clinically hard surface within 4minutes of start of mix)
• Maturation occurs over the next 24hours when the less mobile Al 3+
become bound within the cement matrix, leading to more rigid cross-
linking between poly (alkenoic acid) chains
• Aluminium polyacrylate ultimately predominates in the matrix

41. Few points to remember ….
1. Why not sodium ions ???
2. What happens to fluoride & phosphate ions??
3. Do all COOH convert to COO-
4. Period of vulnerability ??
5. Causes of gelation

42. 1.Why not sodium ions ???
• They cannot displace the hydrogen sphere
• They are not site bound, because of their low ionic charge
• They do not precipitate as polyacrylates
What happens to them ??
• They contribute to formation of orthosilicic acid on the
surface of particles
• As pH rises, this converts to silica gel which assists in
binding the powder to matrix

43. 2.What happens to fluoride & phosphate ions??
• They form insoluble salts and complexes

44. 3. Do all COOH convert to COO-?? …. No
1. When most of the carboxylic acid groups have ionized
• Negative charge on polymer chain increases
• Positively charged H ions now become very strongly bound
to remaining un-ionized carboxylic acid group & not easily
replaced by metal ions
2. As density of cross-links increase
• Hinders movement of metal ions towards carboxyl sites

45. 4. Period of vulnerability ??
• Till soluble ions insoluble matrix
• After material is set, but not fully hardened; a proportion of ions (Ca 2+ ,Al 3+
polyacrylate ions ) are in soluble form
• Can be dissolved out by aqueous fluids
• Weakened cement
• Softened surface
• Opaque restoration
[In a freshly set cement, calcium polyacrylate predominate, they are more vulnerable to
water than aluminium polyacrylates]

46. 5. Causes of gelation
• Multivalent Ca 2+ ,Al 3+ ions displace various hydration spheres
that interpose themselves between cation-anion pairs
• Cation-polyacrylate ion pairs are formed
• Desolvation of hydration spheres renders ionic pairs more
hydrophobic and precipitation occurs
Chain entanglement
Ionic cross-linking
Hydrogen bonds
Involved in matrix formation

47. Ca 2+ bridge 2 chains ; so do Al 3+ bridge 3??
Stearically unlikely because of presence of negatively charged
ligands
Coordination number of Al is 6 in water, therefore it should be
attached to 6 ligands
In glass ionomer cement, ligands are COO-, F-, OH-, water
molecules
Possible molecular structure of the set glass ionomer cement
A- represents F- / OH-
Fig 3-4

48. Stage 3 : Hydration of salts ; Hardening & Slow maturation
• Progressive hydration of matrix salts, leading to sharp
improvement in physical properties
• Continues for about 24hours
• Slight expansion under high humidity
• Further changes occur for >= 1 year
What are the underlying chemical changes ?
What are the indicators of these slow changes ?

49. What are the underlying chemical changes ?
• Increase in bound water (Wilson et al)
• Slow increase in cross-linking (Hill,1986)
• Slow replacement of residue carboxyl hydrogen ions by ,metal ions,
increasing cross-linking
• Increasing predominance of Al over Ca in the matrix
What are the indicators of these slow changes ?
• Translucency improves
• Becomes more resistant to dessication
• Strength continues to increase for atleast 1 year
• Ability to absorb / loose water decreases with age
• Initially the cement is plastic, then as it ages rigidity increases,
approaching that of phosphate bonded cements

50. Cement structure
Hydrogel matrix :
Ca & Al polyacrylates + fluorine
as fluoroaluminium polyacrylate
Water – in bound & free form
Glass core pitted by
selective etching
Siliceous
hydrogel
(with fluorite
crystallites)
Smaller filler
particles; contain
only siliceous
hydrogel
Cohesive forces binding matrix together :
mixture of ionic cross-links, hydrogen
bridges, chain entanglement
This framework is porous ; ions with
small dimensions (Eg. OH- & F-) are
free to move through the material

51. Role of water

52. Glass ionomer cements are water based cements
- they contain water
- make water during setting reaction
Role of water / Significance
 Water plays an important role in
Setting reaction Final structure
-Reaction medium
-Coordinating species
-Hydrating species
-plasticizer
 In the set cement
24% is water
Loosely bound
Tightly bound
As it ages tightly bound : loosely bound increases

53. Early contamination
Loss of calcium polyacrylate chains
Absorption of water
Loss of translucency
Loss of physical properties
Leaves cement susceptible to erosion
Dehydration
Cracking & fissuring of cement
Softening of surface
Loss of matrix-forming ions

54. Factors affecting setting characteristics
• Role of fluoride
• Role of tartaric acid
Role of fluoride
Fluoride forms metal complexes
They retard the binding of cation to
anion sites on polyacrylate chain
Delays gelation & prolongs working
time
Release of H+
Acidity of paste increases
Delays pH dependant gelation

55. Role of tartaric acid
• Tartaric acid is stronger than polyacrylic acid
Forms stronger complex with Al
Therefore increases extraction of Al from glass
• Initially tartaric acid alone complexes cations
As neutalisation proceeds & pH ~ 3
Polyacrylic acid becomes neutralised by metal ions until cement sets at pH ~ 5-5.5
• Also ionization of polyacrylic acid is suppressed & unwinding of the
chain is retarded, resulting in decrease in viscosity & delaying gelation
• Once gelation occurs, tartaric acid accelerates hardening
• Tartaric acid & calcium react preferentially therefore initial set may be due to
formation of calcium tartarate
• Tartaric acid controls initial setting of cement
• Improves
manipulation
• Increases working
time
• Sharpens set by
accelerating
precipitation
• Increases strength

56. Factors affecting rate of setting
1. Glass composition : increase in Al/Si ratio – faster set
2. Particle size : finer – faster set
3. Tartaric acid – sharpens set without shortening working time
4. Relative proportion of constituents – Powder : Liquid
5. Temperature of mixing – increase – faster set
Among these the factors within the province of the clinician are
Temperature of mixing
Powder : Liquid

57. Factors within the province of the clinician
1.Temperature of mixing
• Chilling powder & mixing pad – increases working time up to 25% (Mc
Lean 1970)
• Increase in working time occurs without loss of physical properties
(Makinson 1978)
• Word of warning –
• Chilling of liquid will cause gelation
• Increase in humidity & temperature below dew point – weakens the cement
2. Powder : Liquid
• Increase in powder – faster set
• But insufficient liquid – decrease in translucency of the set cement

58. Setting reaction of resin-modified light cured materials
• 2 distinct mechanisms :
• The original acid – base setting reaction
• Vinyl polymerisation of acrylate groups that can be activated through
the presence of photo initiators such as camphorquinone

59. When mixed, original acid base reaction appears to continue without interruption
Resin component provides as umbrella effect
Some degree of cross linking may be present between 2 matrices ;
both reactions may proceed without interference
Over time, any remaining resin not affected by light - activation may
undergo further chemical setting reaction
A “Dark – cure reaction”
Lead to the term “Tricure” or “Triple-cure”
Light activation

60. Is depth of cure an important factor??? …Yes…
1. Lack of water inhibition of acid-base reaction
2. Residual HEMA in lower levels, closest to pulp
3. Fully light activated restoration is notably superior in
physical properties
Therefore, depth of cure is important ; incremental build up recommended
Unless, a mechanism for chemical curing of methacrylate
groups is incorporated
“Redox” catalyst
Allows for continuing polymerisation in absence of light activation,
thus ensuring activation of any remaining HEMA
Micro – encapsulated potassium persulphate & ascorbic acid

61. The red chains represent fully
activated resins to the depth of
penetration of activator light
Showing influence of resins
incorporated into the glass
ionomer
Note : there is already a degree
of cross-linking between the
polyalkenoic acid chains and
the polymer chains
Showing progress of setting reaction
of resin component of RMGIC
Autocure redox reaction continues
until entire mass is set
Red chains represent completion of
auto cure setting
Note complete cross linking between
polyalkenoic acid chains & polymer chains

62. To summarise..
2 distinct types of setting reaction occur :
Acid-base neutralisation reaction
Free-radical metharylate cure
Relationship between the 2 reactions may take one of 2 forms
Formation of 2 separate matrices
 Ionomer salt hydrogel
 Poly-HEMA matrix
Multiple cross-linking pendant methacrylate groups may replace a small fraction
of carboxylate groups of polyacrylic acid, thus preventing separation of 2 potential
matrices
Cross – linking of polymer chains may take place through 1/more of the
following reactions
Acid – base reaction
Light – cure mechanism
Oxidation – reduction reaction
Full physical properties are not achieved till acid – base reaction continues for
some days

63. Structure of set cement
• RMGIC is presumed to have either
• A multiple cross – linked matrix or
• Matrix containing 2 separate phases
Depth of cure
3-4mm

64. Criticisms against RMGI
1. HEMA – monomer – toxic – relative lack of
biocompatibility, potential for allergic response
2. HEMA – hydrophilic – set material takes up water –
expansion + less resistance to wear & erosion
3. Potential for color change over time (Doray 1994)
4. HEMA – low molecular weight monomer – more
polymerisation shrinkage + substantial exotherm
that can last for sometime

65. Setting reaction of resin – modified auto cure material
• Mixing of powder + liquid
• Usual acid base reaction initiated
• Catalyst in powder will initiate polymeristaion of HEMA &
cross-linkable monomers
• Ultimately, there will be cross-linking between 2 systems
& the entire mass will set hard with uniform physical
properties

66. Setting reaction of light initiated auto cure material
• Involves enhancing speed of acid-base reaction by utilizing a simple physical
principle
• No resin is added
• The glass ionomer is colored (Eg. red) ; on irradiation with a blue halogen activator
light , acid-base reaction will take place more rapidly
• Setting time is reduced dramatically
• No heat generation
• Physical properties not downgraded
• Highly bactericidal
• Flows easily
• Easily identified Uses :
Fissure sealant
Uncooperative patient
Root surface protection
Lining/ base in very deep cavities
Transitional restoration during stabilization phase
Temporary seal for endodontics

67. ADHESION

68. • Glass ionomer cements are the only restorative materials
that depend primarily on chemical bond to tooth
structure.
• They form an ionic bond to the hydroxyapatite at the
dentin surface and also obtain mechanical retention from
microporosities in the hydroxyapatite.

69. Bond strength to dentin : (Richard S. Schwartz et
al JOE,vol.31,no.3,March2005,156)
• Lower initial bond strength compared to resins (around
8MPa)
• Despite this they succeed clinically because of the
following factors:
• They form “dynamic” bond. As the interface is stressed,
bonds are broken, but new bonds are formed.
• Low polymerization shrinkage
• Coefficient of thermal expansion similar to tooth
structure

70. Barriers to adhesion :
1. Water – aqueous fluids in dentin & enamel
• Hydrophilic, highly ionic GIC competes successfully with
water because of its multiplicity of carboxyl groups
that form H bonds with the substrate
2. Dynamic nature of tooth material
• Enamel : ion exchange
• Dentin : living material subject to change
• The adhesive bond must have dynamic character
• Polymeric nature of glass ionomer ensures multiplicity of
bonds between GIC and substrate. Scission of single bond
does not lead to failure because the bond can reform.
Bonding to these is
like trying to bond to
shifting sand

71. Mechanism of adhesion to enamel
& dentin
• Smith (1968): Chelation of calcium contained in apatite – involved in adhesion
• Beech (1973): Suggested interaction of polyacrylic acid & apatite.
• Bonding only to apatite, therefore weaker adhesion of GIC to dentine and non
existence of adhesion to decalcified dentine.
• Wilson (1974):Considered possibility of polyacrylates bonding to collagen.
• Initially, when paste is fluid, adhesion is by H-bonding provided by free
carboxyl groups present in fresh mix.
• As cement ages, H bonds are progressively replaced by ionic bonds, the
cations coming from cement or hydroxyapatite.
• McLean &Wilson (1977): Hypothesized presence of an intermediate later
between cement 7 tooth surface.
• Wilson, Prosser & Powis (1983): Postulated the adsorption phenomenon of bond
to mineralized tissue.

72. Adhesion
Bond to mineralized tissue
• Diffusion
• Adsorption phenomenon
Bond to collagen
• H bonding
• Metallic ion bridging
Bond to mineralized tissue
Phosphate ions are displaced from apatite by carboxyl groups.
To retain electrical neutrality, phosphate takes with it calcium.
Setting of the material + dissolution of enamel & dentin surface results in
buffering of polyacid.
Rise in local pH & reprecipitation of minerals at cement-tooth interface
occurs.
Therefore chemical bond is achieved by a calcium phosphate polyalkenoate
crystalline structure acting as an interface between enamel or dentin & the
set material.
Bond to collagen
May occur by H bonding or metallic ion bridging between carboxyl groups on
polyacid & collagen molecules of dentine.
Chain length may also be an important factor in adhesion.
The GIC is based on a polymer chain that is capable of bridging gaps between
the cement body and the substrate.

73. The poly (alkenoic acid ) chains actually
penetrate the surface of both enamle &
dentine & displace phosphate ions,
releasing them into the cement
Each phosphate ion takes with it
a calcium ion to maintain
electrolytic balance, leading to an
ion-enriched layer at the interface
As the acid is buffered by the release of ions the pH will rise & the interface will set
as a new ion-enriched material between the tooth & the restoration.

74. Bond strength & nature of
polyacid
• Cements based on polyacrylic acid appear to bond
more strongly than those based on copolymers of
acrylic acid with itaconic & maleic acids (Aboush &
Jenkins, 1986)
• Adhesion of cermet cements is inferior to
conventional GIC (Thorton et al, 1986)
• Pretreatment of enamel & dentin with polyacrylic
acid, which is not washed off, so that intermediary
bonding is formed. (Powis, 1986)

75. Improving adhesion – surface
conditioning :
• Surface conditioning – McLean &Wilson (1977) first used the term, to
differentiate from acid etching.
• Powis et al (1982);Aboush & Jenkins (1986) – smoother the surface stronger the
bond.
• Surface irregularity --- air entrapment + stress concentration
• Ideal requirement of surface conditioners (Mount, 1984)
• Isotonic (to decrease osmotic effect)
• The Ph = 5.5 – 8 (neutral)
• Nontoxic
• Compatible with chemistry of cement
• Water soluble, be easily removed
• Not deplete enamel & dentine chemically
• Enhance surface chemically in preparation for bonding.

76. Agents Proposed
by
Conc
entr
ation
D
u
r
at
io
n
Advantage Disadvantage
Polyacrylic acid Powis et
al (1982)
25% Enamel –
etches slightly & removes
polishing marks.
Dentin - Removes debris,
smoothes irregularities &
opens up tubules
May cause sensitivity with
luting agents
Mount
(1984)
1
0
se
c
Long et al
(1986)
30-
35%
Tannic acid Powis et
al
3
0
se
c
Enamel –
smooth featureless
surface without etching/
decalcification
Dentine –
Tubules not opened
Mineralizing
solutions (Eg.
Levine et al
solution & ITS
solution)
2-
3
m
in
Smear layer will be
included in ion-exchange
layer & will not interfere
with adhesion
Forms calcium & phosphate
rich layer between GIC &
tooth - ineffective

77. CLASSIFICATION
1. ByWilson & McLean (1988)
2. By McLean et al (1994)
3. By Smith /Wright (1994)

78. Classification by Wilson & Mclean (1988)
• Type I : Luting & bonding materials
• Type II : Restorative
• Type II.1 : Restorative aesthetic (autocure & resin-modified)
• Type II.2 : Restorative reinforced / Bis-reinforced filling materials
• Type III : Lining or Base

79. Classification by Mclean et al (1994)
• Glass ionomer cement
• Resin modified glass ionomer cement
• Polyacid modified composite resin

80. Classification by Smith / Wright (1994)
• Type I – Luting cement
• Type II – a) aesthetic filling material
b) reinforced resin filling material
• Type III – Fast setting lining cement
• Type IV – Fissure sealing cements
• TypeV – Orthodontic cements
• TypeVI – Core build up material

81. Type I : Luting & Bonding

82. Factors in favor of glass ionomer lute
1. Tensile strength – as high as zinc phosphate
2. Solubility – lower
3. Thixotropic flow properties – allow easier placement ; without need to vent
casting / retain pressure during setting
4. Fine film thickness
5. Fluoride release
6. Potential for postinsertion sensitivity – same as for other cements
4. Fine film thickness2. Solubility – lower

83. Significant factors
• Powder particle size - 4-15 µm
• Film thickness – 10-20 µm
• P/L ratio – 1.5:1
• pH – newly mixed cement – 1.8 ; within 30min – 4.5
• Dispensing & mixing – P/L system & 2 paste system
• Time to mature – less time desirable; break away excess when cement is crisp
& firm
• Adhesion to enamel & dentin – cementation of crown – hydraulic pressure –
penetartion of polyacrylic acid into tubules – post-insertion sensitivity – therefore
seal surface of dentin ; do not remove smear layer
•Adhesion to noble metals – by electroplating the fitting surface with 2-5µm tin
oxide immediately prior to placement

84. •Cementation on vital teeth - 25% tannic acid (for 2min) or dentin bonding
agent containing polalkenoic acid applied just before cementation
Remove temporary
cement
Washed only ; not
conditioned / seal
Mixing time – 25 seconds
String up 2-3 cm
Apply to inside,
especially margins
Seat crown with positive
pressure ; no need to
maintain pressure
Paint small quantity
on tooth
Remove excess when
cannot be indented with
sharp instrument
Remove debris from
gingival crevice
Cemented crown

85. •Cementation on non vital teeth – 10% polyacrylic acid conditioning (for 10-15sec) to
remove smear layer
Preparation cleaned Root surface & post
hole conditioned
Washed & dried with
alcohol
Cement painted on
post
Canal filled to top
with cement
Post seated Inside of crown
painted with cement
Seat crown with positive
pressure ; no need to
maintain pressure
Cemented crown

86. Bonding with glass ionomer - Bonding composite resin
Glass ionomer used as
bonding agent in small shallow
cavities (Yamada et al 1996)
• Prepare cavity
• Condition for 10sec ; wash &
dry
• Paint thin layer of Glass
ionomer bonding agent over
entire cavty including walls
• Blow off excess
• Light activate for 20sec
• Place composite
incrementally ; finish, contour
& polish
Advantage :acid-base reaction
of glass ionomer will continue
& compensate for shrinkage of
glass ionomer
Prepare cavity
Condition
Glass ionomer
bonding agent
Light activate
Place composite
finish, contour & polish
SEM showing interaction
layer / ion-exchange layer
Low viscosity, low P/L ratio, resin-
modified glass ionomer used

87. Bonding with glass ionomer - Bonding amalgam
Long term results – not available
Short term results suggest – reduced
post-insertion sensitivity to
temperature changes in newly placed
restoration
Greatest hazard – potential for
incorporation of fragments of glass
ionomer into amalgam during
condensation – reducing the physical
properties ; unlikely to be sufficient to
prevent cusp loss
Similar clinical technique

88. Type II.1 : Restorative
aesthetic materials

89. Factors in favor :
Adequate aesthetics & translucency
Sufficient physical properties in fully supported restoration
Adhesion achieved
Fluoride reservoir

90. Significant factors
P/L ratio – 2.9:1 to 3.6:1 (if polyacrylic acid is liquid)
6.8:1 (in anhydrous cements)
Time to mature :
Autocure - Initial snap set - 4min from start of mix
Resin modified Require atleast 1 week to mature
Light activation - 20-40sec
Resin glaze : to paint over finished restoration ;
no effect on continuing maturation ;
will seal voids / porosities on surface

91. Matrix checked for
accuracy of fit
Pumice slurry - 5
seconds ; flushed
& dried
10% polyacrylic
acid - 10-15 sec
Cement placed
excess removed
after 4 min
After matrix
removed ; bonding
resin applied
Bonding resin light
activated
Erosion lesion
Finished
restoration

92. Type II.2 : Restorative
reinforced materials

93. Reasons for use :
When fast setting material is desirable
With increased physical property
But where color match not important
Significant factors:
• Resistant to uptake of water in 5min
• But first 2 weeks water loss is a problem
Following material earlier marketed as reinforced ; now considered a misnomer
• Because physical properties not significantly improved
• Adhesion & fluoride release reduced
• Need another material to cover for esthetics
1. Silver cermet
2. Amalgam alloy admix
3. Silver alloy admix
Newer generation high strength glass ionomers

94. Silver cermet
• Manufactured by incorporating 40% by weight of microfine silver particles <
3.5µm in diameter in which powdered glass particles
• The 2 were then sintered under pressure
• Unreacted silver was washed out
• 5% titanium dioxide added to modify color
Advantages :
Surface could be burnished
High density & low porosity restoration
High abrasion resistance
High compressive strength & fracture resistance
Disadvantage :
Earlier used for “core build-up“ but their
physical properties cannot be relied on
Less adhesion (mechanical retention required)
Uses : In repairing chipped &
faulty margins of existing
restorations ; alternative to
replacement
Color : closer to tooth
Radioopacity : same as amalgam

95. Amalgam alloy admix
Spherical amalgam alloy particles incorporated with a fast-setting glass
ionomer powder (Simmons 1983)
Amalgam alloy was incorporated in proportion of 8 parts cement powder
: 1 part alloy by volume
This was then mixed with polyacrylic acid (3:2 by weight)
• black restoration
•Physical properties slightly improved
•Early resistance to water uptake
•Set rapidly
•Adhesion & fluoride release less than unfilled
•Difficult to mix to required consistency by hand ; capsules were later
available

96. Silver alloy admix
Include silver containing alloy in flat brokenpieces rather than
spheres ; flakes would offer larger surface area for reaction with
polyacrylis acid
Higher abrasion resistance because when subjected to wear, the
preparation developed a Beilby – type smear layer on its surface
Physical properties, color, fluoride release, adhesion – better
than above 2
But material has had limited market

97. New generation High strength / Condensable glass
ionomers
Fast setting Auto cure
10-15% better physical properties than resin modified glass ionomer
Available as “normal set” or “fast-set”
Particularly useful as transitional restoration
Changes : powder particle size
particle size distribution
heat history of glass (improvement in surface reactivity of powder )

98. Significant factors :
• P/L ratio : 3:1 to 4:1
• Time to mature : resistant to water uptake / loss as soon as set
• Adhesion : stronger because cement is stronger
• Release of ions : similar to other types of autocure, therefore useful for root
surface caries, tunnels
Physical properties :
• Tensile strength & fracture resistance substantially better than autocure,
marginally better than resin modified glass ionomer
• Abrasion resistance – as they mature they match that of amalgam, composite
resin
• Radioopacity – adequate
Main application :
1. Minimal lesions
2. Transitional restoration

99. Type III :Lining & Base
cements

100. Definition :
Lining – thin layer of a neutral material placed on the floor of a cavity, prior
to final restoration, to make good a deficiency in the cavity design or to
provide thermal protection to the pulp
Base – is identified as a dentine substitute that is placed to make up for
major area of dentine loss prior to lamination of an enamel substitute over
the top
Significant factors :
Lining cements :
• Low P/L 1.5 :1 (do not act as bonding agent ; should not be
left exposed ; low physical properties)
• used in thin sections to fill voids in cavity design ; act as
thermal insulator
Base / dentin substitute :
• P/L : 3:1

101. Properties
• Physical Properties
• Erosion & Longevity
• Aesthetic properties
• Biologic properties

102. Cement
type
Settin
g time
(min)
Film
thickness
(µm)
24hr
compressive
strength
(MPa)
24 hr
Diametral
tensile
strength
(MPa)
Elastic
modulus
(GPa)
Solubility
in water
(wt%)
Pulp
response
Glass
ionome
r luting
7.0 24 86 6.2 7.3 1.25 Mild to
moderat
e
Properties of glass ionomer luting cement
Compressive strength is comparable to zinc phosphate
Diametral strength is slightly higher
Modulus of elasticity is ½ of zinc phosphate
Thus, it is less stiff & more susceptible to elastic deformation
It is thus not as desirable as zinc phophate to support an all ceramic crown,
because greater tensile stress would develop in the crown under occlusal loading

103. Properties of restorative glass ionomers
Compressive
strength
(MPA)
Diametral
tensile
strength
(MPa)
Knoop
hardness
(KHN)
Solubility
(ANSI/ADA
test)
Anticariogenic/
Pulp response
Glass
ionomer
type II
150 6.6 48 0.4 YES/MILD
Cermet 150 6.7 39 - YES/MILD
Hybrid
Ionomer
105 20 40 - YES/MILD

104. Material Fracture
toughness
(MPa.m1/2)
Admixed
amalgam
1.29
Light cured glass
ionomer
1.37
Hybrid composite 1.17
Glass ionomer
lining cement
0.88
Cermet 0.51
Metal-reinforced
glass ionomer
0.30
Fracture toughness – a measure
of energy required to cause crack
propagation that leads to fracture
Restorative glass ionomers
are much inferior to
composites
Also more
vulnerable to wear

105. Erosion & Longevity
1. Dissolution & erosion
2. Durability & longevity

106. Dissolution & erosion
2 aspects
Leaching of soluble
constituents from cement
Actual erosion
Because of chemical &
mechanical wear
Disintegration only if they
are matrix formers
Short term aspects Long term aspects
Because of acids from plaque,
food & beverages
Damage in
technique
Moisture
contamina
tion before
cement
hardened
Desiccation
before cement
fully matured

107. In glass ionomer cement,
anion is a polymer where the
active carboxylic groups are
connected by covalent
linkages impervious to acid
attack.
Only cross-links are ionic, and
many of these have to be
broken before the matrix would
decompose
Fig 7.4 wilson &
mclean
Acid erosion :
Glass ionomer < silicates < zinc phosphate < zinc polycarboxylate

108. Durability & longevity
• Depends on
• Adequate preparation of cement
• Adequate protection
• Conditions of mouth

109. Aesthetic properties
• Translucency
• Glass ionomer cements has a degree of translucency
• Because its filler is a glass (not opaque)
• Because of slow hydration reactions, glass ionomer cements take at least 24hrs to fully mature & develop translucency
• Early contamination with water reduces translucency
• Dark shades are less translucent
• Glass ionomer remain unaffected by oral fluids
• Opacity
• Opacity is also termed as contrast ratio (Cr)
• If Cr=1 – material is opaque
• If Cr = 0 – perfectly translucent
• To match enamel Cr < 0.55
• Glass ionomers Cr < 0.9
• Scattering power & reflectance
• Opacity also depends on the scattering coefficient
• Light reflectance
• Thickness of specimen

110. Biologic properties

111. Biocompatibility
• They elicit greater pulp reaction than ZOE (Plant et al 1984)
• But less than zinc phosphate (Tobias 1978)
• With any glass ionomer cement, it is wise to place a thin layer of
protective liner, such as Ca(OH)2 , within 0.5mm of pulp chamber
(Anusavice)
• Inflammatory response of pulpal tissues resolves within 30 days &
there is no enhancement of reparative or secondary dentine
formation (G J Mount)
• Response of gingival tissues is minimal (Garcia et al 1981)
Effect on pulp & cells

112. Reasons for blandness of polyacrylic acid (McLean
& Wilson, 1974)
• Polyacrylic acid – weak acid
• Dissociated H+ ions remain in neighbourhood of polyanion
chain because of electrostatic attraction from multiple
negative charges.
• When partly neutralized, the negative charge on the chain
increase, tendency of polyacylic acid to dissociate into H+ ions
& polyacrylate ion decreases.
• Diffusion of polyacrylic acid into dentinal tubules is unlikely
because of its high molecular weight & chain entanglement.
• Polyacrylic acid is readily precipitated by Ca+2 in tubules.
• Therefore sensitivity under luting GIC may be due to faulty
technique than chemistry of cement.

113. Fluoride release

114. Biological potential of glass ionomer cements
• Significance of water in glass ionomer cements
• Glass ionomer – water based material
• Water plays important part in
• Setting reaction
• Final structure
• Water is the reaction medium
• Hydrates siliceous hydrogel

115. Once GI sets,
Loosely bound – easily lost shrinkage& cracking & undue
stress on ion exchange
adhesion
Tightly bound - cannot be removed ; associated with hydration shell of
cation-polyacrylate bond
Increase in strength & modulus & decrease in plasticity
One important factor in these materials being water based lies in the
chemical principle that it is only possible to have ion mobility in presence of
water
Which is essential for demineralization-remineralisation of tooth
(anhydrous material can play no part )
Water is in
the form of
As material ages, ratio of tightly bound water : loosely bound water increases

116. • Ionic components of GIC
• Calcium
• Strontium
• Aluminium
• Silica
• Fluoride
• All ions are available for transfer from matrix into surrounding because of presence of water.
• Lower the pH, greater the release of ions.
• Note: (i) Calcium & strontium have similar polarity & atomic size, therefore they can replace each
other in cement & hydroxyapatite.
• (ii) Strontium imparts radioopacity
• (iii) Strontium has anticariogenic properties.
• Therefore strontium can participate effectively in remineralisation.

117. Mineral phase of enamel & dentin
Enamel & Dentin are porous to migrating ions especially dentin
Enamel :
Each crystal of hydroxyapatite is surrounded by a
layer of tightly bound water – hydration shell –
which shows that the crystal is electrically charged
& can attract ions that are able to play a part in
remineralization
Remaining water fills spaces between rods – main
diffusion pathway into & thru enamel
Dentin :
23% water by volume
Water filled pores + inter-tubular lateral
microtubules + dentinal tubules
Increased potential for ion transfer
By weight By volume
By weight By volume

118. • Enamel rods are tightly packed
• Pores are not large enough to allow bacteria
• Only when sufficient disintergration has occurred, process
becomes irreversible
• Outer apatite crystals dissolve from surface
• Increase porosity
• Facilitating acid transport & demineralisation
• Also, ions can return along the same pathway

119. Carious lesion
• 1960’s – Massler, Fusayama & Brannstrom wrote detailed
reports on science of demineralisation & remineralisation ; &
theoritical value of ion exchange
Carious dentin
1st decalcified layer 2nd decalcified layerFusayama et al 1966
Massler 1967 Infected layer Affected layer
Pitts 1983,
Mertz – Fairhurst et al
1992
Actively carious Pre-carious

120. • This concept was reinforced by a clinical study
• Heavily carious 1st molars taken
• Minimal caries removal
• Restored using strontium based high strength glass ionomer cement
• Harvested
• Fl & Sr penetrated both layers of dentin & became part of normal apatite
crystals beyond
• 2 distinct zones identified
Outer layer of non-
remineralised dentine with
minimal Fl & Sr uptake
Deeper zone of well
re-mineralised dentine
Postulated that
Collagen network in outer zone is totally devoid of mineral
Lack of seeding sites
Preventing uptake of mineral ions
Remineralisable dentine contained atleast 20% by weight of mineral onto
which incoming ions were able to absorb

121. External ion exchange
• Glass ionomer acts as fluoride reservoir
• Movement of fluoride out of glass ionomer
• Electrolytic imbalance on surface of restoration
• Cations from plaque & salive are taken up by the restoration
• Balanced state
• Increase in maturation & strengthening of restoration
(Nicholson et al, 1999)
• Also, plaque on surface of glass ionomer will have reduced count of S.mutans,
therefore tissue tolerance of glass ionomer is more & less inflammation is
seen.

122. Internal remineralization
• Dental pulp demonstrates very high level of tolerance to glass ionomer.
• Very mild inflammatory response to freshly mixed GIC seen, with rapid
recovery.
• Snuggs et al, 1993 – dentin bridging in mechanical exposure of pulp
sealed with GIC
• Brannstrom, 1982 – Pulpal irritation is direct result of bacterial activity.
Therefore, if no irritation, no inflammation will occur.
• Glass ionomer demonstrates ion-exchange adhesion, which could be an
ideal sealant, thus preventing ingress of bacterial nutrients.
• Therefore GIC can be placed in very close proximity to pulp without risk
of irreversible pulp inflammation & CaOH sub-lining is not justified.

123. Entire margin of
cavity cleaned down
to sound dentine
Axial wall still in softened
demineralised affected
dentine is retained
10% polyacrylic acid 10
second conditioning
Light initiated autocure
glass ionomer over axial
wall (sublining)
High strength autocure glass
ionomer then placed
Cut back to expose
enamel walls
Entire cavity covered with thin
layer of Resin modified
adhesive glass ionomer
composite
Suggested clinical technique

124. Glass ionomer as bone substitute
• Rober Purrmann – originated the work
• Owing to its properties of bioactivity & biocompatibility, glass
ionomer has been tried as bone cement & bone replacement
material.
• Through ion-exchange mechanism, it can cause stable
integration with bone & can affect both its growth &
development adjacent to surface of material.
• Note : unset GI is strictly contraindicated to be contacted with
neural tissues (because of controversy over Al release)

125. Glass ionomer as bone cement
• Prof. Charnley’s, 1960’s – Use of PMMA to provide stable
mechanical anchor for metallic prosthesis.
• Morphologic fixation / cement fixation
• Owing to disadvantages of PMMA, glass ionomers replaced
them
• Advantage :
• - No exotherm setting reaction
• Chemically bond to bone & some metals & less shrinkage
• Osteoconductive property of material
• In oral surgery,
• Applied to prevention of bone loss following extraction
• Used as filler for bone donor sites & cyst cavities.

126. Clinical applications of glass
ionomer cements

127. Uses
Conservative
• Luting & bonding
• Restorative
• Lining & base
• Minimal intervention – the place of
glassionomer
• Transitional restoration
Endodontics
• Root canal sealing
• Orthograde root canal sealing
• Root-end filling material
• Repair of perforations and root
resorption defects
• Perforation repair
• Repair of root resorption cavities
• Treatment of vertically fractured teeth
• Coronal seal

128. Use of glass ionomer in conventional & surgical endodontics
• Pitt Ford (1979) - Use in root canal first introduced
• Stewart (1990) - made modifications
• to increase working time
• added barium sulphate : increase radioopacity
• Ray & Seltzer (1991) – usable experimental formulation
• Adequate working time
• Adequate radioopacity
• Adequate adhesion to root canal wall
These modifications led to commercialization of Ketac –
Endo (ESPE, Germany) in 1991
RMGIC – Vitrebond (RM)
More recent developments : KT- 308 (GC)
ZUT

129. Minimal intervention cavity designs – The place of glass ionomers

130. Site 1 Size 0 lesions
Site 1 : pit & fissure on occlusal surface of posterior teeth
Size 0 : initial lesion ; not yet resulted in cavitation
Concept of fissure seal – 1st discussed by Simonsen (1989)
The anatomy of enamel within a fissure is covered with a
layer of enamel rods that appear to run parallel with the
surface rather than at right angles. When etched, it will not
develop the usual pattern of porous enamel that allows
penetration of unfilled resin
Wilson & McLean (1988) show that a glass ionomer will
successfully occlude fissure
This is now termed “fissure protection” to differentiate it
from a “resin seal”

131. Neither resin nor glass ionomer will flow into a fissure beyond the point where
fissure narrows to 200µm
Retention thus mainly depends on adhesion to enamel at the entrance to fissure
rather than mechanical interlocking into complexities of fissure
Even though enamel rods lie in different
orientation, glass ionomer will develop ion
exchange adhesion & show acceptable longevity
(Mount & Hume, 1998)
8 years
12 years
Technique involved
In young patient fast set autocure
like light initiated autocure glass
ionomer used

132. Site 1 Size 1 lesions
Size 1 : smallest minimal lesion
requiring operative intervention
Fissures are explored using small tapered
diamond bur #8107 at intermediate high speed
under air water spray then lightly polished with
#3107
Technique
involved
Satisfactory
adaptation of
entire fissure

133. Site 1 Size 2 lesions
Size 2 : Moderate size cavities
Technique
involved Why glass ionomer used as base ?
If resin composite used, might
require removal of more dentin
which would otherwise remineralize

134. Site 2 Size 0 lesions
Site 2 – contact areas between anteriors / posteriors
Size 0 : initial lesion ; not yet resulted in cavitation

135. Site 2 Size 1 lesions
If lesion 3 mm below the crest of marginal
ridge – “Tunnel” cavity design
If lesion < 2mm from the crest of marginal
ridge – “ Slot ” cavity design
If proximal surface accessible – “Proximal
approach”
Site 2 – contact areas between anteriors / posteriors
Size 1 : smallest minimal lesion requiring operative intervention

136. Access through
occlusal surface
Triangular
access cavity
Clean enamel
margins
“Tunnel” cavity design
Glass ionomer syringed
mylar strip in place
Completed
restoration
Note : internal
dimension of cavity
Glass ionomer will flow readily into a
small cavity & has the ability to
remineralise
“ Slot ” cavity design
Glass ionomer is a sound
option because occlusal
load will not be great
“Proximal approach”
Fast set, high strength auto
cure used because
radioopaque & will not be
under occlusal load

137. Site 2 Size 2 lesions
Site 2 – Contact areas between anteriors / posteriors
Size 2 : Moderate size cavities
Laminate technique / bilayered restoration with glass ionomer as the base
If resin modified is used; no
need to etch after placement
because enough resin content
to provide adhsion with
composite
Substantial layer of glass ionomer
across the entire floor is exposed to
oral environment at gingival
proximal box

138. Site 3 lesions
Cervical areas related to gingival tissues including exposed root surface
Glass ionomer ideal : Because can withstand flexure
Root surface not under occlusal load

139. INSTRUCTIONS FOR DENTAL
ASSISTANTS

140. Storage
Powder & liquid by different manufacturers should
not be interchanged
Both bottles firmly closed (water based)
Polyacrylic acid liquid thickens over time, within 12 months
viscosity increases. It can be thinned down by : immerse bottle
with lid on in water at 75°C for 15minutes, place in rubber
bowl, let water from hot tap run over it. Test at 15minutes for
viscosity. Let it cool before use.
Liquid should never be refrigerated.
Mixing slab should cool, but never below
dew point.

141. Full spoon, no excess
Tip liquid bottle to side,
then invert completely
If water / tartaric acid, only
1 drop used.
Hand dispensing

142. Hand mixingLiquid should not stay on paper pad
longer than 1minute (some of it may
soak into it)
First half folded into liquid in 10-15seconds
Second half incorporated in 15 seconds
Small mixing area
Don’t mix beyond 30 seconds
The objective is – only wet the
particle – no dissolving it.

143. Mixing of capsules
• To activate capsule apply pressure
3-4 seconds before placing in
machine
• Ultrahigh speed machine : 4000
cycles/minute
• (< 3000 cycles/minute – not
desirable)

144. Loss of gloss test
This point is reached at 2minutes
after start of mix
10sec in 4000cycles/minute

145. Correct consistency for hand
mixed
Type I : Luting : string up to 3-4cm from
slab
Type II : string 1cm + gloss
Type III : for lining amalgam : 1.5:1 P/L
ratio : 3-4cm string
For base for composite : 3:1 P/L ratio :
1-1.5cm string

146. Clean – up
Before it sets, immerse slab
& spatula in water
If set, chip off / place in
water then clean

147. Summary & Conclusion

148. Review of literature

149. REFERENCES

150. REFERENCES : (Text books)
1. Glass-ionomer cement : Alan D.Wilson / JohnW. Mclean
2. An atlas of Glass Ionomer Cements – A Clinician’s guide (3rd
edition) : Graham J. Mount
3. Preservation & restoration of tooth structure : Graham J.
Mount
4. Phillip’s Science of Dental Materials (11th edition) : Kenneth
J. Anusavice
5. Sturdevant’s Art & Sience of Operative Dentistry (4th
edition):Theodore M. Roberson et al
6. Tylman’s theory & practices of fixed prosthodontics, chapter
21, page 394-406 : Franklin Garcia Godoy et al

151. REFERENCES : (Journals)
1. Proposed nomenclature for glass-ionomer dental cements & related
materials. JohnW. Mclean et al.QI vol. 25, no. 9, 1994 ; 587-589.
2. GIC – Past, present & future. Graham J. Mount. Buonocore memorial
lecture (Michael B.) Operative dentistry 1994, 19, 82-90.
3. Glass ionomer cements in restorative dentistry. JohnW. Nicholson et
al. QI vol. 28, no.11, 1997, 705-714.
4. The need for caries preventive restorative materials.Gordon J.
Christensen. JADA, vol. 131, sept. 2000, 1347-1349.
5. Composite resin & GIC : current status for use in cervical restorations –
WilliamW. Brackett et al. QI 1990; 21: 445-447.
6. Longevity in glass-ionomer restorations: review of successful
technique. Graham J. Mount. QI 1997 ; 28: 643-650.
7. Viscous GIC : a new alternative to amalgam in primary dentition.
Roland frankenberger et al. QI 1997 ; 28:667-676.
8. Adhesion of GIC in clinical environment.G.J.Mount. operative dentistry
1991;16:141-148.
9. Glass ionomer : a review of their current status. G.J.Mount.Operative
dentistry 1999 ; 24 : 115-124.

152. 10.The use of glass ionomer cements in both conventional & surgical
endodontics. (review) M.A.A.De Bruyne et al. IEJ, 37; 2004: 91-104.
11.Pulpal consideration of adhesive materials. Harold R. Stanley.Operative
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