(alumino silicate glass –"ASPA"alumino silicate polyalkenoate)
- supplied as a powder and liquid or as a powder and water
-Some products are supplied as powder/liquid in a capsule
-The powder is calcium fluoroalumino silicate glass
-it contain three main components:
-The particle size of the powder depends upon the purpose for which it is used
-Barium glass may be added to some powder to give radiopacity
-The liquid is an acquous solution of polyacrylic itaconic acid copolymer
together with tartaric acid (not more than 5%).
-tartaric acid increases the working time and decreases the setting time “sharp set “
-In some products the polyacrylic acid is freeze dried and added to the powder
-In such a case the liquid may be water or a diluted solution of tartaric acid
mixing the powder with liquid:
-Dissolution of glass particles by the acid i.e. H + attack to release
(Ca++ . AL+++) and fluoride ions
-Between 20% to 30% of the glass is decomposed by the acid attack.
-Migration of the surface ions Ca++, Al+++ and fluoride ions complex into
-The divalent Ca++ ions will migrate first followed by the trivalent Al+++ ions
-The sodium ions form silica gel on the surface of the particles
3- Reaction and precipitation
-Ca++ ions will react first with the carboxylic group of the acid to form the
cross linked carboxylic salt gel leading to the initial set
-then reaction of the slowly migrated trivalent Al+++ ions occurs
-The later reaction takes longer time and results into a stronger cross linked cement
-The precipitation process of the carboxylic gel salts is a continuous process and may
take 24 hours
-Therefore, the setting material should be protected against premature exposure to
saliva as it affects the setting and the surface hardness
role of water in the setting
-water is a normal component of the liquid
-initially it serves as a reaction medium then it hydrates the matrix
-during initial set ..it is loosely bound water thus if GIC was subjected to dryness
..the reaction will not continue and the surface will crack
-when the reaction proceeds ..water become tightly bound …so if the GIC was
subjected to moisture during initial set …dissolution of the matrix will occur
-so ..both dryness and moisture contamination during initial setting will make the
GIC with lower strength , increased solubility and poor esthetics
The microstructure of the set material
-The set material is a composite cored structure consisting of unreacted glass cores
surrounded by silica gel embedded in a matrix of cross linked polycarboxylic
salt hydrogel of calcium and aluminum
-Aluminium fluorocarboxylate salts constitute the main bulk of the matrix and
provides the final strength.
Type I : For luting applications
Type II : As a restorative material.
Type III: For use as a liner or base.
-Light - curable versions of GIC are also available
1-The glass ionomer cements have a mild effect on the pulp
-In deep cavities, calcium hydroxide lining must be used under GIC
2-Anticariogenic effect : anticariogenic due to fluoride content
-solubility of glass ionomer cements in water after 24
hours immersion is about 1.5% by weight
-protection of GIC from moisture during the 1st 24 hours decreases solubility
-The film thickness of the glass ionomer cement is about 24 microns which is similar
to that of zinc phosphate cement
a) Compressive strength properties:
-from 90-240 MPa.
-if used as a filling material it increase in strength from 160 to 280 MPa between 24
hours and one year.
-strength of GIC improves when the cementis protected from moisture during the first
24 hours after filling.
It is a brittle material. Its tensile strength ranges from 14-24MPa.
-The glass ionomer cements adhere to tooth structure by the reaction of
polyacrylic acid with the calcium and phosphate content of tooth structure
-The bond strength of glass ionomer cement to tooth structure is lower than that of
the polycarboxylate cements because of the sensitivity of the glass ionomer
cements to moisture during setting
-To obtain a good bond to dentin, the surface must be treated with a conditioner to
remove any smear layer which interfere with bonding
-They are translucent. Therefore, they can be used in anterior restoration
in low stress - bearing areas.
Modifications of glass ionomer cement:.
I) Metal modified glass ionomer:
-Trials have been made to incorporate amalgam alloy powder with the glass powder
to increase wear resistance and flexure strength, e.g: “Miracle mixture”
-such trials was not successful because it did not increase the wear resistance
-silver, gold, palladium were sintered with the GIC powder
-Silver is the most commonly used and by sintering it adheres intimately to the glass
-The strength and wear resistance were improved markedly
Glass cermets can be used as:
i) Core build up restorations
ii) a restoration for class I and 11 in deciduous teeth.
-They have higher abrasion resistance, higher flexure strength and higher
fracture toughness than the conventional glass ionomers
-Because of the metal content, they are opaque
-They have lower fluoride release than conventional glass ionomers
They were first used as lining materials under composite resin, then as anterior restoratives, specially class V cavities.
liquid are mixed
is applied to the cement
-the powder is rodiopaque fluroalumino- silicate glass
-the liquid is a modified polyacid with HEMA group
(Hydroxyelhyl methacrylate) which is usually added to the liquid
-The acid base reaction play a significant part of the reaction over the curing reaction
b) Triple cure:
-To ensure effective polymerization of the resin part in deep cavities, the
resin part was modified to allow self curing reaction
-In such case the newly formulated cement will set through three reactions :
ii) Light cure polymerization of the resin.
iii) Chemical cure polymerization of the resin
IV) Compomer "Polyacid modified resin composite materials"
-These are supplied as one paste system
-They are considered as intermediate restoratives between glass ionomers and
-They are more related to composite than glass ionomer materials
-They are a mechanical mixture of glass ionomer particles and composite materials
-The light curing reaction plays a significant part of the reaction over the acid - base
ii) Less sensitivity to moisture after setting.