GLASS-IONOMER CEMENT
Acid-Base Reaction CementsAcid-Base Reaction Cements::
Glass-Ionomer Cement The word glass-ionomer is a generic name
derived from material’s composition
The powder is ion-leachable glass (Calcium-flouro-alumino-silicate) that is able to react with ionomeric acid containing carboxyl groups (e.g. Poly acrylic acid)
Sometimes the name Polyalkenoic cement is used
General Applications Final cementation Cavity base and liner Esthetic Filling material (in eroded cervical lesions) Bonding agent Fissure sealer Endodontic sealer Filling of deciduous teeth Amalgam Bonding
Cementation of orthodontic brackets
Classification of G.I. cements
A. According to the use Type I: Luting material (P.size < 15 m) Type II: Esthetic Filling material (P.size =20-50
m) Type III: Cavity base and liner
B. According to The curing mechanism Chemical-cured: Cement sets via acid-base
reaction Dual-cured: Cement sets via both polymerization
and acid-base reactions Triple-cured: Cement sets via chemically-
activated polymerization, light-activated polymerization and acid-base reactions
Classification of G.I. cements
C. According to the modification Conventional GI: No modification -- Sets via acid-
base reaction Metal-modified: Ketac silver and Cermet--Sets via
acid-base reaction Resin-modified:-- Either dual or triple-cured
Presentation forms1. Powder-liquid
- To be mixed using plastic spatula over paper pad2. Water-settable powder
- Dry powder of PAA copolymer is blended with cement powder in the same bottle. - The material is mixed with regular water
3. Capsules- Both cement powder and liquid are contained in the same capsule and separated from each other by a diaphragm
4. Two-paste system- Recently introduced as a cement (luting material) material. - Equal lengths to be mixed over a paper pad
Conventional G.I. cements
Composition Powder:1. Calcium-fluoro-alumino-silicate glass particles- All compositional ingredients (CaF2, Al2o3, Sio2,
NaF, AlPo4) are fused together at 1100-1500oC ingot then grind into the desired particle size
2. Radio-opaque glass particles in which barium or strontium replaces the calcium
Conventional G.I. cements
Composition Liquid:1. Aqueous solution of Poly-alkenoic acid- PAA or its copolymer with maleic or itaconic acid- Sometimes the acid may present in the dry
powder form to be blended with cement powder in case of water-settable material
2. Tartaric acid To viscosity of PAA and to the setting time
Conventional G.I. cements
Setting reaction Chemical reaction of acid-base type
H+ from the acid attacks the aluminum sites Decomposition of the surface of glass particles Release of Ca++ and Al+++ ions into the aqueous
medium the Ca++ and Al+++ cross-link the poly acrylate
chains by forming poly-acid sol (initial setting) the sol transfers into poly-acid gel forming
cement matrix (hardness and strength) surface of the un-reacted glass particles is coated
with a layer of silica gel
Conventional G.I. cements
Setting reaction The set material is composed of;
Non-reacted powder coated with silica gel in an amorphous matrix of hydrated poly-acid salts (gel (Calcium and aluminium poly-acid gel)
Water is a component of the set material. The loosely bonded water could evaporate out of the material desiccation and contraction
Fluoride ions remain free, and released only when the material becomes wet
Conventional G.I. cements
Manipulation1. Mixing • Mixing is achieved over a paper pad using plastic
spatula• Stainless steel spatula is contraindicated to avoid
the contamination of mix by the abraded metal particles
• Large amount of powder is incorporated into the liquid at once
• Thin mix cementation• Thick mix filling or cavity base
2. Tooth should be cleaned or even conditioned by PAA before cement application
Conventional G.I. cements
Manipulation (Cont.d)3. Restorative material • Should be inserted as one bulk into the cavity• The excess is removed after partial setting using
sharp hand instrument• The material left to set in 24 hrs and then finished
4. Surfaces of fillings or margins of cement should be protected from saliva by applying varnish or resin coating
5. Recoating is strongly recommended after finishing and polishing
Characters of conventional G.I. cements
1. Biological properties • Freshly-mixed cement may cause mild or
moderate pulp irritation, accordingly deep cavities should be lined with calcium hydroxide
• The material provides chemical bonding to both tooth structure and restoration surfaces --> the rate of microleakage
• The fluoride release --> help in the rate of caries recurrence
2. Interfacial properties The material is chemically-bond to the apatite
part of the tooth, base metal alloys and tin-plated gold alloys
3. Chemical properties • The set G.I. cement is more resistant to solubility
in oral fluids than other cements based on the acid-base reaction
• However, fresh cement is easily soluble in saliva and the material should be protected either with resin or varnish coating
4. Mechanical properties The cement is stronger on compression than
other zinc-oxide based cements However, the set material is brittle having low
DTS and fracture toughness
Characters of conventional G.I. cements
5. Esthetic properties • The set G.I. cement is translucent and could be
used to cement ceramic restorations
6. Thermal properties The cement has low thermal diffusivity and could
be used as cavity base under amalgam restorations
7. Practicability The cement is easily mixed on paper pads using
only non-metallic spatulas
Characters of conventional G.I. cements
7. Practicability (Cont.d) Cleaning and conditioning of tooth surfaces
together with using the freshly-mixed material all improve the bond
The material could be used as a liner under composite restorations (Sandwich technique)
Restorative material should be applied as one piece while filling tooth cavities (bulk filling technique) as the increments do not cohere together
Resin or varnish coating is required to protect the setting material
Careful and delayed (after 24 hrs) finishing should followed with resin or varnish coating
Characters of conventional G.I. cements
Metal-ModifiedMetal-Modified Glass-Ionomer CementsGlass-Ionomer Cements
Inclusion of metal particles within the composition or the structure of
cement’s powder
Cement powder is a simple blend of regular glass and amalgam particles
The blend is reacted with regular cement liquid (PAA)
The mixed material sets via acid-base reaction typically as that of the conventional glass-ionomer
1. Ketac Silver
Characters of the modified material
- Shows a little bit higher strength than that of Conventional G.I.
- Shows an increased rate of solubility
- Become opaque with gray metallic color
- Used to fill the primary molars
A small amount of silver is fused with cement’s glass particles at the time of manufacturing
The resulted particles react with regular cement liquid (PAA) and the mixture also sets via acid-base reaction typically as that of the conventional glass-ionomer
Characters of the modified material- Shows higher strength and better resistance to
wearing than the conventional G.I.- The material is also opaque having gray metallic
color- Used for core build-up and as posterior filling in
selected cases
2. Cermet
Resin-ModifiedResin-Modified Glass-Ionomer CementsGlass-Ionomer Cements
(RMGI)(RMGI)Inclusion of resin monomer to form (after its polymerization) a protective matrix in which the regular cement setting takes
place
The resultant material owns a dual mechanism of setting that includes both polymerization and acid-base reactions
Dual-cured CementsDual-cured Cements::
A. Powder Alumino-silicate glass particles Polymerization initiator Chemical initiator (Benzoyl peroxide) in case of
chemically-activated polymerization Photo-initiator (Camphroquinon) in case of light-
activated polymerization Both in case of triple-cured materilas
A. Liquid Aqueous solution of Poly-alkenoic acid Poly-acrylic acid having some carboxylic groups
modified with methacrylate or HEMA monomer
Composition of RMGI
The initial and rapid setting of the material is provided through polymerization of resin monomer
Slow acid-base reaction also takes place within the cured resin matrix. This reaction is responsible for maturing process and the final strength
The water content is too little to complicate the polymerizaton, however its presence is essential for the acid-base reaction.
Setting of RMGI
The modification provides material having
Higher strength and fracture toughness than that of conventional G.I.
Lower solubility of the freshly-set material
Possibility for immediate finishing and polishing
No need for resin or varnish coating
Lower rate of fluoride release
Characters of RMGI
Esthetic filling materials in non-stress bearing areas, cervical erosions
Fissure sealant
cavity base and liner
Bonding agent
Core building-up material
Cement for ceramic restoration
Applications of RMGI
CEMENTS SET BY POLYMERIZATION REACTION
A. Resin composite cementB. Resin compomer cement
Note. Composite = Resin matrix + inorganic fillers +
coupling agent + polymerization initiator Compomer = polyacid-modified composite resin
A. RESIN COMPOSITE CEMENTS
Firstly developed in the early 1970s to be used with adhesive/ resin bonded bridges
They are less heavily-filled composites (filler load = 65%)
These materials set via polymerization reaction
Present materials can be classified according to its mode of polymerization into chemical-cured, light-cured, and dual-cured
RESIN COMPOSITE CEMENTS
A. Chemically-cured composite cement
Many types contain on 4-META (4-methacryloxy ethyl trimellitic anhydride), that provides good bonding to several metal alloys
Used for;1. Cementation of resin-bonded bridges2. Cementation of any metal restoration (inlay, onlay, crown)3. Placement of bonded amalgam restoration
RESIN COMPOSITE CEMENTS
B. Visible light-cured composite cement
VLC materials utilize a polymerization system similar to that of VLC composites
These materials are available in different shades to help in production of good esthetics
Some manufacturers provide a try-in pastes have the same color shade of actual cement (water-soluble paste used during try-in stage)
Used for luting ceramic veneer
Cementing ceramic veneers
Labial veneer
Palatal surface Resin composite
cement
Labial gingiva
RESIN COMPOSITE CEMENTS
C. Dual-cured composite cement
Dual-cured materials could be polymerized by both light or chemical activation (i.e. polymerized even if they do not receive sufficient light)
Usually supplied as two-paste system, one of them are used to determine the shade
Used for luting composite and ceramic inlays, endodontic posts, and ceramic crowns
RESIN COMPOSITE CEMENTSADVANTAGES: Low solubility in oral fluids (resin-based material) Good strength properties (presence of fillers) Low film thickness (low filler loading) Good esthetics (color shade and color stability)
DISADVANTAGES: Poor wear resistance than regular composites Require the use of bonding agent Material’s polymerization could be affected in presence of
moisture or oxygen …… the exposed cement margins should be coated with air-inhibition gel
B. RESIN COMPOMER CEMENTSA kind of resin-based cement, used to cement
cast and metal-ceramic restorations
COMPOSITION:
Powder:Alumino-fluoro-silicate glass, sodium fluoride, self and/or light-cured initiator
Liquid:Methacrylate-carboxylic acid monomer, diacrylic monomer, water
RESIN COMPOMER CEMENTSADVANTAGES:
Provide chemical bonding to tooth structure….. through the present carboxylic acid groups of the monomer
Fluoride release help in inhibition of recurrent caries
High compressive and flexure strengths = composite cement
Higher fracture toughness > glass-Ionomer cement
Self-etching self-adhesive resin cements
All types of resin cements require etching, application of bonding agent to the surfaces (tooth & restoration) to be cemented
These new kind of resin-based cements contain phosphate-based monomer that have the ability to etch and chemically bond to tooth structure
