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GLASS IONOMER CEMENTS
Dr. NITIN B. ROHATGI
CONTENTS INTRODUCTION DEFINITION HISTORY CLASSIFICATIONS COMPOSITION SETTING REACTION PROPERTIES CLINICAL PROCEDURES INDICATIONS and CONTRAINDICATIONS RECENT ADVANCES CONCLUSION
INTRODUCTION
MAN MADE DENTINMAN MADE DENTIN
DEFINITION
WATER BASED MATERIAL THAT HARDENS FOLLOWING AN ACID BASE REACTION BETWEEN BASIC FLUORO ALUMINOSILICATE GLASS AND AN AQUEOUS SOLUTION OF POLYACIDS.
HISTORICAL BACKGROUND SILICATE CEMENTS- FLETCHER (1871) ACID ETCHING- BUONOCARE (1955) COMPOSITE RESIN- BOWEN (1958) POLYCARBOXYLATE CEMENTS- D.C.SMITH (1968) GIC (ASPA I)- B.E.KENT & WILSON (1969) ASPA II (1972) ASPA III & IV- WILSON AND CRISP (1974-75) ASPA X- WILSON,CRISP & ABEL (1977) ANHYDROUS GIC (ASPA V)- PROSSER (1984) CERMET- Mc LEAN & GASSER (1985)
CLASSIFICATIONS
Philips: TYPE I- LUTING
TYPE II- RESTORATIVE TYPE III- LINER & BASE
Davidson/Mjor : - CONVENTIONAL/TRADITIONAL GIC - RESIN MODIFIED GIC - POLYACID MODIFIED RESIN COMPOSITES
Mount:
A) - Auto Cure - Dual Cure - Triple Cure
B) - Type I - Type II * Type II 1 * Type II 2 - Type III
C) Glass Ionomer Cements a. (i) Glass Polyalkeonates (ii) Glass Polyphosphates b. Resin modified GIC c. Polyacid modified composite resin
Sturdvent: 1. Conventional or Traditional 2. Metal Modified GIC - Miracle Mix - Cermet 3. Light Cured GIC 4. Hybrid (resin modified) GIC 5. Polyacid Modified Resin Composites
According to clinical use as: Type I- Luting TYPE II- Restorative Type III- Liner/ Base Type IV- Pit & Fissure Sealant Type V- Luting for Orthodontic Purpose Type VI- Core build up material Type VII- High fluoride releasing command set Type VIII- ART Type IX- Geriatric & Paediatric GIC
COMPOSITION POWDER ALUMINA (28.6%) alumina: silica-- > 1:2 SILICA (41.9%) FLUORIDE CALCIUM FLUORIDE (15.7%) ALUMINIUM PHOSPHATE (3.8%) CRYOLITE Na+, K+, Ca2+, Sr3+ La2O3, SrO
LIQUID POLYACRYLIC ACID(45%) polyacrylic: itaconic-- > 2:1 ITACONIC ACID MALEIC ACID TRICARBOXYLIC ACID TARTARIC ACID(5-15%) POLYPHOSPHATES METAL OXIDES WATER
SETTING REACTION Decomposition
Migration
Gelation
Post set hardening
Maturation
Role of water - reaction medium - hydrate the matrix
Classification - loosely bound water - tightly bound water
Protection - Vaseline - Dentin bonding agents
Optical microscopic section
WITHOUT PROTECTION
PROTECTED WITH RESIN SEALANT
LIFTED SURFACE WITH SURFACE DEGRADATION
EXCELLENT ADAPTATION WITH COMPLETE INTEGRITY
CRACK IN UNPROTECTED GIC CRACK PROPOGATION
WITHOUT PROTECTION
WITH PROTECTION
crack chipping
Factors affecting setting
Chemical constituents - alumina : silica ratio - fluoride - tartaric acid Particle size Powder : liquid ratio Temperature of mixing
PROPERTIES: Adhesion: mechanism of adhesion 1. chelation (Smith) 2. hydrogen bonding (Wilson) 3. diffusion based adhesion (Akinmade) 4. hydroxyapatite & polyacrylic acid reaction (Beech) 5. hydrogen bonding with dentin collagen (Akinmade)
DIFFUSION BASED ADHESION
- Bond strength enamel- 2.6 to 9.6 Mpa dentin – 1.1 to 4.5 Mpa
- Surface conditioners - remove smear layer - increases surface energy - increases wettability and decreases contact angle
Polyacrylic acid- 10% for 15 sec 50% citric acid for 5 sec 25% tannic acid for 30 sec 2% ferric chloride EDTA ITS solution, Levine solution
advantages of adhesion- no microleakage - conservative cavity
form
Biocompatibility - high initial pH mild pulpitis - properties of polyacrylic acid -high mol wt. -weak acid -ppt by Ca in dentinal tubules -electrostatic attraction of H+ ions - sensitivity with luting GIC - high initial pH - low P : W ratio - pre existing pulpitis - decrease dentin thickness
Anticariogenicity - Fluoride Action - physicochemical mechanism - biologic mechanism
- Duration of fluoride release? - Structural degradation? - Fluoride recharge (topping up effect) and
fluoride reservoir
FLUORIDE RECHARGE
FLUORIDE RELEASE
TETRAHEDRON GLASS SKELETAL STRUCTURE
F- ION NOT IN STRUCTURE
Aesthetics- degree of translucency exist Dimensional Stability- ~ 3% contraction Dissolution by - early water contamination - plaque acid/ APF gel application - mechanical wear Clinical Life of the restoration Strength- compressive strength- 150 Mpa - tensile strength- 6.6 Mpa - KHN- 48 Radiopacity
CLINICAL PROCEDURE (DISPENSING)
STANDARDIZE POWDER IN SPOON
DISPENSE LIQUID TO AVOID AIR BUBBLES
MIXING
MIXING POWDER AND LIQUID USING PLASTIC SPATULA
FOLDING TECHNIQUE FOR MIXING
MATRIX APPLICATION
PREFORMED HAWE MATRICES
SOFT TIN MATRIX
FINISHING & POLISHING No finishing for 24 hours. If essential, sharp blade to reduce
gross contour After 24 hours, fine diamond with air/
water spray for gross contour Rubber polishing points for refining Polishing discs for glossy finish sealing with resin sealant or vaseline
INDICATIONS LUTING CEMENT particle size - 4 to 15µ film thickness - 10 to 20µ P : W ratio – 1.5:1 (low viscosity) no application of pressure- GIC has
thixotropic tendency towards plastic deformation Conditioning or no conditioning? on non vital teeth- yes on vital teeth- a dilemma
RESTORATIVE CEMENT erosion/ abrasion lesions class III & V lesions restoration on primary teeth restoration in rampant caries cases laminate restorations ART microcavity preparation small to medium size class I lesion repair of open margins around crowns and
inlays
P : W ratio – 3:1 (2.9:1 to 3.6:1) for conventional GIC
For anhydrous GIC – 6.8: 1
LINER AND BASE-
- as a liner to protect pulp from thermal insult - as base to replace carious dentin - Mount technique for base application - Sandwich technique- - open method- dissolution of open GIC margins
- closed method- GIC margins protected byresin
Exposed margins
Resin covered margins
Pit & fissure sealant Luting of orthodontic brackets and bands Core build up
Cement less than 40% of the total core
In endodontics
Preventive restorations - ART - High fluoride releasing command
set
CONTRAINDICATIONS
Class IV lesions and fractured incisors
Large labial restoration where esthetic is of prime concern
Lost cusp area Class II lesions where conventional
cavities are prepared
RECENT ADVANCES IN GIC
High viscosity GIC1. Developed as an alternative to amalgam.2. Also called as pack able / condensable GIC3. Has increased wear resistance.4. Decrease moisture sensitivity & solubility.5. Highly opaque & limited service life.
Low viscosity GIC1. Also called as flowable GIC2. Use for lining, pit and fisure sealer,
endodontic sealer and for sealing hyper sensitive cervical area.
3. Low P:L ratio thus increase flow.Eg fuji lining LC, ketac – endo etc.
Metal modified GIC1. Seed & Wilson (1980) invented miracle mix2. Mc lean & Gasser (1985) invented cermet3. Minimal improvement in mechanical
property - Compressive strength – 150 Mpa- KHN – 39 - Tensile strenght – slightly more 6.7 Mpa- Slight increase in wear resistance. -
Fluoride release - Max for miracle mix (3350µg, 4040µg)- And min for cermet (200µg, 300µg)
Esthetically poor, may discolour teeth
Chemical adhesion, Anticariogenicity and rapid Hardening makes it use as core build up material
Resin Modified GIC 1. Defined as hybrid cement that sets
partly by acid base reaction and partly by polymerisation reaction
2. Developed by Antonucci & Mithra 3. Powder – Ion leachable glass and
initiators liquid – water, Poly acrylic acid, HEMA
4. Setting reaction – initially acid base reaction, later polymerization reaction superimposes over acid base reaction.
5. Dual cure & tricure according to setting reaction.
Properties
Esthetic – superior than conventional GIC
Fluoride release – same as conventional GIC but more for lining version
Strength –- tensile strength(20 Mpa)- Compressive strength (105 Mpa)- KHN (40)
Adhesion to tooth structure – less than conventional GIC
Adhesion to composite restoration better than conventional GIC
Microleakage – due to polymerization shrinkage and reduce water and PAA content
Water sensitivity considerable reduce Biocompatibility – less than average.
Advantages Long working time due to photo curing Decrease sensitivity to water (but not
significantly, Journal of Conservative Dentistry, June 2005)
Increase early strength Finishing & polishing can be done
immediately Improved tensile strength. Better adhesion to composite restoration Increase fluoride release.
Disadvantage
Biocompatibility is controversial More setting shrinkage leading
increase microleakage and poor marginal adaptation
Uses
As a luting cement As a liner and bases As a pit and fissure Core build up material Retrograde filling material
Polyacid modified composite resin Also called as compomer Defined as : material that contain
both the essential components of GIC but in an amount insufficient to carry out acid base reaction in dark.
They are developed to combine fluoride release of GIC and durability of composite
Composition: one paste system containing ion leach able glass, sodium fluoride, polyacid modified monomer but no water
Recently 2 paste or powder liquid system is introduced. They are self adhesive due to presence of water
Setting reaction 1. Initially light curing forms resin
network around the glass 2. After 2 to 3 month there is water
uptake which initiates slow acid base reaction and fluoride release.
Properties
Adhesion – absence of water thus no self adhesion
Fluoride release minimal. Physical properties better than
conventional GIC but less than composite.
Uses
Pit and fissure sealant Restoration of primary teeth Liners and bases Core build up material For class III & V lesions Cervical erosion / abrasion
Advantages
Ease of use Easy adaptation to the tooth Good esthetics More working time than RM GIC
Self hardening RM GIC Activated purely by chemical
polymerisation reaction Contains benzoyl peroxide and t-
amines Advantages
- ease of handling- fluoride release- higher compressive strength - no additional set up for light activation
Fluoride charged material
Consist of 2 part
Restorative part Charge part
Still under experimental stage
Low pH “Smart” Material
Releases fluoride when pH falls below the critical level
Fluoride release is episodic and not continuous
Bioactive glass Introduce by Hench in 1973 Acid dissolution of glass forms calcium and
phosphate rich layers The glass can form bioactive bonds with bone
cells Better than hydroxyapatite Can grow calcium and phosphate rich layer in
presence of calcium and phosphate saturated saliva.
They are less abrasive than feldspathic porcelain to opposing teeth
uses
Bone cement Retrograde filling material For perforation repair Augmentation of resorbed alveolar
ridge Implant cementation Infra bony pocket correction Ceramic crown
Giomer (operative dentistry 2005) True hybridization of GIC and
composite Combine fluoride release and fluoride
recharge of GIC with esthetic easy polishability and strength of composite
Based on PRG technique. Two types: S- PRG & F- PRG technique Eg Beautifil and Reactmer
S- PRG Giomer are indicated in Class I to Class VI lesions
F- PRG Giomer are indicated only in cervical erosion and abrasion lesions
Advantages Increase wear resistance Increase Radiopacity (glass filler) Shade conformity (improved light
diffusion and fluorescence) High and sustained fluoride release and
recharge Provide almost complete seal against
bacterial microleakage Little mechanical and chemical pulp
irritation Inhibit demineralization
Conclusion
With all its limitation, the future of GIC is hard to measure at this point;
but one thing is obvious- it has a future.
References
Recent advances in restorative dental material – Dr. Nageswar Rao.
Science of dental material – Philips Operative Dentistry – Sturdevant Advances in GIC – Davidson & Mjor An Atlas Of GIC – G.J.Mount Journal of operative dentistry, 2005