glass ionomer cements (2)

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