Glass Ionomers Cements Dr Kilasara/Zubeda

Overview Glass ionomers Characteristics Classification Conventional GIC Resin based GIC Light cured GIC Clinical uses

Glass Ionomer: “glass” refers to the glassy ceramic particles and the glassy matrix (non-crystalline) of the set material, while “ionomer” refers to ion-crosslinked polymer

Glass Ionomer Development Glass ionomer cements are hybrids of the silicate cements and the polycarboxylate cements. The intention was to produce cement with characteristics of both the silicate and polycarboxylate cements. (translucency and fluoride release adhesion kindness to the pulp

Early Glass Ionomers Poor esthetics Prolonged setting reaction rough surface Prolonged setting reaction Poor wear resistance Vulnerable to hydration extremes Handling difficulties

Modern Glass ionomers Refined formulation Improved packaging addition of tartaric acid more reactive acids Improved packaging Metal modification Addition of resin

Advantages Inherent (chemical) adhesion to tooth structure Fluoride release Linear Coefficient of thermal expansion (LCTE) similar to tooth structure Biocompatible

Disadvantages Sensitive to moisture and desiccation Low fracture toughness Low flexure strength Low wear resistance Relatively poor esthetics

Indications Direct restorative Class 5 Root caries Class 3 Pediatric dentistry resin-modified version Tunnel preparations Atraumatic restorative treatment (ART)

Indications Luting agents Liners Caries control Core block-out Occlusal sealant

Contraindications Stress-bearing areas in permanent teeth Class 1, 2 and 4

Classification GICs are commonly classified into four principal types: 1. Conventional Glass Ionomer Cements 2. Hybrid Ionomer Cements Also known as Light or Chemical Cured Resin-modified Glass Ionomer or Dual-cured Glass Ionomer Cements . 3. Tri-cure Glass Ionomer Cements 4. Metal-reinforced Glass Ionomer Cements

Conventional Glass Ionomer Composition powder ion-leachable calcium aluminofluorosilicate glass liquid copolymers of acrylic acid and/or water copolymers freeze-dried, placed in powder maximize shelf-life

Production It is an acid-soluble calcium fluoroaluminosilicate glass similar to that of silicate but has a higher alumina-silicate ratio which increases its reactivity with liquid. The fluoride portion acts as a “ceramic flux”. Lanthanum, Strontium, Barium or Zinc Oxide additives provide radioopacity. The raw materials are fused to form a uniform glass by heating them to temperatures of 1100◦C to 1500◦C. The glass is ground into a powder having particles into a powder in the range of 15 to 50 µm

GIC powder composition Ion-leachable glass silicon dioxide41.9% aluminum oxide 28.6% calcium fluoride15.7% aluminum phosphate 3.8% sodium fluoride 9.3% aluminum fluoride 1.6%

Acid component Polyacids Tartaric acid acrylic maleic itaconic tricarboxylic acid Tartaric acid improves handling extends working time sharpens set increases strength

Setting Reaction (conventional) Ion-leaching phase acid attack on glass H+ from polyacid Al+3, Ca+2, F- migrate and form complexes hydrogel forms around glass particles Ca+2 predominate early NaF formed not native of matrix physical properties not affected by depletion Mn+ H+ COO-

Setting Reaction (conventional) Hydrogel Phase Ca+2 & Al+3 polysalts crosslink polymer chains causes viscosity increase & hardening poor physical properties very susceptible to moisture protect with matrix, bonding agent COOH COO- COO- COO- M1+ COO- M3+ COOH M2+ COO- COO- COO- COOH COOH

Setting Reaction (conventional) Polysalt-Gel Phase slow maturation of matrix Al+3 polyacrylate polymers predominate stronger, less soluble maturation may require 6 months–1 yr Later stage susceptible to dehydration protect with bonding agent

Conventional Glass-Ionomer Setting Reaction COO- H+ Mn+ COO- H+ Mn+ H+ COO- Mn+ Fluoroaluminosilicate Glass COO- H+ COO- H+ COOH COO- COO- H+ Ca2+ Polyacrylic Acid COO- COO- COO- Tooth COO- M1+ COO- Conventional Glass-Ionomer Setting Reaction M3+ COOH M2+ COO- COO- COO- COO- Ca2+ COO- COOH COOH

Resin-Modified Glass Ionomers First developed as liners Modified light- and/or chemically-activated methacrylate side chains on polyacrylic-acid molecules free in solution HEMA Total set resin 4.5–6%

Resin-Modified Glass Ionomer Attempt to combine benefits glass ionomer fluoride release adhesion composite resin strength esthetics Attempt to reduce glass ionomer hydration sensitivities delayed set poor early strength composite polymerization shrinkage microleakage recurrent caries Glass Ionomers RMGI Compomers Composites

Resin-Modified Glass Ionomer Composition powder ion-leachable glass liquid initiators copolymers of acrylic acid methacrylate groups grafted and/or HEMA and/or water copolymers freeze-dried, placed in powder maximize shelf-life

Setting Reaction (RMGI) COO- COOH Poly-HEMA Traditional glass-ionomer acid-base reaction proceeds more slowly Free-radical polymerization similar to composites light initiated chemical Cross-linked resin-reinforced matrix

Free-Radical Polymerization Visible-light photoinitiator camphorquinone most common absorbs blue light initiator reacts with amine activator Chemical mix separate pastes benzoyl-peroxide initiator tertiary-amine activator Forms free radicals Initiates addition polymerization methacrylates grafted and/or free Camphorquinone Benzoyl Peroxide O O O H2C=C-C-O-CH2-CH2-OH CH3 O HEMA

Resin-Modified Glass-Ionomer Setting Reaction Mn+ H+ COO- HEMA H2C=C-C-O-CH2-CH2-OH CH3 O HEMA HEMA HEMA Fluoroaluminosilicate Glass COO- H+ Polyacrylic Acid Poly-HEMA COO- Ca2+ COO- COO- COO- Tooth COO- M1+ Resin-Modified Glass-Ionomer Setting Reaction COO- M3+ COOH M2+ COO- COO- COO- COO- Ca2+ COO- COOH COOH Davidson, GI Cements 1999 Poly-HEMA

Material-Related Variables Fluoride release Adhesion Biocompatibility Physical properties

Fluoride Release Rapid early release from matrix Slow, long-term release from particle Does not take part in matrix formation does not result in loss of physical properties Amount of release similar for both conventional and RMGI F- Al3+ COO-

Adhesion to Tooth Structure M3+ COO- COOH Ca2+ Tooth Conventional GI ion exchange GI – tooth substrate carboxyl groups of GIC bond with Ca+2 of hydroxyapatite Resin-modified GI ion exchange similar to conventional GI resin-impregnated hybrid layer? equivocal

Biocompatibility Favorable large molecules buffering of dentinal fluid limited tubule ingress buffering of dentinal fluid relatively weak acid initial high acidity chemical adhesion minimizes microleakage antimicrobial activity

Properties Strength Polishability Fluoride Release Glass Ionomers RMGI Compomers Composites Strength Polishability Fluoride Release

Classifications Applications Chemistry Type 1: luting cements Type 2: restorative cements esthetic restoratives reinforced restoratives condensable metal-modified Type 3: liners/sealants Chemistry conventional GI traditional acid-base reaction resin-modified (RMGI) acid-base reaction light and/or chemical cure

Luting Cements (Type 1) Conventional Resin-modified (RMGI) Ketac-Cem (3M ESPE) Fuji 1 (GC) Resin-modified (RMGI) greater strength less moisture sensitivity less soluble examples Fuji Plus and FujiCem (GC) Rely X (3M ESPE)                                                    

Orthodontic Luting Agents Fluoride releasing Bonds in moist environment Condition surface etch optional Only light-leveling wires first 24 hrs Examples Fuji Ortho (GC) Fuji Ortho LC (GC)

Endodontic Obturation Fluoride releasing Radiopaque Short working time More difficult to retreat Example Ketac-Endo (3M EPSE)

Applications Type 1: luting cements Type 2: restorative cements esthetic restoratives reinforced restoratives condensable metal-modified Type 3: liners/sealants

Esthetic Restoratives (Type 2) Conventional examples Ketac-Fil (3M ESPE) Fuji II (GC) Glasionomer Type II (Shofu) RMGI Fuji II LC (GC) Vitremer (3M ESPE) Riva Light Cure (SDI)

Esthetic Restoratives Case Selection High caries risk Areas of lower stress permanent Class 3 & 5 esthetics not paramount Pediatric dentistry RMGI version

Esthetic Restoratives Technique Tips Surface must be clean Remove smear layer Tooth must be moist

Esthetic Restoratives Conditioning Dentin Conventional GI polyacrylic-acid conditioner removes smear layer cleans surface promotes adhesion RMGI follow manufacturer’s directions polyacrylic-acid conditioner or adhesive

Esthetic Restoratives Moisture Content Sensitive to moisture levels ion exchange in hydrated medium desiccation extracts water from cement excess water dilutes matrix

Esthetic Restoratives Finishing Conventional GI surface coat wait 15 minutes minimize trauma to surface use blades slow speed

Esthetic Restoratives Finishing RMGI surface coat immediate finishing normal armamentarium fine diamond polishing discs gentle technique

Esthetic Restoratives Surface Protection Protect setting cement early moisture contamination desiccation later Unfilled resins essential conventional optional RMGI more resistant to water loss fills irregularities color stability decreased F release

Esthetic Restoratives RMGI Liners Posterior composite “open-sandwich” technique dentinal gingival margins reduced leakage reduced gap formation examples Fuji II LC (GC) Vitremer (3M ESPE)

Applications Type 1: luting cements Type 2: restorative cements esthetic restoratives reinforced restoratives condensable metal-modified Type 3: liners/sealants

Reinforced Restoratives (Type 2) Condensable Metal-modified

Condensable (Type 2) Conventional GI Indications Examples simplified handling Indications provisionalization pediatric restorations Atraumatic Restorative Treatment field dentistry hand instrumentation Examples Fuji IX (GC) Ketac-Molar (3M ESPE)

Metal-Modified Glass Ionomers (Type 2) Conventional GI silver fused with powder e.g., Ketac-Silver (3M ESPE) amalgam alloy mixed with powder e.g., Miracle-Mix (GC) Improved handling,radiopacity,wear resistance Fluoride release similar or slightly less than conventional

Metal-Modified Glass Ionomers (Type 2) Indications non-stress bearing areas core build-ups low strength minimize size block-out caries control provisionals Atraumatic Restorative Treatment

Applications Type 1: luting cements Type 2: restorative cements esthetic restoratives reinforced restoratives condensable metal-modified Type 3: liners/sealants

Liners (Type 3) Conventional RMGI examples Ketac-Bond (3M ESPE) Lining Cement (GC) RMGI Vitrebond (3M ESPE) Fuji Lining LC (GC)

Sealants (Type 3) Glass-ionomer Resin-based sealants “pre-cooperative” children partially-erupted permanent molars examples Riva Protect (SDI) Fuji Triage (GC) click here for DECS evaluation Resin-based sealants higher retention similar efficacy Simonsen, Pediatr Dent 2002 proper isolation necessary

Compomers Composite and Glass-ionomer Polyacid-modified composite resin Matrix dimethacrylate monomer carboxylic groups Filler ion-leachable glass No water COO-H2C-H2C-H2C-H2C CH2-CH2-CH2-CH2-OOC H2C=CH CH=H2C C C HOOC COOH Matrix Example

Setting reaction Free-radical polymerization reaction similar to resin composites resin-based adhesives No chemical bond to tooth structure Low levels of fluoride release Delayed acid-base reaction water from tubules, absorption

Compomers in Dentistry Direct restorations restoratives flowables Cements

Advantages Easy to place and polish Some fluoride release More esthetic than glass ionomer Better mechanical properties than glass ionomer Glass Ionomers RMGI Compomers Composites

Disadvantages Inferior mechanical properties compared to composite Less fluoride release than glass ionomer minimal recharge No chemical bond to tooth structure

Indications Esthetics Areas of lower stress class 3, 5 pediatric conservative class 1 and 2

Contraindications Stress-bearing areas Poor isolation permanent Class 1 or 2 increased wear loss of marginal integrity Poor isolation

Giomers Resin-based restoratives Pre-reacted glass-ionomer particles (PRG) fillers from conventional GI reaction Free-radical polymerization reaction similar to light-activated resin composites No chemical bond to tooth structure More research needed Example Beautifil (Shofu)

USES Glass-ionomer cements are used for the cementation of cast-alloy and porcelain restorations and orthodontic bands cavity liners or base materials, restorative materials, especially for erosion lesions