Published on March 6, 2014
By: Dr. Hrudi Sundar Sahoo Post-graduate student Dept.Of Conservative Dentistry and Endodontics
Introduction History of GIC Classification Composition Setting reaction & Role Of water Physical properties Adhesion to tooth structure Fluoride release Advantages and disadvantages Modifications in GIC conclusion
Materials used in the body, especially the materials used in various oral cavity regions should be stable and passive without any interactions with the body tissues or fluids. Dental amalgam,composite resins and dental cements are the materials of choice with such properties. The first attempts to produce active materials, which could interact with the human body tissues and fluids were prompted by the concept that fluoride-releasing materials exert useful effects in the body. Dental Research Journal / July 2013 / Vol 10 / Issue 4
The concept of using the “smart” materials in dentistry has attracted a lot of attention in recent years. Conventional glass-ionomer (GI) cements have a large number of applications in dentistry. They are biocompatible with the dental pulp to some extent. GIC are also known as “Man made dentin”, “ASPA or Alumino Silicate Poly Acrylate”, Polyalkenoate Cements and “Dentin Substitue”. Dental Research Journal / July 2013 / Vol 10 / Issue 4
YEAR RESEARCHER MODIFICATION DRAWBACKS 1965-1966 Wilson Mixed dental silicate glass powder with organic liquids Set sluggishly Hydrolytically unstable 1968-1969 Wilson, Kent and Novel glass use Lewis produced hydro. stable cements 1968 Kent Alumina and silica ratio in glass affects setting Kent ASPA I (Glass with high fluoride, usable) 1973,1979 1972 Wilson and Crisp ASPA II (Inc.W.T, S.R) Sluggish set Min.W.T Slow hardening Poor esthetics Sluggish set Liquid gels glass ionomer by Wilson and Mc Lean
YEAR 1973 1977 1977 RESEARCHER MODIFICATION Crisp and Wilson ASPA IV (copolymer of acrylic and tartaric acid) Wilson Inferior properties to ASPA II ASPA IVa Luting Sced, Wilson, Simmons DRAWBACK Miracle-mix (silver-tin alloy) 1973 Crisp and Wilson ASPA IV (copolymer of acrylic and tartaric acid) 1977 Wilson ASPA IVa Luting 1977 Sced, Wilson, Simmons Inferior properties to ASPA II Miracle-mix (silver-tin alloy) glass ionomer by Wilson and Mc Lean
According to characteristics specified by the manufacturer: Type I: Luting cement eg. Fuji I, Ketac cement Type II: Restorative material eg. Ketac fill, Fuji II Type III: a. Bases and liners: weak with low acidity eg. GC lining cement b. Bases and liners: more acidic eg. Ketac Bond, GC dentin cement c. Bases and liners: strong even in thin layer, light cure eg. Vitrebond Type IV: admixtures eg. Ketac Silver, Miracle mix
Newer classification: TRADITIONAL GLASS IONOMER 1. Type I – luting cement 2. Type II – restorative cement 3. Type III – liner and bases METAL MODIFIED GLASS IONOMER 1. Miracle mix 2. Cermet cement LIGHT CURE GLASS IONOMER HEMA added to liquid HYBRID GLASS IONOMER/RESIN MODIFIED GLASS IONOMER 1. Composite resin in which fillers substituted with glass ionomer particles 2. Pre-cured glasses blended into composites
CLASSIFICATION BY WILSON AND MC LEAN: Type I: luting cement Type II: (a) Restorative aesthetic – auto cure and dual cure (b) Restorative re-inforced Type III: Lining or base cements
POWDER: Glass: The glass composition in GIC varies among manufacturers, but it always contains silica, calcia (CaO), alumina (Al O ) and fluorides. 2 3
- Acid attack N O C H C A R H G A E D R G E Inert silica structure Glass Ionomer By Wilson And Mc Lean
S S I A L A L C U A L I M I N A 1.0:2.0 I L I U (OR) C M A I Increased More Loss of corundum N A 0.75:1.0 • More basic & reactive glass • Reduction in setting time Loss of translucency Glass Ionomer By Wilson And Mc Lean
Ratio >1:2 All Aluminum exist in four fold co-ordination Ratio <1:2 Only few Aluminum exist in four fold co-ordination Can replace silica Cannot replace all silica Exist as [AlO4] and cross-link Destabilize the glass network with [SiO4] Stabilize the glass network
GLASS PARTICLE PRODUCTION Components of glasses Fusion 1100-1500°C Melt poured onto a metal plate or into water Grounded Powder Particle size - 50µm (restorative) Particle size - 25µm (luting)
LIQUID Formation of the cement matrix Polyacrylic acid Itaconic acid Polymaleic acid Promotes reaction between the glass and the liquid Prevents gelation of the liquid Reduces the moisture sensitivity Promotes hardening of cement Reaction medium Hydrates the reaction products Water Glass Ionomer By Wilson And Mc Lean
LIQUID Ions extracted Promotes quick setting Tartaric acid Prevents crossLinking of the Polymer chain Until it becomes Linear Hardens the cement Glass Ionomer By Wilson And Mc Lean
1.Decomposition of the glass: liquid Acid attack at surface of the Glass particles Al Ca F Glass Ionomer By Wilson And Mc Lean
2. Migration of ions into the aqueous phase: Calcium ions pH Viscosity Aqueous phase of cement Uncoiling of polyacrylic acid Glass Ionomer By Wilson And Mc Lean
3.Gelation At critical pH & ionic conc. Ppt. of insoluble polyacrylates Initial set Cross-linking of polyacrylate chains by Calcium and Aluminium ions Ca !!!! Water Ca ions vulnerable to leach out of the cement Glass Ionomer By Wilson And Mc Lean
?????GELATION Polyacrylic acid chains H₂O H₂O COO H HOOC A- H₂O Calcium polyacrylate Aluminium polyacrylate Glass Ionomer By Wilson And Mc Lean
Metal ions increasingly polyacrylic acid chain bound to the Cement expands under humid conditions. Initial hardening occurs within an hour and continues till about 24 hours. Glass Ionomer By Wilson And Mc Lean
Improvement in translucency Resistant to dessication Initial plastic character slowly transforms to rigidity. Strength continues to increase for an year Bound water Hydration of the metal-carboxylate links Glass Ionomer By Wilson And Mc Lean
Hydrogel matrix consists of free sodium ions, hydrated calcium and aluminium polysalts containing fluoride. Glass Ionomer By Wilson And Mc Lean
1.Tightly bound water 1. Reaction medium 3. Hydrates the metal-polyacrylate bond 2. Hydrates the siliceous gel 2. Loosely bound water Glass Ionomer By Wilson And Mc Lean
As the cement ages, the ratio of tightly bound to loosely bound water increases. In higher humidities, cement can absorb water and hygroscopic expansion can exceed the setting shrinkage which is clinically advantage. Early contact with water, the cement disrupts by swelling and loss of ions. Protection from early contact with water can be achieved by using copal varnish, or emolients such as petroleum jelly or cocoa butter. Glass Ionomer By Wilson And Mc Lean
Alumina: silica ratio Tartaric acid SETTING TIME Fine powder Temperat -ure of mixing Glass Ionomer By Wilson And Mc Lean
1. Setting Shrinkage occurs during: Polymerisation reaction of monomers Acid base reaction (depending on the moment of light activation) Light activation Immediate Delay (after 2 mins of mixing) Only Polymerisation shrinkage Polymerisation shrinkage and acid-base reaction shrinkage
Shrinkage stress Conventional GIC Resin modified GIC (low) (high) Rubbery stage during setting Elastic yielding Light initiated polymerisation shrinkage
SETTING SHRINKAGE WATER SORPTION HYGROSCOPIC EXPANSION
2. WEAR OF GLASS IONOMER CEMENTS: Insufficient Strength Directly After Placement Sensitivity to acids pH as low as 4 Limited wear resistance of freshly prepared cement Dissolution of cement
3. FLEXURAL FATIGUE: EXTRINSIC WATER ON FRESH CEMENT LEACHES OUT FILLERS FILLER- MATRIX DEBONDING DEBONDED FILLERS STRESS CONCENTRATION SITES DECREASE IN FLEXURAL FATIGUE LIMITS REDUCED MATRIX STRENGTH
4. Aesthetics: TRANSLUCENCY 1. Due to glass fillers 2. Insufficient translucency to match the enamel colour 3. Cement takes 24 hrs to develop full translucency 4. The colour of the cement remains unaffected by oral fluids (ref.Knibbs et al, 1986) unlike the composites which get stained OPACITY 1. Refractive indices (R.I) of the glass fillers and the matrix are not identical 2. More the R.I mismatch, more is the scattering of light,hence , more opaque or opacity 3. Clear glasses minimize the opacity
• Various shades of the GIC are manufactured by the addition of pigments, which are generally metal oxides, such as ferric oxide and carbon black. • Glass ionomer cements are opaque and may become dull and lifeless in due course of time. • Although these cements are aesthetically poor than composites, these do not stain in presence of oral fluids as is the case of composites.
5. DISSOLUTION MOISTURE contamination before cement has hardened DESSICATION before cement has fully matured Leaching of soluble constituents from cement DURABILITY of the cement is lost
6. EROSION CHEMICAL Acid Attack Wilson et al (1986) MECHANICAL Masticatory forces GIC < silicate < zinc phosphate
Wilson et al (1986) GIC < silicate < zinc phosphate The polycarboxylates of the polymer chain are held together by COVALENT BONDS. 1. The IONIC BONDS which form the cross-links, are too many in number, to be broken by acid attack. 2.
Reaction of pulp to glass ionomer: 1.5mm Healthy reparative reaction REMAINING DENTIN THICKNESS 0.5 to 1.0mm Doubtful reparative changes Pulpal haemorrhage <0.5mm Calcium hydroxide as a protective layer under glass ionomer retoration
Adhesion to tooth: COOH Wilson (1974) F Ca Ca PO⁴ Wilson, Prosser & Powis (1983) Al Glass Ionomer By Wilson And Mc Lean
WHY??? 1. WATER: GIC is hydrophilic, displaces water but water can incorporate into cement. 2. DYNAMIC NATURE OF TOOTH MATERIAL Glass Ionomer By Wilson And Mc Lean
Surface Conditioning Conditioners tend to smoothen the cut tooth surface Acid Etching Etchants cause surface demineralization Glass Ionomer By Wilson And Mc Lean
50% CITRIC ACID: Extremely erosive Chelates with metal ions E C C E E C P T T E Surface active microbicidal solns. & DODICIN: Not compatible with GIC A J EDTA: Decalcifying agent R E D D 25% Tannic Acid 2% Ferric chloride Sodium fluoride Mineralizing Solutions like Levine et al & ITS solution 25% Polyacrylic acid Glass Ionomer By Wilson And Mc Lean
1. Acidic 2. Complexes with metal ions SHORTER APPLICATION PERIOD (10 sec) 3. Exposes the dentinal tubules DO NOT PENETRATE BECAUSE OF ITS HIGH MOLECULAR WEIGHT ON CUT DENTIN: Removes surface debris Smooth out surface irregularities Glass Ionomer By Wilson And Mc Lean
1. Temperature of fusion 2. improves the working characteristics of the cement paste 3. Strength moderately 4. Enhances translucency 5. therapeutic value
FLUORIDES: FROM WHERE???? Calcium fluoride strontium fluoride SOURCES Lanthanum fluoride Na-hexaf-alumin AlF3 “CARIOSTATIC”- Fluoride Uptake By Tooth Structure Prevents Secondary Caries Attack
Two reactions are involved: a. Short term reaction of high fluoride release corresponding to initial elution due to the postsetting maturation process b. Long term reaction of low release attributed to equilibrium diffusion process A significant increase in observed at low pH values. fluoride release is GICs can also absorb fluorides from the environment and release it again under specific conditions.
Amalgam alloy admixed cements – fluoride release was higher than or equal to conventional glass ionomer cements – increased porosity increases the effective surface area for release. Silver CERMET cements – reduced fluoride release – effective contact area between the glass particles and the polyalkenoic acid is reduced due to sintered silver particles.
INDICATIONS CONTRA-INDICATIONS • As a pit and fissure sealant • In stress bearing areas • Class I restorations (pits) • Labial build ups • Tunnel restorations • Cuspal coverage • Class III and V restorations • Root caries • As a liner/base • Restoration of deciduous teeth • Luting cement • Endodontic access filling • As a repair material • Core build up
ADVANTAGES DISADVANTAGES 1. Adhesive 1. Debonds readily aesthetic restorative 2. Poor strength 2. Liberates fluoride: Anticariogenic 3. Highly technique 3. Biocompatible sensitive 4. Low oral solubility
1. Metal Modified Glass ionomers CERMET by Simmons, 1983 • Powder contains fluoroalumino-silicate and glass is sintered with silver. MIRACLE MIX • physically blending silver alloy powder with the glass powder in the ratio of 1:7 and mixing with glass ionomer liquid. • Improved toughness • Silver acted as stress absorber • Grey or blackish colour of the cement made it aesthetically unacceptable.
2. Highly Viscous Glass ionomers Contain smaller glass particles Higher P/L ratio – excellent packability, greater compressive strength Designed for posterior restorations Useful in Atraumatic restorative technique, during the early stages of the caries development For core build ups As preventive retorations to seal cavity Eg. Fuji IX and Ketac Molar
3. Low Viscous Glass ionomers Are highly flowable and mixed in a low powderliquid ratios Designed for fissure protection (during teeth eruption period), as liner Restoration for sensitive cervical areas
4. Resin modified Glass ionomers ( Hybrid Glass ionomers ) Incorporation of water soluble resin monomers into an aqueous solution of polyacrylic acid. Undergoes both polymerisation reaction and acid-base reaction. Powder compositions is similar to conventional glass ionomer cements whereas liquid consists of polycarboxylic acid, water and 2hydroxyethylmethacrylate.
• One of the main advantage of RM-GIC is that unlike the conventional GIC, at early stages of setting reaction, water exposure does not inhibit the setting reaction due faster setting promoted by the photopolymerization. • Eg. Fuji II LC, Vitremer and Photac Fil
SETTING REACTION OF RM-GIC 1. Acid base reaction between fluoroaluminosilicate and the polycarboxylic acid is initiated 2. Photopolymerization of HEMA occurs.
SETTING REACTION OF RM-GIC CHEMICAL CURE (OR) “dark cure” REDOX reaction between catalyst-initiator system of the resin
DUAL CURE 1. Acid base reaction between fluoroaluminosilicate and the polycarboxylic acid is initiated 2. Photopolymerization of HEMA occurs. DUAL CURE TRI- CURE CHEMICAL CURE (OR) “dark cure”
The chemical setting reaction continues even after the light initiated setting reaction is complete. HEMA polymer and polycarboxylic acid are linked by hydrogen bond. The double bonds of the polymerized monomer disappear after hardening.
The translucency of the cement declines with the lapse of time. pH of the liquid is about 1.5 and it increases as the acid base reaction advances; stabilises within 24 hours of setting.
ADHESION of RM-GIC to tooth structure: Similar to conventional GIC The ionic reactivity of the RM-GIC can be markedly increased by treating the tooth surface with an acid conditioner. Citric acid or a mixture of ferric chloride and aluminium chloride can be used for conditioning. An aqueous solution of citric acid – ferric chloride or of 20%polyacrylic acid – 3%aluminium chloride can also be used for conditioning.
Unfortunately, 1. More setting shrinkage as compared to conventional GIC due to methacrylate polymerization 2. 3. Lower water and carboxylic acid contents reduce the ability of the cement to wet tooth substrates More microleakage
For restoration As base and liner (quick set, 10 to 40µm thick, releases stress generated from a polymerisation shrinkage of the overlying composite restoration) For fissure protection (high fluidity and ability to penetrate into fissures, long-term fluoride release) For luting purposes (high bond strength) As orthodontic cementing material (high bond strength between enamel and brackets, fluoride release prevents demineralization around the brackets)
5. Polyacid modified resin composite “COMPOMER”- polymerization of an acid monomer in presence of fluoro-aluminosilicate Physical properties quite similar to the composite resin. Differs from RM-GIC: does not contain water and does not self adhere to tooth structure Higher water absorption to complete the acid-base reaction and subsequent fluoride release. Eg. Dyract AP, Compoglass F, Ionosit Fil COMPOSITION: One paste material- fillers are fluoroalumino-silicate (release fluoride)- contains strontium (radio-opaque) Matrix contains acidic monomer and rest similar to composite resin.
ADHESION of COMPOMERS to tooth structure: Require a dentin bonding agent prior to placement in the cavity because they do not contain water which could make them self adhesive. The luting cements consist of powder and liquid (has water) & is self adhesive.
6. GIOMERS (A proprietary product exclusive to Shofu Dental Corporation (San Marcos, CA) Available as one paste form Eg. Beautiful II Pre-reacted glass ionomer technology (PRG) to form a stable phase of GIC The filler particles are of two types- Surface reacted PRG (S-PRG) and Fully reacted PRG (FPRG).
The resin consisted of Bisphenol A glycidyl methacrylate and triethylene glycol. Fluoro-aluminosilicate glass is reacted with polyalkenoic acid in water prior to inclusion into silica filled urethane resin. Are light polymerized and require bonding system for adhesion to tooth structure.
ADHESION of GIOMERS to tooth structure: Single application bonding system 1. SELF ETCHANT PRIMER 2. ADHESIVE • etches the etched enamel and penetrates • Hardens on evaporation of the solvent 3. Thick HYBRID LAYER formed between restoration and tooth surface
PROPERTIES of Giomer: Fluoride release and recharge Biocompatible Smooth surface finish and esthetics Excellent bonding Stable: hardness better than resin modified and polyacid modified glass ionomer cements.
GIC are favourable restorative materials due to their ease of use and unique biocompatibility among direct restoratives. However, brittleness limits their use in the load bearing posterior region. A low abrasion resistance and inferior strength, toughness and fatigue performance currently contraindicates the application as a permanent class I or class II filling materials. Several attempts in improving their mechanical parameters are still underway and some forecast a promising future for GIC as a dental filling material with extended indications.
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