Glass Ionomer Cements (GICs)

Glass Ionomer Cements (GICs).

Zinc Oxide. Poly-Acrylic Acid. Zinc Poly Carboxylate Cement.

Glass Ionomer Cements (GICs). Types Conventional Glass ionomer. Resin modified glass ionomer. Tri cure Glass ionomer. Metal reinforced glass ionomer..

1. Conventional Glass ionomer. Forms: Powder and liquid Pre-proportioned capsules.

Water settable” or “Anhydrous” GIC s. The polyacrylic acid was freeze-dried and added to the glass powder in one bottle. The liquid consists of water or water with tartaric acid Prolonged working time, better stability, and unlimited shelf life..

composition. Powder Acid soluble Calcium alumino-silicate contains Silica (Si02) Alumina (A 1203) Calcium fluoride (CaF2) and NaF Function of the glass powder glass Liquid Copolymer of Acrylic acid 40-50% Itaconic acid Tartaric acidin water Function of each acid Releasing ions responsible for setting and properties of hard cement. Contributes to esthetics. Releasing fluoride Acrylic acid Itaconic acid Tartaric acid Main reactant Increase reactivity Decrease viscosity Reduce gelation Improve handling Increase working time.

image28.tif. Acid-soluble calcium flouro-alumino-silicate glass powder..

Setting reaction. Acid-base reaction Acid attack the surface of the glass particles → leaching out of calcium, aluminum, sodium and fluoride ions into the aqueous medium In the initial stages of the reaction : calcium ions cross-link with the chains of PAA into a network giving a solid mass..

Setting reaction.

Setting reaction. c 00 ¯ c 00 — c 00 — coo — C 00 — c 00 — c 00 — c oo— coo¯ C 00 — coo —.

Setting reaction. Water is essential for setting because * It provides the aqueous medium required for the reaction. During maturing process , for hydration step. Dehydration and over-hydration during the setting process should be avoided. Dehydration of unset cement will cause GIC to shrink and crack. Contamination by water can cause dissolution of the ions that form the matrix → weak and more soluble cement..

Set cement protection. Material must be protected from moisture contamination during the first hours ; otherwise strength and solubility are adversely affected. Varnish (water resistant resin dissolved in a volatile solvent such as ether or ethylacetate) is applied to material surface. long-term protection can be achieved by using a resin- bonding agent or fissure sealant..

image31.tif. GIC Varnish. image32 tif. GIC.

Manipulation & Dentine surface conditioning. Most effective agent is 10–15% poly (acrylic) acid , applied to the tooth surface for 30 seconds then washed off and the tooth dried to remove the precipitated salivary protein. Powder and liquid are proportioned and mixed on Paper pad or glass slab with plastic or bone spatula. Or encapsulated forms are mixed for 10 sec in a mechanical mixer Mix should be used while still shinny..

GIC properties. 1. Mechanical properties Compressive strength: comparable to ZnPO 4 cement. Tensile strength: slightly higher than ZnPO 4 cement but still brittle. Modulus of elasticity: less than ZnPO 4 cement, i.e. less rigid and more prone to elastic deformation..

GIC properties. 2. Bonding PAA provides chemical adhesion to tooth structure . 3. Solubility Good resistance to dissolution under oral conditions and improved by varnish protection. 4. Biocompatibility GICs are as biocompatible as zinc polycarboxylate cements..

GIC properties. 5. Anticariogenic properties GICs possess anticariogenic properties as a result of fluoride release. Mechanism of action of fluoride in caries inhibition, Fluoride + Ca-hydroxy-apatite Fluoro-apatite Lower surface energy less acid solubility.

GIC properties. 5. Anticariogenic properties Other Fluoride effects inhibits the enzymes responsible for carbohydrates fermentation. Shifts the equilibrium balance toward remineralization. act as a catalyst for uptake of calcium and phosphate ions..

GIC Advantages. Advantages of GICs Chemical bonding to tooth structures Biocompatible Long-term fluoride release Good compressive strength Low solubility in oral fluids..

GIC Disadvantages. Technique sensitive to either water contamination or dehydration. Low abrasion resistance. Short working time and long setting time. Brittleness (low tensile strength) and low fracture toughness..

Conventional glass ionomer. Uses; Restoration of cervical erosion lesions Restoration of non stress bearing areas Restoration of primary teeth Luting agent for crown and bridge Pits and fissure sealants Strong base under metallic or resin restoration.

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GIC modifications. Resin Modified Glass Ionomer Cements (Hybrid GICs) Aims to overcome slow acid base reaction of conventional GICs such as; Short working time and long setting time. Cracking on desiccation and moisture sensitivity. Poor resistance to acid attack..

GIC modifications. Resin Modified Glass Ionomer Cements (Hybrid ionomer ) hybrid of two groups of materials; resin and GIC . Composition Methacrylate resins setting by polymerization. Polyacid & ion-leachable glass setting by an acid-base mechanism. HEMA: a hydrophilic methacrylate, which enables both resin and acid components to co-exist in aqueous solution, takes part in the polymerization..

Setting reactions of the Hybrid GICs. Acid-base reaction Free radical polymerization Properties Release of fluoride Ability to bind adhesively to tooth structures A prolonged working time and a rapid setting time High abrasion resistance Higher resistance to desiccation and acid attack.

Tri-Cure Glass Ionomer System. The three curing reactions are : Acid-base glass ionomer reaction. Light-activated polymerization with photointiator . Chemically or self activated polymerization..

GIC modifications Metal Reinforced GIC. Aim to reinforce the cement with metal to overcome , Brittleness Low abrasion resistance Low fracture toughness..

Metal Reinforced GIC. Methods of metal reinforcements 1. Silver alloy admix It is performed by simply mixing of silver amalgam alloy powder to the conventional GIC (hand mix material). 2. Cermet Cement manufactured by fusing glass powder to silver particles through sintering..

Metal Reinforced GIC. Advantages Increase in abrasion resistance Little increase in compressive strength Reduction in solubility Disadvantages Reduction in fluoride release Reduction in bond strength with tooth structures Reduction in esthetic.

Metal Reinforced GIC. Uses Core build up material Posterior filling material for deciduous teeth.

pulp capping.

. Calcium Hydroxide Cements. Direct and indirect pulp capping and lining material. Does not interfere with the polymerization of composite materials. Form, two paste system One paste system.

Calcium Hydroxide Cements Composition. Paste 1 Calcium tungstate Calcium phosphate Zinc oxide Glycol salicylate.

Calcium Hydroxide Cements. Manipulation For chemical cured cement; equal lengths of each paste are dispensed onto a paper pad and mixed to a uniform color. The light cured cement is polymerized by a visible light source for 20 seconds for each 1 mm layer..

Calcium Hydroxide Cements. Setting Reaction Setting results from the formation of an amorphous calcium disalicyalte The cements usually contain radiopaque filler..

Calcium Hydroxide Cements. Properties The freshly mixed cement is alkaline with a pH of 11-12 . Compressive strength, tensile strength and elastic modulus are low . Highly soluble ..

Mineral trioxide aggregate (MTA). An endodontic reparative cement, designed to be used under moist conditions. Two types, grey MTA , dicalcium and tricalcium silicate and bismuth oxide, and white MTA , is primarily composed of tricalcium silicate and bismuth oxide..

MTA. When mixed with water, calcium hydroxide and calcium silicate hydrates are formed which transforms into crystalized and porous solid gel . Advantages Promotes tooth healing and repair. Have high pH that stimulates fibroblasts and neutralize acidic pH. Has an antibacterial and antifungal • Higher compressive strength than that calcium hydroxide..

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Biodentine™. Biodentine™ is a quick-setting bioactive calcium-silicate based dental cement offering bioactivity and sealing properties to replace dentine, and can be used as direct and indirect capping both in the crown and in the root..

Biodentine™. Properties Preservation of pulp vitality High biocompatibility No post-operative sensitivity Less risk of bacterial percolation Long lasting sealing properties High dimensional stability Mineral tags in the dentine tubules.

Biodentine™. Properties Similar mechanical behavior to human dentin; similar strength, stress absorption and flexural behavior as dentin ..

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Resin-based calcium silicate. For example: Thera-Cal LC single paste calcium silicate-based material. Used as as a protective liner with restorative materials, cement, or other base materials. Classified as a 4 th generation calcium silicate material. It is considered as class 2 cement material “in which the setting reaction of the polymerizable component is light-activated.”.

Resin-based calcium silicate. Composition Portland cement (45%), fumed silica as a thickening agent (7%), resin (poly(ethylene glycol) dimethacrylate and bis-GMA as 43%), bismuth oxide (3%), and barium sulfate (3%) as radiopaquers ..

Resin-based calcium silicate. Also sets with hydration chemical reaction (hydraulic silicate material) when comes in contact with water. It depends on the water taken up from the environment. Hence, the manufacturer instructions implement placing the material on moist dentin. TheraCal LC has provided a very alkaline (10.66) pH after 3 hours and calcium ions for remineralization. Adv. Good bond strength with resin-based restoration (composite resin). Disadv . Highly irritant to pulp..

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