Glass Ionomer Cements

• Glass Ionomer Material is presented by Ingrid Fernandes Mathias-Santamaria DDS, MSc, PhD, RSD 814, at the University of Kentucky College of Dentistry.

Glass Ionomer Cements

• These are also known as Glass Polyalkenoate Cements.
• In 1971, Wilson & Kent improved silicate cements by adding a bonding mechanism, translucency, and fluoride release.
• Silicate cement contains fluoride and has low dimensional alteration.
• Zinc Polycarbonate Cement involves polyacrylic acid in its bonding.

Versatility and Biocompatibility

• Esthetic restorations are considered the gold standard for Class V restorations.
• GIC functions as adhesive cement for fixed prostheses and orthodontic appliances.
• GIC is used for intermediate restorations, pit and fissure sealants, as an atraumatic restorative technique (ART), cavity liners and bases, and core build-ups.

WHO Model List of Essential Medicines

• Since 2021, glass ionomer is present at the WHO Model List of Essential Medicines.
• This list represents efficacious, safe, and cost-effective medicines for priority conditions.
• The list includes dental medicines and preparations like gel containing 2500 to 12500 ppm fluoride (any type) and toothpaste, cream or gel containing 1000 to 1500 ppm fluoride (any type).
• Varnish contains 22500 ppm fluoride (any type).
• Single-use capsules contain 0.4 g powder + 0.09 mL liquid.
• Multi-use bottle contains powder + liquid.
• The fluoro-alumino-silicate glass powder contains 25-50% silicate, 20-40% aluminium oxide, 1-20% fluoride, 15-40% metal oxide, 0-15% phosphate, and minimal quantities of polyacrylic acid powder and metals.
• The aqueous liquid contains 7-25% polybasic carboxylic acid and 45-60% polyacrylic acid.
• Resin-based composite (low-viscosity) is available in a single-use applicator or multi-use bottle.
• Examples are of any type for use as dental sealant.
• Resin-based composite (high-viscosity) is available as single-use capsule or multi-use syringe.
• A solution of 38% w/v of silver diamine fluoride is available.

Reaction

• Acid + Base -> Salt + H₂O

• Liquids used include Acrylic acid, Itaconic acid, Maleic acid, Tricarboxylic acid, and Tartaric acid.

• The liquid contributes to adhesion, biocompatibility, working time, and bonding.

• Powders used include Silica, Alumina, Calcium, Fluoride, and other oxides.

• The powder provides resistance and fluoride release.

• An undissolved particle is sheathed by the silica-rich gel.

• Set material consists of undissolved glass particles with a silica gel coating embedded in an amorphous matrix of hydrated calcium and aluminum polysalts containing fluoride ions.

• Glass ionomers bond to tooth structure by chelation of the carboxyl groups of the polyacrylic acids with calcium in the enamel and dentin apatite.

Fluoride Release

• The fluoride release has an initial "burst" for 24-48 hours, and then drops to a lower steady state.

• This release is reported to exist up to 5 years.

• GI materials function as fluoride reservoirs, facilitating uptake and re-release.

• Re-release occurs usually in first 24-72 hours.

• The material can be recharged repeatedly, but only to a fraction of initial Fl level.

• Fluoride release is enhanced by the presence of S. mutans, decreasing chances of secondary caries, according to Hahnel et al., 2017.

• GIC lacks buffering capacity, which means fluoride is responsible for remineralization.

• High-viscosity and resin-modified glass-ionomer restorations release fluoride ions into the adjacent enamel and demineralized dentin when used in primary molars to restore carious lesions.

• Dentinal walls underneath a GIC restoration may contain up to 5000-6000 ppm fluoride per Zafar & Ahmed, 2015.

Cariostatic Properties

• This involves sustained fluoride release, which prevents new and secondary caries lesion development.
• A cariostatic effect happens, but its cruciality is debated.
• Remineralization is more impactful than the Cariostatic effect.
• These properties are observed in laboratory and clinical studies.

Water Balance

• It's the most important and least understood aspect.

• It can be up to 25% of set product.

• Physical and esthetic properties are tied to H2O content.

• Desiccation should be avoided.

• GICs tolerate moisture better than resin composites.

• Prevent considerable H2O uptake very early (imbibition).

• Prevent significant H2O loss possible after set (syneresis).

• Reported annual failure rates vary, including Amalgam at 3%, Composite at 2.2%, GIC at 7.2%, and HV GIC at 6%.

• 40% failure after 6 years in Class II restorations (Scholtanus & Huysmans, 2006).

• GIC vs. RC show both materials presented a similar performance after 6-years

• GIC is indicated for Class I, Class II*, Class III, Class V restorations, ART - anterior and posterior, Pediatric and Geriatric restorations, special needs patients, high caries risk patients, liners and bases, sealants, and as a Luting material.

• For many indications there are ...different GICs

Timeline of GIC Development

• 1969-1970: Invented & reported as a filling material by Wilson and Kent
• 1977: Metal (Silver)-Reinforced GIC by Miracle Mix, GC America and Ketac-Silver, 3M ESPE, Germany
• 1980: Vitrabond™ (3M Dental Products Division) first Resin-Modified GIC
• 1990: Light-cured Resin-Modified GIC (Photac-Fil™ 3M ESPE and Fuji II LC, GC)
• 1991: Vitremer™ Tri-Cure Glass Ionomers System by 3M ESPE.
• 2007: Nano-ionomers technology based resin-modified GIC by 3MESPE Ketac™™
• 2008: Incorporation of nano-sized bioceramics to conventional GICs

Classification

• Conventional (GIC)
• Reinforced by metal
• Resin-modified glass ionomer (RMGIC)
• High-Viscosity (HVGIC)
• Nanoionomers (nano-filled RMGIC)

GIC reinforced by metal (1977)

• Amalgam/silver particles : added to conventional GIC.
• The metal reinforcement led to updated properties, but these were not significantly better than conventional GICs.
• This reinforcement results in less fluoride release.
• Non-esthetic.
• AgNP-modified GICs exhibit significant antibiofilm activity and retain mechanical properties that are equivalent or superior to the non-modified versions.
• AgNP-modified GICs could reduce bacterial colonisation on and around restorations, reducing restoration failure caused by secondary caries.

Resin-modified GIC (1980-1990)

• Features include a light cure system.
• This reinforcement enhanced esthetic and mechanical properties.
• Provides "Control" of the material for proper cure.
• Enhanced properties are still inferior compared to resin composites.
• Greater polymerization contraction.
• Less translucency and color change.

Resin-modified GIC vs. Conventional GIC

• GIC and RMGI physical property performance over time was material dependent
• Polyalkenoate maturation processes finish within 24 h. Important notes,
• Differences in GIC physical properties are noted however, the magnitude is such to be unlikely of clinical significance,
• increases in GIC physical properties were especially noted in flexural modulus and hardness, supports reports of a maturing hydrogel matrix.
• Overall, GIC product physical properties are more stable than RMGI.
• Both RMGI and GIC experienced similar modulus reduction at 6 months, suggesting a polyalkenoate matrix change.
• RMGI exhibited greater flexure strength, flexural toughness, and fracture toughness compared to GIC materials.*

High-viscosity GIC (1998)

• Presents improved mechanical properties
• Features Powder/liquid = 3.6/1
• Acid was incorporated in the powder composition
• Increase in surface resistance
• It is a Quicker reaction
• Less sensibility to contamination and better translucency

Nano-filled resin-modified GIC (2008)

• It contains Nanoionomer
• Incorporation of nano-sized fillers and bioceramic particles to RMGIC
• It aims to improve brittleness, strength, and esthetic properties
• Note, studies showed that nano-filled RMGIC does not hold any advantage over micro-filled RMGIC in terms of mechanical properties and bonding
• Leads to better fluoride release.

Commercialization

• Involves Powder/liquid – hand mixed
• Capsules
• Paste pack – hand mixed or automix Randomized clinical trial of encapsulated and hand-mixed glass-ionomer ART restorations: one-year follow-up
• A study compared encapsulated GICs vs. hand-mixed GICs
• Encapsulated GICs outperformed hand-mixed GICs. With an annual failure rate of 24% compared to hand-mixed's 42%.

High-viscosity conventional GIC - Equia Forte system

• What are the diferences between Equia Fil and Equia Forte?*
• Contains highly-reactive ultrafine fluoro-aluminum-silicate particles in a conventional GIC matrix.
• Features High molecular weight polyacrylic acid and increase strength
• Involves the application of a resin coat as last step
• The composition creates a stronger matrix and increases fluoride release.
• What about the coat?*
• Resinous coat fills porosity to increase physical and esthetical properties, protection against erosion.
• Increase esthetics
• Fills porosities
• Increase flexural resistance in 72%
• Increase fracture resistance in 212%
• It can decrease fluoride release...

EQUIA Forte® Fil EQUIA Forte® Coat

• It is used for use by a dentist or physician in the recommended indications, for Class I Restorations, Stress bearing Class II Restorations, Non-stress bearing Class II Restorations, Intermediate Restorative, Class V and Root Surface Restorations and Core build up. EQUIA Forte Coat is used to seal, strengthen and protect the surface of EQUIA Forte Fil Restorations.

• It is not used for pulp capping or for patients with a history of hypersensitivity to acrylate/methacrylate monomers.

• EQUIA Forte Coat should not be combined with desensitizers and eugenol containing materials.

• Application*

• Prepare tooth using standard techniques. Metal bands should be lubricated with petroleum jelly as extensive mechanical retention is unnecessary. For pulp capping use calcium hydroxide or apply CAVITY CONDITIONER for 10 seconds to prepared surfaces, dry and then apply the material.

• Ater application the material should sets for two minutes, to then apply the surface sealent.

• Applying Cavity Conditioner *

• These have Superficial cleansing in order to enhance bonding, without removing/affecting calcium ions!

• It is a 10% Polyacrylic acid (10% PAA), 20% Polyacrylic acid (20% PAA), 17% EDTA or 37% Phosphoric acid

• GC Cavity Conditioner contains 20% Polyacrylic Acid for partially removing the smear layer

• 3% Aluminum Chloride Hexahydrate to seals dentin tubules

• bonding resistance (enamel and dentin) is not affected by the use of the conditioner for EQUIA Forte material. Laboratory studies point to preconditioning with PAA offering positive effect on the bond strength in GIC however the lack of clinical evidence supported by longitudinal randomized trials indicates a lack of evidence for its use.

• One of the first RMGI restorative materials include Resin-modified GIC - GC Fuji II LC

• Has performed well in Class V studies with root surface margins

• It still has moisture sensitivity problems as conventional GIC

• presents Better finish & esthetics than Equia Forte, but not to level of resin composite

• Retrospective study in US older population - better longevity when compared to CGIC or coated GI (Tsujimoto et al., 2025)

• The bonding Ability of Paste-Paste Glass Ionomer Systems to Tooth Structure reports the microtensile bond strengths is superior when combining nonrinse conditioners and RMGICs to dentin. Using polyacrylic acid and RMGIC (Fuji II LC) led to the least microleakage for cervical locations.

• The clinical evaluation of subgingival open sandwich restorations, Ismail et al., 2023 reported testing materials are suitable after 3 years, reporting 120 Class II w/ 4 different sandwich materials. While et al., 2023 the Long term clinical performance comparing, open-sandwich reporting, AFR 15 years RMGI: 9.7% with AFR 15 years total-etch: 2.9%- 675 class II evaluation GC Fuji Lining LC PASTE PAK reports contains radiopaque and is light Cured Glass Ionomer Lining Cement.

Class indications:

• Class I and II restorations
• Long-term studies indicate GIC materials may serve as definitive restorations in functional areas.

Further Class indications:

• For anterior and cervical restorations, they compromise esthetics in the long term, clinical trials report they the presence of RMGI does not interfere with the health of the periodontium or counts of subgingival, which is important for subgingival procedures
• GIC material can function as a Sealant, Liners/Bases, aids Atraumatically and reports a better preventive effect on new caries over other materials.