Comprehensive Guide To Glass Ionomer Cement (GIC)

Glass ionomer cement (GIC) is a versatile dental material widely used in restorative dentistry due to its unique properties of chemical adhesion, fluoride release, and biocompatibility. It is particularly valued in minimally invasive dentistry and is suitable for a variety of clinical applications.

Definition and Overview

Glass ionomer cement is an acid-base material composed of a reaction between weak polymeric acids and powdered glasses of basic character. It is known for its ability to chemically bond to tooth structure and release fluoride, making it a preferred choice for direct restorative procedures.

Chemical Composition

Powder Component

Fluoro-aluminosilicate Glass

• SiO₂ (Silicon dioxide): 29-50%.

• Al₂O₃ (Aluminum oxide): 16-30%.

• CaF₂ (Calcium fluoride): 15-35%.

• Na₃AlF₆ (Cryolite): 5-10%.

• AlF₃ (Aluminum fluoride): 5-10%.

• AlPO₄ (Aluminum phosphate): 3-10%.

Liquid Component

• Polyacrylic Acid: 45-50%.

• Itaconic Acid: 5-10% (improves properties).

• Tartaric Acid: 5-10% (controls setting time).

• Water: 45-50%.

Classification of Glass Ionomer Cements

Based on Chemical Composition

• Conventional Glass Ionomer Cement (CGIC): Pure acid-base reaction with a water-based system.

• Resin-Modified Glass Ionomer Cement (RMGIC): Includes resin components like HEMA for improved mechanical properties and moisture control.

• High-Viscosity Glass Ionomer Cement (HVGIC): Higher powder/liquid ratio for enhanced strength, used in Atraumatic Restorative Treatment (ART).

Based on Clinical Application

• Type I - Luting Cements: For crown and bridge cementation with a thin film thickness.

• Type II - Restorative Cements: For aesthetic and reinforced restorations, including primary teeth.

• Type III - Lining/Base Cements: For cavity lining and pulp protection.

Based on Presentation Form

• Powder-Liquid Systems: Traditional hand-mixed.

• Encapsulated Systems: Mechanically mixed.

• Paste-Paste Systems: Mainly RMGIC.

Setting Reaction Mechanism

Acid-Base Reaction

• Decomposition Phase (0-4 minutes): H⁺ ions from polyacrylic acid attack the glass surface, releasing ions and forming an initial gel.

• Hydrogel Phase (4-15 minutes): Formation of calcium polyacrylate and initial matrix.

• Polysalt Phase (24 hours - 7 days): Formation of aluminum polyacrylate, increasing mechanical strength and chemical stabilization.

Setting Reaction Equation

• Glass + Polyacrylic acid → Metal polyacrylate + Silica gel + F⁻.

Properties of Glass Ionomer Cements

Mechanical Properties

• Conventional GIC: Compressive strength (150-200 MPa), tensile strength (4-6 MPa).

• RMGIC: Enhanced compressive strength (180-250 MPa), tensile strength (10-15 MPa).

Biological Properties

• Fluoride Release: High initial release with sustained low-level release and recharge capability.

• Biocompatibility: Minimal pulp irritation with proper lining.

Physical-Chemical Properties

• Solubility (0.4-1.5%), water absorption (1-3%), moderate wear resistance, and less translucency compared to composites.

Clinical Applications

Restorative Applications

• Ideal for Class III and V cavities, primary teeth restorations, core build-up, ART technique, and as a base under composites.

Luting Applications

• Used for cementing metal crowns, bridges, inlays, onlays, orthodontic bands, and posts.

Preventive Applications

• Effective for pit and fissure sealants, dentin hypersensitivity treatment, remineralization, and interim therapeutic restorations.

Lining/Base Applications

• Used under amalgam and composite restorations for pulp-dentin complex protection.

Advantages and Disadvantages of Glass Ionomer Cement

Advantages of GIC

Chemical Adhesion

• Bonds to calcium in hydroxyapatite without etching, minimizing microleakage.

Fluoride Release

• Prevents secondary caries with antibacterial properties and promotes remineralization.

Biocompatibility

• Safe for pediatric use with minimal pulp irritation and low cytotoxicity.

Clinical Convenience

• Simple technique, less sensitive to technique, suitable for field conditions, and allows bulk placement.

Disadvantages and Limitations

Poor Mechanical Properties

• Brittle with low fracture resistance, unsuitable for high occlusal forces.

Aesthetic Limitations

• Poor translucency and limited shade range, difficult to polish.

Moisture Sensitivity

• Susceptible to early dehydration and water contamination, requiring surface protection.

Setting Characteristics

• Slow setting with full strength achieved after 24 hours, sensitive to temperature.

Clinical Technique

Cavity Preparation

• Remove carious tissue, clean with polyacrylic acid, rinse gently, and avoid desiccation.

Material Mixing

• Follow manufacturer's P/L ratio instructions, mix for 30-60 seconds using a folding motion to achieve a glossy consistency.

Material Placement

• Work within 2-3 minutes, place incrementally for deep cavities, and avoid air incorporation.

Finishing Procedures

• Conventional GIC requires finishing after 24 hours, while RMGIC allows immediate finishing. Apply protective varnish if needed.

Commercial Products

Conventional GIC

• Fuji IX GP (GC Corporation), Ketac Molar (3M ESPE), ChemFil Rock (Dentsply Sirona).

RMGIC

• Fuji II LC (GC Corporation), Photac Fil (3M ESPE), Vitremer (3M ESPE).

Luting GIC

• Fuji I (GC Corporation), Ketac Cem (3M ESPE), Aqua Cem (Dentsply Sirona).

Recent Developments

Nano-GIC

• Incorporation of nanoparticles for enhanced mechanical properties and polishability.

Bioactive GIC

• Stimulates tissue regeneration and enhanced remineralization with bioactive glass and antimicrobial additives.

Smart GIC

• Features pH-responsive behavior, controlled ion release, and self-healing properties.

Clinical Research and Evidence

• Success Rates: High success in non-stress bearing restorations, primary teeth, ART restorations, and luting applications.

• Failure Modes: Include material loss, bulk fracture, secondary caries, and loss of retention.

• Longevity Factors: Depend on proper case selection, technique, material quality, and patient factors.

Clinical Selection Guidelines

• Ideal Indications: Non-stress bearing cervical lesions, primary teeth restorations, high caries risk patients, and ART approach.

• Contraindications: High stress-bearing areas, high aesthetic demands, bruxism, large cavities, and cusp replacement.

Future Perspectives

• Research Directions: Focus on improving mechanical properties, aesthetics, setting mechanisms, and developing smart materials with regenerative capabilities.

• Clinical Trends: Emphasize minimally invasive dentistry, bioactive restorations, preventive approaches, and sustainable materials.

Conclusion

Glass ionomer cements continue to be valuable materials in modern dentistry. Their chemical adhesion, fluoride release, and biocompatibility make them suitable for specific clinical situations. Understanding their properties, indications, and proper handling techniques is crucial for clinical success. As material science advances, newer formulations will expand the applications of GIC while addressing traditional limitations.

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