Glass Ionomer Cements (GICs) in Dentistry: Properties, Uses, and Advantages
Glass Ionomer Cement (GIC) in Dentistry
Introduction
Glass Ionomer Development (Silicate Cement): This material had relatively high solubility in the mouth, poor abrasion resistance, significant surface and marginal staining, no marginal seal, low initial pH, and was considered a severe pulp irritant. It generally had a short clinical service life.
ASPA (Alumino-Silicate Polyacrylic Acid): This was the first commercial GIC product. It combined the benefits of silicates (translucency and fluoride release) and polycarboxylates (adhesion and biocompatibility).
Glass Ionomers
Dental cements whose powder component resembles that of silicate cement.
Types by Application
- Permanent luting cement
- Filling material
- Base and liner
Forms
- Powder + Liquid (Hydrous)
- Powder + Water (Anhydrous)
- Semi-hydrous (Combination)
- Encapsulated
Composition
Hydrous Powder
- Acid-soluble aluminum fluorosilicate glass
- Liquid (increases reactivity and decreases viscosity and tendency for gelation)
- Tartaric acid (accelerator to shorten setting time and improve compressive and tensile strengths)
Anhydrous Glass Ionomer Properties
- Decreased viscosity
- Least long-term solubility
- Better physical properties
- Improved shelf-life
- More acidic (potential for pulpal irritation)
Classification of GIC
- Type I: Luting
- Type II: Restorative
- II.1: Esthetic restorative
- II.2: Reinforced restorative
- A) Admixture (glass-metal ionomer): Silver-tin particles added to glass powder
- B) Cermet (ceramic-metal ionomer): Silver sintered to glass powder
- Type III: Liner or base
Properties of GIC
Early Conventional Glass-Ionomer Materials
- Slow setting
- Considerably opaque when set
- Sensitive to both desiccation and hydration during setting
- Poor mechanical properties
Modern Glass Ionomers
- Fast setting
- More esthetic
- Hydration and sensitivity problems are relatively limited
- Improved mechanical properties
Setting Reaction of GIC
- Phase I: Ion Leaching Phase (Acid attacks the glass powder and dissolves the outer surface)
- Phase II: Hydrogel Phase (Initial setting takes place; Ca ions form cross-links with polyacid chains)
- Phase III: Poly-Salt Gel Phase (Final set and hardening; Aluminum ions form a polysalt hydrogel)
Modifications of GIC
- Admixture (glass-metal ionomer)
- Cermet (ceramic-metal ionomer)
- Modifications in filler size and loading
Reasons for Modifications
- Produce sufficient working time
- Improve mechanical properties
- Improve esthetic properties
Advantages of GIC
- Adhesion to tooth structure
- Fluoride release and recharge
- Biocompatibility
- Sealing potential
- Dimensional stability
- Good thermal insulating capacity
- Radiopacity
Disadvantages of GIC
- Poor strength properties
- Solubility and disintegration
- Moisture sensitivity
- Questionable esthetics
Available Restorative Materials
Metallic
- Gold foil
- Cast gold
- Amalgam
Non-Metallic
- Glass ionomer cement
- Silicate cement
- Acrylic resin
- Resin composite
- Ceramics
Requirements of an Ideal Restoration
Mechanical
- Sustain normal occlusal load
- Protect remaining tooth structure
- Restore normal function
- Maintain constant relationship with surrounding tooth structure
Esthetical
- Should restore normal esthetics
Biological
- Stop further progress of the lesion
- Restore and maintain arch integrity and periodontium
- Protect and maintain pulp vitality
Requirements of an Ideal Restorative Material
- Insoluble in oral fluids
- Bond chemically or maintain constant adaptation with cavity walls
- Withstand functional forces
- Maintain dimensional stability
- Biologically compatible
- Harmonious color
- Convenient and easy manipulation
- Reasonable cost
Factors Influencing Selection of Restorative Materials
- Factors concerning the available restorative materials
- Factors related to the patient
- Factors related to the condition of the oral cavity
- Factors related to the tooth to be restored
- Factors related to the cavity to be restored
- Factors related to the operator
Indications of GIC
- Restoration of Class III and Class V cavities
- Restoration of root caries
- Pit and fissure sealant
- Luting cement
- Liner/base
- Core buildup in non-stress bearing areas
- Minor repair of restorations and crowns
- Atraumatic Restorative Treatment (ART)
Contraindications of GIC
- Stress-bearing areas (Class II and IV)
- Areas where esthetics is of prime importance
Steps of Application of GIC
- Selection of GIC type
- Isolation of the operatory field
- Application of liner (if needed)
- Conditioning of tooth substrate
- Matrix application (if needed)
- Proportioning of powder:liquid ratio
- Mixing of GIC
- Packing of GIC
- Maintenance of water balance
- Finishing and polishing
Resin-Modified Glass Ionomer (RMGI)
Combines the benefits of glass ionomer (fluoride release and adhesion) and composite resin (strength and esthetics).
Composition
Powder
- Ion-leachable glasses
- Photo initiators or chemical initiators or both
- Polymerizable resin
Liquid
- Polyacrylic acid
- Water
- Methacrylate monomer
- Hydroxyethyl methacrylate monomers (HEMA)
Advantages of RMGI
- Fast setting
- Immediate stabilization of water balance
- Improved esthetic qualities
- Improved strength properties and wear resistance
- Increased wettability
- Facilitates bonding to composite resin
Disadvantages of RMGI
- May discolor over time
- Limitations in depth of cure
- Less fluoride release than conventional GIC
Compomers (Composers)
Combination of composites and glass ionomers.
Advantages of Compomers
- Better mechanical properties than GIC
- More esthetic than GIC
- Can be used and polished easily
Disadvantages of Compomers
- Inferior mechanical properties compared to composite
- Less fluoride release than GIC
- No chemical bond to tooth structure
Indications of Compomers
- Esthetic areas
- Areas of lower stress (Class III, V)
- Conservative Class I, II in pediatrics
Contraindications of Compomers
- Stress-bearing areas (permanent Class I, II)
- Poor isolation
Uses of Compomers
- Direct restorations
- Cements