Glass Ionomer Restoration (2)

Glass Ionomer Restoration (2)

• Glass ionomer cement (GIC) classification is based on composition, chemistry (e.g., CGIC, RMGI, nanoionomer), and clinical use.
• Three compositional forms of GIC: polyacid mixable, water mixable, and mixed.
• Polyacid mixable cement: the polyacid is in an aqueous solution, forming the liquid portion of the cement. The liquid may gel over time.
• Water mixable cement: the polyacid is freeze-dried and added to the powder. The liquid is distilled water or aqueous tartaric acid.
• Mixed cement: part of the polyacid is freeze-dried and the other part is in an aqueous solution.

Chemical Forms of GIC

• Conventional GIC: setting is an acid-base reaction, sensitive to hydration and dehydration, requires sealing against moisture contamination, and should not be finished immediately after placement (after 48hrs). It also has a short working time and extended setting time. Special types are metal-reinforced by adding silver alloy or sintering glass with silver (Cermet cement).
• Resin-modified GIC (Hybrid Ionomer): incorporates water-soluble methacrylate resin monomers (HEMA) into an aqueous solution of polyacrylic acid. Two setting reactions include acid-base reaction and possible photopolymerization (dual cure) or chemical polymerization.

Resin Modification Advantages

• Reduced moisture sensitivity
• No immediate need for a waterproof seal after placement
• Can be finished immediately
• Faster setting and less water sensitivity
• High color stability

Resin Modification Disadvantages

• More shrinkage during setting (compared to conventional GIC)
• Less fluoride release
• Lower water and carboxylic acid contents decrease the cement's ability to wet the tooth substrate (leading to weaker bonding)
• HEMA monomer can cause pulpal inflammation
• Heat generated from polymerization can be a drawback
• Water uptake from HEMA can cause fracture of all-ceramic crowns when used as core buildup or luting cement

Clinical Applications

• Fissure sealant
• Base (sandwich technique)
• Restoration
• Main indications:
  • Class V carious, erosive, or abrasive lesions
  • Pits and fissures sealant
  • Class I and II restorations in primary teeth
  • Luting cement
  • Core and buildups
  • Root surface caries

Contraindications

• Low tensile strength, brittleness, and low resistance to wear of GIC limit its use in Class I and II restorations.

Cavity Preparation

• The adhesive potential of GIC eliminates the need for retentive features. The cariostatic influence limits extension beyond the caries elimination.

Manipulation

• Steps for using Glass Ionomer cement (GIC) restorations: dispensing & mixing, placement, contouring & finishing
• Commercial availability of GICs in two forms:
  • Encapsulated mechanical mixing
  • Powder and liquid for hand mixing

Dispensing

• Capsules provide a consistent powder/liquid ratio ensuring optimum physical properties. The ratio is significant during hand mixing.

Finishing and Polishing

• Contouring and polishing require an air/water spray, fine diamonds (to begin), and aluminum oxide discs (to finish). It can be done after 48 hours or up to a week after placement. Light-cured glass ionomers can be contoured/finished immediately after light curing.

Explore the different classifications and chemical forms of Glass Ionomer Cement (GIC). This quiz covers aspects such as composition, clinical use, and properties of polyacid mixable, water mixable, and mixed cement types. Test your understanding of conventional GIC and its unique characteristics.