Lecture Notes: Glass Ionomer Cement

Introduction

• Glass Ionomer Cement (GIC) is an aesthetic, tooth-colored restorative material.
• Requires minimal cavity preparation and adheres chemically with tooth structure.
• Combines properties of silicate and polycarboxylate cements.
• Composed of glass (for powder) and ionic bonding (inomer).

Applications

• Restorative Material:
  • Used in Class 5 and Class 3 restorations for anterior teeth.
• Luting Agent: Lutes prostheses onto teeth.
• Linings and Bases: Applied as liners or bases in cavities.
• Core Build-up: Used for tooth core before prosthesis.
• Pit and Fissure Sealant: Fills deep pits and fissures to prevent caries.

Classification

• Type 1: Used for luting.
• Type 2: Used for restoration.
• Type 3: Used for liners and bases.

Mode of Supply

• Available as powder and liquid in bottles, capsules, or light-cure systems.

Composition

• Powder: Acid-soluble calcium fluoroaluminosilicate glass with high alumina silica ratio.
• Liquid: Polyacrylic acid copolymer, includes water as reaction medium.

Manufacturing

• Components heated to 1100-1500°C then ground to 20-50 micrometers.

Setting Reaction

• Polyacrylic acid in liquid attacks glass particles, releasing ions forming polysols leading to gel matrix.

Structure

• Unreacted particles surrounded by silica gel in a matrix of calcium and aluminum polysols.

Post Hardening Precipitation

• Initial setting by calcium polysols; over time, aluminum polysols dominate.

Properties

• Mechanical: High compressive strength but low tensile strength.
• Solubility: High initial solubility, reduces over time.
• Adhesion: Ionic bond with tooth surface, more in enamel.
• Biocompatibility: Varied pH impacts, Type 2 is more biocompatible.
• Antikaryogenic: Releases fluoride ions for acid resistance.

Manipulation

• Follow four rules: proper conditioning, accurate manipulation, protection during setting, proper finishing.

Modifications

• Metal Modified GIC: Increases strength, fracture toughness, and wear resistance.
  • Silver alloy admixed or cermet formation.
• Resin Modified GIC: Combines GIC with hydroxyethyl methacrylate for improved properties.

Quiz

1. Initial set of GIC is due to formation of which polysols?
2. Is chemical bonding of GIC more in enamel or dentine?
3. What does polyacrylic acid wash or pumice slurry remove from the tooth?
4. What is GIC with silver particles bonded to glass powder known as?

Conclusion

• Next lecture will cover Zinc Polycarboxylate Cement.
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