Dental Materials: Glass Ionomer Restorations

Glass Ionomer Restoration (1)

• This presentation covers Glass Ionomer Cement (GIC) restorations.
• Key references include Phillips science of dental materials 11th edition, Craig's restorative dental materials 13th edition, and Art and science of dental materials 6th edition (chapter 10).
• Learning Objectives (LOs): To understand the characteristics, indications, contraindications and manipulation techniques of glass ionomer restorative materials.
• Outline: The presentation follows a defined structure for conventional glass ionomers, including definition, composition, setting reaction, and properties/advantages/disadvantages.

Definition

• GIC is a water-based material resulting from an acid-base reaction.
• It's formed by reacting basic calcium-fluoro-alumino-silicate glass powder with an aqueous solution of polyacid.

Composition

• GIC has two primary components:
  • Acid-soluble glass powder (a calcium-fluoro-alumino-silicate glass).
  • Poly-acid liquid (an aqueous solution of polyacrylic acid co-polymerized with organic acids, mainly maleic, itaconic, and tartaric acids).

Setting Reaction

• Setting occurs in three phases:
  • Acid attack: Acid dissociation forms negatively charged carboxylate anions and positively charged hydrogen protons. The hydrogen protons attack the glass surface, releasing cement-forming metal ions (e.g., Ca++, Al+++).
  • Gelation (initial setting): The surface layer of the glass powder reacts with the acid, forming a silica hydrogel. The glass core remains intact, acting as a filler in the cement matrix. Calcium ions react with carboxylate anions, creating a water-soluble calcium polysalt matrix.
  • Maturation and hardening (final setting): Hydrogen ions continue to attack the silicate glass, releasing Al+++. This incorporation forms an insoluble calcium-aluminum-carboxylate gel that isn't susceptible to further hydration or dehydration.
• The final set cement consists of unreacted glass particles embedded in a silica hydrogel matrix with hydrated calcium and aluminum polysalts.

Properties, Advantages, and Disadvantages

• Advantages*
• Cariostatic (anti-cariogenic) due to sustained fluoride release.
• Good adhesive potential (chemical adhesion to tooth structure).
• Low setting contraction.
• Biocompatible (weak acid contents and high molecular weight).
• Excellent thermal insulating capacity.
• Low coefficient of thermal expansion.
• Satisfactory optical properties.
• Ease of manipulation and reasonable cost.
• Disadvantages*
• Poor mechanical properties and wear resistance limit use in areas with high stress (e.g., Class I and II restorations).
• Very sensitive to hydration and dehydration.
• Short working time and long setting time.

This quiz focuses on the fundamentals of Glass Ionomer Cement (GIC) restorations as outlined in key dental materials textbooks. You'll explore the characteristics, indications, and manipulation techniques of GIC, along with its composition and properties. Perfect for dental students and professionals looking to deepen their understanding of restorative materials.