8 Glass Ionomer Restoration Overview

Glass Ionomer Restoration (1)

• Glass ionomer cement (GIC) is a water-based restorative material formed by an acid-base reaction between a calcium-fluoro-alumino-silicate glass powder and an aqueous polyacid solution.

• References: 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 (ILOs)

• Understand the characteristics, indications, contraindications, and manipulation techniques of glass ionomer restorative materials.

Outline

• Definition: A water-based material formed by an acid-base reaction between a basic calcium-fluoro-alumino-silicate glass powder and an aqueous solution of polyacid.

• Composition: Constitutes of two main components:

  • Acid-soluble glass powder (e.g., alumina, silica, with added ions like Na+, K+, Ca++, and St++ to enhance reactivity with polyacids). Fluorides aren't part of the glass structure, allowing them to freely diffuse in and out.
  • Polyacid liquid (e.g., polyacrylic acid co-polymerized with organic acids like maleic, itaconic, and tartaric acids).

• Setting Reaction: An acid-base reaction occurring in three phases:

  • Acid Attack: Acid dissociates into negatively charged carboxylate anions and positively charged hydrogen protons. H+ ions attack glass particles, releasing cement-forming metal ions (Ca++ and Al+++).
  • Gelation (Initial Setting): Glass powder's surface layer reacts with acid, transforming into silica hydrogel. The glass core remains intact. Ca++ ions react with carboxylate anions to create a water-soluble calcium polysalt matrix.
  • Maturation & Hardening (Final Setting): H+ ions continue to attack silicate glass, leading to Al+++ release. Al+++ incorporation results in the formation of a water-insoluble calcium-aluminum-carboxylate gel. This gel is no longer susceptible to hydration or dehydration. The set cement is composed of unreacted glass particles surrounded by silica hydrogel and hydrated calcium and aluminum polysalts.

Properties, Advantages, and Disadvantages

• Advantages:

  • Cariostatic (anti-cariogenic): Sustained fluoride release.
  • Adhesive potential: Chemical adhesion.
  • Low setting contraction: Minimal shrinkage stresses.
  • Biocompatibility: Low acidity and high molecular weight limiting diffusion into the pulp.
  • Thermal insulating capacity
  • Low coefficient of thermal expansion
  • Satisfactory optical properties
  • Multiple clinical applications
  • Ease of manipulation and reasonable cost

• Disadvantages:

  • Poor mechanical properties and wear resistance: Not ideal for high-stress areas.
  • Moisture sensitivity: Vulnerable to hydration and dehydration.
  • Short working time and long setting time: Limits clinical application.

This quiz focuses on the characteristics and applications of glass ionomer cement (GIC) as a restorative dental material. Learn about its composition, manipulation techniques, and the clinical indications and contraindications for its use, based on referenced dental literature.