Glass ionomer cement

Glass ionomer cement is a dental restorative material which has a wide array of uses in dentistry. It is primarily used as a dental sealant for the prevention of caries. It is also used excessively to restore anterior teeth in both deciduous and permanent teeth.

Glass ionomer cement was introduced in 1972 by Wilson and Kent as a derivative of silicate and polycarboxylate cement. It incorporates the fluoride-releasing properties of silicate cement with adhesive properties of polycarboxylate cement.

The ever-increasing new formulations of the glass ionomer cement have extended its functions to restorations for deciduous teeth and cavity bases and liners.

Let’s look into glass ionomer cement in detail.

What is Glass Ionomer Cement (GIC)?

Glass ionomer cement is a dental restorative material, used as a filling and luting material. It is based on the reaction between silicate glass and polyacrylic acid.

It is a popular material because of its better aesthetic and the property to release fluoride ions which helps in preventing caries. (1)

Features of Glass Ionomer Cement

  1. Low solubility
  2. Coefficient of thermal expansion similar to dentin
  3. Fluoride release and fluoride recharge
  4. High compressive strengths
  5. Chemically bonds to tooth structure (2)
  6. Aesthetics identical to the natural tooth
  7. Low flexural strength
  8. Low shear strength
  9. Shrinks on setting and expands with water absorption (3)
  10. Lacks translucency
  11. Rough surface texture
  12. Better biocompatibility to the pulp

Uses of Glass Ionomer Cement

Glass ionomer cement finds many different applications in dentistry, due to its various formulations. These uses are as follows:

  • GIC is used as a restorative material for cavities on the surface near the gingival margin or root of the tooth. It is also used as an anterior aesthetic restoration material for Class III and Class V restorations.
  • GIC is used for sealing deep pits and fissures as a preventive measure against caries. It is used as a fissure sealant in patients with high caries risk, especially in partially erupted posterior teeth.
  • GIC is used as a liner or base under amalgam, resin, ceramics, direct and indirect gold restorations.
  • It is used for core build-ups after crown preparation when at least three walls of the tooth are remaining.
  • It is used as a luting or adhesive agent for cementing crowns, bridges, inlays or onlays and orthodontic brackets permanently to the tooth.
  • It is used as a restorative material for restorations of all types of cavities in deciduous teeth.
  • It is used in lamination of dentin/ Sandwich technique.
  • It is used in splinting of periodontically weakened teeth.

Classifications of GIC

Traditionally, glass ionomer cement was classified according to their uses in clinical practice. The classification was as follows:

  • Type I- for luting
  • Type II- for restorations
    • 1- restorative aesthetics
    • 2- restorative reinforced
  • Type III- for liners and bases
  • Type IV- as fissure sealant
  • Type V- as orthodontic cement
  • Type VI- for core build up

As new formulations of GIC started coming up and functions for GIC increased, it called for a broader classification –

GIC Classification

Manipulation of GIC

Glass ionomer cement comes as a set of powder (silicate powder) and liquid (polyacrylic acid). Its setting reaction is based on an acid-base reaction and water is critical for the reaction to occur. The manipulation of GIC involves the following steps:

Preparation of tooth surface

The tooth is first cleaned with pumice slurry, followed by swabbing with polyacrylic acid. After conditioning and rinsing, the tooth is dried and isolated.

Proportioning and mixing

The powder and liquid are combined in a ratio of 3:6 by weight. The powder is incorporated in the liquid in increments, by a folding method to preserve the gel structure. The finished mixture should have a glossy surface.

Protection of cement during setting

GIC is extremely sensitive to air and water during the setting period.  It should be immediately isolated from the water after being placed in the cavity.

Finishing

The excess material should be trimmed from the margins, using a hand instrument. Additional finishing can be done after 24 hours.

 Advantages of GIC

  1. GIC prevents caries through a steady release of fluoride ions and makes the fissures more resistant to demineralization. It can even cause remineralization of enamel.
  2. It is hydrophilic, which means that it is perfect for conditions where isolation is challenging and possible saliva contamination is possible.
  3. It is easy to manipulate and place in the cavity. GIC doesn’t require acid etching, rinsing and drying of enamel.
  4. It flows deeper into enamel than resin sealants.
  5. It is safe from any allergic reactions.

Disadvantages of GIC

  1. Inadequate retention
  2. Lack of strength and toughness
  3. Limited wear resistance (4)
  4. It requires periodic recalls to replace the lost sealant.

Conclusion

As humans, we have a natural tendency to avoid dental clinics. But it is inevitable that we can’t prevent cavities and tooth decay indefinitely.

The use of dental sealants help us experience fewer occlusal caries, and glass ionomer cement plays a significant role in it.

It is easy to place, releases fluoride ions, allows immature enamel to mineralize and is hydrophilic. The new modifications in formulas of GIC provide for a wide variety of uses for the dental health provider.