Glass Ionomer Restoration (2)

Glass Ionomer Restoration (2)

• Glass ionomer cements are classified according to composition (polyacid mixable, water mixable, mixed), chemistry (conventional, resin modified, highly viscous, nanoionomer), and clinical use (luting, restorative, base).
• Polyacid mixable cement: The poly-acid is presented as a liquid in an aqueous solution. This liquid can gel over time.
• Water mixable cement: The poly-acid is freeze-dried and combined with the powder. The liquid is either distilled water or an aqueous solution of tartaric acid.
• Mixed cement: Part of the poly-acid is freeze-dried, while the other portion is in an aqueous solution.
• Conventional glass ionomer: setting reaction is acid-base. It is susceptible to moisture contamination and should not be finished immediately after placement. They require a longer setting time.
• Resin modified glass ionomer: This cement incorporates water-soluble methacrylate monomers (HEMA) into an aqueous solution of polyacrylic acid. The setting reactions are acid-base or photo-polymerization (dual cure)/chemical polymerization. This type of cement has decreased moisture sensitivity, no immediate water-proofing sealing required after placement. Finishing and polishing can be conducted immediately after light curing.

Advantages of Resin Modified GIC

• Decreased moisture sensitivity
• No need for immediate water-proof sealing after placement
• Can be finished immediately
• Faster setting with less water sensitivity
• High color stability

Disadvantages of Resin Modified GIC

• More shrinkage during setting
• Less fluoride release
• Lower water and carboxylic acid content, therefore reducing ability to wet the tooth surface and creating weaker bonding

Other forms of Glass Ionomer

• Resin modified GIC (Hybrid Ionomer)
• Highly viscous GIC (inc. P/L ratio, for atraumatic restorative technique)
• Nanoionomer (nanofilled RMGI, better aesthetics and polishability)

Modifications of Metal Reinforced GICs

• Sliver alloy admix or Miracle mix
• Cermet

Clinical Applications

• Fissure sealant
• Base (sandwich technique)
• Restoration
• Different types: Luting, Restorative, Base

Indications

• Class V carious, erosive, or abrasive lesions
• Pits and fissures sealant
• Class I and II restoration in primary teeth
• Luting cement
• Core and build-ups
• Root surface caries

Contraindications

• Low tensile strength, brittleness, and low resistance to wear, which precludes use for Class I and II restorations.

Cavity Preparation

• The adhesive potential of the cement precludes the need for retentive features, which, in turn, simplifies the restorative procedure to just eliminating any caries-affected areas.
• Surface pretreatment: removes the smear layer from the cavity to facilitate chemical bonding, using a 10-20% polyacrylic acid for 10-20 seconds. Wash thoroughly for 20-30 seconds and dry without dehydration. Complete isolation is often recommended, and if the cavity becomes re-contaminated reconditioning will be required.

Manipulation

• Dispensing and mixing
• Placement
• Contouring and finishing

Commercially Available Forms

• Encapsulated for mechanical mixing
• Powder and liquid supplied separately for hand mixing

Dispensing

• The capsule provides a consistent powder/liquid ratio to guarantee optimum physical properties. The powder/liquid ratio is crucial for hand mixing

Finishing and Polishing

• Contouring and polishing must always be under air/water spray, using very fine diamonds initially, and finishing with aluminum oxide discs.
• Finishing and polishing can be done after 48 hours up to a week after placement. This allows time for the physical properties to reach a reasonable level before finishing without losing translucency. Light-cured glass ionomers can often be contoured immediately after light curing.

This quiz delves into the classification and properties of glass ionomer cements, including their composition, chemistry, and clinical applications. Understand the differences between polyacid mixable, water mixable, and mixed cements. Explore the significance of conventional and resin-modified glass ionomers in dental restorations.