Clinical Use Of Glass-Ionomer Cements

The Clinical Use Of Glass-Ionomer Cements

Question  1. What are tooth-colored restorative materials? 
Answer:

Tooth-colored restorative materials give the appearance of a natural tooth.

Tooth-colored materials are:

• Composite resin
• Porcelain
• Glass ionomer cement
• Acrylic resin.

Question 2. Write in detail about Recent advancements in glass ionomer cement.
Answer:

Recent Advancements:

1. Metal Modifid GIC:

The metal-modified GIC was introduced to improve the strength, fracture toughness, and resistance to wear and yet maintain the potential for adhesion and anti-cariogenic properties.

Types of  Metal Modified GIC:

• Silver alloy admixed: Spherical amalgam alloy powder is mixed with type II GIC powder (miracle mix).
• Cermet: Silver particles are bonded to glass particles. This is done by sintering of a mixture of the powders at a high temperature.

Uses of Metal Modified GIC:

In the restoration of small class I cavities as an alternative to amalgam or composite resins. They are particularly useful in young patients who are prone to caries. For the core build-up of grossly destructed teeth”

Properties of Metal Modified GIC:

• Mechanical properties:
  • As compared to that of conventional cement the strength of either type of metal-modified cement (150 MPa) is not greatly improved.
  • Fracture toughness of GIC whether modified or not is extremely low.
  • It is far more resistant to wear than type II GI
• Anticarcinogenic property:
  • Both metal-modified ionomers have anti-cariogenic capability due to the leaching of fluoride.
• Esthetics:
  • As they are gray in color because of their metallic phases within them, they are unsuitable for use in anterior teeth.

2. Resin-Modified GIC:

The two drawbacks of conventional GIC, i.e. moisture sensitivity- ity and low early strength which occur due to slow acid base setting reaction are overcome by adding some polymerizable functional group for the additional curing process.

Other names–Are light-cure GIC, dual-cure, Tricure, resin ionomer, compomer, and hybrid ionomer.

Classification of  Resin-Modified GIC:

Depending on the predominant component in them. These materials have been classified by McClean et al, as:

• Resin-modified glass ionomer cement (RMGI), for example. Fuji II LC, Vitremer, Photac-Fil, etc.
• Polyacid-modified composites (PMC), for example. Dyract,
  Variglass VL

Uses of  Resin-Modified GIC:

• Restoration of class I, III, or V cavities
• As bases and liners
• As adhesives for orthodontic brackets
• In the cementation of crowns and bridges
• For repair of damaged amalgam cores or cusps
• As retrograde root filling.

Supplied As  Resin-Modified GIC:

They are supplied as follows:

• Chemically cured
• Light-cured
• Dual-cured (combined chemical and light-cured)

All of them are usually supplied as powder and liquid. The light-cured type is supplied in dark-shaded bottoms for light protection.

Properties of Resin-Modified GICs:

• Strength: When resin-modified GICs are compared to conventional GICs their compressive strength is slightly lower (105 MPa) whereas the diametric tensile strength is greater (20 MPa) due to the plastic nature of the resin component.
• Hardness: Hardness (40 KHN) is comparable to that of conventional GICs.
• Adhesion: The bonding mechanism to tooth structure is the same to that of conventional GICs.
• Microleakage: These materials have a greater amount of microleakage when compared to conventional GICs.
• This may be partly due to the polymerization shrinkage and partly due to the reduced wetting of the tooth by the cement.
• Anticariogenicity: They have a significant anti-cariogenic effect due to the fluoride release.
• Esthetics: They are less translucent due to the significant differences in the refractive index between the resin matrix and powder particles.

3. High Viscous or Packable Glass Ionomers:

Fuji VIII for anterior teeth and Fuji IX for posterior teeth To simplify the insertion of the material, the GIC has to be pressed into the cavity.

To achieve this, the particle size of the powder and the P/L ratio is increased to obtain a highly viscous mix that can be easily packed. This modified, highly viscous GIC has high strength and better physical properties. Fifty percent of the particles have an average particle size of about 8 µm while about 90% of the particles have a particle size of less than

9.6 µm. This resulted in a mix with a thicker consistency that could be easily inserted with minimal hand instruments and pressed into place. These cements are widely used in atraumatic restorative techniques.

4. Compomers:

This class of restorative material combines some of the chemical and mechanical properties of composite resin and ion-leachable glass particles of GICs as filers. By adding aluminosilicate, it was thought that a better composite resin with fluoride-releasing properties was achieved.

Compomers Applications

• As restorative material in pedodontics
• As restorative material in non-stress bearing areas.
• In Class V lesions
• As bases
• In permanent luting

5.  Amino Acid-Modified Glass Ionomer Cement:

The fracture toughness of GIC can be improved by modifying acrylic acid and copolymers with N-acryloyl-glutamic or Nmethacryloylamino acids.

6. Nano-ionomers:

They are the hybrids of resin-modified GIC and nano-filed dental composites. They are designed for quick and easy mix, for example, Ketac nano light curing GIC. These cement have greater wear resistance.

7. Ceramic Reinforced Posterior Glass Ionomer Cement:

They are designed to match the strength and durability of amalgam. It is present in white and universal tooth shades. This is dispensed in powder and liquid form, water settable form is also present.