Dental Materials

Glass Ionomer Cements

Glass Ionomer Cements

Glass ionomer cements are formed when a glass powder is mixed with an aqueous solution of polyacrylic acid.

Glass ionomer cements have become quite popular because of their physical and mechanical properties and their clinical performance.

– A multitude of products are on the market.

– The first glass ionomer cements set by an acid–base reaction, like most other
dental cements.

– We will call them A/B (acid–base) cements. “Resin-modified” or “resin-reinforced” products have become more popular.

They set via two reactions: acid–base and addition polymerization.

A. Products and Uses

1. Luting Materials

Glass ionomer cement is one of the most popular luting materials.

Both A/B and resin-reinforced products exist.

– Resin-modified glass ionomer cement has been called the material of choice for luting all-metal and ceramo-metal crowns.

– These glass ionomer products are stronger and tougher than those products that set solely by an acid– base reaction.

Light-activated, resin-reinforced glass ionomer luting materials had appeared on the market, but problems with their use were soon noted.

– They were intended for use with translucent ceramic crowns.

Unfortunately, light-cure glass ionomer luting materials absorb water in the mouth and swell excessively.

– This causes an unacceptable number of ceramic crowns to fracture after weeks or months of use.

– These products generally are no longer marketed.

2. Restorative Materials

Glass ionomer restorative materials were discussed in Direct Polymeric
Restorative Materials.

The restorative materials have the same setting reactions as luting materials but are thicker, stronger materials with a much higher film thickness.

3. Base/Liner Materials

A number of base and lining AB materials have been developed.

With the introduction of light activated, resin-reinforced glass ionomer liners, however, use of A/B products has greatly diminished.

Light-activated glass ionomer liners have adequate strength for use as a base and are quite popular.

At times, dentists will use a glass ionomer restorative material for a temporary restoration or a large base.

4. Glass Ionomer Cements

Glass ionomer cements are available in three forms.

One form is supplied as a powder and a liquid.

– The powder is measured with a scoop and is mixed with a specific number of liquid drops from a bottle.

– It is important that the cement is mixed quickly and the working time is not exceeded.

The second form is a premeasured, single-dose capsule (much like amalgam).

– These unidose capsules are mixed with an amalgamator.

The capsule has a “spout” where the mixed material is expressed from the capsule with a “gun or dispenser.

” Capsules are easy to use and very popular, but they are also more expensive.

The third system is a paste/paste system common for many dental materials.

– The pastes are dispensed and mixed until they become one homogenous color.

– Many resin reinforced glass ionomer luting materials are paste/paste products supplied in a double barrel dispensing device.

These dispensing devices assure proper proportioning of the two pastes.

B. Properties

1. Glass ionomer materials are the strongest and least soluble dental luting cements (with the exception of composite cements).
They are also adhesive, release fluoride, and have good biocompatibility.
This combination of properties makes them quite popular.

2. Glass ionomer materials bond to tooth structure.
In addition, they bond to stainless steel and alloys for ceramometal crowns.

C. Mixing

1. It is critical that glass ionomer cement is properly mixed and handled.
If it is not, a nonadhesive material results.
The powder is dispensed with a scoop, and the liquid is dispensed as drops.
Cement spatula and paper pads are typically used.
The cement manufacturer supplies special mixing pads that consist of sheets of
plastic-coated paper.
The plastic coating protects the paper from abrasion and prevents the liquid from being
absorbed by the paper.
It is important that the drops form and fall separately.
Glass ionomer cement is not mixed to a desired consistency, as ZOE and zinc phosphate
cements are. The manufacturer’s recommended powder/liquid ratio should be followed.

2. The mixing process is much quicker than that for ZOE or zinc phosphate cement.
Mixing should be completed in 30 seconds or less, and the restoration should be seated within 2 minutes from the start of mixing.
Typically, the powder is mixed into the liquid in two increments.
The mixed material must be placed while the cement surface appears glossy; beyond that time, adhesion is reduced or lost.

3. Clean-up with water is easy and should be done as soon as possible.
Remember that the set material will bond chemically to the stainless-steel cement spatula.


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