Dental Problems

Glass Ionomer Cement – Modified Anhydrous and Compomer

The modified anhydrous and compomer forms of glass ionomer cement are used for the restoration of primary molars. These plastic materials are used to restore the teeth as it is difficulty to restore with gold foils or gold inlays. In this article, there is a brief discussion on the glass ionomer cement modified anhydrous and compomer. Read on to know more.

Take Care of Your TongueModified Anhydrous Glass Ionomer

In this modification the liquid is delivered in a freeze dried form that is then incorporated into the powder. The liquid to be used is clean water only and this may enhance shelf life and facilitate mixing.

Another alternative is to use a dilute tartaric acid as the liquid with dehydrated polyacrylic acid included in the powder. These alternatives make it possible to use a polyacrylic acid with higher molecular weight thus improving physical properties.

The term anhydrous is actually a misnomer as it is not possible for ion transfer to occur, in any material, in the absence of water.

Setting reaction for glass ionomers:

The setting reaction has been described as an acid base reaction. The surface of all the glass particles is softened by the polyacrylic acid and both calcium and aluminium ions are released through the proton attack.

Calcium ions react first and form calcium polyacrylate chains followed a little later by a similar reaction with the aluminium ions. The calcium polyacrylate chains are rather fragile and soluble in water and therefore require protection if they are to be retained. The formation of polyacrylate chains will progress quire rapidly following the initial setting reaction.

These chains are strong and insoluble in water and form the main body of the restoration. Both the calcium and aluminium ions will cross-link as the reaction progresses and forms a rather porous network.

A further ion exchange reaction occurs as part of the setting process where there will be a silica hydrogel formed on the surface of the glass particles. There will be a gradient of ions formed about one third of the way into the glass to the extent that the glass and the matrix become chemically bound and can be regarded as a single mass.

Modified Compomer Glass Ionomer:

This is the term developed by the manufacture with a claim to incorporate some of the properties of a glass ionomer with a composite resin. A compomer is a composite resin that uses an ionomer glass which is the major constituent of a glass ionomer as the filler. There is also a small quantity of a dehydrated polyalkenoic acid incorporated with the filler particles.

The filler particle is help within an anhydrous resin matrix and there is complete absence of water. Hence there can be no ion exchange; acid or base setting reaction and the material initially remains inert. The setting reaction is light activated and there can be no acid base reaction until there has been a degree of water uptake into the restoration.

Following water uptake there will be an ion exchange between the glass and the rehydrated polyalkenoic acid followed by a low grade fluoride release, but this will be neither sustained nor at a higher level. Since fluoride uptake cannot take place a compomer cannot be regarded as a fluoride reservoir.

The most significant difference between the two materials is the absence of an ion exchange adhesion. The adhesive system used with a compomer is based on the acid etch or resin bond system found with all composite reins.

Finally the percentage filler content is relatively low compared to the hybrid composite resins, both the water uptake and the wear factor are relatively high.

Setting reaction of compomer

There are essentially two different systems for initiating polymerization in a composite resin. The original materials were all chemically activated however they exhibited an undesirable color shift. Subsequently a system for light activation was developed and this has proven to be relatively color stable. It is also possible to combine the two systems.

The above article discusses briefly about the

glass ionomer cement with the modified anhydrous and compomer

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