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DENTAL HEALTH…GLASS IONOMER RESTORATIVE MATERIALS
By Dr. Neromini Fagu
Glass Ionomer has been used in dentistry for decades. This dental material was developed in 1965 and introduced to clinical dentistry in 1972. The name Glass Ionomer was termed by its developers, Drs. Wilson and Kent, with
Class V Restoration: Before (A) and After (B)
“glass” being for alumino silicate glass particles and “ionomer” for polycarboxylic acid and with the former being a powder and the latter a liquid. While the language might be a technical, I hope you will be able to glean some useful information from our discussion today.
The glass ionomer powder is an acid soluble calcium fluoroalumino silicate glass. The raw materials are fused to a uniform glass by heating them to a temperature of 1100 °C- 1500°C. Lanthanum, strontium, barium or zinc oxide is added to provide radio-opacity which is extremely useful for radiographic purposes. The resulting glass is ground into a powder having particles in the range of 15-50 µm.
Some favourable properties of the material include its low exothermic reaction, chemical adherence to the tooth structure, less shrinkage as compared to polymerizing resins, and dimensional stability at high humidity. However, the biggest advantage of glass ionomers is their ability to release fluoride during an acidic attack and to uptake fluoride ions when present in the oral environment. It also has antibacterial properties.
Glass ionomer direct restorative materials are simpler to place in bulk and have reduced operator caused post-operative sensitivity than composite restorations. They are not as sensitive to variations in the moisture in the restorative area during placement as composite resins, and have a long-term stable bond to dentine which generally does not diminish over time. The set material has a coefficient of thermal expansion which is similar to tooth structure.
Some of the undesirable characteristics include early moisture sensitivity, poor abrasion resistance and average esthetics. The durability of the material is affected by the preparation of the cement prior to placement and inadequate protection of restoration.
There are many indications for the use of Glass Ionomer. These include as a restorative material for abrasion and erosion lesions without cavity preparation, sealing and filling of occlusal pits and fissures, restoration of deciduous teeth, core build-up to reinforce the teeth and prevent fracture, and in atraumatic restorative techniques cases.
Its versatility also includes usage as a fast setting lining cement and bases for cases such as lining of all types of cavities where a biological seal and cariostatic action are required, and the “sandwich technique” with composite resin to combine the beneficial properties of both materials. It is also useful for cementing crowns and bridges and for placement of orthodontic brackets.
In endodontics it is used for sealing root canals orthogradely and retrogradely, restoring pulp chamber, and perforation repair. It is sometimes used for repairing vertical fracture because of its capacity to bond which enhances seal and re-enforces the tooth, bio-compatibility properties thus minimizing irritation to peri-radicular tissues, and fluoride release actions which import an anti-microbial effect to combat root canal infection.
Some of the contra indications for its usage include restoration of incisal angles, fractured incisors, lesions involving large areas of labial enamel where esthetics is of major importance, interproximal surface restorations in posterior teeth requiring conventional cavity preparations, replacement of existing amalgam restorations, and replacement of lost cusp areas.
Glass Ionomers have enjoyed many firsts in dentistry, being the first materials designed to resist recurrent decay, the first bioactive materials which release fluoride in an acidic environment and recharge or replace lost fluoride ions when they are re-introduced back into the oral environment, and the first easy to use bulk-fill material.
There have been many improvements to the original formulas, and there is now improved handling, strength, wear rates and esthetics. In addition, there are many new applications for Glass Ionomers which no doubt will continue to evolve in the next fifty years.
For more information contact OMNI DENTAL at 295 Quamina Street, Georgetown Tel: 227-0025, Parika Tel: 260-3133 or send emails to [email protected].
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