The Advantages of Using Glass Ionomers in Dentistry

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Bacteria in the teeth produces an acid while they consume the sugars found in drinks and foods, which causes tooth decay. The protective enamel coating of teeth is dissolved by this acid, which also damages the dentine below. If the ensuing cavity is not treated, it can become painful, potentially leading to infection and sometimes tooth loss.

The widely used corrective action for tooth decay is to take out the decayed tooth tissue and fill the cavity with a filling material. There are a number of different filling materials presently in use, including a range of composite fillings, and the traditional silver amalgam. Composite filling materials are becoming popular as many people favor tooth-colored fillings that are less obvious. Composite dental materials can also be used for dental restorations to rebuild broken or chipped teeth. In recent times, glass ionomer cements, which can be used in quite the same way as composite materials, have been launched as an additional substitute material for dental restoration.

The filling material’s quality is a crucial factor in determining the success of a repair. If the filling material is not durable, it will come off while eating, and if it is susceptible to shrinkage, bacteria will settle in the gap between the tooth and the filling leading to secondary caries.

The Materials used in Tooth Fillings

In the 1800s when modern dentistry began, teeth were filled with any metal that was sufficiently soft to mold into the cavity, for instance, silver and tin. This progressed to dental amalgams comprising of a combination of metals including silver, tin, copper, and mercury as technology improved during the 19^th century. Towards the end of the first quarter of the 20^th century, silicate dental cements had been created for dental filling as well as the bonding of other dental restorations².

Currently, amalgam is still the most frequently used filling material. Even after apprehensions were raised about the lethal effects of mercury, amalgam fillings continued to be used because of the substandard quality of alternatives. However, at present, that there are effective alternatives, which have the extra aesthetic advantage of being the same color as the tooth; the proportion of amalgam fillings is progressively decreasing.

Now, there are different types of dental filling materials available, including silver amalgam, porcelain, gold, composite resins, and glass ionomers. However, effective dental filling materials — porcelain and gold — are seldom used because of their high costs. The other key options are compared below.

Amalgam

Amalgam costs the least among the dental filling materials and can be applied most rapidly². It has the extra advantage of being very durable, lasting nearly 10 to 15 years. There are, however, a number of disadvantages to the use of amalgam fillings, the most concerning of which is the possible toxicity from exposure to mercury while placing and removing the amalgam, and also while in situ if an individual habitually grinds their teeth. The use of amalgam fillings also means the removal of a healthy tooth so as to create a space, which is big enough to hold the amalgam. Finally, the tendency of amalgam to expand and contract with varying temperature makes it more likely to fracture or crack and damage the neighboring tooth as a result of drinking cold and hot liquids.

Resin Composites

Dental composites can differ in formulation but all contain a synthetic resin making them quite like plastics in composition. Originally, composite materials lacked the durability and strength of amalgam, but progress in their production means that they can now be both robust and durable. Their key benefit is that they chemically bond to the tooth structure, providing additional support and decreasing the marginal gap that promotes the colonization of bacteria and raises the risk of secondary tooth decay. There is, however, a risk of subsequent shrinkage that can result in gap development. Composite fillings are also aesthetically more attractive since, unlike amalgam fillings, they merge in with the natural tooth surface. Unfortunately, composite materials are still significantly more expensive than amalgam (although still less expensive than porcelain or gold) and are more tedious to apply². Additionally, the successful application of composite fillings is a highly sensitive technique and requires the area to be kept dry during placement.

Glass Ionomer Dental Cements

Glass ionomer cements (GICs) can have a range of compositions, but the chief constituents are alumina, silica, and calcium. A source of fluoride, such as fluorite, is also usually incorporated to offer protection against tooth decay. More minerals can also be added into the GIC to boost demineralization and/or prevent acidification. The glass ionomer may be incorporated with resin for extra strength as well as to reduce the sensitivity level to the presence of moisture on placement³. GICs signify an extremely very flexible dental restoration solution as the physical properties of GIC can be altered to match a particular dental application by modifying the ratios of the constituent chemicals².

Similar to resin composites, GICs are tooth-colored and therefore possess cosmetic appeal. The key benefit of GICs is their chemical bonding to dentin and enamel, which enhances the strength of the restoration and eliminates the need for a bonding agent during placement^2,4. The bond strength of this adhesion is usually increased by incorporation of polycarboxylic acid. GICs have been known to display a contact-free area wear that is five times greater than that of amalgam and three times greater than for resin composite materials². Moreover, in contrast to other restoration materials that can unexpectedly fail because of mechanical fatigue, GICs become stronger over time as water is absorbed and are therefore less susceptible to failure².

Lately, bioactive glass is used for making GIC⁵. Resin-modified GIC comprising of bioactive glass has been demonstrated to result in a thick uniform layer of mineralization on the restoration-dentin interface⁶, enhance the mechanical properties of a filling⁷, and reduce the incidence of secondary tooth decay at restoration margins⁸.

Conclusion

Regardless of silver amalgam being the mainstay dental filling material for a number of decades, there has been a need to minimize its use because of the toxicity concerns. Since substitute products are now available and can provide comparable efficacy, the proportion of dental caries being rectified with amalgam fillings is decreasing. Progress in the formulations of composite and glass ionomer dental materials have given them the needed durability and strength to make them effective products for tooth restoration. Although fillings with these newer materials are more expensive and tedious to place, they are repeatedly the favored choice because of their enhanced aesthetics and low risk of toxicity.

GICs have the extra benefits of strong adhesion to the tooth surface, flexibility in their physical features, and lower failure rate.

The properties of composite as well as glass ionomer dental materials can be enhanced by the addition of bioactive glass.

Mo-Sci manufactures a variety of superior quality glass and bioactive glass powders ideal for use as dental filling materials and for the coating or fixation of dental implants⁹. The precise composition of their glass products can be customized to match a specific application.

References and Further Reading

1. National Institutes of Health. NIDCR Data & Statistics.  Dental Caries (Tooth Decay) in Adults (Age 20 to 64). Available at: https://www.nidcr.nih.gov/DataStatistics/FindDataByTopic/DentalCaries/DentalCariesAdults20to64.htm
2. Lohbauer U. Dental Glass Ionomer Cements as Permanent Filling Materials?—Properties, Limitations Future Trends. Materials 2010, 3(1), 76-96; doi:10.3390/ma3010076
3. Gao W, et al. Demineralization and remineraliza-tion of dentine caries, and the role of glass ionomer cements. Int Dent J. 2000;50(1):51–56.
4. Benelli EM, et al. In situ anticariogenic potential of glass ionomer cement. Caries Res. 1993; 27(4):280–284.
5. Matsuya S, et al. Structure of bioactive glass and its application to glass ionomer cement. Dent Mater J. 1999 Jun; 18(2):155–166.
6. Prabhakar AR, et al Comparative Evaluation of the Remineralizing Effects and Surface Micro hardness of Glass Ionomer Cements Containing Bioactive Glass (S53P4):An in vitro Study. Int J Clin Pediatr Dent. 2010 May-Aug;3(2):69-77. doi: 10.5005/jp-journals-10005-1057. Available at https://www.ncbi.nlm.nih.gov/pubmed/27507915.
7. Chatzistavrou X, et al. Fabrication and characterization of bioactive and antibacterial composites for dental applications. Acta Biomater. 2014;10:3723–3732. Available at https://www.ncbi.nlm.nih.gov/pubmed/24050766
8. Khvostenko D, et al. Bioactive glass fillers reduce bacterial penetration into marginal gaps for composite restorations. Dental materials 2016; 32(1):73–81. Available at http://www.demajournal.com/article/S0109-5641(15)00437-6/pdf
9. Mo Sci website. http://www.mo-sci.com/en/products

About Mo-Sci

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Mo-Sci has become a world leader in the research, development and manufacturing of glasses for specialty applications.

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