It is true to say that at the present time erosion is still only a minor public health problem when compared with dental caries,
but it is something that the soft drinks industry should be aware of, since the disease is linked with high consumption of soft drinks and juices.
Dental erosion is defined as the progressive loss of enamel resulting from acid attack, without the involvement of bacteria. It is caused by frequent contact between the acids and the tooth surface, which dissolves the dental hard tissue layer by layer. This is why excessive consumption of soft drinks can be a problem, but other dietary factors such as high consumption of citrus fruits, vinegar and dry wine are also implicated. Erosion can also be caused by gastric juices in cases of recurrent vomiting.

Changing lifestyle is thought to have played an important role in increasing the prevalence of dental erosion in western societies. A major factor is thought to be the rapid growth in the soft drinks industry in recent years. The rapid expansion in soft drinks consumption since 1979, and the fact that adolescents today are not tending to graduate onto tea and coffee as they get older, are thought to be important contributory factors.

Research on the erosiveness of soft drinks has centred on the way in which the drinks are consumed and comparisons of the erosive potential of different types of soft drink. It has been shown that, if drinks are drunk straight down, there is less of a fall in pH than if they are drunk slowly, e.g straight from the can. Reducing the frequency of contact with acidic drinks, or drinking acid beverages through a straw are also suggested as ways of preventing erosion. Recent research on the acidity of soft drinks has suggested that titratable acidity is actually a better indicator of erosive potential than pH; it correlates better with the amount of calcium and phosphorus released from the hydroxyapatite during demineralization. In terms of levels of titratible acidity, fruit drinks are high and interestingly, pose a higher risk in relation to dental erosion than cola beverages, which have a lower titratable acidity. For example, the titratable acidity (ml) of orange juice is around 13.4, compared with 8.9 for a ready-to-drink squash, and between 1.5 and 2.9 for cola-type drinks. This compares with typical pH values of these drinks of 3.62, 2.64 and 2.4, respectively.

Over the years, there have been a number of studies aimed at reducing the erosive potential of food and drinks products. As far back as 1957, Wagg et al. investigated, with some success, the addition of calcium and phosphate to ice lollies in reducing their erosive potential, and in 1996 Smithkline Beecham filed a patent for "Liquid oral compositions comprising a calcium compound and an acidulant" (PCT Patent Application WO 97/30601). This led to the launch of Ribena Toothkind this year; the reformulated product contains calcium, which is said to bind with the fruit acid in the drink, making it less damaging to teeth. The drink claims to be "Kind to Teeth", protecting against dental caries as well as dental erosion, but the claim has sparked off a row with Action and Information on Sugars (AIS), which recently complained to the standards authority in Hounslow that the claim was misleading. The argument primarily centres on the cariogenicity issue and, in particular, the way in which cariogencity is tested, but, this summer, the standards authority decided not to uphold the complaint from the AIS and so the product claim can still stand.

This development is bound to pave the way for other similar product launches. Smithkline Beecham has already expressed an interest in transferring the technology across a range of its drink products, and other soft drink companies will no doubt follow suit in the future.

References
Wagg (1957) "Inhibition of the erosive properties of water ices by the addition of calcium and phosphorus." British Dental Journal, 119, 118-23.

Further Reading:
Grenby T. (1993). "Dietary aspects of tooth erosion" in "Nutrition and Dental Health." Ed. A J Rugg-Gunn.Oxford Medical Publications.

Author : Angus James, Editor of Leatherhead Food RA's Soft Drinks Bulletin