Fruit drinks — the continuing controversy!

Key Points

• New blackcurrant drinks with reduced carbohydrate content show reduced acidogenic responses in dental plaque.

• The plaque pH did not drop below the 'critical' level considered to be harmful for teeth.

• Consumption of these new drinks does not pose a considerable risk for enamel demineralisation.

• These drinks are safer alternatives for those patients who consume fruit drinks.

Abstract

Objectives

To assess the acidogenic response in dental plaque after challenge with four fruit drinks, including two blackcurrant drinks newly formulated, with low levels of carbohydrate.

Methods

24 adult volunteers rinsed, in randomised order, with each of two new formulations of a blackcurrant drink (7% juice with 0.49% and 10% juice with 0.65% carbohydrate concentration respectively), an apple and blackcurrant drink with no added sugar (0.8%), and a mixed citrus fruit drink with a higher carbohydrate concentration (4.5% w/v). Solutions of 10% sucrose and 10% sorbitol were used as controls. Plaque pH was assessed, in vivo, before and after the acidogenic challenge using the plaque-harvesting technique.

Results

Results showed that the minimum plaque pH after the subjects rinsed with the new blackcurrant drinks was higher as compared with all the other test products and significantly so compared with the mixed citrus drink (P = 0.0001). It was also found that with the 7% blackcurrant juice drink none of the subjects and with 10% blackcurrant juice drink only one subject recorded a pH drop below the pH of 5.7. Ten minutes after consumption, both the new formulation blackcurrant drinks produced significantly higher plaque pH than the mixed citrus drink. In addition, overall change in the hydrogen ion concentration over the study period (ΣΔcH) was significantly less with both new blackcurrant drinks compared with the mixed citrus drink.

Conclusions

It was concluded that the two new formulations with low levels of carbohydrate had a low acidogenic potential and did not depress the plaque pH below the critical level and their consumption could not be considered to pose a significant risk for enamel demineralisation.

Main

Effect on plaque pH of fruit drinks with reduced carbohydrate content Toumba K. J. and Duggal M. S. Br Dent J 1999; 186: 626–629

Comment

It is quite clear that the BDA caused quite a controversy by accrediting 'Ribena Tooth-kind' — not least among the dental profession itself. Although reservations plainly exist about the whole concept of accreditation, surely we need to give scientifically-based helpful information to our patients. Suggesting to most parents of young children that water is the only drink that is safe as far as teeth are concerned may not be advice that is likely to be complied with. We have to approach dietary advice with common sense, particularly with regard to drinks. In the past it was dental caries that was the arch enemy of teeth, but although the prevalence has decreased very significantly in the previous 30 years, it still remains a huge problem, particularly in areas of deprivation.

However, the spectre of dental erosion is also one to be aware of. Erosion differs from caries in that it is the irreversible loss of tooth tissues by a chemical process and does not involve bacteria. Although longitudinal data on the prevalence of erosion are not available there have been several subjective reports suggesting that it is an increasing problem. The consumption of soft drinks has also increased dramatically in the past few years and still continues to escalate. This research project is therefore timely in assessing the acidogenic response in dental plaque after challenge with four drinks, two of which were newly formulated low carbohydrate Ribena blackcurrant drinks.

The participants in the study refrained from brushing their teeth for 48 hours and then, following a baseline reading of their plaque pH, they rinsed their mouths with randomly allocated test drinks for 30 seconds. Plaque samples were tested subsequently 5, 10, 15, 20, 25 and 30 minutes after rinsing. The plaque sampling method used is a recognised standard system but another approach would have been to use an indwelling pH electrode. This would have enabled the immediate pH drop following rinsing to be measured. It is highly likely that sampling at 5 minutes will not record the minimum pH¹ but the authors have acknowledged this possibility in their discussion.

What is quite clear from this study is that a 10% sucrose drink is a serious problem. The mean plaque pH curve in figure 1 probably considerably underestimates this. There are quite a number of commercially available fruit-based soft drinks which will show similar trends. The two newly formulated low carbohydrate blackcurrant drinks and the apple and blackcurrant drink with no added sugar lead to significantly lower acid production in vivo.

The conclusion drawn that the new Ribena drinks with very low levels of carbohydrate had a low acidogenic potential and could not be considered to pose a significant risk for enamel demineralisation seems to be justified on the basis of this research. So, does that mean that they are safe and kind to teeth? To say that anything — apart from de-ionized sterile, water — is entirely safe is to underestimate the dental abuse some of our patients may commit. However, when trying to give advice to parents and young children that is likely to be acted on then suggesting a lower carbohydrate drink with lower acidogenic potential is undoubtedly helpful — and evidence-based!