The erosive potential of some herbal teas
Introduction
Dental erosion may be defined as an irreversible loss of dental hard tissues due to a chemical process without the involvement of microorganisms.1 This process may be caused by either extrinsic or intrinsic agents. Extrinsic agents include acidic substances, beverages, snacks or environmental exposure to acidic agents.2., 3. Intrinsic causes of erosion include recurrent vomiting as part of anorexia or bulimia or the regurgitation of the gastric contents.4
The consumption of tea is seen as a ‘healthy’ alternative to other caffeine based beverages, particularly as tea has been shown to have antioxidant properties.5., 6., 7. More specifically, tea has also been shown to potentially have some oral health benefits. The high fluoride content of teas has been well documented.8., 9. In addition to this, tannic acid has been shown to inhibit the growth of S. mutans10 and specific flavanoids, mainly catechins, have shown inhibitory effects on the growth of cariogenic bacteria.11 In recent years herbal teas have gained in popularity, so that they now account for 3–4% of all tea consumed within the UK.12 These herbal teas do not contain any traditional black tea leaves, but are based on dried fruit products and often contain a mixture of dried berries, dried fruit leaves together with other fillers and flavourings. Many of these teas are based on fruits with a high citric acid content which is known to have a high erosive potential.13
A recent study by Brunton and Hussain14 compared a traditional tea with one popular herbal tea. They found that the traditional tea had a pH of 4.8 and the herbal tea had a pH of 3.2. The pH value of the herbal tea was below the critical pH value of 4.5 at which enamel begins to erode.15 Not surprisingly, the herbal tea had an erosive effect on enamel that was five times that of the traditional tea. As these herbal beverages may be consumed many times per day over many years, the destructive potential in susceptible individuals is obvious.
The aim of this study was to compare a number of commercially available herbal teas and compare this with a traditional tea, water and orange juice. The hypothesis used in this study was that the herbal teas would not be more erosive than orange juice.
Section snippets
Materials and methods
The herbal teas chosen for this study are listed in Table 1. In addition to the herbal teas that were ‘bag based’ products two ‘non-bag’ products were included; Lift Instant Lemon Tea and Lipton Ice Tea. Lift Instant Lemon Tea is a dehydrated powder product while Lipton Ice Tea is a ready-made product intended for consumption directly from the bottle. All the ‘bag teas’ were produced using a standard method. One teabag was added to 250 ml of fresh boiling water and stirred at 0, 2, 4 and 5 min
Results
The results for the initial pH values are given in Table 2. The pH of the teas tested ranged from 3.15 to 7.08 compared to a value of 3.73 for orange juice. Analysis of variance showed that the pH of the traditional black tea (Tesco blend) and camomile tea were significantly more alkaline than the other teas (p<0.001).
The results for the neutralisable acidity values are given in Table 2. These values ranged from 3.54 ml for the traditional black tea to 60.3 ml for the Lipton Ice Tea lemon. The
Discussion
The aim of this study was to compare the potential erosive effects of a variety of herbal teas with a traditional black tea and orange juice. This was assessed by examining the initial pH, neutralisable acidity and the ability to remove enamel in vitro assessed using profilometry.
The critical pH below which enamel erodes is thought to be 4.515 and this is a useful value by which to judge the erosive potential of a material. The traditional black tea and the camomile tea were well above this
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