Neutralizing Plaque Acids

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Chewing gum is a unique food because it is chewed for a prolonged period (often around 20 minutes), while at the same time it contributes relatively few calories. Chewing sugar-free gum enhances production of saliva and its oral health benefits, namely: clearing the mouth of food debris and sugars, neutralizing acids, and supporting. Research shows that people who regularly chew sugar-free gum develop significantly fewer cavities than those who do not.¹

When gum is chewed by healthy subjects, the flow of saliva increases to around 10-12 times the resting rate.2 The effect of stimulation is to increase the concentration of bicarbonate in the saliva entering the mouth. This bicarbonate raises the pH of the saliva and greatly increases its buffering power; the saliva is, therefore, much more effective in neutralizing and buffering food acids and acids arising in plaque from the fermentation of carbohydrate. At the same time, the phosphate of saliva changes as a result of the rise in pH, so that a higher proportion of it is in the form of PO43-. The calcium content of saliva rises as well.3

These changes in the composition of stimulated saliva lead to a greater ability to prevent a fall in pH and a greater tendency to favor hydroxyapatite crystal growth. In addition, the greater volume and rate of flow of stimulated saliva results in an increased ability to clear sugars and acids from around the teeth.4 These three properties of saliva are correlated to the caries susceptibility of the individual and are all enhanced by salivary stimulation.

After fermentable carbohydrates are consumed, plaque pH drops rapidly and within 3-5 minutes falls below the critical value of 5.5. It remains below the critical value for around 20 minutes, before gradually returning to normal.5,6 The action of stimulated saliva is therefore most important during the plaque acid threat during the 20-30 minutes after a cariogenic food intake. However, with most foods, salivary stimulation ceases shortly after the final swallow and salivary composition returns to normal in less than 5 minutes, so the protective effects are not mobilized when most needed.

In order to enhance salivary protection during the acid exposure, a stimulant is needed which is not itself cariogenic and the effects of which last as long as possible.7 Sugar-free chewing gum is a very practical and acceptable stimulus that can be chewed after the intake of fermentable carbohydrates and brings no undue calories. Several studies have shown that chewing sugar-free gum stimulates saliva production which can last up to two hours.8

Published Research

1. Newton JT et al. A Systematic Review and Meta-Analysis of the Role of Sugar-Free Chewing Gum in Dental Caries. JDR Clin Trans Res. 2020 Jul;5(3):214-223.

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2. Dawes C, Macpherson LM. Effects of nine different chewing-gums and lozenges on salivary flow rate and pH. Caries Res. 1992;26:176–82.

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3. de Almeida PD, Grégio AM, Machado MA, et al. Saliva composition and functions: a comprehensive review. J Contemp Dent Pract. 2008;9:72– 80.

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4. Dawes C and Watanabe S. The effect of taste adaptation on salivary flow rate and salivary sugar clearance. J Dent Res. 1987;66:740.

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5. Stookey GK. The effect of saliva on dental caries. J Am Dent Assoc. 2008;139(Suppl.2):11S–17S.

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6. Bowen WH. The Stephan Curve revisited. Odontology. 2013 Jan;101(1):2-8.

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7. Beiswanger BB, Boneta AE, Mau MS, et al. The effect of chewing sugar-free gum after meals on clinical caries incidence. J Am Dent Assoc. 1998;129:1623–6.

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8. Dawes C. Factors influencing Salivary flow rate and composition. In: Edgar M, Dawes C, O’Mullane D, eds. Saliva and oral health. 4th edition. Bicester: Stephen Hancocks Ltd, 2012:37–55.

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