It has long been accepted that sugarfree chewing gum is linked to fresh breath, yet few patients are aware of the clinical benefits. As this article will illustrate, chewing sugarfree gum enhances production of saliva and its oral health benefits, namely: clearing the mouth of food debris and sugars, neutralising acids, and supporting remineralisation – all of which can help reduce the incidence of caries.

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Debris removal and plaque neutralisation

When gum is chewed by healthy subjects, the flow of saliva increases from a resting value of 0.4–0.5 mL/ minute, to approximately 5–6 mL/minute, and gives a 10–12 fold production increase over unstimulated saliva.1 The flow of saliva falls after about 5 minutes to around 2 mL/minute, and slowly thereafter to 1.2–1.5 mL/minute at 20 minutes.1

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 neutralising and buffering food acids and acids arising in plaque from the fermentation of carbohydrate.2 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−.2 The calcium content of saliva rises as well.2

The observation by Hein et al. of a ‘large and sustained rise in plaque pH’ when gum was chewed after sugar intake3 has been confirmed by many studies conducted around the world as reviewed by Imfeld (1999).4 These changes in the composition of stimulated saliva lead to a greater ability to prevent a fall in pH and a greater tendency to favour hydroxyapatite crystal growth.5 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.5 These three properties of saliva are correlated to the caries susceptibility of the individual and are all enhanced by salivary stimulation.

The action of stimulated saliva is most important during the plaque acid threat during the 20–30 minutes after a cariogenic food intake.6 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 mobilised 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 Sugarfree chewing gum is a very practical and acceptable stimulus that can be chewed after the intake of fermentable carbohydrates, and brings no undue calories. Research has shown that chewing sugarfree gum stimulates saliva production which can last up to two hours.8

Figure 1
figure 1

Chewing sugarfree gum for 20 minutes after meals and snacks has been proven to keep teeth healthy

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Enhancing remineralisation

The concentrations of ions which make up the lattice structure of hydroxyapatite (Ca2+, PO43−, OH−) are higher in stimulated than in unstimulated saliva. Therefore, stimulated saliva is a more effective medium for remineralising enamel crystals damaged by initial acid exposure. In an in situ caries study by Leach et al.9 subjects chewed sorbitol gum for 20 minutes after meals and snacks (five times daily). The gain or loss of mineral content of human enamel slabs, bearing artificial lesions and mounted intra-orally for 3 weeks, was then measured and compared with results after similar periods without gum chewing. Remineralisation of the enamel lesions occurred both with and without gum, but with gum the remineralisation was approximately doubled.

This effect was broadly confirmed by Creanor et al.10 and was consistent with a reduction in enamel demineralisation (measured as iodide penetration) by chewing sorbitol gum, as found by Kashket et al.11 The findings of Steinberg et al.12 further confirmed these results. In this study the use of sugarfree gum (sweetened with either xylitol or sorbitol) for six weeks resulted in an increase in plaque calcium and a significant reduction in plaque index, compared with no gum. Remineralisation in vivo is generally considered to be a slow process13 and thus it was noteworthy that significant remineralisation occurred within 3 weeks. These model experiments suggest that sugarfree gum use can help prevent decay by tilting the equilibrium towards remineralisation and away from demineralisation.

Furthermore, the use of sugarfree gum has been associated with a reduction in the quantity and development of plaque,14–17 and a reduction in the acid-forming ability of plaque.18

The potential outcome from these effects of stimulated saliva is a reduction in the incidence of caries. Multiple clinical trials have observed a reduction in the incidence of caries in response to the regular chewing of sugar-free gum, which has been confirmed by two systematic reviews.1920 The reduced incidence has subsequently been reviewed and confirmed in the form of several approved health claims.21–23