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.
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
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.
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
Dawes C, Macpherson L M. Effects of nine different chewing-gums and lozenges on salivary flow rate and pH. Caries Res 1992; 26: 176-182.
de Almeida P D, Grégio A M, Machado M A, et al. Saliva composition and functions: a comprehensive review. J Contemp Dent Pract 2008; 9: 72–80.
Hein J W, Soparkar P M, Quigley G A . Changes in plaque pH following gum chewing and tooth brushing. J Dent Res 1961; 40: 753–754.
Imfeld T. Chewing gum-facts and fiction: a review of gum-chewing and oral health. Crit Rev Oral Biol Med 1999; 10: 405–419.
Dawes C, Watanabe S. The effect of taste adaption on salivary flow rate and salivary sugar clearance. J Dent Res 1987; 66: 740.
European Food Information Council. Food, dietary habits and dental health. Available at: http://www.eufic.org/article/en/diet-related-diseases/dental-care/expid/review-food-dietary-habits-dental-health/ (Accessed September 2015).
Beiswanger B B, Boneta A E, Mau M S, et al. The effect of chewing sugar-free gum after meals on clinical caries incidence. J Am Dent Assoc 1998; 129: 1623–1626.
Dawes C, Kubieniec K. The effects of prolonged gum chewing on salivary flow rate and composition. Arch Oral Biol 2004; 49: 665–669.
Leach S A, Lee G T, Edgar W M . Remineralisation of artificial caries-like lesions in human enamel in situ by chewing sorbitol gum. J Dent Res 1989; 68: 1064–1068.
Creanor S L, Strang R, Gilmour W H, et al. The effect of chewing gum use on in situ enamel lesion remineralisation. J Dent Res 1992; 71: 1895–1900.
Kashket S, Yaskell T, Lopez L R. Prevention of sucrose-induced demineralization of tooth enamel by chewing sorbitol gum. J Dent Res 1989; 68: 460–462.
Steinberg L M, Odusola F, Mandel I D . Remineralising potential, antiplaque and antigingivitis effects of xylitol and sorbitol sweetened chewing gum. Clin Prev Dent 1992; 14: 31–34.
Gelhard T B, Arends J. In vivo remineralisation of artificial subsurface lesions in human enamel. I. J Biol Buccale 1984; 12: 49–57.
Kandelman D, Gagnon G. A 24-month clinical study of the incidence and progression of dental caries in relation to consumption of chewing gum containing xylitol in school preventive programs. J Dent Res 1990; 69: 1771–1775.
Manning R H, Edgar W M . In situ de- and remineralisation of enamel in response to sucrose chewing gum with fluoride or non-fluoride dentifrices. J Dent 1998; 26: 665–668.
Mouton C, Scheinin A, Mäkinen K K . Effect of a xylitol chewing gum on plaque quantity and quality. Acta Odontol Scand 1975; 33: 251–257.
Topitsoglou V, Birkhed D, Larsson L A, Frostell G. Effect of chewing gums containing xylitol, sorbitol or a mixture of xylitol and sorbitol on plaque formation, pH changes and acid production in human dental plaque. Caries Res 1983; 17: 369–378.
Söderling E, Mäkinen K K, Chen C Y, Pape H R Jr, Loesche W, Mäkinen P L . Effect of sorbitol, xylitol, and xylitol/sorbitol chewing gums on dental plaque. Caries Res 1989; 23: 378–84.
Mickenautsch S, Leal S C, Yengopal V, Bezerra A C, Cruvinel V. Sugar-free chewing gum and dental caries – a systematic review. J Appl Oral Sci 2007; 15: 83–88.
Deshpande A, Jadad A. The impact of polyol-containing chewing gums on dental caries. A systematic review of original randomised controlled trials and observational studies. JADA 2008; 139: 1602–1614.
Scientific Opinion on the substantiation of a health claim related to sugar-free chewing gum and neutralisation of plaque acids which reduces the risk of dental caries pursuant to Article 14 of Regulation (EC) No 1924/2006. EFSA Journal 2010; 8: 1776.
Scientific Opinion on the substantiation of a health claim related to sugar-free chewing gum and reduction of tooth demineralisation which reduces the risk of dental caries pursuant to Article 14 of Regulation (EC) No 1924/2006. EFSA Journal 2010; 8: 1775.
Health Canada. Summary of Health Canada's Assessment of a Health Claim about Sugar-Free Chewing Gum and Dental Caries Risk Reduction. January 2014. Available online at: http://www.hc-sc.gc.ca/fn-an/alt_formats/pdf/label-etiquet/claims-reclam/assess-evalu/gum-gomme-dental-carie-dentaire-eng.pdf (Accessed September 2015).