Sugar-free gum in oral health A clinical overview

Working for better oral healthcare

SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW 1 Editorial review board

The Wrigley Oral Healthcare Program would like to thank the following people for their contributions:

• Michael Dodds, BDS, PhD, Oral Health Lead Scientist at the Wrigley Company, USA Contents • Michael Kelley, PhD, RD, Senior Principal Scientist in Scientific and Regulatory Affairs at the Wrigley Company, USA Page Section And further thanks to the authors of the previous version of this 4 Introduction booklet, from which this new version has been adapted. 6 The link between diet, nutrition • Simon M Roland, BDS (Lond) LDSRCS (Eng), Dental Advisor and caries development to Oral Healthcare in Action, General Dental Practitioner St. John’s Wood London, UK 12 Saliva – A review of its role in • Michael Edgar, DDSc, PhD, FDS, RCS (Eng), Emeritus Professor of Dental Science at the University of Liverpool, UK maintaining oral health and • Martin Thornhill MBBS, BDS, PhD, MSc, FDSRCS(Edin), FDSRCSI, preventing dental disease FDSRCS(Eng), Professor of Oral Medicine, University of Sheffield, UK • Colin Dawes, BDS, PhD, Professor Emeritus at the University 18 The oral care benefits of of Manitoba, Canada sugar-free gum About the Wrigley Oral 22 and sugar-free gum Healthcare Program (WOHP) 26 Recognition and endorsement WOHP partners with dental professionals worldwide, helping them improve their patients’ oral health through one extra simple and of sugar-free gum enjoyable step in their daily routine: chewing sugar-free gum after eating and drinking on-the-go. WOHP supports independent clinical 28 Frequently asked questions research into the oral care benefits of sugar-free chewing gum, including saliva stimulation, plaque acid neutralization and tooth 29 References strengthening. For more information, visit: www.wrigleyoralcare.com

Published by the Wrigley Oral Healthcare Program. April 2015.

2 SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW 3 Introduction Dental caries remains the most common of all chronic diseases in a number of countries. With a global prevalence of 35% for all ages combined, untreated caries in permanent teeth was the most common condition evaluated for the Global Burden of Disease (GBD) 2010 study.1 The World Health Organization (WHO) estimates that, worldwide, 60–90% of school children and nearly all (up to 100%) of adults have dental cavities, while almost 30% of people aged 65–74 have no natural teeth.2

Poor oral health has an adverse effect on general The understanding of the Global caries rates wellbeing and places a significant burden on public complex etiology and continue to present health expenditure through the cost of curative dental pathogenesis of dental caries a major public treatment.3 While the fluoridation of water supplies and has advanced significantly health concern. changes in lifestyle have all contributed to an overall over the past decade.5 This downward trend in the prevalence of dental caries,4 global increased level of understanding has led to new insights rates continue to present a major public health concern. and the development and implementation of new caries This suggests that new preventive strategies may be preventive measures, particularly among high-risk required to supplement existing measures in reducing the populations of children and adults.6 risk of dental caries and improving oral health. An important outcome of these shifting trends and insights around caries is an increased understanding of the oral health benefits of chewing sugar-free gum after eating and drinking. Research shows that chewing sugar- free gum results in a 10-fold increase in salivary flow rate, which enhances the ability of saliva to clear the mouth of debris and , neutralize acids, and support remineralization, all of which can help to reduce the incidence of caries.7,8

This booklet provides a detailed summary of the science behind the oral care benefits of sugar-free gum. To download additional resources and learn more, visit: www.wrigleyoralcare.com

4 SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW 5 The link between diet, nutrition and caries development Epidemiological studies have been used to try to establish the relationship between various types of diets and Oral health is related to diet in many ways. Early in development, nutrition their components to caries incidence.9,10 The cariogenic potential of a food is influenced by a number of factors, influences both craniofacial and tooth formation, and later in life, malnutrition including the ability of a food to remain in the oral cavity, may exacerbate periodontal and oral infectious diseases. However, the most its effect on plaque pH, as well as the sequence and frequency of food intake.11 significant effect is the local action of diet on the development of dental caries and enamel erosion.9 Figure 2: The Stephan Curve*

Figure 1: The mechanism of dental caries 7.0

6.5

6.0

Critical 5.5 value

Fermentable Demineralization pH

carbohydrates Acid

Acid 5.0 Acid

Soda Acid 4.5

CRISPS

4.0 0 5 10 15 20 25 30 35 40 Fermentation Minutes after glucose rinse

The Stephan Curve illustrates how plaque pH changes after the consumption of fermentable carbohydrate (i.e. glucose). The curve Acid pH decrease illustrates the pH value before the consumption of fermentable 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 carbohydrates (0min; minimum 12 hours without exposure), the initial decline in plaque pH after exposure to fermentable carbohydrates, the time when pH is below the ‘critical value’ (5.5), and the recovery phase. *Source: Bowen, William H. The Stephan Curve revisited. Odontology. 2013; 101:2–8.

6 SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW 7 Food retention There has been an Table 1: increase in snacking grouped according to food types and potential for plaque acid production following consumption* Research carried out by Edgar throughout the day, et al. regarding the cariogenic often while on-the-go, Least Most potential of a range of snack which can impact acidogenic acidogenic foods illustrates that, contrary oral health. Group 1 Group 6 to popular opinion, foods that are perceived to be “sticky”, such as caramel, tend Dates Peanuts Apple Banana to clear from the oral cavity faster than many other Raisins 12 foods. For example, after 15 minutes, white bread Fruit/Nuts was retained in higher quantities in the oral cavity than cake, chocolate or hard mints. Furthermore, beverages -filled Bread with jam which are perceived to clear quickly from the mouth sandwich Wholewheat cookies bread induce a sustained low pH level for as long a period as Bread with butter Apple pie Crackers Plain cookies 12 Potato chips Chocolate cookies “sticky” . Bagel Doughnuts Starch-based Cream-filled light Most cakes Plaque pH foods sponge cakes Breakfast cereal

Foods which lower oral pH below 5.5, known as the Caramels ‘critical pH,’ can negatively impact oral health.13 The Chocolate Jelly sweets Fruit acidogenicity of a range of snack foods can be seen in Licorice Table 1, taken from Edgar et al.12 It is important to note Soft sweets that a wide range of foods may be considered acidogenic. In addition, studies have demonstrated unanticipated Rock results when comparing the acidogenicity of various Boiled sweets Clear mints foods. A study by Rugg-Gunn et al., for example, found that ingestion of chocolate or apples resulted in a similar Hard sweets pH response.14

Collectively, these studies appear to suggest that the Lemon & lime Apple juice Chocolate- carbonated drink (unsweetened) Milk presence of fermentable carbohydrate from food leads flavoured milk Cola carbonated Orange juice to a decrease in oral pH, although the period of time drink (unsweetened) taken to return to resting pH levels may be related to Soft drinks the carbohydrate concentration. Most importantly, the return to resting pH levels is as equally dependent on Foods were grouped according to their acid-provoking potential, as determined by the lowest plaque pH reached after consumption, the buffering capacity of saliva as it is on the properties and the duration of the pH fall; where Group 1 = Least acidogenic (least reduction in plaque pH / shortest duration of pH fall) and of the food itself. Group 6 = Most acidogenic (greatest reduction in plaque pH / longest duration of pH fall). *Source: Adapted from Edgar WM, Bibby BG, Mundorff S, Rowley J. Acid production in plaques after eating snacks: modifying factors in foods. J Am Dent Assoc. 1975;90:418–25.

8 SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW 9 Frequency of eating Amount of food vs. plaque pH

Worldwide, eating habits are changing. There has been In the frequently cited Vipeholm study, inmates of a Research has demonstrated that even a small amount of an increase in snacking throughout the day, often while Swedish medical institute were fed increased sucrose or fermentable carbohydrate can produce a drop in plaque pH. on-the-go, and a decline in the consumption of the other foods in different patterns, and caries experience traditional three meals-a-day. This increased frequency of was monitored.13 Groups of patients receiving high levels A three-series study by Maiwald compared plaque acid eating can impact oral health by increasing the incidence of sucrose (up to 330g/day) with other meals, experienced development during the chewing of gum containing of dental caries; the more frequently that cariogenic food a minimal increase in caries. But if smaller quantities either sucrose, or , alone or after the is consumed throughout the day, the more frequently of sucrose were consumed between meals, very high consumption of sugar-containing foods, beverages, and the plaque pH falls and the greater the potential risk levels of caries ensued. The authors concluded that the gums. The second of the three series showed that after becomes to teeth for caries development.15,16 relationship was not, therefore, between the quantity of administration of a containing only 10% sucrose, sucrose and caries but rather between frequency of intake plaque pH decreased drastically – reaching a pH of less and caries experience.17 than 4.5 after about 20 minutes. In a third study, Maiwald et al. demonstrated the effect on plaque pH after the Figure 3: Frequency of eating vs. plaque pH* consumption of a “normal” breakfast. During the series, subjects consumed one roll. After consumption of Schematic representation of the changes in plaque pH in an individual who A) limits their food and drink intake to main meals the roll, pH dropped relatively quickly to below 4.5 and it only or B) has frequent food and drink intake during the day. The critical pH is 5.5, below which teeth may begin to demineralize. took an hour before it had begun to rise. After 2 hours, the pH level had still not risen back above 5.5.17 8.0 A further report, of a study by Imfeld, examined the 7.0 correlation between the quantity of substrate and 6.0 intraplaque acid produced by telemetrically recording

Plaque pH Critical pH* 5.0 pH of 4-day old plaque in a subject during and following rinsing with increasing concentrations of aqueous 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time of Day sucrose . The results showed that sucrose is A Cereal, milk, Dinner of pasta, & orange juice Sandwich, banana & a glass of wine quickly fermented in plaques and regardless of the for breakfast carbonated drink for lunch & apple pie concentration, intraplaque pH drops immediately 8.0 following the sugar intake and throughout the entire two 7.0 minute rinsing period. Moreover, even a very low amount

6.0 of sucrose remaining in the mouth after the expectoration of 15 milliliters (ml) of 0.025% sucrose solution (which Plaque pH Critical pH* 5.0 equates to 0.00375 grams) was enough to cause the pH to drop below 5.7.18 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time of Day B Cereal, milk, Crackers & a Packet of raisins Dinner of pasta, & orange juice carbonated drink glass of wine for breakfast & apple pie Sandwich, banana, & a Snacking on a bag Mid-morning carbonated drink for lunch of cookies while coffee & a cookie watching TV

*Source: Adapted from Marsh PD and Martin MV. Oral Microbiology. 5th Edition. Churchill Livingstone, 2009.

10 SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW 11 Stimulated saliva is produced in response to a •  Remineralization of A core goal in caries Saliva – A review of its mechanical, gustatory, olfactory, or pharmacological enamel with calcium prevention is promoting stimulus, contributing to around 40-50% of daily salivary and phosphates the natural protective production.20 The Salivary Flow (SF) index is a parameter •  Tissue repair mechanisms of saliva. role in maintaining oral allowing stimulated and unstimulated saliva flow to be classified as normal, low or very low (hyposalivation). In 2. Facilitating eating and speech adults, normal total stimulated SF ranges 1–3 mL/minute, •  Food preparation, enhancing chewing, low ranges 0.7 –1.0 mL/minute, while hyposalivation is the clearing of food residues and swallowing health and preventing 19 characterized by a stimulated SF <0.7mL/minute. •  Digestion, food breakdown with enzymes •  Enhancing taste dental disease Key functions •  Enabling speech by lubricating the moving oral tissues Saliva plays a significant role in maintaining oral health, helping to build and The two major functions of saliva are:19 1. Protection of the oral and peri-oral tissues In addition, saliva is used in diagnostic testing maintain the health of soft and hard tissues. When saliva flow is reduced, • Lubrication • Bacterial, yeast, and viral counts indicating oral health problems such as dental caries and oral infections can develop. • Dilution of sugars after food and drink intake caries activity and altered immune responses, •  Antimicrobial and cleansing activity, degrading as well as many diagnostic tests for oral and Composition and production some bacterial cell walls and inhibiting growth systemic diseases •  Buffering (neutralizing) acid production •  Hormonal balance to identify steroids and Saliva is an exocrine solution consisting of 99% water. by the autonomic nervous system, while minor glands and controlling plaque pH with bicarbonate sex hormones The remaining 1% consists of a variety of electrolytes and (labial, lingual, buccal and palatine), distributed around proteins.19 These components combined are responsible the oral cavity, produce the remaining saliva (<10%).19 for the various functions attributed to saliva.19 Minor salivary glands in lips and oral mucosa Figure 5: Salivary glands and saliva function (especially buccal) are collectively responsible for At rest, without exogenous or pharmacological 8-10% of unstimulated salivary flow. Saliva is formed primarily (approximately 90%) from the stimulation, there is a small, continuous salivary flow, an Parotid salivary gland secretions of the three paired major salivary glands, the unstimulated secretion, present in the form of a film that • Serous, watery secretions 19 submandibular (around 65%), parotid (around 20%) and covers, moisturizes, and lubricates the oral tissues. This • High inorganic content sublingual (around 5-7%).19 These glands are controlled flow of saliva at rest is in the region of 0.4–0.5mL/minute (calcium, bicarbonate) in healthy subjects.19 • Responsible for 20% of unstimulated salivary flow Figure 4: Factors affecting the development of dental caries This proportion rises to 50-60% for stimulated salivary flow Inside the mouth Outside the mouth • Bacterial composition of the biofilm General health Environment • Plaque pH • Medical history • Diet • Salivary flow rate (stimulated • Hormones • Frequency of eating Submandibular and unstimulated) • Age • salivary gland • Buffering effect of saliva • Genetic heritage • Fluoride • Mixture of serous and mucous • Food retention secretions 2+ 3- • Medical treatment Sublingual salivary gland • Inorganic compounds (Ca and PO4 ) • Responsible for 65% of unstimulated salivary flow • Mucous secretions (more viscous) • Responsible for 5-7% of unstimulated salivary flow

12 SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW 13 Saliva and dental caries Figure 6: The process of tooth remineralization

In addition to moderating microbial factors and encouraging preventive dietary behaviors, a core goal in caries prevention is promoting the natural protective mechanisms of saliva.21

The pH of is a key factor in the balance between acid demineralization of the teeth and the remineralization Demineralization of the initial caries lesion. Plaque pH falls each time acid accumulates in the plaque due to bacterial acid production AcidA following the consumption of fermentable carbohydrates – mainly sugars – in foods and drinks. Conversely, plaque Acid pH rises when the acids are washed away or neutralized by Acid saliva, which contains the important buffer, bicarbonate.19

In healthy teeth, the loss of minerals is balanced by the Acid reparative mechanisms of saliva. This equilibrium can be depicted chemically by the equation overleaf – see 10 Ca2+ + 6 PO 3- + 2 OH- Figure 6 opposite.22 4 Ca (POPO ) (OH)(OO When the saliva pH or the plaque pH is below a ‘critical value’ 10 4 6 2 of about 5.5, the saliva or plaque becomes unsaturated with respect to tooth mineral.23 As a result, can begin to dissolve. However, when the pH is above this value, Saliva the saliva and plaque are supersaturated with respect to tooth mineral. The calcium and phosphate ions in saliva then start to repair any damaged mineral crystals in the enamel – the process of remineralization.19

Thus, acidic conditions contribute to bringing phosphate and hydroxyl ions below saturation levels, allowing the Remineralization solid hydroxyapatite crystals of the tooth mineral to dissolve. If above saturation levels, the chemical reaction will move towards remineralisation and any damaged crystals will be Key: 2+ 3- repaired by the acquisition of ions from the solution.19 Ca PO4

Stimulation of saliva flow results in an increase in the washing out of acids (and sugars), and also an increase in the amount and concentration of bicarbonate buffer and of remineralizing ions.19

14 SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW 15 Salivary gland disorders gland hypofunction, including tricyclic antidepressants, antihistamines, certain antihypertensives and drugs with The importance of the salivary glands – and saliva – sympathomimetic actions (e.g. some bronchodilators).28 tends to go unnoticed until the glands malfunction. The consequences are severe and impact greatly on quality of In the past, it was commonly believed that dry mouth life. Symptoms may start with a constant thirst, difficulty and declining salivary function were purely a natural in speaking, eating, tasting and swallowing foods and consequence of aging. While it is true that salivary progress to and oral infections.24 The most gland dysfunctions are more prevalent in older common salivary gland disorder is , which is populations, studies suggest that salivary gland the subjective feeling of dryness throughout the mouth. dysfunction is due to a combination of aging per se and the higher incidence of chronic illnesses and the Xerostomia greater use of drugs by the aging population – both of which can impact the production of saliva.29 Studies conducted on outpatients and in the general population show that xerostomia affects about 1 in 4 people.25 Salivary flow rate patterns demonstrate both daily and seasonal variation, with peaks in mid- afternoon and higher flow rates in the winter than in the summer. During sleep, saliva flow rate is minimal.26 People who complain of dry mouth do not necessarily have a very low flow rate; conversely, those with a low unstimulated flow rate do not always complain of dry mouth. It is therefore of greater significance to establish whetheror not the flow rate has changed adversely in a particular individual.27

Reduced salivary flow is due to hypofunction of the salivary glands. This may be reversible, due to anxiety, acute infection, dehydration or the effects of some drugs. There are also some permanent causes of xerostomia such as congenital abnormalities, Sjögren’s syndrome, HIV/ AIDS and the result of head and neck irradiation. However, xerostomia is most commonly associated with the use of xerogenic drugs. More than 400 medicines induce salivary

16 SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW 17 The oral care benefits of sugar-free gum Clinical studies have shown that chewing gum stimulates the salivary glands to produce a strong flow of saliva (a 10–12 fold increase over unstimulated saliva).8 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. As this chapter will illustrate, 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 remineralization – all of which can help reduce the incidence of caries.

Debris removal and plaque neutralization

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, falling after about 5 minutes to around 2 mL/minute, and slowly thereafter to 1.2–1.5 mL/minute at 20 minutes.8

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.19 At the same time, the phosphate of saliva changes as a result of the rise in pH, so that 3- 19 a higher proportion of it is in the form of PO4. . The calcium content of saliva rises as well.19

18 SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW 19 The observation by Hein et al. of a “large and sustained salivary stimulation ceases Chewing sugar- Figure 7: Chewing sugar-free gum for twenty rise in plaque pH” when gum was chewed after sugar shortly after the final swallow free gum enhances minutes after meals and snacks has been proven intake30 has been confirmed by many studies conducted and salivary composition production of saliva to help keep teeth healthy around the world.31-39 returns to normal in less than and its oral health 5 minutes, so the protective benefits. These changes in the composition of stimulated saliva effects are not mobilized when lead to a greater ability to prevent a fall in pH and most needed. WITH SUGAR-FREE GUM a greater tendency to favor hydroxyapatite crystal growth.20 In addition, the greater volume and rate of In order to enhance salivary protection during the acid flow of stimulated saliva results in an increased ability exposure, a stimulant is needed which is not itself to clear sugars and acids from around the teeth.20 These cariogenic and the effects of which last as long as WITHOUT SUGAR-FREE GUM three properties of saliva are correlated to the caries possible.41 Sugar-free chewing gum is a very practical and susceptibility of the individual and are all enhanced by acceptable stimulus that can be chewed after the intake salivary stimulation. of fermentable carbohydrates, and brings no undue calories. Several studies have shown that chewing sugar- The action of stimulated saliva is most important during free gum stimulates saliva production which can last up the plaque acid threat during the 20–30 minutes after to two hours. 26 a cariogenic food intake.40 However, with most foods, Enhancing remineralization remineralization was significant with a 30 minute chewing period, but not after a 20 minute chewing The concentrations of ions which make up the lattice period.43 These reports were broadly confirmed by 2+ 3- - 44 structure of hydroxyapatite (Ca , PO4 , OH ) are higher Creanor et al. and are consistent with a reduction in stimulated than in unstimulated saliva; thus in enamel demineralization (measured as iodide stimulated saliva is a more effective medium for penetration) by chewing sorbitol gum, as found by remineralizing enamel crystals damaged by initial acid Kashket et al.45 The findings of Steinberg et al.46 further exposure. In an in situ caries study by Leach et al.42 support these studies; briefly that six-week use of subjects chewed sorbitol gum for 20 minutes after meals sugar-free gum (sweetened with either xylitol or sorbitol) and snacks (five times daily). The gain or loss of mineral resulted in an increase in plaque calcium and a significant content of human enamel slabs, bearing artificial reduction in plaque index, compared with no gum. lesions and mounted intra-orally for 3 weeks, Remineralization in vivo is generally considered to was then measured and compared with be a slow process47 and significant remineralization results after similar periods without occurred within 3 weeks. These model experiments gum chewing. Remineralization of suggest that sugar-free gum use can help prevent decay the enamel lesions occurred both by tilting the equilibrium towards remineralization and with and without gum, but with away from demineralization. gum the remineralization was approximately doubled. Furthermore, the use of sugar-free gum has been associated with a reduction in the quantity and A similar experiment demonstrated development of plaque,48-51 and a reduction in the acid- that, even with sucrose gum, forming ability of plaque.52

20 SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW 21 German and French scientists first discovered xylitol in other bacteriological properties The addition of Polyols and the 1890s. Although approved as a dietary food additive (e.g. less acid production).56 xylitol to sugar-free in 1963 by the U.S. Food and Drug Administration (FDA), gum is a promising the visibility and use of xylitol as an oral care tool These benefits of xylitol are way to deliver the sugar-free gum remained relatively dormant until the 1970s, when particularly relevant in the proven oral health Finnish researchers demonstrated that xylitol possessed context of modern eating habits. benefits of sugar- significant dental benefits.56 Around the world, people free gum to patients. Sugar-free gums are traditionally sweetened with () are eating more frequently The oral health benefits of xylitol relate to its impact throughout the day, often while on-the-go, which puts sweeteners. Examples of polyols include sorbitol, , xylitol, and blends on Mutans Streptococci in the plaque and saliva. teeth at higher risk of decay.15,16 Plaque pH falls due of these compounds.53 Polyols have a positive impact on oral health: they help Research demonstrates that xylitol disrupts the energy to bacterial acid production after eating or drinking 54 production processes of Mutans Streptococci, leading fermentable carbohydrates. When used in oral care to stimulate production of saliva and do not cause a drop in plaque pH. to cell death. Additionally, studies have shown that products such as sugar-free gum, xylitol can help change The net result is an increase in the plaque pH, thereby protecting teeth after people who consumed clinically effective levels of xylitol the bacterial environment in the mouth and help keep demonstrated Mutans Streptococci strains which had a teeth healthy after eating and drinking. eating and drinking. Most recent systematic reviews have concluded that the reduced capacity to adhere to teeth and a reduction in regular use of polyol combination chewing gum leads to a reduction in dental caries and is an effective addition to oral health regimens.55

Xylitol

Xylitol is a five-carbon sugar polyol that is currently approved for use in foods, pharmaceuticals, and oral health products in more than 35 countries around the world. It occurs naturally in small amounts and is the constituent of many , including fruits and vegetables such as raspberries, strawberries, plums, lettuce, , cauliflower and . It is also produced through microbial processes, including fermentation and enzymatic processes in bacteria, fungi, and yeast.56,57 In fact a human adult can make as much as 15 grams of xylitol per day as a by-product of normal glucose metabolism.58 It can also be manufactured, which is the predominant method of obtaining xylitol today. In comparison to other forms of sweetener, including sorbitol and other six-carbon alternative sweeteners, xylitol is bacteriostatic, inhibiting the growth of bacteria.59

22 SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW 23 Figure 8: The role of xylitol in remineralization The author of a review article published in the journal of the American Dental Association (ADA) compared the caries- inhibitory action of sorbitol- and xylitol- sweetened chewing gum and assessed the role of these products in caries prevention by reviewing a range of studies including Fermentable Bacteria Xylitol Remineralization randomized controlled trials with carbohydrates OH substantial numbers of participants, HO OH and observational studies. OH OH Soda

CRISPS He found that when compared with sugar- sweetened gum, sorbitol-sweetened gum No fermentation Saliva stimulation had low cariogenicity when it was chewed no more than three times-per-day and that xylitol-sweetened gum was non-cariogenic No acid pH increase in all of the protocols tested. He also

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 reported that some studies had claimed

2+ 3- that xylitol-sweetened gum had an anti- Key: Ca PO4 cariogenic effect, but suggested that these claims need further study.

The author came to two conclusions:

Building on the work started by the Finnish researchers in While clinical studies of products containing xylitol, 1. That the evidence is strong the 1970s, scientists throughout the past forty years have such as confectionary and lozenges, have shown mixed enough to support the regular conducted numerous studies to measure the oral health results on oral care benefits, studies of sugar-free gum use of xylitol-sweetened gum benefits of xylitol, particularly its effect on dental caries.56 containing xylitol have consistently shown a significant as a way to prevent caries reduction in the incidence of caries over time. Four studies 2.  Xylitol can be promoted as a As noted by the American Academy of Pediatric Dentistry stand out because they included sugar-free gum products public-health preventive measure. in 2011, several clinical studies have demonstrated sweetened with xylitol only, or a mix of xylitol and a decrease in both overall caries rates and the rate of sorbitol. One study observed the greatest reduction in the The authors further concluded that chewing progression of caries in children exposed to daily xylitol risk of additional caries with a gum which contained 100% xylitol-sweetened gum, especially for use for 12–40 months, and long-term benefits in caries of polyol as xylitol.56 patients who like chewing gum, can be reduction have been demonstrated up to five years after a fitted readily into a regimen that includes person ceased consuming xylitol. Xylitol has been shown However, this study also demonstrated that the degree frequent fluoride exposure, good oral to work most effectively on erupting teeth, and some of risk reduction varied as much with the gum form hygiene and regular dental appointments.60 evidence suggests that pregnant women and nursing (e.g. pellets or sticks) as with the proportion of xylitol. mothers who consume xylitol may reduce the acquisition The remaining three studies, however, did not show an of S. mutans and dental caries by their children.56 advantage for xylitol only.56

24 SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW 25 Recognition and Additional recognition of the benefits of sugar-free gum The oral care benefits of chewing sugar-free gum are also Furthermore, the oral care benefits of chewing sugar-free recognized by the World Dental Federation (FDI). In its gum are supported by more than 20 national dental or endorsement of 2014 white paper, entitled ‘Oral Health Worldwide’,58 the dental health associations worldwide. FDI specifically recommended sugar-free gum as a simple and effective way for families and individuals to improve “Chewing sugar-free gum, like Extra, is proven to benefit sugar-free gum their oral health, alongside other equally essential oral dental health as it helps neutralize plaque acids.”- FDI care behaviors such as brushing teeth twice daily and The important role of sugar-free gum in oral care is widely recognized and accepted using fluoride . by experts, dental associations and regulatory authorities around the world.

The European Commission Health Canada

The European Commission (EC) has approved five oral More recently, Health Canada went further with their health claims for sugar-free chewing gum,61 one of the advice. Health Canada concluded that scientific evidence few food categories to gain such recognition. A health exists to support a claim about sugar-free chewing gum claim states, suggests or implies that a relationship and dental caries risk reduction.62 This claim is considered exists between a food category, or one of its constituents relevant and applicable to the general population of and health; they are required to be clear, accurate and Canada, since dental caries often begins to develop evidence-based. during childhood and continue into adulthood. The prevalence of dental caries is much higher in adults than Three claims: general function in children, and the process of caries development is the (EC authorized Article 13 claim) same in adults and children.62 1. Sugar-free chewing gum contributes to the neutralization of plaque acids. Health Claim 2. Sugar-free chewing gum contributes to the “Chewing sugar-free gum, three times per day after maintenance of tooth mineralization. eating/meals, helps reduce/lower the risk of dental 3. Sugar-free chewing gum contributes to the caries/tooth decay/cavities.”62 reduction of oral dryness.

Two claims: disease risk reduction (EC authorized Article 14 claim) 1. Chewing sugar-free gum helps neutralize plaque acids. Plaque acids are a risk factor in the development of dental caries. 2. Chewing sugar-free gum helps reduce tooth demineralization. Tooth demineralization is a risk factor in the development of dental caries.

26 SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW SUGAR-FREE CHEWING GUM IN ORAL HEALTH A CLINICAL OVERVIEW 27 Is there an association between chewing gum evidence, bruxism is best managed by occlusal Frequently and bruxism?68 appliances, counselling, changes in lifestyle, and Sleep bruxism is a stereotyped movement disorder pharmacological interventions. characterized by the grinding or clenching of the teeth asked during sleep. The majority of the population will at In relation to lifestyle interventions, it has been some time during their lifetime grind or clench their suggested that there is a link between chewing gum teeth but it becomes a pathological condition when a and bruxism, and several consumer health websites questions patient presents with severe tooth damage or complains recommend that patients suffering from bruxism should of non-restorative sleep. The cause of bruxism remains stop chewing gum. Whilst there is no clinical evidence unclear but it has been associated with a number of to support the link – nor the recommendations to stop factors including: tooth interference, psychosocial chewing gum – it is, nonetheless, widely accepted that Does chewing gum cause Temporomandibular Can chewing sugar-free gum help with weight loss? and environmental factors, brain transmitter and sufferers should avoid all unnecessary chewing in order joint disorders? Certain studies have suggested that some people may basal ganglia dysfunction. In the absence of definitive not to exacerbate their condition. Temporomandibular joint (TMJ) disorders are a cluster experience reduced desire to snack between meals when of related conditions affecting the masticatory muscles, chewing sugar-free gum. However, there is no specific the TMJ and associated structures. Around 1 in 10 evidence to suggest a correlation between chewing people in the general population have symptoms and sugar-free gum and the achievement or maintenance signs of TMJ disorders.63 The level of disorders of the of a healthy weight. temporomandibular joint and muscles of mastication References and how people respond to them vary widely and the Is it safe to chew sugar-free gum while wearing braces causes of TMJ disorders are not fully understood. Trauma, or dentures? 1. Marcenes W1, Kassebaum NJ, Bernabé E, et al. Global burden of 9. Moynihan P, Petersen PE. Diet, nutrition and the prevention of malocclusion and bruxism have been implicated but All Wrigley’s chewing gums are now specially oral conditions in 1990–2010: a systematic analysis. J Dent Res. dental diseases. Public Health Nutr. 2004;7:201–26. evidence is weak and only a small proportion of people formulated to stick even less to most dental work and 2013l;92:592–7. 10. White-Graves MV, Schiller MR. History of foods in the caries process. J with these disorders develop TMJ disorders.64,65 There teeth. However, there is no clinical evidence to support 2. World Health Organization. Oral health. Fact sheet N°318, April 2012. Am Diet Assoc. 1986;86:241–5. have also been suggestions that psychological factors Wrigley’s sugar-free gum as the most non-stick gum for Available at: http://www.who.int/mediacentre/factsheets/fs318/en/ 11. Touger-Decker R, van Loveren C. Sugars and dental caries. Am J Clin are involved but, while they may be exacerbating or denture wearers. It is advised that patients try various Last accessed November 2014. Nutr. 2003;78(Suppl.):881S–92S. maintaining factors, they are not likely to be causal. Wrigley sugar-free brands and formats in order to 3. World Health Organization. Oral health: what is the burden of oral 12. Edgar WM, Bibby BG, Mundorff S, Rowley J. Acid production in Research has found no evidence to suggest a causal link establish which feels best for them. disease? Available at: http://www.who.int/oral_health/disease_ plaques after eating snacks: modifying factors in foods. J Am Dent between gum chewing and TMJ disorders. burden/global/en/ Last accessed April 2015. Assoc. 1975;90:418–25. Does sugar-free gum provide relief for patients 4. Bagramian RA, Garcia-Godoy F, Volpe AR. The global increase in 13. Gustafsson BE, Quesnel CE, Lanke LS et al. The Vipeholm dental caries What happens to gum that is swallowed? with xerostomia?66,67 dental caries: a pending public health crisis. Am J Dent. 2009;22:3–8. study; the effect of different levels of carbohydrate intake on caries Gum is not designed to be swallowed. However, if it is, There have been a number of studies that have shown 5. Bowen WH. Do we need to be concerned about dental caries in the activity in 436 individuals observed for five years. Acta Odontol it simply passes through the gastrointestinal system that chewing gum increases salivary flow in patients with coming millennium? Crit Rev Oral Biol Med. 2002;13:126–31. Scand. 1954;11:232–64. within a few days, similar to roughage. xerostomia (subjective feeling of dryness throughout the 6. Fontana M, Zero DT. Assessing patients’ caries risk. J Am Dent Assoc. 14. Rugg-Gunn AJ, Edgar WM, Jenkins GN. The effect of eating some mouth) of varying etiology. Research suggests that in 2006;137:1231–9. British snacks upon the pH of human dental plaque. Br Dent J. Are ingredients in sugar-free gum bad for one’s health? xerostomic patients, the initial stimulated salivary flow 7. Stookey GK. The effect of saliva on dental caries. J Am Dent Assoc. 1978;145:95–100. Chewing gum is made of five basic ingredients – rate while chewing sugar-free gum is seven times greater 2008;139(Suppl.2):11S–17S. 15. Euromonitor International. Home Cooking and Eating Habits: Global sweeteners, corn , softeners, flavors and gum than the unstimulated flow rate. Chewing sugar-free 8. Dawes C, Macpherson LM. Effects of nine different chewing- Survey Strategic Analysis, 30 April 2012. Available at: http://blog. base. All of the ingredients used in Wrigley’s products gum has been shown to be one of the most preferred gums and lozenges on salivary flow rate and pH. Caries Res. euromonitor.com/2012/04/home-cooking-and-eating-habits- are safe for consumption and meet high domestic and treatments for xerostomia. 1992;26:176–82. global-survey-strategic-analysis.html Last accessed October 2014. international food regulations.

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