This article is sited from the ADA.
Introduction
The earliest evidence of humans chewing gum-like substances comes from the convergence of anthropology and dentistry at an archeological site in Sweden, where lumps of birch bark tar with tooth impressions of children and adolescents, dating back 9,000 years, have been found. The ancient Greeks seemed to have chewed on a similar substance, known as mastic, from which the word “mastication” likely derives. Native American Indians and Inuit chewed gum from spruce trees, a custom adopted by the Europeans who settled in New England.
The U.S. chewing gum market is divided by product type into sugared chewing gums and sugar-free chewing gums. Only sugar-free chewing gums are considered for ADA Seal of Acceptance. In the case of chewing gum, sugar is defined as monosaccharides (e.g., glucose, fructose, galactose) or disaccharides (e.g., sucrose, maltose, lactose) but does not include polyols such as xylitol, sorbitol, or maltitol. This is because these polyols are non-cariogenic sweeteners, meaning that they provide a sweet taste but are not a suitable substrate for bacteria in the mouth to use as an energy source. Excluding sugared gum from ADA Seal consideration is consistent with efforts to align with recommendations about sugar consumption that suggest limiting sugar intake to 10% or less of energy intake for optimal oral health.
Although there is some evidence that regular chewing of sugar-free gum may reduce caries risk, this is when it is in addition to, rather than a substitute for a regular oral hygiene routine consisting of twice daily brushing with a fluoride toothpaste and daily cleaning between teeth.
Oral Effects of Chewing Gum
Sugar-containing Chewing Gum
Sucrose, a disaccharide, is commonly used in sugar-containing chewing gum. Sucrose and other fermentable carbohydrates can be metabolized by oral bacteria. These bacteria (particularly S. mutans and Lactobacillus spp.) produce dental biofilm and acid, which can lead to enamel demineralization and caries. The potential cariogenicity of sugar-containing gum depends on the physical consistency, oral retention time of the gum, the frequency with which it is chewed, and the sequence of consumption (for instance, chewing sugar-containing gum before eating foods that reduce acid production will be less cariogenic than the reverse).
Sugar-free Chewimg Gum
As defined in the Code of Federal Regulations 101.60(c )(21CF 101.60(c )), a food or food substance such as chewing gum, can be labeled as “sugar-free” if it contains less than 0.5 g of sugars per serving. In place of sugar, high-intensity sweeteners such as acesulfame-K, aspartame, neotame, saccharin, sucralose or stevia are used to sweeten gum. Gum may also be sweetened with sugar alcohols such as erythritol, isomalt, maltitol, mannitol, sorbitol, or xylitol. Unlike sugar, these sweeteners are noncariogenic, since they are metabolized slowly or not at all by cariogenic plaque bacteria. These sweeteners contain fewer calories than sugar, but the U.S. Food and Drug Administration (FDA) categorizes aspartame and all of the aforementioned sugar alcohols to be nutritive sweeteners since they contain more than 2% of the calories in an equivalent amount of sugar.
Chewing sugarless gum after a meal can increase salivary flow by stimulating both mechanical and taste receptors in the mouth. The average unstimulated salivary flow rate for healthy people is 0.3-0.4 mL/min. The physical act of chewing stimulates salivary flow: simply chewing unsweetened, unflavored chewing gum base stimulates the salivary flow rate by 10-12 times that of the unstimulated rate. Flavors also act as salivary stimulants. The stimulated salivary flow rate is significantly greater while chewing sweetened and flavored gum as opposed to unsweetened, unflavored chewing gum base. Increasing saliva volume helps to dilute and neutralize acids produced by the bacteria in plaque on teeth. Over time, these acids can damage tooth enamel, potentially resulting in decay.
There are several mechanisms by which stimulated saliva flow may protect against dental caries. Increased saliva flow carries with it calcium and phosphate which can contribute to remineralization of tooth enamel; the presence of fluoride in the saliva can serve to replace enamel components magnesium and carbonate with the stronger, more caries-resistant fluorapatite crystals. Saliva can buffer the effects of acids in foods or drinks that could otherwise soften teeth’s enamel surface, and swallowing excess saliva created by stimulation clears acid. While unstimulated saliva does not have a strong buffering capacity against acid, stimulated saliva has higher concentrations of protein, sodium, calcium, chloride, and bicarbonate increasing its buffering capacity. Additionally, saliva contributes proteins to dental surfaces, creating an acquired enamel pellicle that protects against dental erosion. Clinical trials have found decreased caries incidence in subjects who chewed sugarless gum for twenty minutes after meals.
A 2021 systematic review and meta-analysis by Nasseripour et al. examined the use of sugar-free gum sweetened with xylitol and reported the use of sugar-free chewing gum resulted in a statistically significant reduction in the S. mutans load. This association between cariogenesis and S. mutans, the -0.42 effect size (95% CI: -0.60 to -0.25) is suggestive of benefit as an adjunct to recommended home oral hygiene.
Functional Chewing Gum
Functional chewing gum is the term given to chewing gum said to have function instead of or in addition to that of traditional chewing gum.
Active Ingredient Delivery System
Although using chewing gum may have appeal as a means of drug delivery, factors such as dosing and local effects of active ingredients on the oral cavity may be of concern. Notwithstanding, nicotine-containing gums are among are first-line pharmacologic therapies to assist with smoking cessation recommended by the U.S. Department of Health and Human Services. In addition, there has been aspirin-containing gum sold as an over-the counter (OTC) product, and there are several caffeine-containing gums, are commercially available OTC, some of which contain additional nutraceuticals for which claims (evidence-based or not) are made.
Enhanced Surgical Recovery
A number of systematic reviews published in the last 5 years have indicated that chewing gum may positively affect postoperative ileus following various types of surgical interventions (e.g., colorectal, gastrointestinal, gynecologic, urological).
Evaluating Masticatory Function
Research studies have utilized chewing gums with layers of color as a tool to evaluate chewing function in adults as well as the elderly. This type of evaluation is currently not in clinical use and availability of the chewing gums for this purpose may be limited.
Oral Mucositis
Oral mucositis is characterized by ulcerative and erosive lesions seen to occur in the oral mucosa after radiotherapy to treat head and neck cancer or high-dose chemotherapy used in the treatment of a variety of cancer. The systematic review used to inform the 2021 update to the American Society of Clinical Oncology (ASCO) clinical practice guidelines for the management of oral mucositis and xerostomia resulted in the inclusion of a new suggestion clarifying that chewing gum is not effective for prevention of oral mucositis in pediatric cancer patients who receive chemotherapy.
Xerostomia
In the 2021 update to the ASCO clinical practice guideline addressing xerostomia induced by nonsurgical cancer therapies, a cited systematic review included both sugar-free lozenges or chewing gum among the recommended interventions to help with xerostomia experienced after cancer treatment by chemotherapy or radiotherapy.