The irrefutable importance of sugar as the principal dietary substrate that drives the caries process has led to a growing interest in sugar substitutes. These can be broadly classified as high-intensity sweeteners, which are noncaloric, and bulk sweeteners, which are caloric. Five high-intensity sweeteners—acesulfame potassium, aspartame, saccharin, sucralose and neo-tame—are classified as generally recognized as safe by the U.S. Food and Drug Administration (FDA). They are used mainly as a table sugar replacement and in diet beverages, and increasingly they are used in many reduced-calorie foods. Bulk sweeteners include a variety of dietary polyols that are used in baked goods and confectionery products such as chewing gum, candies, chocolates and mints; in oral care products such as dentifrices and mouthrinses; and in cough syrups and throat lozenges. The polyols used in the United States include sorbitol, xylitol, erythritol, isomalt (glucomannitol and glucosorbitol), lactitol, maltitol and mannitol.
Most of the perspective on whether sugar substitutes can be considered anticariogenic is shaped by the limitations of the classical methods of measuring caries by using the decayed, missing and filled teeth index with frank caries as the outcome measure, as well as the limited knowledge of the natural history of caries as a disease process. Traditional caries indexes are relatively insensitive to the dynamic nature of caries, as well as to the prospect that the disease process can be arrested and possibly reversed during its early enamel caries stages and even at later stages.
The oral environment is influenced by the presence of saliva, which favors tooth preservation. Demineralization leading to caries occurs when the duration and frequency of ingested fermentable carbohydrates (sugars) that interact with a biofilm-covered tooth surface result in acid formation, which overcomes the protective influences of saliva. In the postfluoride era, the threshold for caries progression has been raised, so a more highly cariogenic diet can be tolerated before caries occurs in many people.1 Any measure that shifts the caries process from demineralization toward remineralization will help support tooth preservation. The replacement of dietary sugar with sweeteners that cannot be metabolized or that are metabolized slowly by plaque microorganisms will prevent enamel demineralization and encourage remineralization in the presence of saliva and fluoride. If the frequency of sugar substitution is high enough, it can shift the caries process toward the maintenance of tooth structure and possibly remineralization, and it can help prevent caries—but not in the therapeutic sense of an agent such as fluoride. The additional mechanical and gustatory salivary stimulation across the extended period of product use is an added benefit of sugar substitutes when used in chewing gum and, to a lesser extent, in candies and mints.
High-intensity sweeteners are nonacidogenic; they cannot be metabolized by oral microorganisms to produce acids. Along with bulk sweeteners, high-intensity sweeteners can be considered noncariogenic when used in foods and beverages that do not contain sugars. No anticariogenic attributes have been ascribed to high-intensity sweeteners yet. Bulk sugar substitutes (polyols) that are hypoacidogenic (isomalt, sorbitol, mannitol, maltitol and lactitol) are considered to be of low or noncariogenic potential, and nonacidogenic sweeteners (xylitol and erythritol) have been characterized as non-cariogenic. Sugar-free foods and confectioneries containing polyols have FDA approval to be labeled with a "does not promote tooth decay" health claim.
Of the bulk sweeteners, xylitol has been the most studied and reviewed, and it is the most controversial.2–5 The controversy revolves around whether xylitol has an anticaries benefit and, therefore, is superior to the other polyols. The results of studies have shown that when sorbitol- and xylitol-containing chewing gum and candies were used three to five times per day, they had a caries-preventive effect in subjects compared with results in subjects who did not use chewing gum or candy, and xylitol generally had a larger caries-preventive benefit.4,5 Questions have been raised about whether the caries-preventive benefit of xylitol-containing chewing gum is due to salivary stimulation or to an antimicrobial effect. Unlike sorbitol, which can be metabolized slowly by some oral bacteria, xylitol has a bacteriostatic effect on mutans streptococci. It also has been reported to reduce mutans streptococci levels in plaque and saliva,6 block mother-to-child transmission of mutans streptococci7 and alter the acidogenic potential of plaque to subsequent sugar challenges.8 The results of direct head-to-head comparisons of sorbitol and xylitol have been mixed, and concerns have been raised about the independence and quality of the research.4
In summary, sugar substitutes can play an important role in shifting the caries process in favor of maintaining dental health, and they should be recommended as part of an overall preventive treatment plan for patients at high risk of developing caries. Although xylitol has anticariogenic properties, there is not sufficient evidence to recommend xylitol as a first-line anticaries strategy in light of the large body of evidence on the effectiveness of topical fluoride and dental sealants. However, xylitol-containing chewing gum and mints can be recommended as an adjunct to other preventive intervention strategies if cost considerations do not outweigh effectiveness.
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