Cavities, technically called dental caries, are caused by a bacteria called Streptococcus mutans. This bacteria lives in the mouth and thrives on sugar and other carbohydrates. In the presence of carbohydrates, S. mutans produces acids that dissolve the enamel of teeth, causing cavities.

Strong evidence indicates that fluoride toothpastes help prevent cavities. These toothpastes are so widely used, in fact, that water fluoridation is probably of little to no value except in poorer, less developed countries where use of fluoride toothpastes is not so universal.23

Fluoride rinses may offer some additional benefit.16 However, there is little to no scientific support for the use of the much more expensive, professionally applied, fluoride varnishes.2

Principal Proposed Natural Treatments

Double-blind studies enrolling almost 4,000 people, mostly children, have found that the natural sugar xylitol can prevent cavities.3-8 These trials used xylitol-sweetened gum, candies, or toothpaste. The best evidence regards xylitol gum. One study suggested that gummi bears may be an effective alternative method of administering xylitol to children.24

In one of the largest of these trials, researchers tested gum sweetened with various concentrations of xylitol and/or sorbitol against gum sweetened with sucrose and a control group receiving no gum.4 This 40-month trial was completed by 861 children. Gum containing 100% xylitol reduced the incidence of cavities the most. However, all of the xylitol and sorbitol gum groups showed significant reductions in cavities as compared to the control group. In contrast, the children receiving sucrose-sweetened gum had a slight increase in cavities compared to the control group.

A double-blind, placebo-controlled study of 1,677 children compared a standard fluoride toothpaste with a similar toothpaste that also contained 10% xylitol.8 Over the 3-year study period, children given the xylitol-enriched toothpaste developed significantly fewer cavities than those in the fluoride-only group. Studies in adults and children have shown similar results for xylitol gum and candy.6,9

Another series of studies suggests that children acquire cavity-causing bacteria from their mothers, and that regular use of xylitol by a mother of a newborn child may provide long lasting protection to the child as well.10-12

Xylitol is thought to prevent cavities by inhibiting the growth of the Streptococcus mutans bacteria.13

For more information, including dosage and safety issues, see the full Xylitol article.

Other Proposed Natural Treatments

Another sugar substitute called sorbitol may work as well as xylitol for the prevention of cavities in children.3 However, xylitol appears to work better than sorbitol for preventing cavities in adults.

Friendly bacteria ( probiotics) have been proposed for the prevention of cavities, on the ground that they can fight harmful cavity-causing bacteria.17 The best evidence regards a probiotic product called Lactobacillus GG (LGG). In a double-blind, placebo controlled trial, 594 children aged 1-6 years old were given either normal milk or milk with LGG had been added.14 After the 7-month trial, the results showed significantly fewer cavities in the children receiving LGG.

One very preliminary study found suggestive evidence that use of a toothpaste containing the herb sanguinaria (bloodroot) plus fluoride is more effective for cavity prevention than fluoride alone.18

Weak evidence hints at benefits with chewing gum that contains chitosan.20 Cranberry juice has also shown a bit of promise,19 as has a special extract of hops called “hop bracts polyphenols.” 22

One study failed to find benefit through the use of calcium-rich chewing gum.21

Other natural treatments advocated for preventing cavities, but that lack any meaningful scientific support, include black tea, myrrh, and propolis.