How does xylitol prevent cavities?

Xylitol produces its anti-cavity effect by way of several different mechanisms.

The first research evaluating the use of xylitol to prevent tooth decay was performed in Finland in the late 1960's. Since that time a number of observation studies and field trials have been performed, throughout the world.

Burt (2006), as a part of his work associated with the paper "The use of sorbitol- and xylitol-sweetened chewing gum in caries control" published in the Journal of the American Dental Association, reviewed much of this literature. Included in his overview was a table that listed the different oral benefits that studies had attributed to the consumption of xylitol products. We've listed these effects here and with each have provided an explanation of the science associated with them. You will no doubt notice that few of the individual explanations stand totally on their own but instead each is typically similar to and overlapping with other explanations.

(You may find that you want to read our brief outline describing how cavities form before reading on.)

Xylitol is a true tooth decay preventive.

What's so wonderful about xylitol is that its use can actually help to prevent conditions where the process of tooth decay formation is capable of taking place. This is in direct comparison to the mechanism of fluoride whose preventive nature relies upon its ability to help in the repair tooth enamel that has already been damaged. This is not to imply that one is better than the other. Both approaches are very valuable and both should be taken advantage of.

The mechanisms of xylitol:

1) The bacteria that cause tooth decay are not able to ferment xylitol.

(More information about this topic: Why can't cariogenic bacteria metabolize xylitol? >> )

Tooth demineralization (cavity formation) is prevented.: Since the cariogenic (cavity forming) bacteria that live in dental plaque do not ferment xylitol, collectively they produce reduced quantities of acidic byproducts. This means that the environment at the tooth-dental plaque interface will be comparatively less acidic. As a result, conditions that favor the tooth demineralization process (tooth decay formation) will be less likely to exist.
The cariogenic bacteria that live in dental plaque do not proliferate.: All of the different types of bacteria whose presence can cause tooth decay are collectively known as cariogenic bacteria. A characteristic that each of these types of bacteria has in common is that they all thrive in a low pH (acidic) environment. Because the presence of xylitol inhibits the ability of these bacteria to create acidic byproducts, the dental plaque environment in which they live is less hospitable to their growth.

2) Xylitol exposure has an inhibiting effect on the growth of cariogenic bacteria and this may create a permanent change in their oral population.

The presence of xylitol creates a starvation effect on the population of cavity-forming bacteria that live in dental plaque (due to the fact that they cannot metabolize it). As a result, their population does not thrive and grow. The net effect is a suppression of the number of these bacteria in dental plaque. Due to these reduced numbers, it is less likely that they can create conditions suitable for the formation of tooth decay.

(More information about this topic: Why can't cariogenic bacteria metabolize xylitol? >> )
Long-term xylitol exposure has an affect on selecting which specific strains of cariogenic bacteria will predominate in dental plaque. The growth of xylitol-sensitive strains, types of bacteria that do not thrive in the presence of xylitol, will be inhibited. In comparison, the numbers of xylitol-resistant bacteria, those types that have altered metabolic pathways and therefore are not affected to the same degree by the presence of xylitol, will over time predominate. Because xylitol-resistant bacteria are less capable of causing tooth damage than their more virulent counterparts, the population change created by the long-term consumption of xylitol produces an anti-cavity effect.

(More information about this topic: The effect of xylitol on populations of cariogenic bacteria. >> )

3) Xylitol reduces the accumulation of dental plaque on tooth surfaces.

Due to the inability of cariogenic bacteria to metabolize xylitol, they will experience a starvation effect. This reduced state of nutrition will affect their ability to proliferate. The growth in the quantity of dental plaque will therefore be stifled.

(More information about this topic: Why can't cariogenic bacteria metabolize xylitol? >> )
It has been suggested that with long-term xylitol exposure, the predominant type of cariogenic bacteria that live in dental plaque changes from xylitol-sensitive strains to xylitol-resistant ones. Research has suggested that xylitol-resistant bacteria are less capable of adhering to and therefore colonizing tooth surfaces.

(More information about this topic: The effect of xylitol on populations of cariogenic bacteria. >> )

4) Xylitol use promotes conditions that favor tooth remineralization.

Tooth demineralization takes place when the environment at the tooth-dental plaque interface is acidic (pH 5.5 and below). During those times when the environment at this interface is relatively less acidic, tooth remineralization (a process where mineral content available in the oral environment is redeposited on the tooth in those localities where demineralization has previously occurred) has potential to take place.
Since with xylitol use the pH of dental plaque remains comparatively less acidic (due to the fact that fewer acidic byproducts are created by the bacteria that live in the plaque), a condition exists where tooth remineralization can occur more frequently, even to the point of being the dominantly occurring process.
The xylitol molecule itself may help to promote the remineralization of demineralized tooth structure. Studies have shown that samples of demineralized tooth enamel immersed in a solution that provides a suitable environment for tooth remineralization and includes 20% xylitol showed a greater degree of remineralization (especially in middle and deep layers) than remineralizing solution that did not contain xylitol. It has been suggested that this is proof that xylitol facilitates the movement of the calcium ion, therefore helping to promote tooth remineralization.

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