How does xylitol work?
The first dental research to investigate the use of xylitol in preventing cavities was performed in Finland (the "Turku Sugar Studies," published in 1975). Since that time, a number of additional studies have been performed, throughout the world.
In 2006, Burt reviewed this accumulation of data as a part of his work for the paper "The use of sorbitol- and xylitol-sweetened chewing gum in caries control." (Published in the Journal of the American Dental Association.)
Included in this publication was a tabulation of different dental-health benefits that various studies had attributed to xylitol use. We've outlined them below, and with each have provided an explanation of the science associated with them.
Xylitol can be used in conjunction with fluoride to prevent cavities.
Note: Xylitol is a true preventive.
Xylitol is special because it actually helps to prevent the conditions that allow cavities to form. That's in direct comparison to fluoride whose preventive nature is based upon its ability to assist in the repair of tooth enamel that has already been damaged.
This isn't to imply that one is better than the other. Both approaches are very valuable and both should be taken advantage of.
How xylitol prevents cavities -
1) Some types of cariogenic bacteria can't digest xylitol.
The inability of some types of decay-causing bacteria to use xylitol as a food source is beneficial in several ways.
a) Tooth demineralization is prevented.
Demineralization takes place when a tooth's surface is exposed to the acidic byproducts created by cariogenic bacteria as they feed on sugars.
Since some strains of these bacteria can't metabolize xylitol (a type of sugar), if it's provided for them as a food source less acid formation will take place. This, in turn, means that conditions favorable for tooth demineralization will be less likely to exist.
b) A less-than-ideal living environment is promoted.
Cariogenic bacteria thrive best when living in an acidic environment. Since they have trouble metabolizing xylitol, if it's given to them as a food source they'll produce fewer acidic waste byproducts. That means the dental plaque environment in which they live will be less favorable for their growth.
c) The starvation effect.
The presence of xylitol in a person's mouth creates a starvation effect for the cariogenic bacteria that live there. Due to the fact that they try but can't use it as food.
As a result, their population will not thrive and grow. And due to these reduced numbers, a lower level of acidic waste byproducts will be created and therefore it will be less likely that the conditions needed for cavity formation will exist.
d) Population changes.
Long-term xylitol exposure will ultimately influence which types of cariogenic bacteria are the dominant ones living in a person's mouth.
When it's present, the growth of xylitol-sensitive" strains (types of bacteria that cannot use it as a food source) will be inhibited. In comparison, the number of resistant bacteria (those types that can tolerate its presence) will, over time, predominate.
Because xylitol-resistant bacteria are less capable of causing tooth damage than their more virulent counterparts, this population change makes it harder for cavities to form.
2) Xylitol causes changes in dental plaque.
a) Less dental plaque.
As mentioned previously, the inability of some types of cariogenic bacteria to metabolize xylitol can result in a reduction in their numbers (and therefore reduce the total amount of dental plaque that forms). This can be due to both the Starvation-effect and Less-than-ideal-living-environment phenomenons described above.
b) Less adherent plaque.
With long-term xylitol exposure, the predominant types of cariogenic bacteria that live in dental plaque tends to change from xylitol-sensitive to resistant strains (see above). Research suggests that resistant types are less capable of adhering to, and therefore colonizing, tooth surfaces. (Being able to do so is an important step in cavity formation.)
3) Xylitol use promotes tooth remineralization.
Remineralization is a process that helps to reverse the damage caused by demineralization (the process that causes tooth decay). Two different mechanisms may be responsible for how xylitol is able to promote the former.
a) Less acidic plaque.
Demineralization takes place when the dental plaque lying on a tooth's surface is acidic (pH 5.5 and below). During those times when plaque is relatively less acidic, tooth remineralization has the potential to take place.
With xylitol use, the pH of dental plaque tends to remain relatively less acidic (see above). As a result, it's more likely that conditions will exist where tooth remineralization can occur more frequently, even to the point of being the dominantly occurring process.
b) Molecular-level effects.
The xylitol molecule itself may help to promote tooth remineralization.
Studies have demonstrated that samples of demineralized tooth enamel immersed in a solution that provides a suitable environment for remineralization and includes 20% xylitol show a greater degree of repair (especially in middle and deep layers of enamel) than equivalent solutions that didn't. This evidence suggests that xylitol assists in the movement of calcium ions.