Wednesday, May 1, 2013

The weekly dose: xylitol-- a good augment to fluoride?

{About once a week we will examine the evidence pertaining to a health-related matter-- usually something that would be of interest to families with young children.  You should expect a thought out and concise summary of the issue along with several solid references-- there may or may not be a true conclusion.  Sometimes, “more research is needed”  really is the best answer that can be given.  Please leave me a comment if you have thoughts, questions, or another topic idea that you’d like addressed.}

When I was reading and writing about oral hygiene for children under two, I came across an interesting recommendation from the American Academy of Pediatric Dentists regarding maternal oral hygiene. In their recommendations on Infant Oral Health Care, they say that, "Evidence suggests that the use of xylitol chewing gum (at least 2-3 times a day by the mother) has a significant impact on mother-child transmission of MS [mutans Streptococci] and decreasing the child’s caries rate.”  It seems likely to me (or at least biologically plausible) that if chewing xylitol gum can reduce the transmission of bacteria it could also reduce the mother's susceptibility to get cavities herself.  I wanted to see what the evidence had to say about xylitol and gum chewing.

The question I'm interested in today is, is xylitol chewing gum effective at preventing dental cavities?

It turns out that xylitol has been talked about and studied for some time in relation to dental cavities.  The oldest applicable reference on Pubmed is from 1970-- "The effect on rat fissure caries of xylitol and sorbitol."  Despite the fact that study was published 43 years ago, and that there have been multiple published trials in the last decade there is still no firm consensus about xylitol, especially when it comes to the adult population (1).   The American Dental Association published a report on Non-fluoride Caries Preventative agents in 2011 and addressed many different preventative treatments to supplement fluoride use (2).

ADA recommendations (2)
In the report published by the ADA, the panel concluded that the evidence supporting adults chewing xylitol gum was relatively non-existent, and so this recommendation only earned a strength of "expert opinion".  In the figure I attached you can see that the strength of the recommendation for chewing xylitol (or another polyol gum) is actually "stronger" for children. This is because most of the research that has been done surrounding xylitol and chewing gum as an anti-caries agents have focused on children.

When studying xylitol chewing gum it can be difficult to distinguish between the gum and the xylitol, since it is  biologically plausible that gum chewing in itself could reduce the incidence of cavities.  This is because the act of chewing might both increase the rate at which any left over food is removed from the mouth, and increasing salivation(2).  Because of this, it is unfortunate that there has not been a study that compared xylitol gum to other sugar free gums.  This fact significantly contributes to the "weak," or "expert opinion" ratings that you see in the figure for the recommendations to use xylitol gum(2).

Earlier this year, a fascinating 3-year trial was published that looked at the effects of xylitol on the incidence of cavities in adults (1) (Medscape has a pretty good summary here, if you're interested but don't want to read the original).  This study did not look at chewing gum, but instead used xylitol lozenges.  Even though this study doesn't directly relate to my question, I think it is a well designed study (well, at least the study lasted longer than a year and was a randomized controlled trial)  and can contribute to our understanding of xylitol. The authors concluded that in adults, xylitol lozenges have little or no effect on caries.  Although they did see a small reduction in the incidence of cavities in the experimental group, it was not large enough to be significant.  One interesting observation the authors make is that because of the small magnitude of reduction in cavities (~10%), previously published trials could have either missed or magnified this relationship due to unintentional incorporation of bias.

So, where does all this leave us?  After nearly two weeks of thinking off and on about xylitol gum, do I have an answer for my question?  Is chewing xylitol gum an effective measure against dental cavities?  I think I can conclude that there is no strong, evidence-based support for this, but that there is a possibility that chewing (sugar free) gum may mildly help to reduce the incidence of dental cavities.  And, since the gum I buy contains xylitol, I will be chewing xylitol gum.  But, since the recommendations are so weak, I won't be seriously working on changing my gum chewing habits.  (Although, to be honest I'm chewing gum right now, and I think I've chewed a little more than previously since starting the post. ;) )

How about you? What are your gum-chewing habits?

(1) Bader, JD, et al. Results from the Xylitol for Adult Caries Trial (X-ACT). J Am Dent Assoc. 2013 Jan;144(1):21-30. Accessed from on 4/30/2013.

(2) Rethman, MP, et al. Non-fluoride Caries Preventative Agents: Full report of a systematic review and evidence-based recommendations. ADA Center for Evidence Based Dentistry, 3/24/2011. Accessed from on 4/30/2013

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