This week, we offer the first of a two-part series on water fluoridation. The practice of adding fluoride to drinking water to prevent tooth decay has been controversial for some time. Why? What should we know about it?

You could listen through your local public radio station or get the live stream at 7 am EDT on your computer or smart phone (wunc.org).  Here is a link so you can find which stations carry our broadcast. If you can’t listen to the broadcast, you may wish to hear the podcast later. You can subscribe through your favorite podcast provider, download the mp3 using the link at the bottom of the page, or listen to the stream on this post starting on February 10, 2025.

Tooth decay is uncomfortable. When it leads to periodontal disease and tooth loss, it can have a negative impact on cardiovascular and cognitive health, as well as quality of life. Fluoridation has been employed as a public health intervention to improve dental health. What is fluoride and how does it work? Our guest, Dr. Gary Slade, explains the mechanisms that help fluoride strengthen tooth enamel. In particular, it becomes incorporated into the crystalline structure of the enamel in places where it has been attacked by acid.

It is very difficult to determine exactly how effective water fluoridation may be at reducing dental problems because it started before there were randomized controlled trial conducted. Comparing countries that use this technique to those that do not is imperfect, since there are often many other differences among them. One important difference could be the rigor of data collection and analysis. The only way to overcome that problem is to conduct a randomized controlled trial.

Dr. Slade and his colleagues have already begun exactly such a trial in Lenoir County, North Carolina. Families are assigned to either fluoridated or unfluoridated water. Because each household is provided with big 5-gallon jugs of water for their consumption, they have no way of telling which group they belong to. Nor does anyone else. This creates an effective “double-blind” situation for the trial. The investigators don’t yet have data on dental outcomes. That will be forthcoming, and it will provide a much better assessment of exactly how well fluoridation protects teeth.

Joe recalls the dentist of his childhood cautioning him to avoid sugar. Dr. Slade agrees that limiting the number of times a day that one consumes sweet snacks or sugar-sweetened beverages can make a difference in reducing tooth decay. We asked him to explain the difference between “caries” and “cavities.” Caries is the term for the process of tooth surface deterioration. A cavity is the result of that process. Cutting the amount of sugar we eat can definitely discourage that process.

Clearly, brushing teeth is critical to keeping them healthy. We discussed the amount of fluoride toothpaste we need to put on the toothbrush. It’s not nearly as much as depicted in toothpaste commercials. Dr. Slade also explained that flossing is most impactful when it comes to gum health rather than preventing caries. That is important, too. Healthy gums make it easier to keep your teeth and also promote general health.

Fluoridated water is the primary source through which we are exposed to fluoride. On the other hand, it is not the only source. Next week’s guest points out that formula-fed infants get a much higher dose, relatively speaking, than adults if their formula is made with tap water. In addition, we are all exposed to fluoride from nonstick pans and stain-resistant fabrics, antidepressants and anesthetics and a host of other sources. Next week, Dr. Bruce Lanphear will explain why he thinks this is a problem.

Gary D. Slade, BDS, DDPH, PhD, is the John W. Stamm Distinguished Professor of Dentistry at the University of North Carolina Adams School of Dentistry in Chapel Hill, NC. He conducts epidemiological studies of oral diseases including public health interventions for prevention of dental decay. His website is

Gary Slade, BDS, DDPH, PhD, is the John W. Stamm Distinguished Professor of Dentistry at the University of North Carolina Adams School of Dentistry in Chapel Hill, NC.

Bruce Lanphear, MD, MPH, is Professor of Health Sciences at Simon Fraser University in Burnaby, BC. His website is https://www.sfu.ca/fhs/about/people/profiles/bruce-lanphear.html

Bruce Lanphear, a health sciences professor at Simon Fraser University and an expert on lead toxicity.

The podcast of this program will be available Monday, February 10, 2025, after broadcast on Feb. 8. You can stream the show from this site and download the podcast for free. Next week, the show will focus on Dr. Lanphear’s research.

Download the mp3.