Therapeutic doses of fluoride (1 ppm) like those supplemented in the drinking water in many areas of the United States serve to strengthen the enamel in children in their developing tooth buds. If the doses of fluoride in drinking water exceed 1 ppm the therapeutic affects are lost and you begin to see the detrimental effects like those in seen here in my patient. I imagine 50 % of my patients have fluorosis some much more severe than this.
Clearly the water must have excessive fluoride levels. We took water samples recently and recorded fluoride levels in excess of 8 ppm (8 times the therapeutic dose). Well I began to wonder why the fluoride levels were so high. Fortunately my sister in-law Ana is a geologist and was able to provide the following explanation:
As it turns out, the Rift Valley is quite renowned for the amount of fluorite deposits it contains. Fluorite is a calcium fluoride mineral that is typically found in hydrothermal deposits--basically the entire Rift Valley. It can occur in large crystal form or be nearly visible to the eye. It's very likely that since it's dissolvable, the river near your house is picking up fluoride as it flows over the basalt rocks. There isn't really anything you can do about that since it isn't a point source but rather occurs everywhere. Oddly enough, the WHO has found a connection with dental fluorosis and altitude. Even with similar fluoride concentrations in water, children at higher elevations seems to suffer more from dental fluorosis.
Furthermore, the black tea sold in Kenya has abnormally high amounts of fluoride, probably due to growing the tea leaves in volcanic soils enriched in fluorite. And, when you boil water containing fluoride it works to concentrate the fluoride (not get rid of it as some people think). So, even though it seems like a national past-time in Kenya, drinking Kenyan chai is most likely contributing quite a bit to the overdose of fluoride in the population there. A case study in Tibet showed that dental fluorosis improved when people limited their black tea intake. Also, do people cook with coal in Kenya? It's also been proven that high-fluoride ash (from high-fluoride coal) can be breathed in or ingested on food (like grilled maize) and this contributes, too.
Ana's explanation accurately portrays the habits of our area of Kenya. Black tea (chai) is taken at nearly every meal and in between, Kijabe and Tenwek Hospitals are at high elevation (over 6700 ft), people commonly cook with coal, drinking water is usually taken from the river or boar holes, and maize is a staple food. All of these additive habits cause fluorosis in the population in this area of Kenya and also in many missionary kids.
Is it treatable? The stains are somewhat intrinsic and difficult to hide. A procedure called "masking" entails removing the outer layer of enamel and hiding the stain with a thin layer of composite has reasonable results.
Interestingly enough I once asked one of my co-workers Erick an Oral Health Officer what the Kenyan's believed caused this staining of their teeth. "Eating hot potatoes causes your teeth to turn brown."