Juneau, Alaska, may want to rethink their policy on water fluoridation after a paper published in BMC Oral Health found that the average number of carie procedures per child under six has jumped from 1.55 to 2.52 per year since the city voted to stop adding fluoride to the water supply in 2007.

Despite a raft of evidence to the contrary, some people believe fluoridated water can cause health problems such as cancer, osteoporosis, Down syndrome, chronic kidney disease, high blood pressure, and even lower intelligence. The truth is that science has repeatedly shown that in low levels (that is, less than one part per million) fluoride is perfectly safe – and can even be beneficial from a dental point of view.

When the city voted on the motion in 2007, experts anticipated a rise in dental cavity (or carie) procedures. Soon after, local dentists anecdotally said that this was indeed the case. Now, the numbers are in and a study examining Medicaid records before and after fluoridation ceased show that there has been a significant upsurge in the number of procedures taking place, just as predicted.

To test the effects of fluoridation, researchers at the University of Anchorage, Alaska, compared the Medicaid records of under 18s in 2003 (pre-fluoride cessation, when there was "optimal" community water fluoridation (CWF) exposure) to those of under 18s in 2012 (post-fluoride cessation, when there was "sub-optimal" CWF exposure). They found a positive correlation between fluoride cessation and the number of carie procedures for all age groups, but this trend was more extreme among the younger age bracket (i.e., children under 6 years old), most of whom would have never been exposed to fluoridated water. 

Based on the records of 853 children in 2003 and 1,905 children in 2012, overall rates of cavity procedures increased from 2.02 per year in 2003 to 2.35 per year in 2012. However, there was a rise of almost one procedure per year (1.55 versus 2.52) among children who were under six years old. The researchers suspect this is because the younger children would not have benefited from early exposure to fluoride, like the older children. 

"By taking the fluoride out of the water supply… the trade-off for that is children are going to experience one additional caries procedure per year, at a ballpark (cost) of $300 more per child," lead author Jennifer Meyer, a public health researcher, told local news outlet KTOO.

This is not the first study to link fluoridated water to better dental health, although studies specifically examining CWF discontinuation have been small in number and have produced mixed results. In fact, the science goes back to the 1940s when American researchers realized there were lower rates of tooth decay in areas with naturally higher levels of fluoride in the drinking water. This was reconfirmed in 2016, when the most comprehensive study of its kind found that fluoridation can reduce tooth decay by as much as 26 to 44 percent. 

But it's not just Juneau turning its back on fluoride. In 2011, Calgary became the largest city in the world to take fluoride out of their water supply – and in just five years, researchers noted an almost two-fold increase in cavities among elementary school children. And only last month, a city in Ontario, Canada, had to re-introduce fluoride to their water supply after everyone got tooth decay.