Fluoride is widely accepted as a cavity fighter today. However, at the start of the 20th century, it was completely unknown. The history of fluoride is interesting and strange.

The mystery of brown teeth

In 1901, Frederick McKay moved to Colorado Springs, Colorado to open a dental practice. He quickly observed that many of the locals suffered from brown stains on their teeth. Some of the stains were as dark as chocolate. McKay searched for a cause of the stains. In 1909, a dental researcher named Dr. G.V. Black arrived in Colorado to help McKay with the investigation. They worked together for six years and found that over 85% of children native to the town had brown stains, which they named “mottled teeth.” They were surprised to discover that mottled teeth were highly resistant to tooth decay. They noted the anti-cavity effects of the stain but did not tie it to a source at that time.

Mottled teeth in the 1920s

McKay went from Colorado Springs to Oakley, Idaho in 1923 to investigate new reports of tooth mottling in Oakley. Families reported that the stains began appearing shortly after Oakley built a new water pipeline to a warm spring five miles away. McKay advised town leaders to abandon the pipeline and use a nearby spring as their water source. The town did so, and the brown stains disappeared within a few years.

McKay also traveled to Bauxite, Arkansas, a town owned by an aluminum plant. The residents of Bauxite had mottled teeth while people in nearby towns did not. McKay asked the town to study the water. The aluminum plant’s chief chemist analyzed the water with sophisticated tools and found high levels of fluoride in the water at Bauxite. He wrote a letter informing McKay of the findings. He urged McKay to test samples from the other areas and look for increased levels of fluoride.

Enamel Fluorosis linked to fluoride

The National Institute of Health conducted a study on fluoride and enamel fluorosis (formerly referred to as teeth mottling) in the 1930s. The NIH concluded that fluoride levels up to 1.0 ppm could not cause enamel fluorosis, the brown stains on teeth. Researchers then looked again at McKay’s findings of anti-cavity effects and determined that low levels of fluoride would significantly improve oral health.

We know much more about fluoride in the 2010s and value its cavity fighting ability. Many municipalities add it to water sources. Most toothpastes, rinses and professional treatments also contain fluoride.