Ancient Egyptians used a homemade paste of crushed ox hooves, ashes, and burnt eggshells to clean their teeth — around 5,000 years ago.
Healthy Teeth
In the early 1900s, a dentist in Colorado Springs noticed something strange: some of his patients had permanently stained teeth — and almost no cavities.
Why This Matters
Brushing, flossing, and going to the dentist are things most people do without thinking twice. But behind those everyday habits is a surprisingly recent, surprisingly weird scientific history.
For most of human history, nobody knew why some people got cavities and others didn't. That mystery wasn't solved by a toothpaste company — it was solved almost by accident, in a small town in Colorado.
The Science Story
In 1901, a young dentist named Frederick McKay opened a practice in Colorado Springs, Colorado. He immediately noticed something odd: many of his patients had brown, mottled stains on their teeth — a condition locals called "Colorado Brown Stain." Nobody knew what caused it.
McKay spent the next three decades investigating the stains, testing theories about diet, local minerals, and even the water supply. Along the way, he noticed something else strange: patients with the stained teeth almost never had cavities.
It wasn't until the 1930s, when chemist H. Trendley Dean joined the search, that the pieces came together. Dean measured fluoride levels in drinking water across dozens of towns and compared them to cavity rates in local children. Towns with naturally high fluoride had both more staining — and far fewer cavities.
That discovery led scientists to study fluoride's effect on teeth more closely, and eventually to test adding small, carefully measured amounts of it to toothpaste and some water supplies. A stain nobody wanted turned out to be the clue researchers weren't looking for.
Did You Know?
The toothbrush most of us recognize today — nylon bristles on a plastic handle — wasn't standardized until the 1930s.
Frederick McKay spent almost 30 years chasing the cause of "Colorado Brown Stain" before scientists connected it to fluoride.
H. Trendley Dean's research compared fluoride levels and cavity rates across 21 different towns to find the pattern.
What the Coloring Book Covers Coming Soon
The Healthy Teeth coloring book follows a curious young detective — much like Dr. McKay — piecing together clues about teeth, brushing habits, and the tools people have used to care for their smiles throughout history. Kids color their way through a dental office, a Colorado town, and a timeline of toothbrushes from twigs to nylon bristles.
For Parents & Educators
- Dr. McKay noticed the stains and the missing cavities for years before anyone figured out why. What questions would you ask if you noticed something unusual like that?
- What other everyday habits do you think scientists might still be studying today, the way McKay studied teeth?