What causes cavities? The TED-Ed animation watched 7.6 million times, explained
Video: TED-Ed (external content, rights belong to the creator; HK Dental Guide adds commentary only) Original video · TED-Ed 網站顯示 760 萬次觀看（2026 年 9 月）
TED-Ed's animation "What causes cavities?", presented by Mel Rosenberg, has more than 7.6 million views on the TED-Ed site. It starts with archaeology — human remains from around 15,000 years ago already show cavities — then zooms into the tooth surface to show how bacteria in plaque turn sugar from food into acid that slowly dissolves the tooth. The World Health Organization says untreated decay in permanent teeth is the most common health condition worldwide.
What it means for you
Decay isn't "eat sugar, get a cavity" — it is plaque, sugar and time working together. Knowing how it happens explains why brushing, fluoride toothpaste and less sugar actually work.
Editors' take: the background
The World Health Organization (fact sheet, March 2025) explains that plaque converts free sugars in food and drinks into acids that destroy the tooth over time, and that adequate fluoride exposure is essential for prevention — it advises brushing twice a day with toothpaste containing 1,000 to 1,500 ppm fluoride. The NHS also advises spitting out after brushing rather than rinsing, so the fluoride stays on the teeth longer.
The video explains the mechanism; treatment and cost depend on the stage of decay. Our tooth-decay stages guide explains the difference between early decay and decay that needs root canal treatment.
Key points
- Decay happens when plaque bacteria turn sugar into acid that dissolves the tooth
- Brush twice a day with fluoride toothpaste (1,000–1,500 ppm)
- Spit out after brushing — don't rinse straight away
Source: TED-Ed
This is a news summary written by our editors, not medical advice. Please refer to the original source and seek professional advice for your own situation.
Questions readers ask
What fluoride strength should toothpaste have?
WHO advises adults to brush twice a day with 1,000–1,500 ppm fluoride toothpaste; for children, follow your dentist's or the Department of Health's guidance on amount and strength.
Should I rinse after brushing?
The NHS advises spitting out after brushing and not rinsing straight away, so the fluoride stays on the teeth longer.
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