Enamel is the hardest substance in the body — but it can't regrow. Acids from bacteria feeding on sugar dissolve it.
How it works, step by step
Mouth bacteria ferment sugars into acid.
Acid pulls calcium and phosphate out of enamel.
Saliva and fluoride help put minerals back.
When acid wins too often, a cavity forms.
Evidence & sources
Fluoride helps prevent tooth decay by making enamel more resistant to acid and helping repair early decay. Evidence: strong. Known: Decades of research. Unknown: — Source: US CDC, About Fluoride (Community Water Fluoridation) (Current revision).
WHO recommends limiting free sugars to under 10% of energy, partly to reduce dental caries. Evidence: regulatory. Known: Based on systematic reviews. Unknown: — Source: World Health Organization, Guideline: Sugars intake for adults and children (2015).