Caries is the medical term for tooth decay, the process where bacteria in your mouth create acid that eats tiny holes in your teeth. When your dentist examines your teeth and says “no caries,” that's good news: it means no cavities.

Here's how it happens: bacteria living in your mouth feed on sugars from food and produce acid as waste. That acid gradually dissolves the hard outer layer of your tooth, called enamel, creating weak spots that eventually become cavities. If left untreated, caries can spread deeper into the tooth, causing pain and potentially requiring a filling or even a root canal.

Dentists use this technical term, but when they talk to patients, they usually say “cavity” instead.

You can prevent caries through regular brushing and flossing, which removes bacteria and food particles before they can produce acid. That's why dentists recommend brushing twice a day and limiting sugary snacks. Unlike a scraped knee that heals on its own, teeth can't repair significant caries without a dentist's help, which makes prevention especially important.