A cavity is a hole in your tooth caused by plaque, a bacteria-filled biofilm that produces acid from sugar, damaging the tooth. Brushing removes plaque from tooth surfaces, while flossing cleans between teeth where brushes can’t reach, preventing cavities—end of story.
We ask you to brush and floss twice a day because it takes 24 hours for bacteria to harm your teeth. Brushing at night is crucial since saliva, which protects against acid damage, decreases while you sleep. Going to bed with clean teeth prevents bacteria from running wild, especially as saliva slows with age or medication use.