floss
n. uncountablen. a thin, strong thread used to clean the tight spaces between your teeth. Using it every day helps keep your gums healthy and prevents cavities.
n. a soft thread of silk or nylon used to remove food particles and plaque from between the teeth. Often coated with wax or fluoride to facilitate movement through tight interdental spaces.
You should use floss every night before you go to bed.
The dentist recommended a specific brand of waxed floss to help clean the narrow gaps between my back molars.
Regular use of dental floss is clinically proven to reduce the incidence of gingivitis by disrupting the bacterial colonies that thrive in areas inaccessible to standard toothbrush bristles.
Uncountable when referring to the material in general; countable when referring to a specific piece or type.