noun
dental floss
Standard term for dental floss; literally 'thread toothpick'.
毎晩、寝る前に糸ようじを使っています。
I use dental floss every night before bed.
Compound of 糸 (thread) and 楊枝 (toothpick), literally 'thread toothpick'. The spelling 糸ようじ is common because 楊枝 is often written in kana.