Does swallowing saliva after Fajr, while the taste of toothpaste lingers in the mouth, invalidate the fast?

Flavored dental floss does not harm the fast if used before Fajr, because saliva removes the flavor due to its scarcity, and it does not leave a substance. This is similar to the lingering taste of coffee or the like after brushing and rinsing; what is difficult to avoid does not break the fast. Scholars have a consensus that tiny food particles remaining between the teeth, which cannot be spit out and are swallowed, do not break the fast due to the difficulty of avoiding them. The hadith indicate the permissibility of using a siwak for a fasting person, which suggests that the lingering taste of it in the mouth does not affect the fast.