Answered by Shaykh Faraz Rabbani
Question: Assalamu alaikum wa rahmatullahi wa barakatuh,
My understanding is that ghusl is invalidated if, as a result of food pieces stuck between the teeth, water is unable to reach certain parts of the mouth. Would it then be advisable to floss each time one performs ghusl, as a precaution?Answer: Walaikum assalam wa rahmatullahi wa barakatuh,
I pray this finds you in the best of health and spirits.
Flossing isn’t required in ghusl.
Food that remains in the mouth or between the teeth is excused–or isn’t considered to prevent water from reaching the entire mouth–and thus doesn’t affect the validity of one’s ritual bath (ghusl).
There is no requirement nor expectation of flossing one’s teeth in one’s ritual bath (ghusl). It is an emphasized sunna to brush one’s teeth in the ritual ablutions (wudu).
Occasional cleaning between the teeth–which the Prophet (Allah bless him and give him peace) did using a fine toothstick (khilal)–is recommended, and flossing fulfills this.
[ref: Ibn Abidin, Radd al-Muhtar; works on Prophetic conduct (shama’il)]
And Allah alone gives success.