I saw the Messenger of Allah ﷺ using the tooth-stick while fasting. Musaddad added in his version, "more times than I could count or number."
حدثنا محمد بن الصباح حدثنا شريك ح و حدثنا مسدد حدثنا يحيى عن سفيان عن عاصم بن عبيد الله
رأيت رسول الله ﷺ يستاك وهو صائم زاد مسدد ما لا أعد ولا أحصي
[Its chain of transmission is daif] Tirmidhi narrated it, in the Book of Fasting, chapter on what has been said about using the tooth-stick for the fasting person, hadith no. 725, from the hadith of Sufyan Thawri through this route, and he said, Hasan.Asim bin Ubaydullah is daif.