In The Name of Allaah, The Most Merciful, The Bestower of Mercy.

Abu Burda narrated, “My father [Abu Musa – may Allaah be pleased with him] said, ‘I came to the Prophet [peace and blessings of Allaah be upon him] and saw him carrying a Siwaak in his hand and cleaning his teeth, saying, ‘U’, ‘U’, as if he was retching while the Siwaak was in his mouth'”.

Brief Reminder Regarding This Hadeeth

It is legislated to use the Siwaak on the tongue for a longer time. As for the teeth, what is more desired is that the Siwaak is made to come into contact with them widthways – across the mouth. Siwaak is not specified for use on the teeth only. (1)

Listen here: The Virtues Of The Siwaak By Shaikh Abu Khadeejah [may Allaah preserve him]: https://www.salafisounds.com/the-virtues-of-the-siwaak-by-abu-khadeejah/

The Siwaak – By Ustaadh Abu Humayd [Saalim – May Allaah preserve him]
https://learnaboutislam.co.uk/2017/08/08-explanation-fiqh-abu-humayd-saalim-manchester/

[Ref 1: Saheeh Al-Bukhaari. Hadeeth Number 244. Excerpt from ‘Faithful Baari 1/462-463. Publisher: Daarus Salaam 1st edition 1421AH (2000)]