Wa alaykum salam wa rahmatuLlahi wa barakatuHu,

Using siwak in front of others is not disliked. This is because it is established that the Prophet Muhammad did so. (‘Umdat al-Mufti wa al-Mustafti v. 1, p. 22) For example, Imam Bayhaqi related on the authority of Abu Musa that he entered upon the Prophet Muhammad while the Prophet (SallAllahu alahie wa sallam) was using siwak. (al-Sunan al-Kubra v. 1, p. 35)

And Allah knows best.

Shafiifiqh.com Fatwa Dept.