Established Sunnahs of the Prophet:
Using the Siwak Frequently.
Abu Hurairah (may Allah be pleased with him) reported
that the Messenger of Allah (peace and blessings of Allah be upon him) said:
"Were it not that I might cause hardship for my Ummah,
I would have commanded them to use the siwak before every prayer."
Agreed upon.
It is also from the Sunnah
to use the siwak upon waking from sleep,
when performing ablution (wudu),
when the odor of the mouth changes,
when reciting the Qur'an,
and upon entering the house.