Narrated Abu Huraira: Allah’s Messenger (ﷺ) said,

Were I not afraid that it would be hard for my followers, I would order them to use the siwak (as obligatory, for cleaning the teeth).

Sahih Bukhari
Reference: Sahih al-Bukhari 7240 (Wishes)
In-book reference: Book 94, Hadith 15

Let’s have a critical reasoning of this:

He didn’t make it fard, why? Lest it becomes hard for people. Therefore, doesn’t it imply that it is FARD when doing it is easy? Then let’s ask ourselves these questions.

Is it hard to keep a miswak in the pocket?

Is it hard to keep a miswak in the bathroom?

Is it hard to keep a miswak in the kitchen?

See, same language Rasulullah sallillahu alaihi wa sallam used for Tarabeah salat. And you know how Muslim took it. They make it like a FARD prayer! If I say tomorrow, or if some other so pious brother tomorrow see me not praying Tarabeah, he will think I am out of Islam. That’s how serious we took Tarabeah. Then think how the same person treats the same expression of the hadith of miswak, it is totally gone to oblivion. Oh! It’s just Sunnah!

On a side note, this also shows, people mostly follow the tradition not being thoughtful what they actually do, how important it is what they are doing, are the doing less preferable one leaving the most preferred one? etc.

For me, I tried to replace the regular paste and brush with siwak. I asked people who do it, tried to learn from them but I didn’t find any who actually does it as a total replacement of brush and toothpaste. I sincerely want to do this, a total replacement, if any brother knows about it please let me know.