Bukhari :: Book 2 :: Volume 13 :: Hadith 13
Narrated Anas: “Allah's Apostle I said, "I have told you repeatedly to (use) the Siwak. (The Prophet put emphasis on the use of the Siwak.)”
Use of miswak is sunnah, and we know that there is no practice of Muhammad s.a.w.w that is not beneficial for us. Whatever He s.a.w.w ordered has a benefit hidden that science has revealed after more than 1400 years.
Miswak’s benefits are so much that it is now used as a marketing component in the toothpastes. Science has also counted the immense benefits of using miswak and has proved that it is much more good to use miswak then to use toothpaste and toothbrushes. In 1986, world health organization recommended the use of miswak for the immense hygiene benefits is has. And in 2000, it proposed to revise the document to add more benefits of miswak. In 2003, a clinical research proved that miswak was better than the toothbrush and people who used it experimentally were satisfied. Dr. Rami Muhammad Diabi spent his life in medicine and research and his research resulted that the use of miswak is greatly benefitial for the smokers who are addicted. Dr. Otaybi of Saudi Arabia showed that the use of miswak has positive effects on the immune system.
So, a sunnah is not only a practice of our beloved prophet (s.a.w.w) but it is also proved by science that sunnah has benefits of us. Prophet Muhammad s.a.w.w used to do miswak even when He was observing fast.
Bukhari :: Book 3 :: Volume 31 :: Hadith 154
Narrated Abu Huraira: “The Prophet said, "If somebody eats or drinks forgetfully then he should complete his fast, for what he has eaten or drunk, has been given to him by Allah." Narrated 'Amir bin Rabi'a, "I saw the Prophet cleaning his teeth with Siwak while he was fasting so many times as I can't count." And narrated Abu Huraira, "The Prophet said, 'But for my fear that it would be hard for my followers, I would have ordered them to clean their teeth with Siwak on every performance of ablution." The same is narrated by Jabir and Zaid bin Khalid from the Prophet who did not differentiate between a fasting and a nonfasting person in this respect (using Siwak).”
Also, He (s.a.w.w) said:
Bukhari :: Book 2 :: Volume 13 :: Hadith 12
Narrated Abu Huraira: “Allah's Apostle said, "If I had not found it hard for my followers or the people, I would have ordered them to clean their teeth with Siwak for every prayer."”
This shows how important it is to use miswak. It is not just health benefitial but also when we follow a sunnah we earn swab.
Aisha said, "The Prophet said, "It (i.e. Siwak) is a purification for the mouth and it is a way of seeking Allah's pleasures." Ata' and Qatada said, "There is no harm in swallowing the resultant saliva."
Islam has given us an ideal way to lead life without any trouble and with simplicity. Also, if we follow the Islamic system of life, we will be happy in this world and in the hereafter. Also whatever Muhammad s.a.w.w tells us to do, we should do that for our own good.
ALLAH swt has said in Quran:
Surah Aal-e-Imran[3]:132
"And obey Allah and the Messenger that you may obtain mercy."
AND
surah najam- verses 2-4
“Your companion (Muhammad SAW) has neither gone astray nor has erred. Nor does he speak of (his own) desire. It is only a Revelation revealed. “