In the light of this information we may understand the advice given by the Prophet, peace, and blessings of Allah be upon him, to take care of the teeth by cleaning the mouth, as he said: “The Siwak is cleansing for the mouth and pleasing to the Lord.” (Narrated by Al-Bukhari in a Mu‘allaq report, and by Ibn Hibban and Ibn Khuzaimah; its isnad is saheeh)
In the Saheehain it is narrated that the Messenger of Allah, peace, and blessings of Allah be upon him, said: “Were it not that it would be too difficult for my Ummah, I would have enjoined them to use the Siwak at the time of every prayer.”
According to another report, it is mentioned: “...at the time of every Wudhoo’.”
Hence, it is clear that the one who uses the Siwak will be in the best shape because he is repeatedly removing plaque by using the Siwak several times every day.