Miswak In Islam

A 2003 scientific study comparing the use of miswak with ordinary toothbrushes concluded that the results clearly were in favor of the users who had been using the miswaak, provided they had been given proper instruction in how to brush using it. The World Health Organization (WHO) recommended the use of the miswaak in 1986 and in 2000 an international consensus report on oral hygiene concluded that further research was needed to document the effect of the miswak.

Prophet Mohammed (pbuh) recommended its use.

Narrated Abu Huraira(RA):

Allah’s Apostle(pbuh) said, “Were I not afraid that it would be hard on my followers, I would order them to use the siwak (as obligatory, for cleaning the teeth) Volume 9, Book 90, Number 346:Sahih Bukhari

Narrated Hudhaifa(RA) :
Whenever the Prophet(pbuh) got up for Tahajjud prayer he used to clean his mouth (and teeth) with Siwak. Volume 2, Book 21, Number 237: Sahih Bukhari
Abu Hurayrah (RA), who reported that the Prophet (peace and blessings of Allaah be upon him) said: “Were it not for the fact that I did not want to make things too hard for my ummah, I would have commanded them to use the siwaak at every time of prayer.” (Reported by al-Bukhaari, 2/299 and Muslim, 1/151).
Allah knows the best.