Rasulullah (SAWS) has said,

 
"As sewaako shatrul wuzu."
Cleaning of teeth is half of ablution.

Cleaning of teeth brings fragrance to the mouth and leads to the pleasure of Allah. Whenever Rasulullah (SAWS) travelled, he always took six things along with him: a bottle of 'itr (attar, perfume), a pair of scissors, a collyrium case (surma-daani), a mirror, a comb and a tooth-stick.

Rasul-e-Akram (SAWS) said, whenever Jibraeel (AS) came to me, he always directed me to clean the teeth as the mouth is the path of the Qur'an through which the words of Allah is recited. He further said, if I were not apprehensive of the burden it would entail on my community, I would have rendered the use of the tooth-stick obligatory together with the ablution.

At one time Rasulullah (SAWS) asked Jibraeel (AS), what has stopped you of revealing the commands of Allah to me for three long days? He replied, 'O Mohammad, how could the angels come to you when you do not clean your teeth and do not cleanse yourselves with water?' Rasulullah (SAWS) said, 'To every faithful who arises in the middle of the night and cleanses his teeth with the tooth-stick, and purifies himself in the most approved manner, and goes to the mosque, there come an angel who places his mouth on the faithful's mouth. Every word that the faithful utters enters the mouth of the angle. On the Day of Judgement the angel comes to him as a witness and intercessor.'

Cleaning of teeth prevents the diseases of mouth. Teeth should be cleansed horizontally, not vertically. The cleansing of teeth with the thumb and the index finger during ablution is equivalent to the use of the tooth-stick. Use of reed (or cane), or shoot of an aromatic plant (or sweet basil), or a pomegranate tree as a tooth-stick is forbidden because it activates the roots of leprosy.