Praise be to Allah.
Encouragement to use the siwaak as part of the Sunnah is mentioned in many hadeeths, and the effect of using the siwaak is described as purifying the mouth, cleansing it of dirt, making it smell good, and preventing disease. It is a general word which affirms that siwaak possesses all powers of purification and protection.
Dr. ‘Abd-Allaah ‘Abd al-Razzaaq al-Sa’eed says:
It is indeed a miracle of the trustworthy and unlettered Messenger (blessings and peace of Allah be upon him), who said: it was narrated from ‘Aa’ishah (may Allah be pleased with her) that the Prophet (blessings and peace of Allah be upon him) said: “Siwaak is purifying for the mouth and pleasing to the Lord.” Narrated by al-Nasaa’i (hadeeth no. 5). Al-Bukhaari narrated it as a mu’allaq majzoom report in Kitaab al-Sawm, Bab Siwaak al-Ratab wa’l-Yaabis li’l-Saa’im. It was classed as saheeh by al-Mundhiri in al-Targheeb wa’l-Tarheeb (1/133) and classed as hasan by al-Nawawi in al-Majmoo’ (1/267). In an addition mentioned in al-Mu’jam al-Awsat by al-Tabaraani (7/278) it says “and clearing to the eyesight”, but this is very weak. See al-Silsilah al-Da’eefah by al-Albaani (no. 5276).
How can the siwaak not be purifying to the mouth when the unlettered Prophet (blessings and peace of Allah be upon him) did not speak on the basis of his own whims and desires, who was taught (the Qur’aan) by one mighty in power [Jibreel (Gabriel)] (cf. al-Najm 53:5), enjoined us to use the siwaak, thus giving us basic guidelines to protect our teeth and mouths from disease by cleaning them, which is what preventive dentistry tells us now. As it is said, prevention is better than cure because it gives us a life that is filled with happiness.
All the means that may be followed to keep the mouth and teeth clean are very valuable in preventive medicine. One of these means is the stick from the araak tree, which is mentioned in many hadeeths from the Prophet (blessings and peace of Allah be upon him). This stick is called siwaak.
Prof. Dr. Muhammad Sa’eed al-Jareedli – head of the Mouth Disease department at Cairo University – said:
The siwaak is many times better than the toothbrush and toothpaste in chemical and mechanical terms.
After carrying out research he found that the substance which is in the siwaak kills germs and heals our mouths from disease. By itself it can take the place of the toothbrush and toothpaste because of the numerous substances it contains which are superior to those contained in toothpaste. Similarly, strong, gentle natural fibres work better than the fibres of the toothbrush and do not damage the gums. They also effectively remove what is left in our mouths and clings to our teeth of leftover food, which can cause disease and damage to the mouth and teeth. Up until today, in our civilised world, there is no toothpaste that contains the substances contained in the siwaak. Similarly, it says in the weekly magazine American Dentist that most of the toothpastes used in the United States of America are not good or healthy.
For example, we see that most of the toothpastes on the market are commercial and cheap, aimed at nothing other than making a profit, and the mouth and gums do not benefit from them at all. But in the case of siwaak, it was found -- after scientific research -- that it contains a lot of effective substances carried in its fibres, including cleansers such as sinigrin, astringents which strengthen the gums, such as gallic acid, volatile oils which give the mouth a good smell, sodium chloride, sodium bicarbonate, potassium chloride, calcium oxalate and a number of substances which clean the teeth. Some substances in the siwaak also kill germs, so it has an effect similar to that of penicillin.
So the siwaak is indeed the purifier for the mouth and teeth. Blessings and peace of Allah be upon you, O Beloved of Allah, O intercessor for creation, O Trustworthy Messenger, until the Day of Judgement; you brought us the Qur’aan from the Lord of the worlds, the most wise of judges, and you spoke the truth when you said: “Siwaak is purifying for the mouth and pleasing to the Lord.” End quote.
Al-Siwaak wa’l-‘Inaayah bi’l-Asnaan (p. 9-14)
In the research of Dr. James Turner, of the Faculty of Medicine in the American University of Tennessee, which is published in the journal Oral Medicine and Dentistry, it says: The miswaak of the araak tree contains substances which purify and kill microbes, the most important of which are sulphur and sitosterol B (or β-sitosterol), as well as sodium.
Research and experiments indicate that the siwaak contains a substance which stops bleeding, purifies the gums and sterilises wounds in the gums. It also contains in its fibres large amounts of mineral salts and ions such as calcium, iron, phosphates and sodium.
Siwaak contains vitamin C, and it is well known to scientists that the interaction between this vitamin and antibiotics is regarded as one of the most effective of remedies. It also contains tannin which helps to strengthen the gums.
See also the answer to question number 2577.
And Allah knows best.