Medicinal benefits of siwaak in the Sunnah
Question

                I have read and heard that there are numerous benefits to using miswak (e.g. curing of headaches, prevention of memory loss, etc.) I was wondering if anyone has come across some hadeeth to support this.
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.