The Miswak is one of the most overlooked aspects of Islam.
Using a miswak has many benefits:
1. Miswaak strengthens the gums and prevents tooth decay.
2. Miswaak assists in eliminating toothaches and prevents further increase of decay which has already set in.
3. Miswaak creates a fragrance in the mouth.
4. Miswaak is a cure for illness.
5. Miswaak eliminates bad odors and improves the sense of taste.
6. Miswaak sharpens the memory.
7. Miswaak is a cure for headaches.
8. Miswaak creates lustre (noor) on the face of the one who continually uses it.
9. Miswaak causes the teeth to glow.
10. Miswaak strengthens the eyesight.
11. Miswaak assists in digestion.
12. Miswaak clears the voice.
13. The greatest benefit of using miswaak is gaining the pleasure of Allah.
14. The reward of Salaah (Prayers) is multiplied 70 times if Miswaak was used before it.
"Abu Ayyub (R) narrates that Rasulullah (Sallallahu Alayhi Wasallam) said:
'Four things are amongst the practices of the Ambiyaa —circumcision, application of perfume, Miswaak and marriage'.
(AHMAD AND TIRMIZI)
Abu Umamah (R) narrates that the Messenger of Allah (Sallallahu Alayhi Wasallam) said:
'Use the Miswaak, for verily, it purifies the mouth, and it is a Pleasure for the Lord. Jib-ra-eel (A.S.) exhorted me so much to use the Miswaak that I feared that its use would be decreed obligatory upon me and upon my Ummah. If I did not fear imposing hardship on my Ummah I would have made its use obligatory upon my people. Verily, I use the Miswaak so much that I fear the front part of my mouth being peeled (by constant and abundant brushing with the Miswaak)'."
The use of a miswak has other benefits, too, such as sharpened memory and sharpened intelligence. Don't ask me how it does it, because I don't know. All I know is that Hadhrat Ali (R) said that "Miswaak sharpens the memory." and there is a hadith that states:
"Four things increase the Intelligence—
(i) Shunning of nonsensical talks
(ii) Use of the Miswaak
(iii) Sitting in the company of the pious, and
(iv) Sitting in the company of the Ulama."
(TIBBE NABAWI)
There is so much information about the Miswak. To learn more, go to:
http://www.islam.tc/Miswaak/ 
