Advantages of Miswak (i.e. Cleaning Teeth With Any Raw Branch of Tree):

(From the book of Allama Majlisi: Tehzeeb-ul-Islam)

According to many reliable traditions from Imam Ja'far-e-Sadiq (a.s.),
miswak is the sunnat of all Prophets. The Holy Prophet (s.a.w.a.) used to
say that Hazrat Jibrael asked him to do miswak so often, that he started
fearing that his teeth would be rubbed off.
According to Imam Ja'far-e-Sadiq (a.s.), there are twelve advantages of
miswak:
a) It is the sunnat of Prophets
b) Cleans the mouth
c) Increases brightness of the eyes
d) Causes God's goodwill
e) Takes out sputum
f) Increases memory
g) Teeth are whitened
h) The reward of good deeds increases manifold
i) Stops weakness and falling of teeth
j) Strengthens roots of the teeth
k) Increases appetite in a healthy manner
l) Angels are happy with all those who do miswak
According to a tradition from Hazrat Ali (a.s.), the Holy Prophet
(s.a.w.a.) had advised people to do miswak at the time of every prayer.
According to Hazrat Moosa Kazim (a.s.) and Imam Ali Reza (a.s.),
among the sunnats of the Prophet Ibrahim (a.s.), there are five things
about the upper half of the body and five about the lower part of the
body. Among those that are concerned with head are:
a) To do miswak
b) Trimming the moustache
c) Parting hair to have place for masah
d) To gargle
e) To put water in the nose
The five things that are sunnat about the lower part of the body are:
a) To get circumcised
b) To remove unwanted hair on the lower abdomen
c) To remove hair under armpits
d) To cut nails
e) To clean with water after urination

According to Imam Ja'far-e-Sadiq (a.s.) when one gets up for Namaz-e-
Shab (night prayer) one should do miswak as an angel descends from heaven and keeps his mouth on one's mouth and whatever one is reciting;
Quran, prayers or durood, he takes it to heaven. Therefore it is necessary
that one's mouth should be smelling good. (If there is not enough
time, it is better to clean one's teeth with fingers only.)
According to the Holy Prophet (s.a.w.a.), there are three things which
sharpen memory and cure all pains - chewing kundoor, doing miswak
and reciting the Quran-e-Majeed.
Another tradition quotes the Holy Prophet (s.a.w.a.) as saying that two
rakat prayers with miswak is better than seventy rakat prayers without
it.
According to Mohammed Baqir (a.s.), doing miswak in the bathroom
causes one's teeth to fall and also one should never stop doing miswak
even if it is done once in three days.