Molar Picture Root Canal Back Bottom Molar Question?

Root canal back bottom molar question? - molar picture

my very back molar soil is ruined .... I had a cavity, which can not fill cracked, then I'm missing a whole corner of my tooth like in this picture, I tried to do with color lol

http://i35.tinypic.com/2f08280.jpg

Black is the area where my tooth exposed maoh theres nothing left

I wondered what I do, I do not know if I get a root canal treatment more ... or what. Do you think it would just back from the tooth?