There is no way to tell if the root canal has been successful anyway. I currently have a dead tooth which is infected all throughout it. Yet the only symptoms I have are

A) a slight ache and slight pain when pressed
B) a hazy area on the tip of the root on the xray

These are fairly minor symptoms and could easily be missed. In fact the first time I saw a dentist, he never suspected any problem and told me the pain was normal. Even the xray was 'inconclusive'.

Now imagine if I had a root canal. As long as you removed the dead tissue inside the canal, my symptoms would likely disappear. But that doesnt mean the infection is gone.

Sorry but this is all non scientific. I have heard some people say root canal is great and others say its terrible. The first dentist I saw said there is no problem with removing my tooth except cosmetics. Everybody says something different. We need more objective data to support these highly variable opinions.