After researching about the safety of root canals by reading a few recent refereed scientific papers I found the following.
There is a published link,in refereed scientific journals, for root canal treated teeth being linked to heart attack.For example this paper (published in the journal of cardiology)
DNA of Pathogens typical for periodontal infection and ...
This is an important question.
The article that you have mentioned is an excellent article explaining almost everything in detail.
Now as mentioned in that article, root canal treatment is indicated in irreversible pulpitis or when the pulp is dead or necrosed.
Now how does one know whether he/she has irreversible pulpitis or dead pulp?
As the name suggests ...