First of all let me say that all teeth have "root canals" some have several canals; it just depends on the tooth. The root canal houses the "nerve" which supplies the tooth with a blood supply carrying vital nutrients to keep the tooth alive, healthy and functional. A root canal procedure or root canal therapy is "preformed" to remove the "nerve or blood supply" in these canals, which has suffered an irreversible trauma or deep decay which has or will lead to the death of the nerve causing an eventual "abscess" to develop. It's the presence of this "abscess" that causes the patient to feel this excruciating pain due to the inflammation, swelling and infection.
Now with that said if your dentist has informed you that you are in need of two root canal procedures on two different teeth then it’s probably what she has seen on your x rays this last cleaning appointment. Most likely you have some recurrent decay in these teeth that is deep enough that its removal will expose the nerve, resulting in a root canal procedure to be preformed to save these teeth. A restoration can’t be placed once the nerve is exposed, it must have either a root canal procedure preformed or be extracted.
Or she may have seen the beginning of the nerve abscessing by viewing the x rays, either by a darkening at the apex of the tooth or possibly an enlargement of the canals which are ways of diagnosing the pending dying nerve of a tooth, which will need a root canal procedure in the near future. Obviously she has noticed something from the x rays. I would suggest you discuss this with her; I’m sure she can show you on the x ray or explain her reasoning behind advising you of the upcoming need of these.
She may have brought this to your attention just as we have always done for patients. Usually when deep decay is resting on, or just above a nerve we tell the patient that a root canal procedure will be needed. Occasionally we are wrong about the diagnosis. X rays aren’t always as accurate as we like to consider them to be, an actual view and feel of the inside structure of the tooth once the decay is removed is always much more accurate. When the decay is excavated leaving a sound tooth structure without exposing the nerve, a restoration can be placed restoring the tooth to its normal function without the need of a root canal therapy. The patient is always pleased when this occurs, but it’s always better to be prepared for the possibility of the needed root canal procedure and the expense that goes with it, rather than have it come as a complete surprise.
I hope that I’ve been of some help with this and that you will discuss this with your dentist allowing her the opportunity to explain. If you’re really unsure, you can always obtain a second opinion. It’s easier and less expensive if you ask her to explain and show you on the x rays rather than seek another opinion which will most likely be the same advise. Don’t put this off too long, abscesses are very painful and usually will need to be treated with antibiotics prior to the procedure. Good luck!