Stated very simply, a root canal is a process by which a dentist removes the nerve of the tooth. The nerve of the tooth usually goes through the center of the tooth and down the root. A dentist will place an apparatus called a rubber dam over the tooth to isolate it from the other teeth and the rest of the mouth. A rubber dam is a thin piece of flexible rubber approximately 6 inches square. It is held in place by a clamp that fits over the tooth and a frame that holds the piece of rubber comfortably in place. The dentist then gains access to the nerve through the top or crown of the tooth. Once in the nerve canal the dentist will remove the nerve and go through the process of widening the canal by using a series of files that progressively get larger. Once the dentist is comfortable with the shape of the canal he or she will fill this space with the root canal filling. Once the root canal is finished there are a number of alternatives for restoring the tooth
As for whether or not you should save your teeth, I would encourage you to go ahead with the root canals as long as your dentist is confident it is in your best interest that they are done. One important reason for me recommending saving your teeth is that you have not lost any thus far. This would mean that the need for a fixed bridge or a partial removable denture can be avoided. As always, I would encourage you to talk with your dentist about your concerns. Together you will be able to come up with a solution that makes good sense.
What you have explained is very possible. For various reasons you may, in fact, have a residual infection at the tip of the tooth. The procedure that they are recommending is called an apicoectomy. The dentist will flap back the gums thereby exposing the bone below. They will then gain access to the bone at the tip of your tooth. This area will be less hollow than the rest of the bone because of the presence of the infection. The dentist will spoon out the infected tissue and scrape the bone clean. He will then seal the tip of the tooth and suture the tissues' back in place. This procedure is very predictable and successful.
You are among the great majority of the population that thinks that because a tooth has had a root canal the tooth is now "dead". Though the main blood and nerve supply to the tooth is removed in the process of doing a root canal, the tooth still has nourishment going to it. Let us talk about the reasons why you may need a crown on a tooth that has had a root canal. If the reason for the root canal was a large amount of decay that went to the nerve of the tooth, there is a good chance that you also had a filling in place already and therefore there is very little supportive tooth left. If this is the case, the reason for the crown is to protect the tooth from the forces of chewing and thereby avoiding its breakage beyond the point that it can be repaired. Your dentist will probably suggest that he or she either place a post in the tooth and build it up or simply build the tooth up without a post. Both of these procedures are used to reestablish the contours of the tooth so that a crown can be made.
It sounds as though your husband needs to be on antibiotics. Have him give his dentist a call and explain what you have told me. I am sure he or she will call a prescription in for him. If he simply doesn't want to go back to this dentist have him see an endodontist (a specialist for root canals) or a general dentist who does root canals routinely. I am surprised to hear that he was in pain all through the procedure - there are many different techniques and anesthetics available these days to make a patient feel comfortable. I am also surprised that the root canal was not completed in one visit. Most root canals can be performed in one visit though there are some circumstances where you would be better off having it done over two visits. In addition, your husband could have a fracture in the tooth that is keeping the area irritated. A fracture can usually be seen during the procedure - I am sure that your dentist would have discussed this with you. All in all, my suggestion would be to go back to the dentist to discuss his concerns. I am sure that once discussed there will be a solution or explanation. I have found that there are so many times that a lack of communication leads to unnecessary anxiety.