Expert: Frederick R. Liewehr DDS, MS, FICD - 11/21/2007

Question
Hi,  

I had a toothache and a sinus infection at about the same time back in February of 2007.  I treated the sinus infection with an antibiotic, but my toothache persisted, and I went to an endodontist who showed me I had a dead nerve and I got a root canal to extract the second premolar on the left upper side (#13).  During the root canal, I could taste a bleachlike drainage, but the mild discomfort I had felt since my sinus infection seemed to go away and I felt much better after the whole procedure.

I recently have had another more persistent sinus infection with the exact same symptoms as I had when I needed the root canal, but I think that the infection started off as a cold and became a sinus infection later.  I have taken a full 14 days of amoxicillin, and that helped, but didn't quite kill the infection.  I am now on Sulfameth/Trimethoprim for another 14 days (about 7 days into my prescription).  It seems to have gotten rid of the horrible smelling yellow green mucus coming from my left sinus, but I have a bit of a toothache now, right above my molar and cannot tell if I may need another root canal, or if the original crown was put on too early before it adequately drained.  My question is whether sinus infections can lead to dead nerves and the need for a root canal, or if a dead nerve can lead to a sinus infection (if one causes the other) or not?  I see that a sinus infection can feel like a toothache, but what I'm trying to figure out is if there is a causal relationship between the two things?  The condition right now is not that bad, but I'm afraid that after stopping the antibiotic, it will come back again.

Answer
If a tooth is pneumatized, which means that the sinus (which is just a cavity in your bone) has grown down around the root of a tooth, the bone may be eggshell thin between the tooth and sinus. If the pulp ("nerve") of the tooth necroses and becomes bacterially infected, there will be a reaction in the bone at the end of the root. This reaction will erode bone, and can lead to a communication between the tooth and the sinus. The bacteria in the tooth can then enter the sinus and cause an infection there. The reverse, however, is not true. Sinus infections, however, can produce toothache-like symptoms, due to pressure on the nerves that lead to the teeth that run along the floor of the sinus. A competent endodontist should be able to help you make the diagnosis.