I have what thought to be an abscess on a root canal. I'm a hygienist so I am aware this can happen. However, after the apico procedure and antibiotics, I have contined to have slight swelling and tenderness in the maxillary sinus. I was put on a second round of antibiotics, and I am almost done, but the symptoms are still present...not as severe as prior to the apico, but enough that it does not feel like it is healing. To complicate matters, I have had numerous health issues that I have been having diagnostic testing for. On an MRI of my head/brain, it was noted I had fluid in my right maxillary sinus. This did not come as a surprise but rather, confirmation of the stuffiness I have felt for months. At the time of the MRI i had bigger issues of concern, and the sinus area was merely aggravating. No one mentioned concern with fluid in the sinus so I merely registered it as confirmation of what I had been feeling, but apparently no concern. In late August I developed severe pain in my sinus that spread to my eye and across my right upper face. I also had a very bad headache. I had to see the Endodontist as an emergency patient. The apico was done and I felt the problem was surely solved. However, despite my diligent home are..I'm a dental hygienist so im pretty disciplined!..and despite antibiotics, I am sure I have fluid remaining. The headaches are starting again, but not as intense. Little bit of throbbing now and then. I can feel the tenderness and and its swollen some, but very firm. The fluid was a definite observation on the MRI. Could this be the cause of my trouble?? The apico did not arrest the symptoms and now, I wonder if it is the proble:-(. ?