It's not unusual for dental problems to leak infection into the maxillary sinuses. Nasal odors seem to be caused by bacteria that don't always produce enough infection to cause PND. If the infection is restricted to your maxillary, then a $13 Neilmed Sinus Rinse should get rid of it. If it does, keep on rinsing for several days after the odor disappears, or it grows back.
If the infection has gone higher up in your sinuses, the only thing that seems to get rid of it is a Flip-Turn Sinus Flush.
It's kinda risky because you have to bend over, preferably in a shower, but you can also do it outside in a bathing suit.
My dentist applied an antibiotic to my gums when I had gingivitis, rather expensive, but worth it. If you don't kill it, the bacteria can cause problems with your circulatory system (as well as your sinuses) He also drags me for teeth cleaning every six months, instead of yearly. You pay more for the extra office visit, but you rarely have to cough up the money for expensive treatments.