Infected teeth & Infected sinuses

We've seen it often enough here.  Discharge out of one nostril.  Treatment with antibiotics helps, but the infection returns in a week or two.  Hello, Dentist?

According to the abstract of this paper on  Sinus Surgery in the Horse, "the most common cause of sinus infection is extension of infection from a diseased tooth or as an aftermath to tooth repulsion." 

Long story very short........if your horse has a persistent or recurring nasal discharge, think "teeth."  To see just how little barrier there