Mandibular fracture with subsequent sequestrum formation and tooth-root abscess in a 3-year-old mare.

A 3-year-old quarter horse cross mare was presented to the Atlantic Veterinary College (Charlottetown, Prince Edward Island) for evaluation of a persistent draining tract on the ventral aspect of the left mandible, associated with a previous fracture. Radiography and ultrasonography confirmed the presence of a chronic sequestrum separated from the parent bone. Sequestrectomy and surgical debridement of the mandible were carried out, and the horse was discharged. Three months later, the mare was presented again to the Atlantic Veterinary College, as the draining tract had not resolved. A CT scan of the mare's skull revealed infection of Tooth 310. The tooth was surgically removed. The animal was discharged, and clinical signs were resolved at the 1-month recheck examination. Key clinical message: The importance of CT in diagnosing tooth involvement secondary to a mandibular fracture is described. In addition, the growing prevalence of antibiotic resistance to trimethoprim-sulfamethoxazole due to prolonged use and frequent usage in equine practice is highlighted.