The purpose of the study was to compare bedside ultrasound (US) and panorex radiography in the diagnosis of a dental abscess in emergency department (ED).A retrospective review of ED records of adult patients with atraumatic facial pain, swelling, and toothache who received a panorex x-ray and bedside US was performed. Medical records were reviewed for ED evaluation and disposition. Sensitivity and specificity of US and panorex x-ray were calculated to determine the clinical utility of the 2 tests.A total of 19 patients were identified. No periapical abscess was reported on panorex x-rays in 7 (37%) of 19 patients. Ultrasound agreed with panorex x-rays in 6 (86%) of 7 cases. One case where US disagreed with x-rays was evaluated by dentistry consultants; and incision and drainage were performed, confirming the presence of an abscess. An x-ray diagnosis of periapical abscess was made in 12 (63%) of 19 patients. Ultrasound agreed with panorex x-ray in 10 (83%) of 12 cases. In 1 of the 2 cases where US disagreed with panorex x-rays, x-ray abnormalities were reported on the nonsymptomatic side. The other patient was given antibiotics and recommended outpatient follow-up. Follow-up information was not available to further confirm the presence of an abscess. Assuming that the patient who was lost to follow-up had dental abscess, the sensitivity and specificity of US in diagnosing a dental abscess were 92% and 100%, respectively.Bedside US is nonionizing, is readily available, and can provide an alternative to panorex x-rays in the evaluation of a dental abscess in ED.