Recurrent Aphthous Stomatitis By Bernard J Hennessy, DDS, Texas A&M University, College of Dentistry Reviewed / Revised Feb 2022 | Modified Sep 2022 View Patient Education Etiology Symptoms and Signs Diagnosis Treatment Topic Resources Minor Aphthous Ulcer (Lip) Major Aphthous Ulcer Recurrent aphthous stomatitis (RAS) is a common condition in which round or ovoid painful ulcers recur on the oral mucosa.