Ryan treats patients with periodontal disease at the Stony Brook dental clinic, is a tenured full professor in the School of Dental Medicine, serves as the dental school's associate dean for strategic planning and external affairs, is on the medical staff at Stony Brook University Medical Center and serves on several advisory boards, such as Colgate-Palmolive Company. Her most important contribution to science, her colleagues say, is her research on oral health and its link to chronic diseases, such as diabetes and heart disease.