For small health-care groups like dentist’s offices, one sick staff member can mean a day’s worth of cancelled appointments. Such offices can either continue short-staffed, which could negatively affect patient care, or reschedule appointments, potentially delaying critical procedures and screenings. The MIT alumnus-founded Stynt is solving that problem by helping health care offices fill last-minute shift openings for positions including dental hygienists, assistants, office managers and dentists. Stynt’s online platform lets offices post openings that qualified professionals can then bid on. “We’re a software-as-a-service marketplace with a focus on health…