This study will evaluate whether a program of systematic oral care can help prevent hospital-acquired respiratory infections in patients in intensive care units. Such infections occur five times more often in critically ill patients compared with patients in general hospital wards and result in longer hospital stays and an increased risk of death. The rate of respiratory infection among critically ill patients correlates strongly with the presence of disease-causing bacteria in the mucosal areas of the mouth, gums, and teeth, indicating that assiduous oral care is especially important in this patient population. This study will compare a program of meticulous oral care using oral assessments taught by a dentist and dental hygienist with the standard care typically given in intensive care units.