Furthermore, in a number of cases, the incubation period between the dental procedure and the onset of symptoms of IE was van der Meer and colleagues85 published a study of dental procedures in the Netherlands and the efficacy of antibiotic prophylaxis to prevent IE in patients with native or prosthetic cardiac valves. They concluded that dental or other proce- dures probably caused only a small fraction of cases of IE and that prophylaxis would prevent only a small number of cases even if it were 100% effective. These same authors86 performed a 2-year case-control study. Among patients for whom prophy- laxis was recommended, 5 of 20 cases of IE occurred despite receiving antibiotic prophylaxis. The authors concluded that prophylaxis was not effective. In a separate study,87 these authors reported poor awareness of recommendations for pro- phylaxis among both patients and healthcare providers. Strom and colleagues2 evaluated dental prophylaxis and cardiac risk factors in a multicenter case-control study. These authors reported that MVP, congenital heart disease (CHD), rheumatic heart disease (RHD), and previous cardiac valve surgery were risk factors for the development of IE. In that study, control subjects without IE were more likely to have undergone a dental procedure than were those with cases of IE (P 0.03). The authors concluded that dental treatment was not a risk factor for IE even in patients with valvular heart disease and that few cases of IE could be prevented with prophylaxis even if it were 100% effective. 