These and other factors have led to a heightened awareness among patients and healthcare providers of the possible association between dental procedures and IE, which likely has led to substantial overreporting of cases attributable to dental procedures. Although the absolute risk for IE from a dental procedure is impossible to measure precisely, the best available esti- mates are as follows: If dental treatment causes 1% of all cases of viridans group streptococcal IE annually in the United States, the overall risk in the general population is estimated to be as low as 1 case of IE per 14 million dental procedures.41,90,91 The estimated absolute risk rates for IE from a dental procedure in patients with underlying cardiac conditions are as follows: MVP, 1 per 1.1 million procedures; prosthetic cardiac valve, 1 per 114 000; and previous IE, 1 per 95 000 dental procedures.41,91 Although these calculations of risk are estimates, it is likely that the number of cases of IE that result from a dental procedure is exceedingly small. Therefore, the number of cases that could be prevented by antibiotic prophylaxis, even if 100% effective, is similarly small. One would not expect antibiotic prophylaxis to be near 100% effective, however, because of the nature of the organisms and choice of antibiotics. Risk of Adverse Reactions and Cost-Effectiveness of Prophylactic Therapy Nonfatal adverse reactions, such as rash, diarrhea, and GI upset, occur commonly with the use of antimicrobials; however, only single-dose therapy is recommended for dental prophylaxis, and these common adverse reactions are usually not severe and are self-limited. 