Because children are recom- mended to have dental cleaning procedures every 6 months, this suggests that office-based bacteremia may occur upwards of twice per year. Data from bacteremia studies strongly sug- gest that the incidence of bacteremia annually from tooth- brushing and other daily activities far exceeds that of dental office procedures, perhaps by hundreds of times per year.43,68 It is unknown whether frequency of bacteremia is more impor- tant than magnitude with regard to risk for IE, but current data support the importance of a focus on maintenance of good oral hygiene, prevention of gingival and dental disease, and access to routine dental care for children at risk for IE. Cases of IE from oral bacterial pathogens in children most likely result from exposure to relatively frequent, low-grade bacteremia from these activities of daily living. Results of Clinical Studies of IE Prophylaxis for Dental Procedures There has not been a prospective, randomized, placebo- controlled study of the efficacy of antibiotic prophylaxis to prevent IE in people whose risk is from dental procedures. The few published retrospective, epidemiological studies that relate to this question have had varied outcomes with respect to benefit from antibiotic prophylaxis. When an invasive pro- cedure has occurred in close proximity to the onset of symp- toms of IE, it cannot be determined that it caused IE, because there may have been episodes of bacteremia from natural causes in the same time frame. Table 2. 