In these circumstances, it is important to obtain blood cultures and other relevant tests before administration of antibiotics intended to prevent IE. Failure to do so may result in delay in diagnosis or treatment of a concomitant case of IE. Regimens for Dental Procedures Previous AHA guidelines on prophylaxis listed a substantial number of dental procedures and events for which antibiotic prophylaxis was recommended and those procedures for which prophylaxis was not recommended. On the basis of a critical review of the published data, it is clear that transient viridans group streptococcal bacteremia may result from any dental procedure that involves manipulation of the gingival or periapical region of teeth or perforation of the oral mucosa. It cannot be assumed that manipulation of a healthy-appearing mouth or a minimally invasive dental procedure reduces the likelihood of a bacteremia. Therefore, antibiotic prophylaxis is reasonable for patients with the conditions listed in Table 3 who undergo any dental procedure that involves the gingival tissues or periapical region of a tooth and for those procedures that perforate the oral mucosa (Table 4). Although IE pro- phylaxis is reasonable for these patients, its effectiveness is unknown (Class IIa, LOE C). This includes procedures such as biopsies, suture removal, and placement of orthodontic bands, but it does not include routine anesthetic injections through noninfected tissue, the taking of dental radiographs, placement of removable prosthodontic or orthodontic appli- ances, placement of orthodontic brackets, or adjustment of orthodontic appliances. Finally, there are other events that are not dental procedures and for which prophylaxis is not recommended, such as shedding of deciduous teeth and trauma to the lips and oral mucosa. In this limited patient population, prophylactic antimicro- bial therapy should be directed against viridans group strep- tococci. 