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The findings of Al-Karaawi and colleagues in the present issue are disturbing.1 One may conclude from their work that antibiotic prophylaxis against infective endocarditis should be applied more largely for dental procedures for which guidelines usually do not recommend such prophylaxis. At the same time, the usefulness of antibiotic prophylaxis is debated by many authors.2 3Fortunately, prophylaxis is still recommended by authors who debate about it, and Al-Karaawi and colleagues do not draw the conclusion suggested above.
Antibiotic prophylaxis and dental treatments: to be extended to more patients?
In 136 children with severe congenital cardiac disease who underwent dental procedures, Al-Karaawi and colleagues calculated a cumulative exposure to bacteraemia over one year for several dental procedures, which were considered as prophylaxis or non-prophylaxis procedures according to the current US guidelines.4 They found that the cumulative exposure was as high or higher in many dental procedures for which prophylaxis is not recommended than for those for which prophylaxis is recommended. This was especially so for rubber dam placement.
The cumulative exposure was the product of the intensity of bacteraemia by the proportion of positive blood cultures by the length of bacteraemia by the number of times a given dental procedure was performed annually. This was a retrospective study, and since many data were not available in the files, the authors obtained the information from the literature, except for the number of times a given dental procedure was performed annually in a given child. It would have been much more interesting to use real data, and since most of the children were treated under general anaesthesia, at least in them drawing blood for cultures looks easy to do. Duration of bacteraemia was set at 15 minutes, whatever the type of dental procedure and whatever the child. Everybody who has to go to his or her dentist knows very well that the duration of a given dental procedure—and thus of bacteraemia—varies greatly in the same person according to the difficulty of the procedure! These are reasons why the results must be interpreted cautiously. The authors are aware of it, since the title clearly states that this is a theoretical analysis and since they draw very cautious conclusions: “The data raise important questions about the appropriateness of current guidelines for antibiotic prophylaxis of bacterial endocarditis.” It looks timely to perform a prospective study, and to really measure all the components of cumulative exposure.
Unfortunately, some missing information would have been very useful. We know that the children had severe congenital cardiac disease, but we do not have any details about the types of cardiac diseases, although the risk of infective endocarditis depends on the underlying congenital heart disease.5 Not being dentists, and since the bacteraemia cannot occur without bleeding during the dental procedure, we wonder whether the bacteraemia after rubber dam placement is due to the rubber dam placement itself or to the work the dentist does before placing the rubber dam.
Antibiotic prophylaxis and dental treatments: to be restricted to fewer patients?
Numerous guidelines have been issued in many countries. Beside the British recommendations,6 the most recent ones come from USA4 and from a European group of experts.7The US guidelines give a very precise list of dental procedures for which prophylaxis of infective endocarditis is recommended and for which it is not recommended4—the same list which is given in the paper by Al-Karaawi and colleagues.1 In the European text—not cited by Al-Karaawi and colleagues—all dental procedures require prophylaxis in cardiac patients at risk, the only exceptions being procedures without risk of bleeding such as superficial caries and bloodless supragingival prosthetic preparations.7
In spite of numerous guidelines on prophylaxis of infective endocarditis, the incidence of infective endocarditis does not decrease over time.8 Several explanations for this apparent discrepancy can be proposed9:
compliance of physicians, dentists, and patients with guidelines is not good;
prophylaxis of infective endocarditis is not efficacious;
prophylaxis of infective endocarditis is efficacious, but its effect on the incidence of infective endocarditis is counterbalanced by the increasing frequency of patients at risk and of procedures at risk.
Efficacy of prophylaxis is not demonstrated, and it probably never will be. The only way to demonstrate efficacy would be a randomised trial, which appears unethical and not feasible; it has been calculated that over 6000 patients would be needed.10 Results from several case–control studies are conflicting—the protective efficacy of prophylaxis goes from less than 50%11 12 to more than 90%.13 The link between dental procedures and infective endocarditis is not definitely established.14 Most of the data on efficacy of prophylaxis come from experimental infective endocarditis in animals, and this may not be extrapolated to mankind.15
Some apparent failures of prophylaxis have been described, 92% of which occurred after a dental procedure.16 But in the large majority of the cases, the prophylaxis did not perfectly conform to the American Heart Association recommendations.
In his editorial accompanying the Strom case–control study,14 Durack goes as far as advising prophylaxis only in cases of dental extraction or gingival surgery (including implant placement), only in patients with prosthetic valves or previous infective endocarditis.2 “As a first approximation, it should be possible to retain at least 80% of any putative benefits from currently recommended prophylaxis for less than 20% of the costs”.2
A clear answer to the question, “Which patient, and for which dental treatment, should receive antibiotic prophylaxis against infective endocarditis?” does not exist yet, and much more work is needed in order to make clear the procedures at risk of infective endocarditis and to estimate the efficacy of prophylaxis.