Researchers in Finland have found that periodontitis may impact on the effectiveness of antibiotics that are used to prevent repeat heart attacks. A three-month course of treatment with antibiotics lowered recurrence of heart attacks in patients without periodontitis, while the medication was found to have no effect in patients with periodontitis, according to researchers at the Institute of Dentistry, University of Helsinki. This is the first time dental infections have been linked to the effectiveness of treatment with antibiotics designed to prevent heart attacks.

According to the results, long-term antibiotic medication would prevent myocardial infarcts in patients that do not have periodontitis, or related signs of inflammation such as disease-causing bacteria or antibodies to those bacteria. Periodontitis appears to be such a significant chronic infection that the effect of antibiotic treatment in preventing cardiovascular events is lost in patients that suffer from it. During one year of observation, patients with no signs of periodontitis were more likely to avoid new cardiovascular events. A total of 79% survived without a new cardiovascular event compared with 74% of patients without teeth and 66% of those with periodontitis.

The differences in patients under the age of 65 were even more noticeable: 90% of non-periodontitis subjects completed the year without a new cardiovascular event, compared with only 64% of those with periodontitis and 50% of those without teeth. In patients under the age of 65, periodontitis may cause a fivefold increase in the risk of recurrent, acute cardiovascular events in comparison with healthy people.

The researchers examined 141 patients that were hospitalised for acute cardiovascular events (myocardial infarct or unstable angina pectoris). The double-blind trial involved registering the recurrence of new cardiovascular events over one year of observation following the administration of a three-month course of clarithromycin (or placebo). Radiographs were used to evaluate the status of teeth and tooth-supporting tissues. The presence of Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis, the two most important periodontal pathogens, was studied in the saliva, and the serum antibodies for these bacteria were measured using a method developed and used only at the Institute of Dentistry, University of Helsinki. The findings are published in the January issue of the journal Atherosclerosis.