[How sensible are bacteriological tests in periodontology?]

Periodontitis is a mixed infection with subgingival bacteria that belong to the microflora of the host. The bacteriological tests (Microscopy, Culture, Omnigene, Affirm DP and Evalusite) are mainly aimed at spirochetes or A. actinomycetemcomitans, P. gingivalis and P. intermedia. The detection limits of the different tests vary and, therefore, the detection levels are between 0.01-10% of the subgingival microflora. However, threshold levels to distinguish between diseased and carrier state are not established and the low sensitivity and specificity of the tests limit their diagnostic usefulness. The correlation between the tested bacteria and periodontitis does not mean a causal relationship. As a result, the justification of the elimination of the tested bacteria is questionable. The tests of the subgingival plaque do not only add to the microbiological knowledge, but might also promote the overtreatment with antibiotics, such as the in the Netherlands popular combination of amoxicilline and metronidazole. The balance between host and microflora can be restored in most patients by mechanical elimination of the mainly Gram negative anaerobic subgingival plaque. In special occasions metronidazole can be empirically prescribed in order to support the subgingival debridement. In the relatively rare occasions of superinfection, a sensitivity test of the subgingival microbiota is recommended.