DIFFERENTIAL-EFFECTS OF SYSTEMIC METRONIDAZOLE AND AMOXICILLIN ON ACTINOBACILLUS-ACTINOMYCETEMCOMITANS AND PORPHYROMONAS-GINGIVALIS IN INTRAORAL HABITATS

48 adult patients with untreated periodontitis harboring subgingival A ctinobacillus actinomycetemcomitans and/or Porphyromonas gingivalis we re randomly assigned to receive full mouth scaling alone (control) or scaling with systemic metronidazole plus amoxicillin and supragingival irrigation with chlorhexidine digluconate (test). Subgingival plaque and swab samples from tongue, tonsils, and buccal mucosa were taken at baseline, 10 days and 3, 6, 9, and 12 months. A. actinomycetemcomitan s was detected in the oral cavity, i.e., subgingival plaque and/or muc ous membranes, less frequently in test patients compared to controls a t 9 and 12 months (p < 0.01), whereas, the intraoral detection frequen cy of P. gingivalis was significantly reduced only 10 days following t herapy (p < 0.001). At any time after therapy, A. actinomycetemcomitan s was not detected intraorally in 5 of 10 (50%) test and 1 of 13 (8%) control patients harboring this pathogen at baseline; P. gingivalis wa s not detected in only 1 of 18 (6%) test and none of the 17 control pa tients harboring this pathogen at baseline. Although the data indicate d that the assessed antimicrobial therapy may suppress A. actinomycete mcomitans from the entire oral cavity below detectable levels over a m inimum of 12 months, P. gingivalis persisted or reoccurred.