The efficacy of
metronidazole and
doxycycline in preventing recurrent
periodontitis was studied in 23 patients.
After treatment in the previous 7 months with either bimonthly scaling and 3 weeks of systemic
doxycycline (11 subjects) or scaling and placebo (12 subjects), patients were monitored for recurrent
periodontitis and were scaled every 2 months. When either a
periodontal abscess or greater than 2 mm loss of gingival attachment was observed,
metronidazole was administered (250 mg every 8 hours) for 10 days. In the placebo plus
metronidazole group, 5 patients (42%) exhibited recurrent
periodontitis after the
metronidazole regimen compared with only one (9%) in the
doxycycline plus
metronidazole group (P less than 0.096). Subgingival plaque samples at study and healthy control sites were screened for the presence of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Eikenella corrodens, and Fusobacterium nucleatum by immunofluorescence and for spirochetes using Ryu's
stain. Presence/absence analysis of the sum of scores of the 6 individual pathogens demonstrated large reductions (P less than 0.005) in the frequency of detection of pathogens in the former
doxycycline compared with the placebo plus
metronidazole group at both study and control sites before and one month after
metronidazole. By 7 months after
metronidazole, there was no detectable difference between groups. These results indicate that prevention of recurrent
periodontitis with
metronidazole may be enhanced by previous treatment with
doxycycline.