Effect of systemic doxycycline administration on the subgingival microbial flora: a dark-field microscopy study

The effect of systemically administered doxycycline hydrochloride on subgingival microbial plaque morphotypes was evaluated using dark-field microscopy. After 1 week of drug administration, while the percentage of coccoid bacteria showed a significant increase, the percentages of spirochetes, motile rods and non-motile rods tended to decrease. Since spirochetes and/or motile rods are considered to be associated with the pathogenesis of periodontal disease, the significant decrease in the proportions of these bacteria are considered to be important. Therefore, it is suggested that doxycycline may be beneficial for the treatment of periodontal disease as an adjunct to traditional therapeutic methods.