Long-term treatment with subantimicrobial dose doxycycline exerts no antibacterial effect on the subgingival microflora associated with adult periodontitis.
BACKGROUND
The purpose of this study was to determine whether treatment with subantimicrobial dose doxycycline (SDD), 20 mg bid, exerted an antimicrobial effect on the microflora associated with adult periodontitis.


METHODS
Following the approval of the protocol and informed consent forms by the respective IRBs at the University of Florida and West Virginia University, 76 subjects with adult periodontitis were entered and randomly assigned to receive SDD or placebo. A split-mouth design was utilized, with each subject receiving subgingival scaling and root planing (SRP) in two quadrants immediately following baseline data collection, while the remaining two quadrants were left unscaled (non-SRP). Microbial samples were collected prior to treatment, after 3, 6, and 9 months of treatment, and after 3 months of no treatment. The samples were examined by microscopy and by enumeration on selective and non-selective media.


RESULTS
All treatments resulted in statistically significant decreases in the proportions of spirochetes and motile rods (P <0.05) and in an increase in the proportion of coccoid forms (P <0.0001) relative to baseline. No between-treatment differences were detected between the SDD and placebo treatments in either the SRP or non-SRP design, with the exception of the small and large spirochetal groups. The spirochetal proportions present in the SDD group were significantly lower (P<0.05) than the paired placebo group during the 9-month treatment and was preceded by a significant decrease (P<0.01) in the proportion of microbiologic sample sites that bled on probing. No between- treatment differences were detected in any of the other microbial parameters.


CONCLUSIONS
The microbial differences observed were attributed to the anticollagenase and anti-inflammatory properties of SDD and not to an antimicrobial effect.
Walker
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Periodontal Disease Research Clinics, University of Florida, Health Science Center, Gainesville 32610, USA. walkerc1@ufl.edu
Thomas
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Nangó
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S
Lennon
J
J
Wetzel
J
J
Powala
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C
D000328:Adult; D000704:Analysis of Variance; D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000008:administration & dosage*; D001421:Bacteria, Anaerobic / Q000187:drug effects*; D016009:Chi-Square Distribution; D015169:Colony Count, Microbial; D003773:Dental Plaque / Q000382:microbiology*; D012534:Dental Scaling; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004318:Doxycycline / Q000008:administration & dosage*; D006801:Humans; D061965:Matrix Metalloproteinase Inhibitors; D010518:Periodontitis / Q000188:drug therapy* / Q000382:microbiology* / Q000628:therapy; D011480:Protease Inhibitors / Q000008:administration & dosage*; D013144:Spirochaetales / Q000187:drug effects; D018709:Statistics, Nonparametric; D013997:Time Factors
D000900:Anti-Bacterial Agents; D000894:Anti-Inflammatory Agents, Non-Steroidal; D061965:Matrix Metalloproteinase Inhibitors; D011480:Protease Inhibitors; D004318:Doxycycline