The Effect of Adjunctive Low-dose Doxycycline Therapy on Clinical Parameters and Gingival Crevicular Fluid Matrix Metalloproteinase-8 Levels in Chronic Periodontitis

Background: Low-dose doxycycline (LDD) is recognized to have non-antimicrobial properties that can therapeutically modulate the host response. The aim of the present randomized, double-blind, placebo-controlled, parallel-arm study was to examine the effectiveness of LDD in combination with non-surgical periodontal therapy, compared to non-surgical periodontal therapy alone, on gingival crevicular fluid (GCF) matrix metalloproteinase-8 (MMP-8) levels and clinical parameters over a 12-month period in patients with chronic periodontitis.

Methods: GCF samples were collected, and clinical parameters including probing depth (PD), clinical attachment level, gingival index (GI), and plaque index were recorded. Thirty chronic periodontitis patients were randomized either to a low-dose doxycycline (LDD) or placebo group. The LDD group received low-dose doxycycline (20 mg) b.i.d. for 3 months plus scaling and root planing (SRP), while the placebo group was given placebo capsules b.i.d. for 3 months plus SRP. The patients were evaluated every 3 months during the 12-month study period. At each visit, all clinical measurements and GCF sampling were repeated. GCF MMP-8 levels were determined by a time-resolved immunofluorescence assay. Intragroup comparisons were tested by the Friedman test followed by Wilcoxon signed-rank test to analyze significance of changes over time. The Mann-Whitney test was used to determine differences between the LDD and placebo groups.

Results: Significant improvements were observed in all clinical parameters in both groups over the 12-month period (P < 0.0125). The LDD group showed a significantly greater reduction in mean PD scores at 9 and 12 months and in mean GI scores at all time points than the placebo group (P < 0.05). From baseline to 12 months, GCF MMP-8 levels were significantly reduced in both groups (P < 0.0125). The GCF MMP-8 level in the LDD group was significantly lower than that of the placebo group at 6 months (P < 0.05).

Conclusions: The present results indicate that low-dose doxycycline therapy in combination with scaling and root planing can reduce GCF MMP-8 levels and improve clinical periodontal parameters in patients with chronic periodontitis. These results provide additional information about the usefulness of low-dose doxycycline therapy as an adjunct to non-surgical periodontal therapy in the long-term management of periodontal disease. The effectiveness and course of low-dose doxycycline therapy can be monitored conveniently by assessing GCF MMP-8 levels.