Repeated Local Minocycline Effect on Biochemical Markers of Inflammation During Periodontal Maintenance

Objectives: The aim of this study was to examine the effect of repeated local application of minocycline microspheres (MM; designed to reduce bacteria and subsequent periodontal inflammation) on inflammatory biomarkers in patients diagnosed with moderate chronic periodontitis undergoing periodontal maintenance therapy (PMT). Specifically, this study evaluated the ratios of interleukin (IL)-1β (pro-inflammatory cytokine) and IL-1 receptor antagonist (ra; anti-inflammatory and IL-1 blocking cytokine) in gingival crevicular fluid (GCF) at baseline, 6-month, and 12-month PMT recalls.
Methods: Subjects undergoing 6-month PMT for chronic periodontitis at the UNMC College of Dentistry were randomized by gender and smoking status into two experimental site treatment groups: 1) root planing plus minocycline microspheres (RP+MM, n= 19) or root planing alone (RP, n=20). Thirty-second GCF samples and bleeding on probing measurements were obtained at the experimental site (baseline ≥ 5 mm posterior interproximal probing depth that bled on probing) during normal PMT recalls at baseline, 6 months and 12 months. The cytokine levels were determined by an enzyme-linked immunosorbent assay and ratios (IL-1β pg/ml ÷ IL-1ra ng/ml) evaluated relative to group and time by analysis of variance.
Results: The IL-1β/IL-1ra ratio at baseline was similar in both the RP (4.56 ± 3.60) and RP + MM (5.89 ± 3.69) groups (p = 0.80). A non-significant decrease was seen in both groups at 6 months (2.98 ± 3.69 and 2.71 ± 3.69, respectively), but at 12 months a significant increase was noted in the RP + MM compared to RP (20.11 ± 3.79 versus 4.80 ± 3.60, p = 0.0046). However, the clinical measure of inflammation (bleeding on probing) stayed significantly lower than baseline at 12 months (p < 0.0001).
Conclusions: The preliminary study suggests that two 6-month MM applications demonstrated an unexpected increase in inflammatory biomarkers after one year, suggesting that multiple MM applications do not create a long-term biochemical anti-inflammatory effect.