Tetracyclines (doxycycline/minocycline) are used in periodontics. What is their mechanism of action relevant to periodontal disease management?

Correct answer: D. Inhibit collagenase (matrix metalloproteinases) AND concentrate in gingival crevicular fluid

• A. Tetracyclines are bacteriostatic, not bactericidal, and their benefit in periodontics goes beyond antibacterial effects.
• B. Tetracyclines do not promote osteoblast activity — they are anti-resorptive through MMP inhibition.
• C. Tetracyclines do not directly block IL-1.
• D. Correct. Tetracyclines (especially doxycycline at sub-antimicrobial doses in Periostat) have a dual mechanism in periodontics: (1) They inhibit matrix metalloproteinases (collagenases) that degrade collagen, slowing connective tissue destruction; (2) They concentrate in GCF at therapeutic levels, making them effective locally. Minocycline microspheres (Arestin) are placed locally into periodontal pockets.