What structural feature of bacteria makes them most resistant to antimicrobials and host immune defenses in dental biofilm?

Dental plaque is a classic biofilm — a structured community of bacteria embedded in an extracellular polymeric substance (EPS) matrix attached to tooth surfaces. Biofilm bacteria are significantly more resistant to antimicrobials (up to 1,000 times more resistant than planktonic bacteria) due to: reduced antibiotic penetration through the EPS matrix, altered metabolic activity of bacteria deep within the biofilm, presence of persister cells, gene expression changes, and protection from host immune cells and antibodies. Dental caries and periodontal disease are both biofilm-associated diseases. Mechanical disruption (toothbrushing, scaling) is the most effective way to control dental biofilm.