Which of the following is the MOST effective measure to control infection in the dental setting?

Correct answer: A. Not letting symptomatic patients into the office

• A. CORRECT. Source control — preventing infected individuals from entering the clinical environment — is the highest-level infection control measure because it eliminates pathogen exposure before it occurs. No downstream measure (PPE, sterilization, handwashing) can fully compensate for an active infectious source in the operatory.
• B. Instrument sterilization eliminates pathogens from reusable devices but does not prevent transmission from an infected patient who should not be in the office.
• C. Handwashing is critical for preventing contact transmission but does not address airborne or droplet sources from symptomatic patients.
• D. PPE protects the dental team and patient from transmission but is a downstream measure; it relies on an infectious agent already being present. It is essential but not the highest-level control.