Which is the most effective method to control microbial contamination of dental unit waterlines from retraction of oral fluids?

Anti-retraction valves prevent suck-back of oral fluids into the waterlines, and combined with line treatment, flushing, and quality monitoring they keep counts within the recommended limit (<=500 CFU/mL).Other options: Pressure and temperature changes do not control biofilm; visual clarity does not indicate microbial safety.Key exam takeaway: Control waterline contamination with anti-retraction valves plus treatment, flushing, and monitoring (<=500 CFU/mL).