Microbial contamination of dental units and ultrasonic scalers.

Microbial contamination of the water system in 12 dental units and nine ultrasonic scalers was investigated. Water samples from ultrasonic scalers, high-speed handpieces and water syringe lines showed microbial concentrations of up to 2.6 million, 3.3 million and 190,000 colony forming units/ml respectively. Flushing the lines for 2 minutes reduced the microbial levels, but complete elimination of all bacteria was not achieved. The infectious potential of contaminated water, to the dentists and patients, particularly the compromised host is discussed.