The effect of distillation and line cleaning on the quality of water emitted from dental units.

PURPOSE

To monitor water emitted from dental units connected to centralized water distillation units fitted with reservoirs for dispensing chemicals designed to control biofilms.

METHODS

Three private practice dental offices participated in the study. None of the office operatories had independent water reservoir (bottle) systems or any other type of water treatment equipment. Initially, 5.0 mL water specimens were obtained from the handpiece and three-way syringe service lines as well as from the sink faucets in three operatories in each office. Specimens were collected at the end of the workweek. Specimens were neutralized for residual chlorine, diluted and spiral plated onto R2A agar. Aerobic incubation was allowed for 7 days at 21 degrees C. Numbers of colonies were then determined and expressed as CFU/mL. If water specimens containing more than 200 CFU/mL were detected, the offices were equipped with water distillers with attached cleaning solution dispensers. The units allowed distilled water to move under normal pressure to all connected dental units. When cleaning, the distillers were inactivated, which allowed cleaning fluid to move under pressure from the dispensers through all unit waterlines. The waterline-cleaning scheme followed the manufacturer recommendations. The presence of no more than 200 CFU/mL in emitted water was then established and a regimen of weekly cleanings applied for 3 weeks. Water specimens were always collected on the last workday of the week. Then, cleaning was suspended and weekly monitoring performed. Cleaning was restored immediately after detection of more than 200 CFU/mL.

RESULTS

Levels of microbial contamination prior to the initiation of cleaning indicated marked variability (720-332,000 CFU/mL) and that water containing less than 200 CFU/mL was not being emitted from any operatory water source. However, sought-after water was consistently obtained over a period of 3 weeks from all unit sources after line-cleaning processes were completed. Water containing less than 200 CFU/mL was obtained from all unit sources in the three offices after skipping of one weekly cleaning. In one office, cleaning was suspended for 3 weeks without affecting water quality. Resumption of weekly cleanings produced desirable water from all sources in the three offices within 2 weeks. Results indicate that dental units attached to centralized combined water distillation-cleaning solution distribution systems can produce water with less than 200 CFU/mL and that the missing of one weekly cleaning did not negatively affect water quality.