Dental Water System Contamintion Control with Electrochemically Generated ClO₂

Objectives: To utilize shock concentrations (60 and 20 ppm) of chlorine dioxide to control biofilms and irrigant concentration (2 ppm) chlorine dioxide in controlling planktonic organisms in water. Methods: An automated dental unit water system with 4 units (each with 4 handpiece lines and 1 air/water syringe line) containing naturally occurring mature biofilms and effluent contamination of >80,000 cfu/mL was used as a test system. The electrochemical ClO2 generator was retrofitted to the system. One unit was a control that was not cleaned initially and periodically and used municipal water as irrigant. In the first month, Treatment Unit 1 used 60 ppm ClO2 (10 min) daily, Treatment Unit 2 used 60 ppm ClO2 (10 min) weekly, and Treatment Unit 2 used 60 ppm ClO2 (10 min) monthly. All treatments of 60 ppm (10 min) was dropped to 20 ppm (5 min) for the remaining 2 months. The treatment units used 2 ppm ClO2 (600 mL in municipal water) daily as irrigant. Baseline and weekly water samples were plated on R2A agar from all unitsfor heterotrophic plate counts (HPC). Baseline and post-study line samples underwent Scanning Laser Confocal Microscopy to study biofilm control. Results: The control unit showed >80,000 cfu/mL contamination througout the study. All treatment units showed HPC of <10 cfu/mL from the second week onwards. Mature biofilms were seen in all baseline samples and post-study line sample of the control unit. Post-study line samples of all treatment groups showed complete removal of biofilms. Conclusions: Initially and periodic cleaning with higher concentrations of ClO2 and use of low concentration of ClO2 in municipal water as irrigant can effectively control contamination in dental unit water system. Support: NIH NIDCR SBIR Phase I Grant # 1R43 DE16178-01 subcontract through Lynntech Inc. to TAMRF