Controlling Bacterial Contamination in Dental Unit Waterline by Plasma Sterilizing System

Objectives: To investigate the effectiveness of plasma sterilization system on reducing bacterial contamination and eliminating biofilms in dental unit waterlines.
Methods: Ten dental chair units (DCUs) of the same model were utilized. Five DCUs were installed with an automated plasma sterilization system (PSS) and another five DCUs were kept as non-treatment control (CTL). Water flushed form airotor-line will be served as dental unit waterlines (DUWLs) output water. The water samples will be collected at the beginning as baseline and weekly for 4 months to enumerate bacterial contamination in CFU/ml. Scanning Electron Microscope (SEM) was utilized to investigate amount of biofilm in the waterlines. Biofilms viability was observed by Live-Dead staining and confocal microscope. All statistical analyses were performed using Mann Whitney U test. A value of p<0.05 was considered significant.
Results: The dental unit output water was found to be heavily contaminated with bacteria. PSS installation effectively reduce bacteria contamination to be with standard level of less than 500 CFU/mL from the first week and throughout 4 months of experiment. The reduction in bacterial count was significant when compared with CTL group (p<0.05). Although PSS could not eradicate the exiting biofilms in the waterlines, it does reduce biofilms mass and viability. Moreover, treatment with PSS did not induce a selective shift in composition of microorganisms found in output water, as analyzed by Gram staining.
Conclusions: The Plasma sterilization system which is a part of electrochemically activated water effectively reduce bacterial contamination and reduce biofilms in dental unit waterlines.