| Background. Dental unit water systems not regularly cleaned grow biofilms, and the effluent water from these units that are used for patient care may show contamination levels of more than a million colony forming units/milliliter (CFU/mL). Initial and periodic cleaning of dental water system with a cleaner disinfectant helps control biofilms, and use of chemically treated water beneficial in controlling the effluent dental treatment water contamination. Hydrogen Peroxide was evaluated in this study to control contamination of the water system.Materials and methods. To study the effects of H 2O2 on contamination control, 4 units of an automated dental unit water system simulation device was used for 12 weeks. All units were initially cleaned to control biofilms and inorganic deposits. H2O 2 at concentrations of 1%, 2%, 3% was used weekly for periodic cleaning in three treatment group units (units 1, 2 & 3), with 0.05%, 0.15% and 0.25% H2O2 in municipal water used as irrigant respectively. The control unit (unit 4) did not have weekly cleanings and used municipal water as irrigant. Laser Scanning Confocal Microscopy and Scanning Electron Microscopy were used to study deposits on lines, and weekly heterotrophic plate counts done to study effluent water contamination. A 24 hour in vitro challenge test with 7%, 3% and 2% H2O2 on mature biofilms was conducted using harvested waterlines to study biofilm and inorganic deposit removal.Results. By the end of study, heterotrophic plate counts of effluent water showed that the control unit reached contamination levels in excess of 400,000 CFU/mL while all treatment units showed contamination levels <500 CFU/mL through most of the 12 weeks. All treatment units showed varying levels of biofilm and inorganic deposit control in this short 12 week study. The in vitro challenge test showed although there was biofilm control, there was no eradication even when 7% H2O 2 was used for 24 hours.Conclusions. In this study we inferred that 2% H 2O2 used as a periodic cleaner, and diluted to 0.05% in municipal water for irrigation was beneficial in controlling biofilm and planktonic contamination in dental unit water systems. However, to remove well established biofilms, it may take more than 2 months when initial and multiple periodic cleanings are performed using H2O2. |
