The efficacy of disinfectants in the decontamination of dental unit water lines: an in vitro laboratory study

OBJECTIVES/AIMS: This in vitro laboratory study compared the efficacy of water, sodium percarbonate (SPC) and chlorine dioxide (ClO(2)) solutions in the disinfection of dental unit water lines (DUWLs). MATERIALS AND METHODS: New DUWL tubes were cut, split open, and mono-culture and mixed-culture biofilms of Staphylococcus aureus, Enterococcus faecalis and Streptococcus mutans were grown. Harvested biofilms from the sectioned DUWL tubes were exposed to sterile distilled water, SPC or 5 and 10 p.p.m. ClO(2) in both a stationary phase and through a constant flow. Bacterial counts were compared using the Kruskal–Wallis nonparametric rank test. RESULTS: In the mono-culture biofilms, SPC, 5 and 10 p.p.m. ClO(2) significantly reduced all the test organisms (P<0.01). However, no significant difference was found between SPC and ClO(2). In the mixed-culture biofilms exposed to disinfectant without flow, ClO(2) significantly reduced the biofilm (P=0.02) compared with water and SPC. Similarly, in the constant flow study, ClO(2) proved to be superior to water. CONCLUSION: At low concentrations, ClO(2) with and without flow significantly reduced the mixed-culture biofilm grown in vitro on the sections of the DUWL tubes. Therefore, it has the potential to be used in the patient treatment water, as it is potable at these concentrations, and to decontaminate and limit the biofilm formation in the water lines.