Effectiveness of a Water Disinfection Method Based on Osmosis and Chlorine Dioxide for the Prevention of Microbial Contamination in Dental Practices

Initial waterline contamination by Pseudomonas aeruginosa in newly installed dental chairs

Water contamination in dental unit waterlines (DUWLs) is a potential source of healthcare-associated infection during dental care. The aim of this study was to evaluate the microbiological quality of DUWLs water from newly installed dental chairs in a French University Hospital. The microbiological quality of water from 24 new DUWLs initially disinfected by ICX Renew-prior to use of the dental units for patient treatment-was assessed for total culturable aerobic bacteria at 22°C and 36°C, Legionella sp., Pseudomonas aeruginosa, and total coliforms. Among the 24 samples analyzed, 21 were compliant with the water quality levels: 19 had no bacteria, and 2 contained only 4 and 1 CFU/mL for total culturable aerobic bacteria at 22°C and 36°C, respectively. Three samples were non-compliant due to contamination by P. aeruginosa (4, 2, and 2 CFU/100 mL). Controlling and preventing the microbiological contamination of DUWLs, especially by pathogenic bacteria, at the time of the installation of the new dental chairs are crucial to prevent healthcare-associated infection in dentistry.

IMPORTANCE

Dental unit waterlines (DUWLs) of new dental chairs may be contaminated before their first clinical use, so an initial shock disinfection is crucial at the time of their installation. The microbiological analyses are crucial to control the water quality of DUWLs before their first clinical use because their disinfection does not guarantee the elimination of all bacteria.

Comparison of antimicrobial efficacy of different disinfectants on the biofilm formation in dental unit water systems using dip slide and conventional methods: A pilot study

OBJECTIVE

Biofilm formation in dental waterlines brings opportunistic infections, especially for immunosuppressive patients. This study aimed to determine biofilm-forming microorganisms by various methods and investigate disinfectants' effects on biofilm.

MATERIALS & METHODS

In the study, samples were obtained from the waterlines of 10-15 aged six dental units, before (0 min.) and after chlorine dioxide (ClO2) and hypochlorous acid (HOCl) treatment (1, 5, 10, 20, and 30 min.), and total colony counts were performed using conventional surface smear method (SSM) and dip slide method (DSM). The Congo red agar and Christensen methods were used to examine the biofilm-forming properties of the isolates. Monitoring of biofilm presence was also visualized by SEM scanning.

RESULTS

When DSM and SSM are compared in all units where ClO2 and HOCl are applied, DSM can detect bacterial growth even during periods of greater exposure to disinfectant application. Although DSM can achieve a value approaching 3% even at the 10th minute in units treated with HOCl; SSM does not show reproduction at the same disinfectant exposure and duration; It was observed that in the units where ClO2 was applied, the growth was no longer observed at the 10th minute with DSM, and SSM, 50% growth in the first minute of the units treated with ClO2 could not be detected in the 5th minute.

CONCLUSIONS

It is concluded that it can be advisable to routinely disinfect the dental unit water systems with non-toxic doses of ClO2 application before patient treatments in clinics and also to perform contamination controls at regular intervals with DSM, which is a sensitive and very practical method.

RESEARCH HIGHLIGHTS

It has been observed that the dip slide method can count bacteria more sensitively than conventional methods in dental water systems without the need for experienced personnel and equipment. The difference between biofilm formation in water systems before and after disinfectant exposure in SEM examinations is remarkable. The effects of ClO2 and HOCl on biofilm were investigated and bacterial growth was inhibited in dental units between 5 and 10 minutes with both disinfectants.

Bactericidal Mechanisms of Chlorine Dioxide against Beta-Hemolytic Streptococcus CMCC 32210

Chlorine dioxide is a globally recognized green and efficient disinfectant. This study aims to investigate the bactericidal mechanism of chlorine dioxide using beta-hemolytic Streptococcus (BHS) CMCC 32210 as a representative strain. BHS was exposed to chlorine dioxide, the minimum bactericidal concentration (MBC) values of chlorine dioxide against BHS were determined by the checkerboard method in preparation for subsequent tests. Cell morphology was observed using electron microscopy. Protein content leakage, adenosine triphosphatase (ATPase) activity, and lipid peroxidation were determined by kits, and DNA damage was determined using agar gel electrophoresis. The concentration of chlorine dioxide during disinfection showed a linear relationship with the concentration of BHS. Scanning electron microscopy (SEM) results showed that chlorine dioxide caused significant damage to the cell walls of BHS at a concentration of 50 mg/L, but had no significant effect on Streptococcus exposed to different exposure times. Furthermore, the extracellular protein concentration increased with increasing chlorine dioxide concentration, while the total protein content remained unchanged. The activities of Na⁺/K⁺-ATPase and Ca²⁺/Mg²⁺-ATPase decreased with increasing chlorine dioxide concentration. Chlorine dioxide treatment led to significant lipid peroxidation and DNA degradation in BHS. Leakage of intracellular components indicated that chlorine dioxide damaged the cell membrane of BHS. Chlorine dioxide exposure resulted in oxidative damage to lipids and proteins, which negatively impacted the cell wall and membrane of Streptococcus. This caused increased permeability and inactivation of key enzymes (Na⁺/K⁺-ATPase and Ca²⁺/Mg²⁺-ATPase) involved in respiratory metabolism, ultimately leading to DNA degradation and bacterial death due to either content leakage or metabolic failure.