Chlorine dioxide (ClO₂) may be an effective disinfectant for dental chair unit (DCU) waterlines, as it appears to eliminate microbial contamination and biofilm buildup. The study was recently published in PLoS One.
Furthermore, continuous low-dose ClO₂ flushing may maintain low microbial levels in DCUs, while occasional high-dose treatments can be used to remove biofilms, with ongoing application needed for effective disinfection, the authors wrote.
“Our results prove that permanent low-dose ClO₂ application of DCU waterlines is recommended for sustainable water disinfection,” wrote the authors, led by Julian Winkler, PhD, of the University Hospital Münster Institute of Hygiene in Germany (PLoS One, March 5, 2026, Vol. 21:3, e0342347).
DCUs typically use nonsterile tap water, which can lead to high microbial loads, particularly after periods of stagnation. This study evaluated flushing protocols using low-dose ClO₂ for continuous disinfection and high-dose shock treatments for biofilm removal, noting that frequent high concentrations are restricted and may damage equipment. The goal was to assess whether continuous low-dose ClO₂ is more effective than intermittent high-dose use in maintaining long-term microbial control.
Automated flushing protocols using varying concentrations of ClO₂ were tested to evaluate their effectiveness in reducing microbial contamination and biofilms in DCUs. After periods of stagnation, shock disinfection with greater than or equal to 15 mg/L ClO₂ was used, followed by repeated rinsing with tap or filtered water to monitor microbial reduction under different conditions, they wrote.
Additional cycles combined multiple ClO₂ treatments at lower concentrations (1.2 to 2.4 mg/L) with staged flushing and stagnation periods to assess sustained disinfection effects. A separate protocol used repeated low-dose ClO₂ flushing after initial tap water rinses to evaluate continuous disinfection performance over several days. Microbial load was measured using agar culturing for colony-forming units and flow cytometry to count total and damaged bacterial cells, they wrote.
High-dose shock disinfection achieved greater reductions of up to 2.54 log₁₀, lowering intact cell counts (ICC) to 4.13 log₁₀, though levels quickly returned to near baseline afterward. When filtered water and high ClO₂ concentrations were used, ICC decreased from 4.46 to 3.10 log₁₀ in the syringe and from 4.48 to 3.4 log₁₀ in the cup filler.
Additionally, total cell counts increased by about 0.5 log₁₀ due to biofilm disruption. Continuous low-dose ClO₂ (1.2 mg/L) provided more sustained reductions (up to 2.51 log₁₀) than single high-dose treatments (22.7 mg/L), demonstrating effectiveness in reducing both microbial contamination and biofilms.
However, the findings were limited in generalizability because they were based on a single DCU and lacked real-world patient use simulation, the authors added.
“ClO2 seems to be a suitable disinfectant that removes both microbiological contamination and biofilms from the DCU,” Winkler and colleagues concluded.
For a broader look at DUWL treatment strategies, including a recently covered study on electrochemically activated solutions, DrBicuspid's waterline coverage offers useful context. Practices looking to strengthen their protocols can also explore DrBicuspid's full interview series on dental unit waterlines, which covers testing, training, compliance, and product selection in depth. Additionally, research covered by DrBicuspid found that training gaps remain a significant barrier to effective DUWL infection control across many practices.
