Biweekly versus triweekly hydrogen peroxide shock treatment for controlling dental unit waterline contamination: a single-center pilot randomized clinical study

Background This single-center pilot randomized clinical study compared the efficacy of biweekly and triweekly 1.41% hydrogen peroxide (H 2 O 2 ) shock treatments, combined with continuous 0.0141% H 2 O 2 disinfection, for controlling microbial contamination and biofilm formation in dental unit waterlines (DUWLs). Methods Eight dental chair units (DCUs) were randomized to Group A (triweekly shock treatment, n = 4) or Group B (biweekly shock treatment, n = 4). After standardized baseline biofilm removal using BRS®, total viable counts (TVCs) and biofilm architecture assessed qualitatively by scanning electron microscopy (SEM), were monitored for 6 weeks. One randomly selected DCU (group A1 and B1) from each group underwent an exploratory additional 6-week observation, with the resulting data analyzed descriptively. Results Group B maintained a 100% compliance rate (≤ 100 CFU/mL) throughout the 6-week period, whereas Group A showed a significantly lower compliance rate of 78.47%, with recurrent microbial rebound during the third week of each cycle. Biweekly shock treatment increased the probability of compliance by 21.53 percentage points compared with triweekly treatment (95% CI: 13.74–29.32, Wald χ 2 = 29.34, P < 0.001). Significant between-group differences in TVCs emerged by day 17 ( P < 0.05). During the 12-week observation, Group B1 remained compliant, whereas Group A1 showed recurrent non-compliant TVCs during the third week of several cycles. SEM observations showed biofilm-like structures in the sampled tubing segment from Group A after 6 weeks, whereas no obvious mature biofilm-like structure was observed in the sampled segment from Group B. Conclusions Within the limitations of this single-center pilot study, continuous disinfection with 0.0141% H 2 O 2 combined with biweekly 1.41% H 2 O 2 shock treatment was associated with more consistent water-quality compliance than triweekly shock treatment after initial BRS® biofilm removal. These preliminary findings require confirmation in larger multicenter, year-round studies incorporating longer follow-up and microbial identification before any change to routine clinical protocols can be considered.