Evaluation of a hydrogen peroxide disinfectant for dental unit waterlines

Abstract

The purpose of this study was to investigate the use of a hydrogen peroxide-based dental unit waterline, or DUWL, treatment to reduce the colonization and growth of heterotrophic bacteria. Twenty-three dental units with self-contained water systems were randomly selected. Three of the units and tap water served as controls. Twenty-four water samples were taken at baseline and once a week for five weeks. They were serially diluted, spread-plated in duplicate onto R2A agar plates and incubated at 37 C for seven days. At baseline, the tap water control had a mean count of 0 colony-forming units/milliliter, or CFU/mL, the three control DUWLs had a median count of 8,440 CFU/mL and the 20 treated DUWLs had a median count of 9,760 CFU/mL. By week 1, 19 (95 percent) of the 20 treated DUWLs had counts of less than 200 CFU/mL, and by week 4, the median count for all of the treated DUWLs was 0 CFU/mL. The measurement at week 5 showed that the reduction to below 200 CFU/mL had been maintained. Scanning electron micrographs from processed DUWL tubing samples revealed a similar pattern of results, with biofilm accumulation more evident in the untreated control specimens. Following the parameters of this study, the authors used a hydrogen peroxide-based disinfectant to achieve the ADA goal of no more than 200 CFU of heterotrophic, mesophilic bacteria per milliliter of unfiltered output water. An easy-to-use hydrogen peroxide-based DUWL disinfectant demonstrated effectiveness in improving the quality of water used for intraoral procedures. Protocol compliance meets the ADA year 2000 goal.