Effects of Hydrogen Peroxide on Dental Unit Biofilms and Treatment Water Contamination

Abstract

Objectives:To study effects of various concentrations of hydrogen peroxide on mature waterline biofilms and in controlling planktonic (free-floating) organisms in simulated dental treatment water systems; and to study in vitro the effects of 2%, 3%, and 7% hydrogen peroxide on the removal of mature biofilms and inorganic compounds in dental waterlines.Methods:Four units of an automated dental unit water system simulation device was used for 12 weeks. All units were initially cleaned to control biofilms and inorganic deposits. H2O2 at concentrations of 1%, 2%, 3% was used weekly for periodic cleaning in three treatment group units (units 1, 2 & 3), with 0.05%, 0.15% and 0.25% H2O2 in municipal water used as irrigant respectively. The control unit (unit 4) did not have weekly cleanings and used municipal water as irrigant. Laser Scanning Confocal Microscopy and Scanning Electron Microscopy were used to study deposits on lines, and weekly heterotrophic plate counts done to study effluent water contamination. A 24 hour in vitro challenge test with 7%, 3% and 2% H2O2 on mature biofilms was conducted using harvested waterlines to study biofilm and inorganic deposit removal.Results:Heterotrophic plate counts of effluent water showed that the control unit reached contamination levels in excess of 400,000 CFU/mL while all treatment units showed contamination levels <500 CFU/mL through most of the 12 weeks. All treatment units showed varying levels of biofilm and inorganic deposit control in this short 12 week study. The in vitro challenge test showed although there was biofilm control, there was no eradication even when 7% H2O2 was used for 24 hours.Conclusions:2% H2O2 used as a periodic cleaner, and diluted to 0.05% in municipal water for irrigation was beneficial in controlling biofilm and planktonic contamination in dental unit water systems. However, to remove well established biofilms, it may take more than 2 months when initial and multiple periodic cleanings are performed using H2O2.

Bacterial contamination of dental unit waterlines

“…According to American Dental Association (ADA), dental water should not have more than 200 cfu/ml of aerobic, mesophilic, heterotrophic bacteria, and according the ADA and the Center for Disease Control and Prevention's conclusion, maximum contamination of dental treatment water should be <500 cfu/ml (Lin et al 2011). Generally, bacterial contamination detected in the unit reservoirs examined by the authors very significantly exceeded the recommended values.…”

“…This points to the strict necessity of a DUWL decontamination protocol. The advantages of a closed dental unit water system should be used, as well as the possibility to apply different biocides (Liaqat and Sabri 2010; Lin et al 2011). …”

Update on infectious risks associated with dental unit waterlines

“…Large amounts of carcinogenic trihalomethanes are produced when NaOCl is in contact with organic matter such as biofilms (Lin et al ., ). H 2 O 2 is relatively less harmful than NaOCl, and does not produce any disinfection by‐products (Lin et al ., ). In addition, Roberts et al .…”

“…For example, while sodium hypochlorite is effective in improving microbial quality of DUWL water, it is highly corrosive and damaging to the DUWL system. Large amounts of carcinogenic trihalomethanes are produced when NaOCl is in contact with organic matter such as biofilms (Lin et al, 2011). H 2 O 2 is relatively less harmful than NaOCl, and does not produce any disinfection by-products (Lin et al, 2011).…”

Development of a Universal Fluorescent Probe for Gram‐Positive Bacteria

“…Theu niversal selectivity of BacGO was also confirmed by flow cytometry using DAPI to stain the nuclei (Supporting Information, Figure S4). While BacLight TM Green is commonly used for detecting all bacteria, [28] it showed as omewhat stronger tendency to stain Gram-positive bacteria. While BacLight TM Green is commonly used for detecting all bacteria, [28] it showed as omewhat stronger tendency to stain Gram-positive bacteria.…”