Low Electric Current Enhancement of a Dental Unit Waterline Cleaner

Objective: Evaluate, by bacterial culture, the effect of low amperage current on ClO₂ control of planktonic effluent and biofilm in a simulated dental unit waterline (DUWL). Methods: The 15' reservoir-to-air-water-syringe distance of a DUWL was simulated by three 5' sections of 1/8" polyurethane tubing joined by barb fittings. One length containing 0.2mm diameter platinum wire and a parallel length without wire (control) were connected via Y-fitting to a peristaltic pump and a 10L carboy of sterilized water. During experiments the pump was run 5min every half-hour, 9AM-5PM, 5 days-a-week. The water was inoculated with Pseudomonas aeruginosa (10⁴CFU/ml) and the system run until there was a steady state of effluent bacterial counts. The system was then supplied with sterile water or a 1/10 dilution of 0.1% stabilized ClO₂ (MicroClear, Rowpar Pharmaceuticals Inc.). An electric potential (15V DC, 10mA) was applied to the wire as cathode or anode with opposite polarity at barb fittings. Effluent was sampled every other day, serially diluted, spread in triplicate on Pseudomonas-selective agar, and incubated aerobically (22°C, 48h). Colony counts were converted to colony-forming units (CFU)/ml. After trials, biofilm formation was determined by culture of 2.1cm sections of tubing, as described above, and expressed as CFU/cm². Mean±S.D. counts were compared by t tests. Results: Effluent counts of water with or without current did not significantly differ, however biofilm counts near barb anode were 3.7x10¹±0.03x10¹ CFU/cm² with current and 2.0x10⁴±9.5x10³ CFU/cm² without (P≤0.02). Over 4 weeks, with ClO₂ and wire as cathode or anode, effluent counts were usually zero, whereas counts from samples without current were statistically greater. Biofilm counts near barb cathode or anode were zero, whereas without current counts ranged from 5.3x10¹± 3.2x10¹ to 5.8x10²±2.0x10² (P≤0.05). Conclusion: A 10mA current significantly enhanced efficacy of a buffer stabilized ClO₂ waterline cleaner against planktonic bacteria and biofilm.