Abstract
Objectives: A standard method to assess antimicrobial efficacy in dental unit waterlines (DUWL) using a microbial consortium and a chemical disinfectant has previously been presented by ADA/ANSI Working Group 9.48. The simple DUWL model described in this study is designed to replicate biofilm growth during clinical use, using tap water as source water, and measure its reduction and prevention with rechargeable antimicrobial dental tubing. Methods: The model was first calibrated during a four-week, preliminary period using one experimental line comprised of detachable 5-cm sections of polyurethane tubing that led from a carboy, containing 1,500 mL of tap water, to a collection flask. A computerized system pumped water through the line, simulating a typical workday at a predoctoral dental teaching clinic. Then, the same model was modified to test rechargeable antimicrobial tubing (T) for eight weeks compared to a treated control line (RC) and a negative control line (C). Weekly, samples of source water, effluent, and adherent bacteria from inside three 5-cm sections of each line were cultured on R2A agar. The internal surfaces of T, RC, and C were examined for the presence of biofilm using scanning electron microscopy (SEM). Results: Biofilm growth was constant on the inner walls of C and was confirmed with SEM. The antimicrobial agent initially prevented, and then reduced biofilm growth for limited periods of time in T and RC. There was a significant difference in bacterial counts between T and RC versus C (p=0.002). Conclusions: This DUWL model effectively replicated biofilm formation inside DUWL with tap water as source water and was used to test the efficacy of rechargeable antimicrobial tubing compared with a treated and an untreated control line. The model can also be used as a simple, reproducible method to test the efficacy of DUWL disinfectant products.
