Evaluation of Dental Unit Waterlines treated with Sterisil PureTubeTM

The bacterial load in water from untreated dental unit waterlines (DUWs) can exceed 10⁶ CFUs/ml due to formation of biofilms.  Since 2003, the Centers for Disease Control and Prevention and the American Dental Association have recommended that heterotrophic bacterial counts in DUWs be <500 CFUs/ml for non-surgical procedures.  The Sterisil PureTube is a DUW treatment that uses silver ions as an antimicrobial agent. 

Objective: The purpose of this study was to evaluate the Sterisil PureTube’s ability in a clinical setting to keep DUWs heterotrophic bacterial counts <500 CFUs/ml.  

Method: Twelve units in an orthodontic clinic were tested on Mondays before the start of the clinic day.   DUWs were rinsed for 30 seconds before collecting 40ml of water from the air-water syringe.  Source water (commercially bottled dH₂O) was also collected.  After baseline collection, 6 randomly selected units were installed with the Sterisil PureTube and Antimicrobial Bottle (Sterisil, Castle Rock, CO).  The remaining 6 units were used as controls.   Water samples were collected at baseline and after installation at 3 and 20 months.  All samples were treated with sodium thiosulfate to neutralize residual chlorine.  Samples were serially diluted and 0.1ml was plated on R2A agar plates in duplicate.  Plates were incubated aerobically at 37^oC for 7 days.  

Result:  At baseline, all units exceeded the recommended 500 CFUs/ml (mean = 237,000 CFUs/ml).  Three months after installation, Sterisil PureTube units had no detectable levels of heterotrophic bacterial counts while all untreated units were >300,000 CFUs/ml.  At 20 months, all untreated units were >500 CFUs/ml (mean = 72,853 CFUs/ml) but Sterisil PureTube units remained below the recommended 500 CFUs/ml (mean = 43 CFUs/ml, range = 0-150 CFUs/ml).

Conclusion: The Sterisil PureTube was effective in reducing and maintaining the recommended <500 CFUs/ml of heterotrophic bacteria in DUWs after 20 months of use in an orthodontic clinic.