Dental Unit Waterline Testing Practices: An 11-Year Retrospective Study

Abstract

Abstract Objectives This retrospective study examined the dental unit waterline (DUWL) testing practices of numerous Saskatchewan clinics over a period of 11 years, with an emphasis on their responses after identification of high microbial levels. Materials and Methods Dental clinics (n = 129) aseptically collected samples of output water from their air/water syringes, handpieces, and ultrasonic scaler lines using Sigma-Aldrich® waterline test kits and delivered them to a quality assurance laboratory. Tests were incubated for seven days at room temperature, and those with heterotrophic plate counts > 500 CFU/mL were reported as failures. Statistical analyses were performed on a database containing 3,567 test results. Results Participating clinics submitted an average of 10 DUWL tests per year. Overall, 21% of tests failed, and a moderate positive association (rs = .48, p < 0.001) was found between clinics’ DUWL testing frequency and failure rate. Only 7% of failed DUWL tests were followed up by collection of a subsequent test within 14 days, of which 46% still exceeded the 500 CFU/mL threshold. Conclusions Our findings demonstrate an association between DUWL testing frequency and detection of unacceptable microbial levels, along with infrequent retesting and often-inadequate intervention after a failed test. This suggests the need for further efforts at the regulatory and educational levels to maintain adequate water quality during dental treatment. Clinical Relevance: Procedural water can become contaminated in DUWLs and endanger patients. Regular DUWL monitoring and evidence-based interventions to treat contaminated systems are necessary to safeguard patient health.