Bacterial contamination of dental unit waterlines

Abstract

Safety of patients and dental personnel requires the appropriate microbiological water quality in dental units. During treatment, patients and dental workers are exposed both to direct contact with bacteria-contaminated water in the form of splatter and with contaminated water aerosol emitted during work by unit handpieces, including rotating and ultrasonic instruments. The aim of the study was to determine the qualitative and quantitative contamination of water in dental unit reservoirs with aerobic and facultative anaerobic bacteria. The study material included water sampled from 107 dental unit reservoirs located in dental surgeries of public health centres. Conventional microbiological methods were used to identify microorganisms. The study shows that the contamination of water in dental unit reservoirs with aerobic and facultative anaerobic bacteria is commonplace. The mean concentration of mesophile bacteria in dental unit reservoir water exceeded 1.1 × 105 cfu/ml. The prevailing species were Gram-negative bacteria of the families Burkholderiaceae, Pseudomonadaceae, Ralstoniaceae and Sphingomonadaceae. The most numerous bacteria were Ralstonia pickettii, constituting 49.33 % of all the identified aerobic and facultative anaerobic bacteria. Among Gram-positive rods, the most numerous were bacteria of the genus Brevibacterium (5.83 %), while the highest percentage shares (13.25 %) of all Gram-positive microorganisms were found for Actinomyces spp. The study confirms the necessity of regular monitoring of microbial contamination of dental unit waterlines (DUWL) and use of various water treatment procedures available to disinfect DWUL.

The microbial profiles of dental unit waterlines in a dental school clinic

“…This finding is in accordance with many of the previous studies. 15,16,17 This bacterium is known to be isolated from water regardless of its source. It could be isolated from municipal drinking water, bottled water, dental waterline tubes, hospital water supplies, standard purified water, laboratory-based highpurity water systems and industrial ultra-pure/ high purity water.…”

“…These findings are similar to previous studies. 22,23 Sphingomonas paucimobilis was reported to cause outbreaks of bacteremia among immunocompromised patients in hematology and oncology units due to bacterial contamination of hospital water systems. 24 It is now emerging as an opportunistic pathogen that is frequently reported in clinical settings.…”

“…Contaminated water in DUWLs causes a health threat to both patients and dental staff who are regularly exposed to aerosol and splatter. 1 The patients with the highest risk of infection from contaminated water are immunocompromised patients, elderly patients and patients with recent surgeries and open wounds. Bacteria responsible for DUWL contamination can originate from municipal water piped into the dental chair unit or from patients' oral cavities through a process known as back-siphonage.…”

“…The statement recommended improving the dental unit design so that by the year 2000,water delivered to patients during non-surgical dental procedures would contain no more than 200 colony forming units (CFU)/ml of aerobic mesophilic heterotrophic bacteria. 1,11,12 This was equivalent to the standard for dialysate fluid. In 2003, the Center for Disease Control's (CDC) guidelines for infection control in dental health care settings stated that coolant/irrigant water used in non-surgical dental procedures should meet the Environmental Protection Agency (EPA) regulatory standards for drinking water which is less than or equal to 500 CFU/ml of heterotrophic bacteria.…”

“…In 2003, the Center for Disease Control's (CDC) guidelines for infection control in dental health care settings stated that coolant/irrigant water used in non-surgical dental procedures should meet the Environmental Protection Agency (EPA) regulatory standards for drinking water which is less than or equal to 500 CFU/ml of heterotrophic bacteria. 1,13 RAK College of Dental Sciences (RAKCODS), UAE moved into a new building in 2011. The main water supply to the college is through the Municipality network.…”