The effect of drying dental unit waterline biofilms on the bacterial load of dental unit water

Disinfection methods of dental unit waterlines contamination: a systematic review

Background. Severe contamination of dental unit waterlines was found in healthcare settings. The benefits of decontamination methods are controversial. The aim of this review was to systematically evaluate disinfection methods in contamination control of dental unit waterlines.Methods. The terms 'dental unit waterline(s) or DUWL(s) or dental unit water line(s)' were searched through PubMed, Cochrane Library, Embase, Web of Science and Scopusup to 31 May 2021. The DUWLs' output water was incubated on R2A agar at 20-28 °C for 5-7 days to evaluate heterotrophic mesophilic bacteria. The risk of bias was evaluated by a modified Newcastle-Ottawa quality assessment scale.Results. Eighteen papers from the literature were included. One study indicated that water supply played a crucial role in disinfecting DUWLs. Three studies indicated that flushing decreased bacteria counts but did not meet the American CDC standard (500 c.f.u. ml^-1). All chlorine- and peroxide-containing disinfectants except sodium hypochlorite in one of 15 studies as well as three mouthrinses and citrus botanical extract achieved the standard (≤500 c.f.u. ml^-1). The included studies were of low (1/18), moderate (6/18) and high (11/18) quality.Conclusion. Independent water reservoirs are recommended for disinfecting DUWLs using distilled water. Flushing DUWLs should be combined with disinfections. Nearly all the chlorine-, chlorhexidine- and peroxide-containing disinfectants, mouthrinses and citrus botanical extract meet the standard for disinfecting DUWLs. Alkaline peroxide would lead to tube blockage in the DUWLs. Regularly changing disinfectants can reduce the risk of occurrence of disinfectant-resistant strains of microbes.

Management of dental unit waterline biofilms in the 21st century

Dental chair units (DCUs) use water to cool and irrigate DCU-supplied instruments and tooth surfaces, and provide rinsewater during dental treatment. A complex network of interconnected plastic dental unit waterlines (DUWLs) supply water to these instruments. DUWLs are universally prone to microbial biofilm contamination seeded predominantly from microorganisms in supply water. Consequently, DUWL output water invariably becomes contaminated by high densities of microorganisms, principally Gram-negative environmental bacteria including Pseudomonas aeruginosa and Legionella species, but sometimes contain human-derived pathogens such as Staphylococcus aureus. Patients and staff are exposed to microorganisms from DUWL output water and to contaminated aerosols generated by DCU instruments. A wide variety of approaches, many unsuccessful, have been proposed to control DUWL biofilm. More recently, advances in biofilm science, chemical DUWL biofilm treatment agents, DCU design, supply water treatment and development of automated DUWL biofilm control systems have provided effective long-term solutions to DUWL biofilm control.

First report of an acute purulent maxillary sinusitis caused by Pseudomonas aeruginosa secondary to dental implant placement in an immunocompetent patient

STUDY DESIGN

In this case report, we present maxillary Pseudomonas aeruginosa sinusitis in an immunocompetent patient who underwent an autologous bone transplant for the insertion of dental implants.

RESULTS

The infection was eradicated after removal of the dental implants and long-term antibiotic therapy.

CONCLUSION

Despite the infection resolution, severe complications were observed with important legal consequences.

An audit improves the quality of water within the dental unit water lines of general dental practices across the East of England

OBJECTIVE

To evaluate and improve upon the quality of water emanating from the dental unit waterlines (DUWLs) which supply irrigation for dental handpieces and triple spray syringes in general practice.

DESIGN

A prospective clinical audit.

SETTING

Seventy-two general dental practices in the East of England.

METHODS

In 2006, 124 dentists initially registered to participate in the audit. By 2007, 72 had begun and by 2008, 68 had completed the project. This involved collecting samples of water discharged from the DUWLs in the dental practices both before the start and mid-way through a morning session. These were tested microbiologically at a United Kingdom Accreditation Service testing laboratory.

INTERVENTIONS

Before the audit, 56% of the DUWLs were reportedly flushed through for 2 minutes at the start of the day, 29% were purged for 20 seconds in between each patient, 50% were treated with a wide range of different disinfectant solutions, 44% were drained down dry at the end of the day and 9% had no cross-infection control measures applied to them at all. In the audit, 100% used a disinfectant solution alone, predominantly either Alpron or Sterilox.

MAIN OUTCOME MEASURES

The minimum audit standard set was for the water samples to meet the United States' Centers for Disease Control and Prevention (CDC) guideline on the quality of DUWL water, namely that the United States' Environmental Protection Agency (EPA) regulatory standards for drinking water be adopted, in that no more than 5% of water samples should be contaminated with total coliforms and that they should not have more than 500 colony forming units per ml (cfu/ml) of heterotrophic water bacteria. However, the participating dentists were encouraged to try and achieve the more stringent European Union (EU) standards for potable (drinking) water, namely for the water samples to have neither Escherichia coli nor any other faecal coliforms present and for the aerobic colony count to be less than 100 cfu/ml at 22°C after 72 hours of culturing.

RESULTS

In the pre-audit survey, none of the 72 DUWL water samples were contaminated with E. coli but in five of them (7%) coliforms were recovered. Only 25% reached the EU potable water standard, of which 11% had zero planktonic bacterial contamination. Three percent were above the EU standard but below the CDC guideline/EPA regulatory drinking water standard, while alarmingly, 72% of them failed to reach this minimum audit standard altogether. However, after the application of a suitable disinfectant for at least a month, the audit revealed that E. coli still remained absent in the water samples taken from the 68 DUWLs that completed the project and in only one (1.5%) were coliforms recovered. Remarkably, nearly 81% reached the EU potable water standard, of which 54% had zero planktonic bacterial contamination, with nearly an additional 6% reaching the American CDC/EPA standard and with only 13% failing outright.

CONCLUSIONS

Clinical audit using appropriate DUWL disinfectants can result in the improvement of the quality of water that is discharged through DUWLs, thereby minimising both the risk of cross-infection to vulnerable patients as well as to dental staff chronically exposed to contaminated aerosols.

Legionella in the dental office

OBJECTIVE

This study aimed to assess the microbiology of dental unit water and municipal water in terms of Legionella species and total bacteria levels.

METHODS

The presence of Legionella species was investigated using the culture method, direct fluorescent antibody and polymerase chain reaction techniques in collected dental unit water and municipal water samples from 71 dental offices in Ankara, Turkey. In addition, total bacterial counts were assessed using the culture method.

RESULTS

In 27% of the dental unit water samples and in 13% of municipal water samples, the number of colony-forming units (cfu ml(-1)) significantly exceeded acceptable values for high-risk group patients. No Legionella spp. was found in the dental unit water samples. Legionella SG3 was found in only one municipal water sample.

CONCLUSION

The dental unit water systems examined in this study did not include Legionella spp., but other bacteria at high numbers were determined. This is a potential threat, especially for elderly people, the medically compromised patients receiving regular dental treatment and the dental clinic staff.

The effect of ultrafiltration on the quality of water from dental units

AIM

The purpose of the present study was to evaluate the effect of an ultrafiltration system on the bacteriological water quality in dental units.

DESIGN

A BIN-X UF-45R ultrafiltration system with a pore membrane of 0.03 microm was mounted at the water supply of six older dental units while six control units were disinfected with sodium hypochlorite according to a standard procedure. As the water quality in the test units deteriorated in spite of ultrafiltration the test units were subjected to chlorination at different concentrations several times during the test period.

OUTCOME MEASURE

The number of colony forming units (cfu)/ml in water was determined according to European Standards on water quality.

RESULTS

While the median number of cfu/ml in control units never exceeded 7.6x10(1) the median cfu/ml in test units increased up to >1x10(5) in 3-4 days every time chlorination of the units was interrupted.

CONCLUSION

The ultrafiltration system mounted at the water supply for six dental units was not able to control the bacteria originating from the existing biofilm in the water lines and deliver water of an acceptable quality.

Mycobacteria in drinking water distribution systems: ecology and significance for human health

In contrast to the notorious pathogens Mycobacterium tuberculosis and M. leprae, the majority of the mycobacterial species described to date are generally not considered as obligate human pathogens. The natural reservoirs of these non-primary pathogenic mycobacteria include aquatic and terrestrial environments. Under certain circumstances, e.g., skin lesions, pulmonary or immune dysfunctions and chronic diseases, these environmental mycobacteria (EM) may cause disease. EM such as M. avium, M. kansasii, and M. xenopi have frequently been isolated from drinking water and hospital water distribution systems. Biofilm formation, amoeba-associated lifestyle, and resistance to chlorine have been recognized as important factors that contribute to the survival, colonization and persistence of EM in water distribution systems. Although the presence of EM in tap water has been linked to nosocomial infections and pseudo-infections, it remains unclear if these EM provide a health risk for immunocompromised people, in particular AIDS patients. In this regard, control strategies based on maintenance of an effective disinfectant residual and low concentration of nutrients have been proposed to keep EM numbers to a minimum in water distribution systems.

The effect of Sterilex Ultra for disinfection of dental unit waterlines

AIM

To evaluate the effect of a disinfectant agent based on hydrogen peroxide (Sterilex Ultra, Sterilex Corporation, Maryland, USA) on the microbiological water quality in dental unit waterlines (DUWL).

SETTING

Six older dental units were disinfected with Sterilex Ultra and another six units with sodium hypochlorite. The results were compared to six non-disinfected units examined during a period without patient treatment.

OUTCOME MEASURE

The number of colony forming units of bacteria (cfu)/ml of water was determined according to European Standards on water quality.

DESIGN

The water quality was initially determined during a six week period, and subsequently in more detail for two weeks. Finally, the effect of prolonged administration of Sterilex Ultra was investigated for six weeks.

RESULTS

Instillation of Sterilex Ultra according to the recommendations of the manufacturer initially reduced the number of bacteria in DUWL to <10(2) cfu/ml. However, following daily, as well as prolonged administration of Sterilex Ultra a gradual recolonisation was observed resulting in bacterial numbers >10(4) cfu/ml in a number of units. Major differences between the number of cfu/ml in individual units were observed.

CONCLUSION

Neither daily nor extended administration of Sterilex Ultra was capable of maintaining an acceptable water quality in these older dental units.

The genetics of nontuberculous mycobacterial infection

The molecular aetiology of familial susceptibility to disseminated mycobacterial disease, usually involving weakly pathogenic strains of mycobacteria, has now been elucidated in more than 30 families. Mutations have been identified in five genes in the interleukin-12-dependent interferon-gamma pathway, highlighting the importance of this pathway in human mycobacterial immunity. Knowledge derived from the study of these rare patients contributes to our understanding of the immune response to common mycobacterial pathogens such as Mycobacterium tuberculosis and Mycobacterium leprae, which remain major public health problems globally. This knowledge can be applied to the rational development of novel therapies and vaccines for these important mycobacterial diseases.