Evaluation of the efficacy of Alpron disinfectant for dental unit water lines

An Evaluation of Two Systems for the Management of the Microbiological Quality of Water in Dental Unit Waterlines: Hygowater® and IGN Calbénium®

Water in dental unit waterlines (DUWL) represents a risk for vulnerable patients if its microbiological quality is not controlled. The aim of this prospective study was to evaluate two systems for its management under real conditions: Hygowater® and IGN Calbenium®. Samples of the output water of DUWL were obtained for 5 previously contaminated units connected to Hygowater®, and 5 non-contaminated units connected to IGN Calbenium®, which was already effective for more than 1 year, as a control group. Samples were regularly collected up to 6 months after the implementation of Hygowater®, and were then cultured and analyzed. With IGN Calbenium®, except for a technical problem and a sample result in one unit at 6 months (Heterotrophic Plate Count (HPC) at 37 °C of 66 colony forming units (cfu)/mL), the results showed an absence of contamination. Hygowater® took a couple of weeks to be effective on initially contaminated DUWL (over 200 cfu/mL for all the units), then showed its efficacy for 2 months (HPC at 37 °C with a mean of 40.2 ufc/mL, and HPC at 22 °C with a mean of 0.2 ufc/mL). At 6 months, results were satisfactory for HPC at 22 °C (mean of 12 ufc/mL), but HPC at 37 °C gave non-satisfactory results for 4 of the 5 units (mean of 92.2 ufc/mL). Both systems have an effect on the microbiological quality of DUWL. IGN Calbenium® appears to be more reliable on a long-term basis.

Heterogeneity in the efficacy of dental chemical disinfectants on water-derived biofilms in vitro

Conditions in dental unit waterlines are favourable for biofilm growth and contamination of dental unit water. The aim of this study was to assess the effect of several chemical disinfectants on bacteria in a biofilm model. Water-derived biofilms were grown in a static biofilm model (Amsterdam Active Attachment model), using two growth media. Biofilms were challenged with Alpron/Bilpron, Anoxyl, Citrisil, Dentosept, Green & Clean, ICX and Oxygenal in shock dose and maintenance doses. The concentration and the composition of the chemical disinfectants influenced the number of culturable bacteria in the biofilms. The application of a single shock dose followed by a low dose of the same chemical disinfectants resulted in the greatest suppression of viable bacteria in the biofilms. Exposure to Citrisil and ICX consistently resulted in failure to control the biofilms, while Alpron/Bilpron had a substantial and relevant effect on the number of bacteria in the biofilms.

Efficacy of BRS® and Alpron®/Bilpron® Disinfectants for Dental Unit Waterlines: A Six-Year Study

Biofilms in dental unit waterlines (DUWL) are a potentially significant source of contamination posing a significant health risk as these may come into contact with patients and dental staff during treatment. The aim of this study was to evaluate the microbiological quality of DUWL water treated by Biofilm-Removing-System^® (BRS^®) and Alpron^®/Bilpron^® disinfectant solutions for six years in a French university hospital. The microbiological quality of water supplied by 68 dental units—initially shock treated with BRS^®, then continuously treated by Alpron^® with sterile water during working days and Bilpron^® during inactivity period, and combined with purging every morning and after each patient—was assessed biannually during six years for total culturable aerobic bacteria at 22 °C and 36 °C, Legionella sp., Pseudomonas aeruginosa, and total coliforms. A total of 628 samples were analyzed, 99.8% were compliant with extended microbiological levels, and we never detected pathogen bacteria like Legionella sp. and P. aeruginosa. Only one sample (0.2%) was noncompliant with the level of total culturable aerobic bacteria at 36 °C, which exceeded 140 colony forming units per mL. The protocol implemented in our university hospital gives excellent results and enables control of the microbiological quality of DUWL water in the long term.

Dental Unit Water Lines and their Disinfection and Management: A Review

The perceived threat to public health from dental unit water line (DUWL) contamination comes from opportunistic and respiratory pathogens such as Legionella spp, Nontuberculous Mycobacteria (NTM) and pseudomonads. These organisms can grow and multiply in the DUWL biofilm to reach infective concentrations, with the potential for inhalation leading to respiratory infections or direct contamination of surgical wounds. In this paper we discuss current legislation and practical methods for delivering water within the DUWL that meets the standards for safety. Clinical relevance: Understanding the clinical relevance and methods for decontaminating DUWL is essential to create a safe working environment in dentistry.

Substantivity of hypochlorous acid-based disinfectant against biofilm formation in the dental unit waterlines

Objective:

The purpose of the study was to examine the substantivity of a new disinfectant against biofilm formation in the dental unit waterlines.

Materials and Methods:

Twenty dental units were selected for the study and divided into two groups: Group A (dental unit waterlines treated with the disinfectant) and Group B (untreated dental unit waterlines). Biofilm formation was monitored in both groups by removing the one dental unit waterline from each group for the period of 10 days. One inch of the dental unit waterline tube was cut at random site, and the inner lumen of the cut sections was analyzed using the scanning electron microscope (SEM) (TESCAN VEGA3 SBU).

Results:

On examination, SEM images showed that there was no slime layer or bacterial cells seen in cut section for the period of 7 days in the treated dental waterlines, which means that there is no evident of biofilm formation. In the untreated dental unit waterline cut section, slime layer was observed from day 1.

Conclusion:

Disinfectant solution was proved to be effective for 7 days against biofilm formation. This technique could be used as a valid method for disinfection of dental unit waterlines.

Contamination of dental unit waterlines: assessment of three continuous water disinfection systems

OBJECTIVES

To assess the efficacy of three continuous water disinfection systems for dental units under real conditions of dental care.

DESIGN AND SETTINGS

A prospective study carried out from 45 days to 20 months on the water microbial quality of the dental units is benefited from three different systems: two chemical treatment systems (IGN EVO/Calbenium/IGN Cartridge and Sterispray) and one physical treatment system (BacTerminator). Studied items were six dental units of the Dental Medicine and Oral Surgery Center within the University Hospital of Strasbourg (HUS), France.

RESULTS AND DISUCUSSION

The IGN EVO/Calbenium/IGN Cartridge and Sterispray systems showed an immediate and long-term efficacy on contaminated dental unit waterlines. However, the first system offers ergonomic advantages (automatic system, action on the water from the water supply network). The BacTerminator system took longer to be effective and was less effective than the other two.

Dental unit waterlines disinfection using hypochlorous acid-based disinfectant

Objective:

The purpose of the study was to investigate the efficacy of a new disinfectant to disinfect the dental unit waterlines.

Materials and Methods:

New dental unit waterlines were installed in 13 dental chairs, and biofilm was allowed to grow for 10 days. Disinfection treatment procedure was carried out in the 12 units, and one unit was left untreated. The dental unit waterlines were removed and analyzed using the scanning electron microscope (SEM) (TESCAN VEGA3 SBU).

Result:

On examination, SEM images showed that there was no slime layer or bacterial cells seen in any of the 12 cut sections obtained from the treated dental waterlines which mean that there was no evident of biofilm formation. Untreated dental unit waterlines showed a microbial colonization with continuous filamentous organic matrix. There was significant biofilm formation in the control tube relative to the samples.

Conclusion:

The tested disinfectant was found to be effective in the removal of biofilm from the dental unit waterlines.

Biofouling of surgical power tools during routine use

Surgical power tools (SPTs) are frequently used in many surgical specialties such as dentistry, orthopaedics, ophthalmology, neurology, and podiatry. They have complex designs that may restrict access to cleaning and sterilization agents and frequently become contaminated with microbial and tissue residues following use. Due to these challenges, surgical power tools can be considered the weak link in the decontamination cycle and present a potential for iatrogenic transmission of infection. We aimed to review the existing literature on the decontamination of surgical power tools and associated iatrogenic transmission of infection. A search of the medical literature was performed using Ovid online using the following databases: Ovid Medline 1950-2014, Embase 1980-2014, and EBM Reviews Full Text--Cochrane DSR, ACP Journal Club, and Dare. Despite challenges to decontamination processes, reported episodes of iatrogenic infection directly linked to SPTs appear rare. This may reflect a true picture but more likely represents incomplete reporting, failure to investigate power tools, or lack of surveillance linking surgical site infections (SSIs) to power tools. Healthcare professionals should be aware of the complexities associated with the decontamination of different SPTs, and should review manufacturers' reprocessing instructions prior to purchase. More clarity is required in the manufacturers' validation of these reprocessing instructions. This particularly applies to the emerging surgical robot systems that present extreme challenges to decontamination between uses. Investigation of cross-infection incidents or SSI surveillance should include an element of assessment of SPT decontamination to further elucidate the contribution of SPTs to skin and soft tissue infections.

Evaluation of microbial contamination and distribution of sulphate-reducing bacteria in dental units

Although bacterial contamination is widely researched in dental unit water systems, we have been unable to find any published reports to date about the presence and distribution of sulphate-reducing bacteria (SRB) in dental unit waterlines (DUWLs). The aim of this study was to evaluate microbial contamination and to determine the presence and distribution of SRB in DUWLs. One hundred twenty-three water samples were collected from the air-water syringes, high-speed drills and water sources from 41 dental units in Istanbul, Turkey. The counts of aerobic heterotrophic bacteria and SRB were investigated in the water samples. In addition, the presence of free-living amoebae (FLA) was examined. In this work, we evaluated microbial contamination and reported for the first time the distribution of SRB in DUWLs. We determined that only ten out of 123 water samples were able to meet the American Dental Association's limit (≤200 CFU ml( - 1)). SRB were observed in 102 out of 123 samples (82.9%). In addition, SRB were detected in all of the air-water syringes and high-speed drills. FLA were established in 103 out of 123 samples (83.7%).

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.

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.

Comparison of the microbial load of incoming and distal outlet waters from dental unit water systems in Istanbul

This is a cross-sectional study of the incoming and distal outlet water quality from 41 dental units in Istanbul, carried out to compare the total microbial loads using traditional culture method versus epifluorescence microscopy. The possible presence of Legionella pneumophila using traditional culture method was also analyzed. One hundred and twenty three samples were taken from the high-speed handpiece lines, air-water syringe lines and source (incoming) water supplies from 41 dental units. The samples were assayed for live/dead bacteria, heterotrophic bacterial counts and presence of L. pneumophila bacteria. Thirty nine out of 41 dental units (91%) were not able to meet the standard limit of 200 CFU/ml in dental unit waters. The live bacterial counts were 1-1.5 orders of magnitude higher than aerobic mesophilic heterotrophic bacteria. L. pneumophila (serogroup 2-14) was isolated from five out of 41 units. Some dental units were using commercially bottled (19 l) drinking water as a source. The source water of eight dental unit was heavily contaminated which were fed up by commercially bottled drinking water.

Microbial biofilm formation in DUWS and their control using disinfectants

OBJECTIVES

Due to the presence of extended narrow bore tubing and long periods of stagnation, dental unit water systems (DUWs) can be prone to relatively high levels of microbial contamination, including the formation of biofilm and the presence of opportunistic pathogens, irrespective of the source and quality of the inflowing water. Whilst the European Union (EU) has yet to set a definitive microbiological guideline, the American Dental Association (ADA) has set a maximum of <200 colony forming units (cfu)/ml for DUWs water in the USA. The objective of this review is to discuss why microbial contamination and biofilms are so prevalent in DUWs, as well as the role of disinfectants and their potential for achieving microbial water quality levels recommended by the ADA.

STUDY SELECTION

The review outlines the principal factors responsible for biofilm formation in DUWs and a number of mechanisms used for microbial control.

SOURCES

The source material contained in this review is taken from the peer-reviewed literature.

DATA

A variety of disinfectants are available for use, but controlled laboratory and clinical studies have shown that they can vary markedly in their efficacy and suitability for use. Some products have been shown to successfully remove biofilm and consistently reduce the microbial load of out-flowing water to <200 cfu/ml.

CONCLUSIONS

The effective delivery of approved disinfectants can control the level of microorganisms in DUWs at acceptable levels.

An audit improves the quality of water within the dental unit water lines of three separate facilities of a United Kingdom NHS Trust

OBJECTIVE

To improve the quality of water emanating from dental unit waterlines (DUWLs).

DESIGN

A prospective clinical audit.

SETTING

Three geographically separate district dental facilities of a United Kingdom NHS Trust, involving two community clinics and one hospital orthodontic department, which were evaluated between 2002 and 2004.

METHODS

Samples of water discharged from the DUWLs were collected prior to the start and midway through a morning session. These were tested microbiologically at a United Kingdom Accreditation Service testing laboratory within six hours of sampling.

INTERVENTIONS

One of the clinics followed the contemporaneous BDA advice of flushing water through its DUWLs while the other two clinics used separate intermittent disinfection purging regimes instead. One of them used a two stage protocol of Ethylene Diamine Tetra-Acetic acid followed by hydrogen peroxide, while the other used Bio 2000 as a single agent, which was subsequently superseded by the continuous use of super-oxidised water (Sterilox).

MAIN OUTCOME MEASURE

To assess whether the samples either met the American Dental Association's guideline on the quality of DUWL water, or the more stringent European Union standards for potable (drinking) water.

RESULTS

The two units which used a disinfection regime both complied with the ADA guideline and the EU potable water standard. However, the unit which only flushed through its DUWLs without using a disinfectant failed to comply with either of them. After all three dental facilities subsequently standardised their DUWL disinfection regimes by using Bio 2000, the colony counts from all of the water samples thereafter remained well below the EU recommended level. The unit which progressed to using Sterilox as a continuous disinfectant achieved and maintained zero readings from its water samples.

CONCLUSIONS

Clinical audit 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.

The presence of Pseudomonas aeruginosa in the dental unit waterline systems of teaching clinics

OBJECTIVE

The objective of this study was to evaluate the extent of Pseudomonas aeruginosa contamination of Dental Unit Water (DUW) at a Dental Teaching Center in Jordan.

METHODS

Water samples were collected from 30 dental units, 10 from each of three teaching clinics, namely conservative dentistry, periodontology, and prosthodontics. Samples were collected from the outlet of the air/water syringe, high-speed handpiece and water cup filler, at the beginning of the working day (before use), after 2 min flushing, and at midday.

RESULTS

P. aeruginosa was detected in 86.7% (26/30) of the dental units at the beginning of the working day, and in 73.3% (22/30) after 2 min of flushing and at midday. Conservative dentistry units had the highest counts, followed by periodontology and prosthodontics (P<0.05). Overall, the highest counts (log10 count CFU ml-1) were at the beginning of the working day (1.38+/-1.05), and the lowest counts after flushing for 2 min (1.10+/-1.03), and higher numbers were seen again at midday (1.15+/-1.04) (P<0.05).

CONCLUSIONS

86.7% of the dental units were contaminated with P. aeruginosa, the conservative dentistry units had the highest amount of contamination. Flushing the DUW for 2 min significantly reduced the counts of P. aeruginosa.

Attitudes of general dental practitioners in Europe to the microbial risk associated with dental unit water systems

Dental Unit Water Systems (DUWS) are used in dental practices to provide water for cooling of dental equipment and irrigation of the oral cavity. However, they have been demonstrated to be contaminated with micro-organisms. There are currently no European Union (EU) Commission guidelines for the microbial quality of water discharged by DUWS. This study was part of an EU research programme to investigate the microbial contamination of DUWS in general dental practice (GDP) in the UK, Denmark, Germany, The Netherlands, Ireland, Greece and Spain.

OBJECTIVE

To undertake a questionnaire survey on the type of DUWS in use and determine the attitude of GDPs to the risk of microbial infection from DUWS.

MATERIALS AND METHODS

The questionnaire was written and translated into the language of each country before being posted to each participating dentist. Dentists were asked to complete the questionnaire survey and return it by post.

RESULTS AND CONCLUSIONS

The major findings were that the majority of dentists did not clean, disinfect or determine the microbial load of their DUWS, and that dentists would welcome regular monitoring and advice on maintaining their DUWS; the introduction of guidelines; and recommendations on controlling the microbial load of DUWS.

Comparison of the efficacies of disinfectants to control microbial contamination in dental unit water systems in general dental practices across the European Union

Water delivered by dental unit water systems (DUWS) in general dental practices can harbor high numbers of bacteria, including opportunistic pathogens. Biofilms on tubing within DUWS provide a reservoir for microorganisms and should be controlled. This study compared disinfection products for their ability to meet the American Dental Association's guideline of <200 CFU x ml(-1) for DUWS water. Alpron, BioBlue, Dentosept, Oxygenal, Sanosil, Sterilex Ultra, and Ster4Spray were tested in DUWS (n = 134) in Denmark, Germany, Greece, Ireland, The Netherlands, Spain, and the United Kingdom. Weekly water samples were tested for total viable counts (TVCs) on yeast extract agar, and, where possible, the effects of products on established biofilm (TVCs) were measured. A 4- to 5-week baseline measurement period was followed by 6 to 8 weeks of disinfection (intermittent or continuous product application). DUWS water TVCs before disinfection ranged from 0 to 5.41 log CFU x ml(-1). Disinfectants achieved reductions in the median water TVC ranging from 0.69 (Ster4Spray) to 3.11 (Dentosept) log CFU x ml(-1), although occasional high values (up to 4.88 log CFU x ml(-1)) occurred with all products. Before treatment, 64% of all baseline samples exceeded American Dental Association guidelines, compared to only 17% following commencement of treatment; where tested, biofilm TVCs were reduced to below detectable levels. The antimicrobial efficacies of products varied (e.g., 91% of water samples from DUWS treated with Dentosept or Oxygenal met American Dental Association guidelines, compared to 60% of those treated with Ster4Spray). Overall, the continuously applied products performed better than those applied intermittently. The most effective products were Dentosept and Oxygenal, although Dentosept gave the most consistent and sustained antimicrobial effect over time.

Inhibitory effect of PVDF tubes on biofilm formation in dental unit waterlines

OBJECTIVES

It has been reported that dental unit waterlines (DUWLs) are contaminated with bacterial biofilm, and that water discharged from a DUWL contains bacteria that might be opportunistic pathogens. This study aimed to investigate the ability of polyvinylidene fluoride (PVDF) tubing to inhibit bacterial contamination in DUWLs.

METHODS

Newly installed dental units were equipped with either a conventional polyurethane tube (unit A) or a PVDF tube (unit B), and the numbers of bacteria discharged from high- and low-speed handpiece lines were counted using R2A agar plates. Bacterial attachment on surfaces was observed with a scanning electron microscope (SEM) up to 185 days. Bacterial outflow during 1-day clinical service from a DUWL after 1-year usage was also examined. The surface free energy of each tube was determined based on the measurement of contact angles.

RESULTS

The number of bacteria discharged from unit B was lower than from unit A at 80 days and thereafter. SEM examination demonstrated that the unit A tube was covered by biofilm constituting rods and filaments after 94 days, while no biofilm was observed in the unit B tube even after 185 days. After 1-year of usage, the unit B released significantly less bacteria than the unit A at every sampling period of 1-day clinic work. Surface free energies, calculated from contact angles measured, of PVDF and polyurethane tubes were 37.7 and 77.8, respectively.

SIGNIFICANCE

The present results indicate that PVDF tubes, which have lower surface free energy than the conventional tubes, were effective in inhibiting biofilm formation and reducing bacterial outflow from DUWLs.

An investigation of the efficacy of super–oxidised (Optident/Sterilox) water for the disinfection of dental unit water lines

AIMS

To determine the efficacy of super-oxidised water (Optident/Sterilox) in the decontamination of dental unit water lines.

METHODS

Dental units (10) were first purged with concentrated super-oxidised water. After purging, a 5% (v/v) super-oxidised water was used as a maintenance dose. Samples for microbiology were taken after 0,1,2,3,4,5,6,7 d, and each week for a further 13 weeks.

RESULTS

After purging, 5% (v/v) super-oxidised water was successful in reducing the microbial counts to zero, although in three of the units some bacteria were intermittently isolated in the first week of treatment.

CONCLUSIONS

Super-oxidised water was successful in the removal of bacteria from dental unit water supplies. Complete removal required the treatment with a purge phase of concentrated disinfectant and a maintenance phase of at least two weeks.

Microbiological evaluation of dental unit water systems in general dental practice in Europe

A range of opportunistic pathogens have been associated with dental unit water systems (DUWS), particularly in the biofilms that can line the tubing. This study therefore aimed to assess the microbiology of DUWS and biofilms in general dental practices across seven European countries, including the United Kingdom (UK), Ireland (IRL), Greece (GR), Spain (ES), Germany (D), Denmark (DK) and the Netherlands (NL). Water supplied by 51% of 237 dental unit water lines exceeded current American Dental Association recommendations of < or = 200 colony-forming units (CFU) ml(-1). Microbiological loading of the source waters was between 0 (Denmark, the Netherlands and Spain) and 4.67 (IRL) log CFU ml(-1); water line samples from the DUWS ranged from 1.52 (ES) to 2.79 (GR) log CFU ml(-1); and biofilm counts ranged from 1.49 (GR) to 3.22 (DK) log CFU.cm(-2). Opportunistic pathogens such as legionellae (DK and ES), including Legionella pneumophila SG1 (DK and GR), and Mycobacterium spp. (DK, NL, GR, D and ES) were recovered occasionally. Presumptive oral streptococci (ES and NL), oral anaerobes (GR), Candida spp. (UK, NL and ES) and blood (GR and IRL) were detected at relatively low frequencies, but their presence indicated a failure of the 3-in-1 antiretraction valve, leading to back siphonage of oral fluids into the water and biofilm phase. These findings confirm that a substantial proportion of DUWS have high levels of microbial contamination, irrespective of country, type of equipment and source water. The study emphasizes the need for effective mechanisms to reduce the microbial burden within DUWS, and highlights the risk of occupational exposure and cross-infection in general dental practice.

Microbiological evaluation of a range of disinfectant products to control mixed-species biofilm contamination in a laboratory model of a dental unit water system

Dental unit water system (DUWS) tubing harbors complex multispecies biofilms that are responsible for high microbial levels at the distal outlet. The aim of this study was to use an established biofilm laboratory model to simulate biofouling of DUWS to evaluate practical, cost-effective, and evidence-based methods of microbial decontamination. Reproducible biofilms were developed in the model over 14 days; decontamination was assessed using total viable counts (TVC) and microscopic-image analysis techniques to view the inner surface of tubing. Flushing did not reduce the biofilm coverage or TVC. Combizyme and ozone did not completely eliminate the viable bacteria (70 and 65% reduction in biofilm TVC, respectively), nor did they remove the biofilm (45 and 57% reduction in biofilm coverage, respectively). Chlorhexidine and Bio2000 (active agent: ethanol and chlorhexidine), Tegodor and Gigasept Rapid (aldehyde based), and Grotanol (hydroxide based) completely eliminated the TVC but did not completely remove biofilm (31, 53 33, 34, and 64.9% reduction of biofilm coverage, respectively). Other products including Grotanol Flussig (phenol based), Betadine (povidone-iodine based), Alpron (chlorite based), and the hydroxide-containing products Sporklenz, Sterilex Ultra, Dialox, Sterilox, Sanosil, Oxigenal, and Grotanat Bohrerbad resulted in a 100% reduction in the biofilm TVC and a >95% reduction in biofilm coverage. The study demonstrated that while many disinfectants achieve a sufficient reduction in TVC they may not necessarily remove unwanted biofilm from the tubing surfaces as tested in this laboratory-controlled biofilm model.