Microbial contamination of dental unit waterlines: the scientific argument

Dental unit waterline testing practices: an 11-Year retrospective study

OBJECTIVES

This retrospective study examined the dental unit waterline (DUWL) testing practices of Saskatchewan dental 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 = 137) 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 4,093 test results.

RESULTS

Participating clinics submitted an average of 11 DUWL tests per year. Overall, 21% of tests failed, and a moderate positive association (rs=.52, 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 two weeks, of which 47% 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.

The Effect of Hydrogen Peroxide Colloidal-Ag Used in Dental Unit Waterline on Shear Bond Strength of Orthodontic Brackets

BACKGROUND

The quality of the water passing through the water lines is crucial to dental procedures. Studies on bracket adhesion of hydrogen peroxide colloidal-Ag, which is widely used to prevent biofilm formation, are limited in the literature.

AIM

To determine whether disinfecting the dental units' waterlines (DUW) with hydrogen peroxide colloidal-Ag has any effect on the shear bond strength (SBS) of orthodontic brackets bonded to enamel.

MATERIALS AND METHODS

Sixty premolar teeth were divided randomly into two groups. The study and control groups consists of 30 teeth that were etched for 30 seconds with 37% phosphoric acid. Study groups washed with hydrogen peroxide colloidal-Ag water and the control group washed with municipal water. Transbond XT adhesive system was used to bond stainless steel brackets on all the teeth. A 300-g force was applied using a tension gauge to ensure a uniform adhesive thickness and light cured with 6 seconds. The SBS was quantified by means of a universal testing machine. The residual adhesive on the enamel surface was evaluated after debonding using the adhesive remnant index (ARI).

RESULTS

The t-test results indicated that there were no significant differences in the SBS. The comparison of the results of ARI scores was found statistically insignificant.

CONCLUSION

It has been found that hydrogen peroxide colloidal-Ag, which is used to reduce the amount of biofilm in DUW, does not have a negative effect on the adhesion of the brackets.

Microbiological Evaluation of Water Used in Dental Units

In modern dentistry, dental units are used for the treatment of patients’ teeth, and they need water to operate. Water circulates in a closed vessel system and finally reaches the mucous membranes of the patient as well as the dentist themselves. Therefore, the microbiological safety of this water should be a priority for physicians. This study aims to identify and determine the microbial count, expressed in CFU/mL, in water samples from various parts of the dental unit that are in direct contact with the patient. Thirty-four dental units located in dentistry rooms were analysed. The dentistry rooms were divided into three categories: surgical, conservative, and periodontal. It was found that in surgical rooms, the bacterial count was 1464.76 CFU/mL, and the most common bacterium was Staphylococcus pasteuri—23.88% of the total bacteria identified. In dentistry rooms where conservative treatments were applied, the average bacterial concentration was 8208.35 CFU/mL, and the most common bacterium was Ralsonia pickettii (26.31%). The periodontal rooms were also dominated by R. pickettii (45.13%), and the average bacterial concentration was 8743.08 CFU/mL. Fungi were also detected. Rhodotorula spp., Alternaria spp., and Candida parapsilosis were found to be the most common bacteria which are potentially harmful. This study indicates the need for effective decontamination of the water that is used in dental units and for constant monitoring of the level of contaminants present in the closed vessel system.

A program to improve the quality of dental unit water in a medical center

The water quality of dental unit waterlines (DUWLs) is associated with patient safety. No program for DUWL water quality improvement has been formulated since the time they were established 20 years ago. This study provides an improvement program for the quality of dental unit water. The improvement program was implemented step by step: discharge of DUWLs for 5 minutes in the morning before clinical service to flush out the water left in the pipeline overnight; weekly disinfection of the handpiece connector with 75% alcohol and replacement of the old connector when the water quality of the same dental chair unit (DCU) was continuously found to be unqualified; monthly disinfection of the water supply system and pipeline; and establishment of DCU maintenance work standards and staff education and training. From 2016 to 2018, the water quality of 18 DCUs was tested by microorganism culture. The colonies >200 colony forming unit were categorized as unqualified. This program was divided into a pre-test phase, Phase 1, a maintenance phase, and Phase 2. A Chi-square test was used to calculate the difference of unqualified water quality numbers between each phase of the improvement program. In the pre-test phase, the water quality rate (high quality number/high-quality number + low-quality number) was 58.3%. In Phase 1, the quality rate before and after the intervention was 64.8% (35/54) and 92.2% (83/90) (P < .001), respectively. After Phase 1, the quality rate reached 100%. However, the quality rate dropped to 75% during the maintenance phase. Then, we proceeded into Phase 2 of the improvement program by further monthly disinfection to DUWLs. In Phase 2, the quality rate was 62/73 (84.9%) and improved to 142/144 (98.6%) after the intervention (P < .001). The quality rate reached 100% once again and was maintained at 100% thereafter. In conclusion, the 4 steps of the improvement program improved the water quality of the DUWL, which is important for patient safety.

Environmentally friendly antibiofilm strategy based on cationized phytoglycogen nanoparticles

Biofilm tolerance to antibiotics has led to the search for new alternatives in treating biofilms. The use of metallic nanoparticles has been a suggested strategy against biofilms, but their potential environmental toxicity and high cost of synthesizing have limited their applications. In this study, we investigate the potential of polysaccharidic phytoglycogen nanoparticles extracted from corn, in treating cyanobacterial biofilms, which are the source of toxins and pollution in aquatic environments. Our results revealed that the surface of cyanobacterial cells was dominated by the negatively charged functional groups such as carboxylic and phosphoric groups. The native phytoglycogen (PhX) nanoparticles were dominated with non-charged groups, such as hydroxyl groups, and the cationized phytoglycogen (PhXC) nanoparticles showed positively charged surfaces due to the presence of quaternary ammonium cations. Our results indicated that, as opposed to PhX, PhXC strongly inhibited biofilm formation when dispersed in the culture medium. PhXC also eradicated the already grown cyanobacterial biofilms. The antibiofilm properties of PhXC were attributed to its strong electrostatic interactions with the cyanobacterial cells, which could inhibit cell/cell and cell/substrate interactions and nutrient exchange with the media. This class of antibacterial polysaccharide nanoparticles may provide a novel cost-effective and environment-friendly strategy for treating biofilm formation by a broad spectrum of bacteria.

Comparative Evaluation of Efficacy of Chlorhexidine and Herbal Mouthwash as a Preprocedural Rinse in Reducing Dental Aerosols: A Microbiological Study

Objective. The risk to dentists, assistants, and patients of infectious diseases through aerosols has long been recognized. The aim of this study was to evaluate and compare the efficacy of commercially available preprocedural mouth rinses containing 0.2% chlorhexidine (CHX) gluconate, Befresh™ herbal mouthwash, and water in reducing the levels of viable bacteria in aerosols. Materials & Methods. This was a single-center, double-masked, placebo-controlled, randomized, three-group parallel design study. 30 patients (10 patients in each group) were recruited in the study. Patient rinsed mouth with 10 ml of CHX, 10 ml Befresh™, or 10 ml water. All the patients underwent supragingival ultrasonic scaling for a minimum of 30 min. The aerosol collection was done using a blood agar plate. The blood agar plates were kept approximately 12 inches from the patient’s mouth. The microbial culture was analyzed. The colony-forming unit (CFU) counting in all three groups was assessed using one-way ANOVA test to compare among the groups (p value <0.001). The intergroup comparison was done using the post hoc Tukey test. Result. There was a marked reduction in the CFU in the CHX group in all three areas. This was followed by Befresh™ (Sagar Pharmaceuticals) mouthwash. There was no reduction in the CFU of the water group. Conclusion. This study proves that a regular preprocedural mouth rinse could significantly reduce the majority bacteria present in aerosols generated by the use of an ultrasonic unit, and Befresh™ mouth rinse was found to be equally effective in reducing the aerosol contamination to 0.2% CHX gluconate.

Colonization of Dental Unit Waterlines by Helicobacter pylori: Risk of Exposure in Dental Practices

Dental unit waterlines (DUWLs) can be considered one of the possible routes of H. pylori transmission, although its presence in DUWLs has not yet been investigated thoroughly. The present study aimed to discover the prevalence of H. pylori and oral streptococci (S. oralis and S. mutans) in DUWLs to evaluate the risk of exposure to human pathogens in dental practices. We collected the output water from 60 dental chair units (DCUs) in 26 private dentistry settings in Turin, searching for H. pylori and oral streptococci (OS) DNA, with a polymerase chain reaction (PCR) technique. At the same time, dentists completed a questionnaire about their DCUs, their main activities, the presence of anti-retraction devices, their attitudes about disinfection, etc. No dental chair unit tested was contaminated with H. pylori or S. mutans; only one dental chair was contaminated with S. oralis (1.7%). Considering the results, we can state that: (i) the lack of H. pylori DNA in water samples analyzed, suggests that municipal water is presumably treated with a sufficient chlorine level to inactivate DNA over time; (ii) the aspiration of oral fluids is limited by anti-retraction valves fitted distally to hand pieces; (iii) propidium monoazide qPCR (PMA-qPCR) could be a good technique to investigate and monitor potential environmental sources of infections such as DUWLs.

WITHDRAWN: Ozone therapy for the treatment of dental caries

BACKGROUND

Dental caries is a bacterially mediated disease characterised by demineralisation of the tooth surface, which may lead to cavitation, discomfort, pain and eventual tooth loss. Ozone is toxic to certain bacteria in vitro and it has been suggested that delivering ozone into a carious lesion might reduce the number of cariogenic bacteria. This possibly could arrest the progress of the lesion and may, in the presence of fluoride, perhaps allow remineralisation to occur. This may in turn delay or prevent the need for traditional dental conservation by 'drilling and filling'.

OBJECTIVES

To assess whether ozone is effective in arresting or reversing the progression of dental caries.

SEARCH METHODS

We searched the Cochrane Oral Health Group's Trials Register (to 7 November 2003); Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2003, Issue 3); MEDLINE and PREMEDLINE (OVID) (1966 to November 2003); EMBASE (OVID) (1980 to November 2003); CINAHL (OVID) (1982 to November 2003); AMED (OVID) (1985 to November 2003). Quintessence was handsearched through 2002 and KaVo were contacted as manufacturers of the HealOzone apparatus for any additional published or unpublished trials.

SELECTION CRITERIA

Inclusion was assessed independently by at least two reviewers. Trials were only included if they met the following criteria: randomisation in a controlled trial; single surface in vivo carious lesion accessible to ozone application; clear allocation concealment; ozone application to the lesions in the intervention group; no such application of ozone in the control group; outcomes measured after at least 6 months.

DATA COLLECTION AND ANALYSIS

Reviewers independently extracted information in duplicate. A paucity of comparable data did not allow meta-analytic pooling of the included studies.

MAIN RESULTS

Three trials were included, with a combined total of 432 randomised lesions (137 participants). Forty-two conference papers, abstracts and posters were excluded (from an unknown number of studies). The risk of bias in all studies appeared high. The analyses of all three studies were conducted at the level of the lesion, which is not independent of the person, for this reason pooling of data was not appropriate or attempted. Individual studies showed inconsistent effects of ozone on caries, across different measures of caries progression or regression. Few secondary outcomes were reported, but one trial reported an absence of adverse events.

AUTHORS' CONCLUSIONS

Given the high risk of bias in the available studies and lack of consistency between different outcome measures, there is no reliable evidence that application of ozone gas to the surface of decayed teeth stops or reverses the decay process. There is a fundamental need for more evidence of appropriate rigour and quality before the use of ozone can be accepted into mainstream primary dental care or can be considered a viable alternative to current methods for the management and treatment of dental caries.

Comparison between Two Types of Dental Unit Waterlines: How Evaluation of Microbiological Contamination Can Support Risk Containment

Infection risk management in a dental unit waterline (DUWL) involves healthcare personnel and patients and is related to routine exposure to water and aerosols that may contain bacterial species. To improve water safety plans, maintenance, and sanitation procedures, analyses of heterotrophic plate counts (HPCs) at 36 °C, and two other microorganisms frequently associated with biofilms, Pseudomonas aeruginosa and Legionella spp., were performed in order to evaluate differences in microbiological contamination between two types of DUWLs: Type A, provided by a water tank, and Type B, directly connected to municipal water. The data showed that the water supply and water safety plan differentially influenced microbiological contamination: Type A DUWLs were more contaminated than Type B DUWLs for all microbiological parameters tested, with significant changes in the percentage of positive samples and contamination levels that were beyond the limits of standard guidelines. The results obtained show how the storage tank, the absence of anti-retraction valves, and the disinfection procedures performed are the main critical points of Type A DUWLs, which confirms that dental unit management (maintenance/sanitization) is often missed or not correctly applied by stakeholders, with an underestimation of the real risk of infection for patients and operators.

Three key factors influencing the bacterial contamination of dental unit waterlines: a 6-year survey from 2012 to 2017

BACKGROUND

The contaminated output water from dental unit waterlines (DUWLs) is a potential risk to both patients and dental personnel who are frequently exposed to this water or aerosols.

AIM

The purpose was to evaluate the contamination level and prevalence of bacteria in the output water of DUWLs, and to identify key factors to provide technical support for formulating relevant policies.

METHODS

We developed a special sampling connector designed for collecting dental handpiece output water and a measurement device to assess retraction of a dental chair unit (DCU). Output water from dental handpieces and air/water syringes were collected as representative of DUWLs. Water samples were tested with reference to China's national standard.

FINDINGS

From 2012 to 2017, 318 DCUs were randomly selected from 64 hospitals in Tianjin, China. Of these DCUs, 78.93% had no disinfection to prevent DUWL contamination. Three-hundred and forty-three (56.14%) samples complied with the guidelines on DUWL output water. The highest concentration of bacteria was 1.8 × 10⁶  colony-forming units (CFUs)/mL. The three key factors of influence were as follows: daily or weekly disinfection of DUWLs; water supply source being hospital self-made purified water or purchased purified bottled water; and DCU with a valid anti-retraction valve. Potential infectious agents, including Bacillus cereus, Burkholderia cepacia and Pseudomonas aeruginosa, were isolated.

CONCLUSION

There was a high rate of contamination in DUWLs. This highlights the need to develop national standards. There is a need to disinfect the DUWLs periodically and use a cleaner source of water; more attention should be paid to the efficacy of DCU anti-retraction valves.

High throughput sequencing-based analysis of microbial diversity in dental unit waterlines supports the importance of providing safe water for clinical use

This study aims to explore the water quality of dental unit waterlines (DUWLs) and the diversity of microbial communities in DUWLs. Water samples from 33 dental chair units (DCUs) were collected, diluted and then spread on sterilized R2A plate for incubation. Subsequently, the microbial colony-forming units per milliliter (CFU/ml) were recorded by an automatic colony analyzer. Total DNA extracted from the rest of the samples was tested on the Illumina MiSeq PE300 platform. T-test and Kruskal-Wallis rank test were adopted for statistical analysis. Significance was assumed at a P<0.05. After incubation, the average total microbial count was 21,413.13±17,861.00CFU/ml. High-throughput sequencing revealed 10 bacterial phyla, including 9 identified and 1 unclassified phyla. Totally 63 sequences were identified at the genus level, including 42 genera, 3 tentative species and 18 unclassified genera. In addition, 7 potential human pathogenic bacteria were detected. In summary, department, brand and service life of DCUs do not influence the water quality of DUWLs significantly. The diversity of microbial communities in DUWLs is abundant and includes both pathogenic and some unknown bacteria.

Risk of Fungal Infection to Dental Patients

Fungi can cause various diseases, and some pathogenic fungi have been detected in the water of dental equipment. This environment offers suitable conditions for fungal biofilms to emerge, which can facilitate mycological contamination. This study verified whether the water employed in the dental units of two dental clinics at the University of Franca was contaminated with fungi. This study also evaluated the ability of the detected fungi to form biofilms. The high-revving engine contained the largest average amount of fungi, 14.93 ± 18.18 CFU/mL. The main fungal species verified in this equipment belonged to the genera Aspergillus spp., Fusarium spp., Candida spp., and Rhodotorula spp. Among the isolated filamentous fungi, only one fungus of the genus Fusarium spp. did not form biofilms. As for yeasts, all the Candida spp. isolates grew as biofilm, but none of the Rhodotorula spp. isolates demonstrated this ability. Given that professionals and patients are often exposed to water and aerosols generated by the dental procedure, the several fungal species detected herein represent a potential risk especially to immunocompromised patients undergoing dental treatment. Therefore, frequent microbiological monitoring of the water employed in dental equipment is crucial to reduce the presence of contaminants.

Nanosilver as a disinfectant in dental unit waterlines: Assessment of the physicochemical transformations of the AgNPs

Dental unit water lines (DUWL) are susceptible to biofilm development and bacterial growth leading to water contamination, causing health and ecological effects. This study monitors the interactions between a commonly used nanosilver disinfectant (ASAP-AGX-32, an antimicrobial cleaner for dental units, 0.0032% Ag) and biofilm development in DUWL. To simulate the disinfection scenario, an in-house DUWL model was assembled and biofilm accumulation was allowed. Subsequent to biofilm development, the disinfection process was performed according to the manufacturer's instructions. The pristine nanosilver particles in the cleaner measured between 3 and 5 nm in diameter and were surrounded by a stabilizing polymer. However, the polymeric stabilizing agent diminished over the disinfection process, initiating partial AgNPs aggregation. Furthermore, surface speciation of the pristine AgNPs were identified as primarily AgO, and after the disinfection process, transformations to AgCl were observed. The physicochemical characteristics of AgNPs are known to govern their fate, transport and environmental implications. Hence, knowledge of the AgNPs characteristics after the disinfection process (usage scenario) is of significance. This study demonstrates the adsorption of AgNPs onto biofilm surfaces and, therefore, will assist in illustration of the toxicity mechanisms of AgNPs to bacteria and biofilms. This work can be an initial step in better understanding how AgNPs transform depending on the conditions they are exposed to during their lifetime. Until this date, most research has been focused on assessing the impacts of pristine (lab synthesized) nanomaterials on various systems. However, it is our belief that nanoparticles may undergo transformations during usage, which must be taken into consideration. Furthermore, this experiment is unique as it was conducted with a commonly used, commercially available nanosilver suspension leading to more realistic and applicable findings.

Monitoring of bacterial contamination of dental unit water lines using adenosine triphosphate bioluminescence

Bacterial contamination of dental unit waterlines (DUWLs) was evaluated using ATP bioluminescence analysis and a conventional culture method. Water samples (N=44) from DUWLs were investigated for heterotrophic bacteria by culture on R2A agar, which gave counts ranging from 1.4×10³ to 2.7×10⁵ cfu/mL. The ATP bioluminescence results for DUWL samples ranged from 6 to 1189 relative light units and could be obtained within 1min; these correlated well with the culture results (r=0.727-0.855). We conclude that the results of the ATP bioluminescence assay accurately reflect the results of conventional culture-based testing. This method is potentially useful for rapid and simple monitoring of DUWL bacterial contamination.

Detection and Quantification of Dental Unit Water Line Contamination by Oral Streptococci

Objective.

(1) To investigate the prevalence of oral streptococci (OS) and biological indicators of water contamination by oral fluids in water from dental unit water lines (DUWs) by detection and quantification and of saprophytes indigenous to the oral cavity. (2) To test whether measurement of the total cultivable mesophilic flora (TCF), the parameter commonly used to monitor water quality in DUWs, is an effective predictor for OS contamination.

Design.

Survey of 21 dental units equipped with antiretraction devices. Water samples were collected from air-water syringes, cup fillers, tap water, and before and during the working day.

Setting.

Units were from 7 public dental offices selected for convenience from among those in proximity of the microbiological laboratory.

Methods.

For detection of OS, samples were plated on an enriched medium, to revitalize the organisms. Colonies were subcultured on a selective medium and biochemically identified (lower detection limit, 1 cfu/mL). For measurement of the TCF, samples were plated on a nutrient-poor medium. Cultures with colony counts greater than 200 cfu/mL were considered to be TCF positive. The sensitivity and specificity of TCF positivity in predicting OS detection was calculated.

Results.

Prevalence rates for OS contamination and for TCF positivity were, respectively, 34.4% (11 of 32 samples) and 25.0% (8 of 32 samples) for syringes, 27.8% (10 of 36 samples) and 8.3% (3 of 36 samples) for cup fillers, and 0.0% (0 of 7 samples) for tap water. OS contamination levels ranged from 1 to 6 cfu/mL. No statistically significant differences were found between samples obtained before and during the working day. TCF positivity did not predict OS contamination effectively, because of low sensitivity.

Conclusions.

Given the absence of OS in tap water, the reported prevalence of OS contamination suggests that oral fluids are aspirated during dental therapy with relatively high frequency and that DUWs can potentially expose successive patients to bloodborne cross-infections.

Investigation of the bacterial load and antibiotic susceptibility of dental units

The aim of this study was to evaluate the bacterial contamination level and to determine the antibiotic susceptibility of the isolated bacteria from dental unit waterlines (DUWLs) in Istanbul. Bacterial quality of DUWLs is very important, as patients and dental staff are regularly exposed to water and aerosols generated by the unit. If opportunistic pathogens such as Staphylococcus aureus, Pseudomonas aeruginosa, and Legionella pneumophila are present in DUWLs, patient and dental staff can be infected. One hundred water samples were collected from high-speed drills and input waters from 50 dental units. Aerobic heterotrophic bacteria counts and the presence of Legionella, Pseudomonas, oral streptococci, and Staphylococcus were investigated in dental unit waters and aerosol samples. In addition, the antibiotic susceptibility of the isolated and identified bacteria from DUWLs was examined. This research found that 37 out of 50 dental unit water samples exceeded the American Dental Association's limit of 200 colony-forming units (CFU)/mL(-1). Legionella, oral streptococci, and S. aureus were not detected in any water or aerosol samples, but P. aeruginosa was isolated in three DUWLs. Also, Pseudomonas and Staphylococcus were found in water and aerosol samples. Cefoperazone, ofloxacin, gentamicin, ciprofloxacin, and piperacillin were the most effective antibiotics against the isolated bacteria from DUWLs.

Mycological contamination in dental unit waterlines in Istanbul, Turkey

Studies on dental units (DUs) are conducted either for the prevention or the reduction of the density of bacterial contamination in dental unit waterlines (DUWLs). However, the existence of fungi in the these systems requires more attention. During dental treatment, direct contact with water contaminated with fungi such as Candida, Aspergillus, or inhalation of aerosols from high-speed drill may cause various respiratory infections, such as asthma, allergies, and wounds on mucose membranes, especially on immunocompromised patients and dentists. The aims of this study are to investigate the number and colonization of fungi in DUWLs in the city of Istanbul, Turkey. Water samples were collected from air-water syringes, high-speed drills, and inlet waters from 41 DUs. The aerobic mesophilic fungi count in high- speed drills was higher than inlet waters and air-water syringes. Non-sporulating fungi were found in 7 DUs. The isolated fungi were identified as Penicillium waksmanii, Cladosporium spp., Penicillium spp., Candida famata, Cryptococcus laurentii, Candida guilliermondii, Penicillium verrucosum, Aspergillus pseudoglaucus, Penicillium decumbens, and Acremonium sp. Some of these fungal genera are known as opportunistic pathogens that led to respiratory diseases such as allergic rhinits. This study shows the importance of regular control of mycological contamination on water at DUs.

Mechanized scaling with ultrasonics: Perils and proactive measures

Mechanized scaling for plaque removal is a routine procedure in the practice of periodontics. Though it appears innocuous by itself, there are retinues of hazards associated with it on various organ systems in the body. Some of these unwanted effects and measures to avoid or ameliorate the same are elaborated here. Exposure to ultrasonic scaling is inevitable before any other treatment procedure. Aerosol contamination, vibrational hazards, thermal effects on the dental pulp, altered vascular dynamics, disruption in electromagnetic device, diminished hearing and dental unit waterline contamination are some of the probable off-shoots a patient has to bear. Uses of barrier devices, proper attention to usage of equipment, protection for ear and water treatment are few of solutions for the same. Though documented evidence for the existence of all effects is lacking, it is never the less significant for the overall safety of the patient. A conscientious clinician should therefore inculcate the available steps to overcome the hazards of ultrasonic scaling.

Bacterial contamination of dental unit waterlines

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 × 10(5) 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.

Microbial contamination of dental unit waterlines in dental practices in Hesse, Germany: A cross-sectional study

The quality of water from dental units is of considerable importance since patients and dental staff are regularly exposed to water and aerosols generated from the dental unit. This study analyzed the microbial quality of water obtained for periodical monitoring from 56 dental units in different dental practices in Hesse. Contamination by Legionella spp., Pseudomonas aeruginosa, and increased total colony counts were detected in 27.8%, 3.5%, and 17% of samples. Legionella pneumophila serogroup 1 accounted for 28% of Legionella isolates. The Legionella concentration was >100 cfu/100 ml in 84% of contaminated samples. Samples collected from an instrument channel were more frequently contaminated by Legionella than those from cup filler (41.7% vs. 18.6%, p = 0.02). After release of these results, decontamination measures were performed in units that had revealed unsatisfactory results. The outcome of the intervention was followed-up by microbiological analysis. At follow-up, 65.2% and 72.7% of waterlines that had previously been contaminated by Legionella or had shown increased total colony counts were free of contamination. Our results show a high rate of contamination of water from dental units in dental practices in Hesse. They highlight the risk of exposure for patients and personnel and the need for effective strategies to reduce microbial contamination.

The antimicrobial effect of 0.1 ppm ozonated water on 24-hour plaque microorganisms in situ

Ozone is a known oxidant present in the atmosphere and is commercially produced by simple ozonizer machines. It is a powerful antimicrobial agent in its gaseous and aqueous forms. Ozone readily dissolves in water and retains its antimicrobial property even in the dissolved state. In this study, the effect of 0.1 ppm ozonated water was analyzed on 24-hour supragingival plaque (SP) samples in situ. SP was collected from the two most posterior teeth in the contra-lateral quadrants before and after a 30-second rinse with either distilled water (control group) or 0.1 ppm ozonated water (test group). The plaque was used to count the number of total bacteria, total anaerobic bacteria, Streptococcus mutans, and Candida albicans on selective agar media. The statistical analysis of the number of colony forming units (CFUs) obtained demonstrated a significant antimicrobial effect of ozonated water on the total bacteria (p = 0.01) and anaerobes (p = 0.02). A reduction in the post-rinse CFU count for Streptococcus mutans was also observed, but the effect was not statistically significant (p = 0.07). The Candida species was only grown from one sample. Ozonated water at the 0.1 ppm concentration was effective in reducing the load of 24-hour plaque bacteria, but it did not eliminate them completely.

Update on infectious risks associated with dental unit waterlines

Modern dental chair units consist of a network of interconnected narrow-bore plastic tubes called dental unit waterlines (DUWLs). The water delivered by these DUWLs acts as both a coolant for a range of instruments and an irrigant during dental treatments. The quality of water is of considerable importance because both patients and dental team are regularly exposed to water and aerosols generated by dental equipment. Studies have demonstrated that DUWLs provide a favourable environment for microbial proliferation and biofilm formation, and that water is consequently often contaminated with high densities of various microorganisms (bacteria, fungi, protozoa, viruses). The presence of high levels of microbial contamination may be a health problem for dentists and patients, especially those who are immunocompromised. The current status of knowledge on microbial contamination of DUWLs is presented, with an emphasis on the infectious risk associated with DUWLs and on the various approaches for disinfecting and protecting DUWLs.

Testing for aerobic heterotrophic bacteria allows no prediction of contamination with potentially pathogenic bacteria in the output water of dental chair units

Background: Currently, to our knowledge, quality of output water of dental chair units is not covered by specific regulations in the European Union, and national recommendations are heterogeneous. In Germany, water used in dental chair units must follow drinking water quality. In the United States of America, testing for aerobic heterotrophic bacteria is recommended. The present study was performed to evaluate whether the counts of aerobic heterotrophic bacteria correlate with the presence of potentially pathogenic bacteria such as Legionella spp. or Pseudomonas aeruginosa.

Methods: 71 samples were collected from 26 dental chair units with integrated disinfection device and 31 samples from 15 outlets of the water distribution pipework within the department were examined. Samples were tested for aerobic heterotrophic bacteria at 35°C and 22°C using different culture media and for Legionella spp. and for Pseudomonas aeruginosa. Additionally, strains of Legionella pneumophila serogroup 1 were typed with monoclonal antibodies and representative samples of Legionella pneumophila serogroup 1 were typed by sequence based typing.

Results: Our results showed a correlation between different agars for aerobic heterotrophic bacteria but no correlation for the count of aerobic heterotrophic bacteria and the presence of Legionella spp. or Pseudomonas aeruginosa.

Conclusion: Testing for aerobic heterotrophic bacteria in output water or water distribution pipework within the departments alone is without any value for predicting whether the water is contaminated with potentially pathogenic bacteria like Legionella spp. or Pseudomonas aeruginosa.

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.

Microbial biofilm control within the dental clinic: reducing multiple risks

This short review focuses on biofilms in the dental clinic environment. Microbial biofilms are potentially a significant source of cross-contamination and cross-infection in the dental clinic. Biofilms in dental chair unit waterlines (DUWLs), suction hoses and fittings pose the most significant risk as these may come into contact with the patient during treatment. These can be managed effectively by regular disinfection using chemical disinfectants and procedures that have proven efficacy. As dental chair units (DCUs) are classified as medical devices, there is a requirement for DCU manufacturers to provide detailed guidance for their decontamination. Planned routine preventive maintenance of the dental clinic water network and good quality water will considerably minimise infection risks from microorganisms in tap water and has benefits for the operation of other clinic equipment. Regular and effective cleaning and disinfection of taps, sinks and splash-backs will help to minimise reservoirs and disseminators of potentially pathogenic bacteria from these areas.

Assessment of inhibitory effects of fluoride-coated tubes on biofilm formation by using the in vitro dental unit waterline biofilm model

This study aimed to establish an in vitro model to simulate biofilms formed in dental unit waterlines (DUWLs) and to investigate the ability of polyvinylidene fluoride (PVDF)-coated tubes to inhibit biofilm formation using this model. The water and biofilm samples were obtained from DUWLs which had been clinically used for 2.5 years, and the predominant bacteria were identified. A conventional polyurethane tube was incubated for 24 to 96 h in the mixed flora of isolated bacteria, and the optimal incubation conditions to simulate a clinically formed biofilm were determined by observation with a scanning electron microscope. Biofilm formation on a PVDF-coated tube was observed using this in vitro model, and the adherence of different bacterial species to conventional and PVDF-coated tubes was assessed. Sphingomonas paucimobilis, Acinetobacter haemolytics, and Methylobacterium mesophilicum were predominantly isolated from contaminated DUWLs. Incubation of the polyurethane tube with the mixed flora containing these three species for 96 h resulted in the formation of a mature biofilm similar to the one clinically observed. The PVDF-coated tube was significantly less adhesive to all three bacterial species than the polyurethane tube (P < 0.05 by the Mann-Whitney U test), and the attachment of small amounts of rods was observed even after incubation with the mixed flora for 96 h. In conclusion, an in vitro biofilm model was obtained by using a mixed flora of bacteria isolated from DUWLs, and the PVDF-coated tube was found to be effective in preventing biofilm formation using this model.

Microbiological evaluation and antibiotic susceptibility of dental unit water systems in general dental practice

OBJECTIVE

The microbial quality of water in a dental unit water systems (DUWS) is of considerable importance because patients and dental staff are regularly exposed to water and aerosol generated from the dental units. The objective of this study was to evaluate the 20 DUWS in general dental practices and to determine the antibiotic susceptibility of the colonizing bacteria.

METHODS

Three water and one biofilm samples from each DUWS were investigated for total viable count (TVC), oral streptococci, Pseudomonas spp., Enterobacteria, Candida albicans and Legionella pneumophila.

RESULTS

A total of 44 morphologically different colonies were obtained from water samples and 20 types of colonies (45.5%) could be identified using API test strips. The mean TVC values were 4.36 log CFU ml(-1) for source waters, 4.95 log CFU ml(-1) for 3-in-1 syringe samples, 4.91 log CFU ml(-1) for air rotor samples and 3.66 log CFU cm(-2) for biofilm samples. Susceptibilities of the isolates were tested against piperacillin, ampicillin, ceftazidime, meropenem, gentamicin, tetracycline, ofloxacin and chloramphenicol by using microdilution method according to NCCLS. The meropenem and ofloxacin have shown the broadest spectrum against to the tested isolates.

CONCLUSION

The study emphasizes the need for effective mechanisms to reduce the microbial contamination in DUWS, and highlights the risk for cross-infection in general dental practice.

The role of manufacturers in reducing biofilms in dental chair waterlines

OBJECTIVES

This paper reviews how dental chair unit (DCU) manufacturers can contribute practically to resolving the problem of biofilm formation in dental unit waterlines (DUWs).

STUDY SELECTION

The review concentrates on how novel developments and changes in a range of specific areas have, and might contribute to DUW biofilm control. These include (i) DCU engineering and design changes; (ii) improvements to DCU supply water quality; (iii) development of automated DUW treatment procedures that are effective at controlling biofilm in the long-term, safe for patients and dental staff, environmentally friendly and which do not exhibit adverse effects on DCU components after prolonged use.

SOURCES

The majority of the material contained in this review is based on, or supported by the peer-reviewed literature.

DATA

The current consensus from the literature reveals that the emphasis on DUW biofilm and its control has focused on describing the problem and its control using a range of periodic and residual DUW treatment agents. Unfortunately, until recently, DCU manufacturers have provided very little specific guidance in this regard. Indeed, ensuring that DCUs provide good quality output water has generally been regarded to be the responsibility of dental practitioners. Some recent studies have shown that novel DCUs with integral semi-automated or automated DUW cleaning systems can effectively control DUW biofilm in the long-term. However, there are other potential DCU engineering and design changes that DCU manufacturers could undertake to further improve DUW biofilm control.

CONCLUSIONS

DCU manufacturers can significantly contribute to controlling the problem of DUW biofilm.

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.

Optimisation of the long-term efficacy of dental chair waterline disinfection by the identification and rectification of factors associated with waterline disinfection failure

Although many studies have highlighted the problem of biofilm growth in dental chair unit waterlines (DUWs), no long-term studies on the efficacy of DUW disinfection using a large number of dental chair units (DCUs) have been reported.

OBJECTIVES

To investigate the long-term (21 months) efficacy of the Planmeca Waterline Cleaning System (WCS) to maintain the quality of DUW output water below the American Dental Association (ADA) recommended standard of < or =200cfu/mL of aerobic heterotrophic bacteria using once weekly disinfection with the hydrogen peroxide-and silver ion-containing disinfectant Planosil.

METHODS

Microbiological quality of DUW output water was monitored by culture on R2A agar for 10 DCUs fitted with the WCS. The presence of biofilm in DUWs was examined by electron microscopy.

RESULTS

During the first 9 months a high prevalence (28/300 disinfection cycles; 9.3%) of intermittent DUW disinfection failure occurred in 8/10 DCUs due to operator omission to disinfect all DUWs (10/28 failed cycles), incorrect compressed air pressure failing to distribute the disinfectant properly (4/28 failed cycles) and physical blockage of disinfectant intake valves due to corrosion effects of Planosil (14/28 failed cycles). On rectification of these faults through engineering redesign and procedural changes, no further cases of intermittent DUW disinfection failure were observed. Independently of these factors, a rapid and consistent decline in efficacy of DUW disinfection occurred in 4/10 DCUs following the initial 9 months of once weekly disinfection. There was a highly significant difference (P<0.0001) in the prevalence of strongly catalase-positive Novosphingobium and Sphingomonas bacterial species (mean average prevalence of 37.1%) in DUW output water from these 4 DCUs compared to the other 6 DCUs and DCU supply water (prevalence <1%), which correlated with biofilm presence in the DUWs and indicated selective pressure for maintenance of these species by prolonged disinfectant usage. Planosil was reformulated to a more concentrated form (Planosil Forte) and when used once weekly was found to maintain bacterial density in output water below the ADA standard for all 10 DCUs.

CONCLUSIONS

A variety of factors can contribute to failure of DUW disinfection in the long-term, including human error, disinfectant corrosion of equipment and natural selection of naturally disinfectant-tolerant bacterial species.

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.

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.

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.

A novel automated waterline cleaning system that facilitates effective and consistent control of microbial biofilm contamination of dental chair unit waterlines: A one-year study

Microbial contamination of dental chair unit (DCU) output water caused by biofilm growth in dental unit waterlines (DUWs) is a universal problem and a potentially significant source of cross-infection. The microbial quality of output water from a Planmeca Compact i DCU equipped with the novel Water Management System (WMS), an integrated and automated DUW cleaning system, was investigated over a 12-month period with the hydrogen peroxide- and silver ion-containing disinfectants Planosil and Planosil Forte. Four weeks after connection to the potable-water quality mains supply the density of aerobic heterotrophic bacteria, rose from the low levels consistently found in the supply water throughout this study (mean average 77 cfu/mL) to 15,400 cfu/mL. Disinfection of DUWs once weekly with Planosil for 10 weeks resulted in a dramatic reduction in bacterial density immediately following disinfection (mean average 26 cfu/mL). Bacterial density rose steadily between disinfections and by 7 days post-disinfection, water quality failed (mean average 384 cfu/mL) the American Dental Association DCU water quality standard of <or=200 cfu/mL. The DCU was then disinfected once weekly for 40 weeks with Planosil Forte. The average bacterial density immediately post-disinfection was 20 cfu/mL and 7 days post-disinfection was 113 cfu/mL. Electron microscopy showed that improved output water quality following disinfection with both disinfectants was associated with marked elimination of DUW biofilm, but deterioration of water quality following disinfection was associated with its regrowth. The most common bacterial species cultured from the mains water and the DCU output water were Microcococcus luteus and Sphingomonas spp., respectively, the latter of which are known opportunistic pathogens. The findings of this study show that the Planmeca Compact i DCU equipped with the easy to use and automated WMS, that requires minimal effort on the part of the operator, consistently provides output water that passes the ADA quality standard of <or=200 cfu/mL for up to 7 days following once-weekly disinfection with Planosil Forte.

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.

Evaluation of the potential risk of occupational asthma in dentists exposed to contaminated dental unit waterlines

INTRODUCTION

Most of the organisms isolated from dental unit waterlines (DUWL) are Gram-negative bacteria, which contain cell wall endotoxin. A consequence of endotoxin exposure is the exacerbation of asthma.

OBJECTIVES

This study examined the prevalence and onset of asthma among dentists and determined whether or not these were associated with the microbiological quality of DUWL in their practices.

METHODS

266 randomly selected dentists (100 from rural Northern Ireland, 166 from London) completed a health questionnaire, which included questions on prevalence and time of onset of asthma. Water samples taken from the dental handpieces and surgery washbasin cold taps in all the practices were analysed using standard techniques. The questionnaire data were evaluated using both single and multivariable logistic regression. The variables considered were: smoking; surgery location; time treating patients per week; DUWL counts of Pseudomonas aeruginosa, total Pseudomonas spp., fungi, Mycobacterium spp., total aerobic colony counts (ACC) at 22 degrees C and 37 degrees C.

RESULTS

There was no significant association between any of the variables tested in dentists and a history of asthma. A subgroup analysis was performed on dentists (n=33) who reported developing asthma since they started dental training. The final multivariable model indicated that passive smoking (OR 0.08, 95% CI 0.01-0.87, P=0.038) and total aerobic counts of >200 cfu/ml at 37 degrees C (OR 6.72, 95% CI 1.15-39.24, P=0.034) were significant variables for developing asthma since starting training as a dentist. ACC were significantly higher in London (P<0.0001) and London dentists were more likely to have developed asthma since they started training than their Northern Ireland counterparts (OR 4.4, 95% CI 1.09-17.72, P=0.033).

CONCLUSIONS

This study suggests that the temporal onset of asthma may be associated with occupational exposure to contaminated DUWL among dentists in London and Northern Ireland.