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Objective  To assess the efficacy of three disinfectants in disinfecting the ultrasonic scaling unit waterline.   Methods  Twelve periodontal ultrasonic scalers were randomly divided into four groups based on the disinfection protocol: distilled water (A group), 3% hydrogen peroxide (B group), 500 mg/L chlorine disinfectant (C group) and 5% povidone-iodine (D group). Each scaler was used for daily periodontal treatment and worked effectively for 6 hours per day. Water samples were collected at baseline, after disinfection, and 1-7 days post-disinfection. Scanning electron microscopy (SEM) was used to observe biofilm formation. Culturable bacteria were counted, isolated and purified, then identified through 16S rRNA gene sequencing. Sequences of 16S rRNA gene amplicons were clustered by operational taxonomic units (OTUs).  Results  Baseline colony counts exceeded 100 CFU/mL in all groups. However, after disinfection, the colony counts decreased significantly in all groups (P < 0.05). The colony counts remained below 100 CFU/mL within 3 d after disinfection with 3% H2O2, within 6 days after disinfection with 500 mg/L chlorine-containing disinfectant, and within 4 d after disinfection with 5% povidone-iodine (P < 0.05).Pathogens such as Stenotrophomonas maltophilia were detected in the ultrasonic scaler unit water circuit. SEM showed thinner biofilm thickness in the 3% H2O2 and 5% povidone-iodine groups compared to the control group (P < 0.05).  Conclusions  Bacterial contamination is present in the ultrasonic scaling unit waterline, posing a potential infection risk to periodontal staff and patients. In the context of increasingly severe nosocomial infections, appropriate disinfection protocols should be developed based on clinical realities. [ABSTRACT FROM AUTHOR]

To systematically review the effect of different types of water sources on dental unit waterline (DUWL) contamination. 5 databases were searched from their inception to December 23, 2023. Two reviewers independently extracted the data and assessed the quality of the literature. The risk ratio (RR) was used as measure of effect size in meta-analysis. The Grading of Recommendations, Assessment, Development and Evaluation (GRADE) was used for evaluating quality of the evidence. Meta-analysis was completed by RevMan 5.4.5 studies involving 561 water samples were quantified for meta-analysis. The results indicated that no significant differences were found in view of contamination rate (RR = 1.01; 95 % CI, 0.72–1.41; P = 0.96, I2 = 62 %; GRADE low)and detection rate of Pseudomonas aeruginosa (RR = 0.78; 95 % CI, 0.15–4.13; P = 0.77; I2 = 83 %; GRADE very low) between using purified water and tap water as water sources of DUWL. The available evidence suggests that there is no significant difference between purified water and tap water in controlling DUWL contamination. However, the conclusions need to be further validated through more randomized controlled trials with robust design and a large sample size.

Abstract Background In dentistry, nosocomial infection poses a great challenge to clinicians. The microbial contamination of water in dental unit waterlines (DUWLs) is ubiquitous. Such infected DUWLs can transmit oral microbes in the form of aerosols. Previous studies have suggested treating DUWLs with various disinfectants to reduce cross-contamination. The literature lacks a comparative evaluation of the effect of the use of 0.2% chlorhexidine (CHX) and 0.1% sodium hypochlorite (NaOCl) in DUWLs on aerosolized bacteria generated during dental procedures. Objective To compare the effect of NaOCl and CHX in DUWLs on aerosolized bacteria generated during restorative and endodontic procedures. Materials and methods A total of 132 patients were equally divided into three groups (n = 44 in each group) according to the content of DUWL as follows. Group I—0.1% NaOCl Group II—0.2% CHX Group III—distilled water (Positive control) One-way ANOVA was performed and the Kruskal–Wallis test was used for intergroup comparison. Results For the restorative procedure, inter-group comparison of mean colony-forming units (CFU) scores showed a statistically significant difference between the groups (p - .001) with the score of group 3 higher than group 2 followed by group 1. For the endodontics, an inter-group comparison of CFU scores showed a statistically significant difference between the groups (p - .003) with the mean score in group 1 being the lowest and group 3 being the highest. Conclusion The addition of NaOCl or CHX in DUWLs shows an effective reduction in aerosolized bacteria compared to distilled water.

Background: In dentistry, nosocomial infection poses a great challenge to clinicians. The microbial contamination of water in dental unit waterlines (DUWLs) is ubiquitous. Such infected DUWLs can transmit oral microbes in the form of aerosols. Previous studies have suggested treating DUWLs with various disinfectants to reduce cross-contamination. The literature lacks a comparative evaluation of the effect of the use of 0.2% chlorhexidine (CHX) and 0.1% sodium hypochlorite (NaOCl) in DUWLs on aerosolized bacteria generated during dental procedures. Objective: To compare the effect of NaOCl and CHX in DUWLs on aerosolized bacteria generated during restorative and endodontic procedures. Materials and methods: A total of 132 patients were equally divided into three groups (n = 44 in each group) according to the content of DUWL as follows. Group I—0.1% NaOCl Group II—0.2% CHX Group III—distilled water (Positive control) One-way ANOVA was performed and the Kruskal–Wallis test was used for intergroup comparison. Results: For the restorative procedure, inter-group comparison of mean colony-forming units (CFU) scores showed a statistically significant difference between the groups (p -.001) with the score of group 3 higher than group 2 followed by group 1. For the endodontics, an inter-group comparison of CFU scores showed a statistically significant difference between the groups (p -.003) with the mean score in group 1 being the lowest and group 3 being the highest. Conclusion: The addition of NaOCl or CHX in DUWLs shows an effective reduction in aerosolized bacteria compared to distilled water. [ABSTRACT FROM AUTHOR]

This study investigated the effect of water at high temperature on the physical and mechanical properties of polyurethane and on biofilm removal, aiming for its applicability in dental unit waterlines. The evaluations were carried out after simulating a 1-year period of daily immersion and measured changes in color, microhardness, surface roughness, and tensile strength before and after reproducing a disinfection protocol. For antibiofilm activity measurement, fragments of waterline were contaminated with Pseudomonas aeruginosa and submitted to the disinfection protocols. Relative to effects on the physical and mechanical properties, immersion in water at 60°C did not promote changes in color and tensile strength. However, lower values were observed for microhardness and increased values for surface roughness. Regarding antibiofilm action, water at 60°C significantly reduced the microbial load and promoted substantial changes in cells morphology. In conclusion, disinfection with water at 60°C demonstrated possible application in controlling cross-contamination in dentistry. [ABSTRACT FROM AUTHOR]

Abstract Backgrounds Numerous studies have shown that dental unit water lines (DUWLs) are often contaminated by a wide range of micro-organisms (bacteria, fungi, protozoa) and various prevalence have been reported for it in previous studies. Therefore, this review study aims to describe the prevalence of bacterial biofilm contamination of DUWLs. Methods This is a systematic review and meta-analysis in which the related keywords in different international databases, including Medline (via PubMed) and Scopus were searched. The retrieved studies were screened and the required data were extracted from the included studies. Three standard methods including American Dental Association (ADA), The Center for Disease Control and Prevention (CDC) and contaminated > 100 CFU/ml(C-100) standards were used to assess the bacterial biofilm contamination of DUWLs. All studies that calculated the prevalence of bacterial biofilm contamination of DUWLs, and English full-text studies were included in the meta-analysis. Studies that did not have relevant data or used unusual laboratory methods were excluded. Methodological risk of bias was assessed by a related checklist and finally, the data were pooled by fixed or random-effect models. Results Seven hundred and thirty-six studies were identified and screened and 26 related studies were included in the meta-analysis. The oldest included study was published in 1976 and the most recent study was published in 2020. According to the ADA, CDC and C-100 standards, the prevalence of bacterial contamination was estimated to be 85.0% (95% confidence interval (CI): 66.0–94.0%), 77.0% (95%CI: 66.0–85.0%) and 69.0% (95%CI: 67.0–71.0%), respectively. The prevalence of Legionella Pneumophila and Pseudomonas Aeruginosa in DUWLs was estimated to be 12.0% (95%CI: 10.0–14.0%) and 8.0% (95%CI: 2.0–24.0%), respectively. Conclusion The results of this review study suggested a high prevalence of bacterial biofilm in DUWLs; therefore, the use of appropriate disinfecting protocol is recommended to reduce the prevalence of contamination and reduce the probable cross-infection.

Bacterial contamination is a problem in dental unit water lines with the consequence of implementing regular disinfection. In this study, the short-term impact of chlorine dioxide (ClO2) treatment was investigated on the microorganisms Legionella pneumophila and L. anisa, Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus. The environmental background was proven as an important factor regarding the tolerance to 0.4 mg/L ClO2 as saline and phosphate-buffered saline resulted in a higher bacterial reduction than tap water. Gram-positive microorganisms demonstrated higher robustness to ClO2 than Gram-negative, and microorganisms adapted to tap water showed increased stability compared to cultured cells. At high densities, substantial numbers of bacteria were able to withstand disinfection, whereby the use of 4.6 mg/L ClO2 increased the inactivation rate. A massive cell decrease occurred within the first 5 minutes with subsequent plateau formation or slowed cell reduction upon further exposure. This biphasic kinetics cannot be explained by a ClO2 depletion effect alone, because the probability of bacterial subpopulations with increased tolerance should be taken into account, too. Our results prove high disinfection efficiency to microorganisms that were rather found in correlation to the level of bacterial contamination and background solutions than the chosen concentration for ClO2 treatment itself. [ABSTRACT FROM AUTHOR]

Backgrounds: Numerous studies have shown that dental unit water lines (DUWLs) are often contaminated by a wide range of micro-organisms (bacteria, fungi, protozoa) and various prevalence have been reported for it in previous studies. Therefore, this review study aims to describe the prevalence of bacterial biofilm contamination of DUWLs. Methods: This is a systematic review and meta-analysis in which the related keywords in different international databases, including Medline (via PubMed) and Scopus were searched. The retrieved studies were screened and the required data were extracted from the included studies. Three standard methods including American Dental Association (ADA), The Center for Disease Control and Prevention (CDC) and contaminated > 100 CFU/ml(C-100) standards were used to assess the bacterial biofilm contamination of DUWLs. All studies that calculated the prevalence of bacterial biofilm contamination of DUWLs, and English full-text studies were included in the meta-analysis. Studies that did not have relevant data or used unusual laboratory methods were excluded. Methodological risk of bias was assessed by a related checklist and finally, the data were pooled by fixed or random-effect models. Results: Seven hundred and thirty-six studies were identified and screened and 26 related studies were included in the meta-analysis. The oldest included study was published in 1976 and the most recent study was published in 2020. According to the ADA, CDC and C-100 standards, the prevalence of bacterial contamination was estimated to be 85.0% (95% confidence interval (CI): 66.0–94.0%), 77.0% (95%CI: 66.0–85.0%) and 69.0% (95%CI: 67.0–71.0%), respectively. The prevalence of Legionella Pneumophila and Pseudomonas Aeruginosa in DUWLs was estimated to be 12.0% (95%CI: 10.0–14.0%) and 8.0% (95%CI: 2.0–24.0%), respectively. Conclusion: The results of this review study suggested a high prevalence of bacterial biofilm in DUWLs; therefore, the use of appropriate disinfecting protocol is recommended to reduce the prevalence of contamination and reduce the probable cross-infection. [ABSTRACT FROM AUTHOR]

Aerosol generation in a dental setting is a critical concern, and approaches that aim at decreasing bacterial load in aerosols are of high priority for dental professionals. The objectives of this study were to evaluate the relative effect of various endodontic procedures on the generation and dissemination of aerosols and the effect of 0.1% sodium hypochlorite (NaOCl) in dental unit waterlines (DUWLs) on the bacterial load in the generated aerosols in a clinical setting. The study was completed in 2 phases. The classic passive sampling technique using brain-heart infusion agar plates was used. Agar plates were strategically placed throughout the operatory at predefined locations. In phase 1, to evaluate the effect of different endodontic procedures on the generation and dissemination of aerosols, we collected a total of 38 samples. After baseline collection, test samples were collected during vital pulp therapy (VPT) full pulpotomy (n = 10), nonsurgical root canal therapy (NSRCT, n = 10), surgical root canal therapy (SRCT, n = 10), and incision and drainage (n = 8) procedures. Bacterial growth was expressed as colony-forming units at 48 hours after sample collection. Data were analyzed using 1-way analysis of variance with the Tukey multiple comparison post hoc test. In phase 2, to evaluate the effect of 0.1% NaOCl in the DUWL on the bacterial load in the generated aerosols, a total of 30 samples were collected. All procedures including VPT (n = 10), NSRCT (n = 10), and SRCT (n = 10) were performed with 0.1% NaOCl in the DUWL. Bacterial growth was expressed as colony-forming units at 48 hours after sample collection. Data were analyzed using 2-way analysis of variance with the Tukey multiple comparison post hoc test. All endodontic procedures generated aerosols at all tested locations, except incision and drainage. Aerosols were disseminated as far as 3 m from the patient's head with no significant difference between various locations (P >.05). VPT procedures generated the maximum number of aerosols compared with NSRCT and SRCT. Adding 0.1% NaOCl to DUWLs significantly reduced the bacterial load in the generated aerosols in all treatment groups compared with groups treated with untreated waterlines (P <.05). No significant difference was noted in the bacterial load between all groups with treated waterlines (P >.05). All tested endodontic procedures led to the generation and dissemination of contaminated aerosols, and the addition of 0.1% NaOCl as a biocide to the DUWL led to a statistically significant reduction in the bacterial load. [ABSTRACT FROM AUTHOR]

Bacterial contamination is a problem in dental unit water lines with the consequence of implementing regular disinfection. In this study, the short-term impact of chlorine dioxide (ClO2) treatment was investigated on the microorganisms Legionella pneumophila and L. anisa, Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus. The environmental background was proven as an important factor regarding the tolerance to 0.4 mg/L ClO2 as saline and phosphate-buffered saline resulted in a higher bacterial reduction than tap water. Gram-positive microorganisms demonstrated higher robustness to ClO2 than Gram-negative, and microorganisms adapted to tap water showed increased stability compared to cultured cells. At high densities, substantial numbers of bacteria were able to withstand disinfection, whereby the use of 4.6 mg/L ClO2 increased the inactivation rate. A massive cell decrease occurred within the first 5 minutes with subsequent plateau formation or slowed cell reduction upon further exposure. This biphasic kinetics cannot be explained by a ClO2 depletion effect alone, because the probability of bacterial subpopulations with increased tolerance should be taken into account, too. Our results prove high disinfection efficiency to microorganisms that were rather found in correlation to the level of bacterial contamination and background solutions than the chosen concentration for ClO2 treatment itself.

To systematically review the effect of different types of water sources on dental unit waterline (DUWL) contamination. 5 databases were searched from their inception to December 23, 2023. Two reviewers independently extracted the data and assessed the quality of the literature. The risk ratio (RR) was used as measure of effect size in meta-analysis. The Grading of Recommendations, Assessment, Development and Evaluation (GRADE) was used for evaluating quality of the evidence. Meta-analysis was completed by RevMan 5.4.5 studies involving 561 water samples were quantified for meta-analysis. The results indicated that no significant differences were found in view of contamination rate (RR = 1.01; 95 % CI, 0.72-1.41; P  = 0.96, I 2  = 62 %; GRADE low)and detection rate of Pseudomonas aeruginosa (RR = 0.78; 95 % CI, 0.15-4.13; P  = 0.77; I 2  = 83 %; GRADE very low) between using purified water and tap water as water sources of DUWL. The available evidence suggests that there is no significant difference between purified water and tap water in controlling DUWL contamination. However, the conclusions need to be further validated through more randomized controlled trials with robust design and a large sample size., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Legionella pneumophila is an opportunistic bacterial respiratory pathogen that is one of the leading causes of drinking water outbreaks in the United States. Dental offices pose a potential risk for inhalation or aspiration of L. pneumophila due to the high surface area to volume ratio of dental unit water lines—a feature that is conducive to biofilm growth. This is coupled with the use of high-pressure water devices (e.g., ultrasonic scalers) that produce fine aerosols within the breathing zone. Prior research confirms that L. pneumophila occurs in dental unit water lines, but the associated human health risks have not been assessed. We aimed to: (1) synthesize the evidence for transmission and management of Legionnaires' disease in dental offices; (2) create a quantitative modeling framework for predicting associated L. pneumophila infection risk; and (3) highlight influential parameters and research gaps requiring further study. We reviewed outbreaks, management guidance, and exposure studies and used these data to parameterize a quantitative microbial risk assessment (QMRA) model for L. pneumophila in dental applications. Probabilities of infection for dental hygienists and patients were assessed on a per-exposure and annual basis. We also assessed the impact of varying ventilation rates and the use of personal protective equipment (PPE). Following an instrument purge (i.e., flush) and with a ventilation rate of 1.2 air changes per hour, the median per-exposure probability of infection for dental hygienists and patients exceeded a 1-in-10,000 infection risk benchmark. Per-exposure risks for workers during a purge and annual risks for workers wearing N95 masks did not exceed the benchmark. Increasing air change rates in the treatment room from 1.2 to 10 would achieve an ∼85% risk reduction, while utilization of N95 respirators would reduce risks by ∼95%. The concentration of L. pneumophila in dental unit water lines was a dominant parameter in the model and driver of risk. Future risk assessment efforts and refinement of microbiological control protocols would benefit from expanded occurrence datasets for L. pneumophila in dental applications. [ABSTRACT FROM AUTHOR]

Purpose: The aim is to evaluate the bacterial contamination in dental unit waterlines (DUWLs) before and after the use of the disinfectant 1% (Lysoformin 3000) for its efficacy also assess the awareness about the same among the practicing dental surgeons of Vadodara city. Methodology: A volume of 20 ml water samples from the DUWLs from the clinics of the practicing dental surgeons of Vadodara city was collected. And were asked to answer a validated questionnaire in private. Disinfection of the waterlines was performed twice a week for 2 weeks with 1% disinfectant (Lysoformin 3000) and the samples were again collected. Qualitative and quantitative microbiological analysis was performed for both the predisinfected and postdisinfected samples. Results: Predisinfection samples showed a mean colony count of 670.35 colony forming unit (CFU)/ml which was reduced to 63.90 CFU/ml (P < 0.001) postdisinfection. Questionnaire assessment showed that 70% awareness of the participants about DUWL infections and the microorganisms associated. However, only 20% practiced any type of DUWL disinfection. Conclusion: Lysoformin 3000 can be promising to be used a DUWL disinfection solution as an easy to use and readily available solution with great antibacterial properties. However, still more long-term studies are required to check for its efficacy in anaerobic bacteria as well as resistant species of microorganisms.

Objectives: To test the efficacy of an intermittent use, dental unit waterline cleaner, containing 0.12% chlorhexidine, in a proprietary formulation, to reduce bacterial levels in three functioning dental units with independent water reservoir systems. Method and materials: Baseline water samples were first taken from six units. Two ounces of the undiluted test product was run through lines, left overnight, and flushed out the next morning. This was repeated for 6 nights initially, and once a week thereafter for 12 weeks. Three control dental units did not have chemicals added. Weekly samples were collected in bottles containing sodium thiosulphate on the afternoon before overnight treatment, plated on R2A agar, and incubated at room temperature for 7 days. Results: Mean colony-forming units per millimeter (CFU/mL) in treatment units declined from 23,389 (± 20,085) at baseline, to 6 (± 10) in week 4, to 5 (± 2) in week 12. Statistical analysis showed a significant difference between treatment and control units. Conclusion: Intermittent treatment of dental unit waterlines with 0.12% chlorhexidine gluconate (CHX), in a proprietary formulation, resulted in significantly reduced bacterial counts to levels that were consistently below the American Dental Association's goal of 200 CFU/mL for 8 weeks. (Quintessence Int 2004;35:630-634) [ABSTRACT FROM AUTHOR]

Objectives: The purpose of this research was to demonstrate the effectiveness of hydro peroxide ion-phase transfer catalyst (HPI-PTC) cleaners and disinfectants for maintaining dental unit waterlines free of planktonic organisms. Method and materials: Water samples were taken from 117 sites, which included a variety of dental units and samples from the sink faucets of most operatories. Samples were plated on appropriate bacteriologic media and incubated. The presence or absence of biofilms was confirmed by scanning electron microscopy. Twenty-two of the dental units were retrofitted with independent water systems; the cleaning procedure involved an overnight application of an HPI-PTC cleaner followed by a 2-minute water rinse. Results: Water from both the air-water syringe and the high-speed handpiece lines from all untreated units contained at least 6x10! colony-forming units per milliliter of planktonic or free-floating bacteria; the average was 1.4x10s CFU/mL An initial 5% solution of HPI-PTC successfully cleared the lines of any apparent biofilm when applied tor 3 consecutive days. Thereafter, once weekly use of the cleaner maintained the dental unit water supplies free of significant numbers of planktonic organisms. Conclusion: Routine weekly use of an HPI-PTC cleaner controlled dental unit waterline biofilm and reduced, with minimum effort, the microbial contamination level of water used for patient treatment to less than 200 CFU/mL. [ABSTRACT FROM AUTHOR]

"nBackground and Aim: According to infection possibility in high risk patients, assessment of microbial contamination in water sources utilized at medico-dental units has become a recent concern. The purpose of this study was to evaluate the microbial contamination in dental units waterlines at the department of operative dentistry, Tehran university of medical sciences in the year 2006. "nMaterials and Methods: In this cross-sectional study, six dental units in the department of operative dentistry were selected to assess microbial contamination in water sources. Samples were taken on Saturdays (the first working day in a week) and in the midweek, 64 and 16 hours respectively after turning the units off. Moreover, for investigating the effect of flushing, sampling was done at 30, 60, 90 and 120 seconds after flushing and were taken from three parts of each unit including air/water syringe, turbine handpiece and also cup filler water. Samples were transported in closed sterile containers to microbiology laboratory of the school pharmacy. Data were analyzed by Kruskal-Wallis and Dunn tests with p

The quality of water in a dental unit is of considerable importance because patients and dental staff are regularly exposed to water and aerosol generated from the dental unit. The aim of this study was to evaluate the occurrence of microbial contamination in dental unit waterlines. Water samples were collected aseptically from the waterlines (reservoir, triple-syringe, high-speed) of 15 dental units. After serial dilution to 1:10(6) in APHA, the samples were seeded by the pour-plate technique and cultured in plate count agar (Difco) for 48 h at 32masculineC. Analysis was based on the number of colony forming units (CFU). The Wilcoxon non-parametric test indicated that the levels of water contamination were highest in the triple-syringe (13 of 15) and in the high-speed (11 of 15); both levels were higher than those of the water reservoir. There was no significant statistical difference between the level of contamination in the triple-syringe and the high-speed as determined by the Mann-Whitney test [p(H0) = 40.98%; Z = - 0.2281]. Because biofilm forms on solid surfaces constantly bathed by liquid where microorganisms are present, these results indicate that the water in the dental unit may be contaminated by biofilm that forms in these tubules.

Introduction. Legionella is frequently detected in Dental Unit Waterlines (DUWLs). Although such a high occurrence is not necessarily associated with high risk for Legionnaire's disease among patients and staff, it is prudent to monitor DUWLs for Legionella periodically. Since this procedure is long and expensive, surrogate markers are frequently used. Aim. To investigate whether surrogate markers are predictive of Legionella detection in DUWLs in a highly colonized dental hospital. Material and methods. DUWLs from a dental hospital where legionellae were detected intermittently throughout a period of ten years was considered. The investigated predictors were total viable flora (TVF) at 37°C and at 22°C, Pseudomonas (legionellae competitor) occurrence and season. Multivariate analysis was made and, using the best fitting logistic regression model, the probability to detect legionellae in water from DUWLs was estimated. Results. Legionellae were detected in 52% water samples collected in summertime and never detected in wintertime at levels ranging between 0 and 200 colony forming units(CFU)/L. The odds ratio of legionellae occurrence were 25.0 for Pseudomonas undetected vs. detected, 108.3 for summertime vs. wintertime, 2.2-2.3 for TVF levels at 37°C and 22°C >200 CFU/mL vs. ≤200 CFU/mL. A 29% probability to detect legionellae from DUWLs, where Pseudomonas was undetected, TVF levels were >200 CFU/mL and in summertime, was estimated. Conclusion. Despite legionellae were ubiquitous in the dental hospital during the study period, in the most favourable conditions for Legionella growth (lack of competitor, high biofilm and hot weather), legionellae were detected in almost one third of DUWLs. [ABSTRACT FROM AUTHOR]

Introduction. Professional toothcleaning with ultrasonic scaler produces microbial aerosols. These microorganisms come from dental unit waterlines (DUWLs) --thus potentially including opportunistic pathogens, or from patients --thus potentially including human pathogens. Aim. To investigate the association between levels and quality of contamination of air samples and DUWLs during professional toothcleaning, thus providing information regarding the nature of air contamination produced by ultrasonic scaler use. Material and methods. Before treating the first patient of the day, 100 mL of water was aseptically collected from the DUWL designated for the ultrasonic scaler, water was not disinfected or flushed. Aliquots were plated on Plate Count Agar to determine total viable flora (TVF) and Charcoal-Yeast Extract Agar supplemented with a Growth Supplement to determine Legionella. Two sets of settle plates were placed on the tray in front of the patient, one before and another during patient treatment to determine TVF and Legionella. The association between TVF and Legionella levels and prevalence in DUWLs and in air samples was assessed using correlation coefficients. Results. 82 testing occasions were performed. The mean TVF levels in DUWLs and air were 21.2 (95% confidence interval, 95CI, 13.8-32.6) CFU/mL and 12.4 (95CI, 9.7-15.8) CFU/plate/h, respectively. The mean Legionella detection rates were 1.2% (DUWLs) and 0% (air). Correlations between air and water TVF and Legionella were not significant. Conclusion. Air contamination during ultrasonic scaler use was frequent and high, but it was not associated with DUWL contamination, suggesting that airborne microorganisms could come from patients and be potentially pathogens for humans. [ABSTRACT FROM AUTHOR]

Microorganisms that have been identified in dental unit waterlines (DUWLs) are of concern because they can cause infections, especially in immunocompromised patients. This study aimed to assess the incidence of microbial contamination in DUWLs before and after intervention to reduce contamination, and to investigate the presence of coliforms, Escherichia coil and Pseudomonas aeruginosa. Water samples were collected aseptically from the waterlines. The high-speed hand-piece and dental chair units were served by one distillation apparatus, which was fed by the potable tap water of four dental clinics. Different interventions were used: chlorination, flushing before clinics and between patients, draining at the end of the day, and freshly distilled water on a daily basis. There was a significant difference between the level of contamination in the high-speed hand-piece (1.5-2.7 log CFU/ml) and dental chair unit water (2.0-3.5 log CFU/ml). Coliforms (0.9%) E. coil (0.9%) and Pseudomonas (1.8%) were detected during 2008. This study indicates the need to monitor water quality regularly and prevent stagnation in DUWLS to reduce the number of viable bacteria to <100 CFU/ml. We recommend flushing the DUWL for 2 min before the first patient and for 10-20 s between patients, flushing the dental unit at the end of the day and draining it overnight to reduce the development of biofilms, and chlorination of the DUWLS. [ABSTRACT FROM AUTHOR]

Aim: To determine the effect of sodium bicarbonate (SB), sodium metaperiodate (SMP) and sodium dodecyl sulfate (SDS) combination on biofilm formation and dispersal in dental unit waterline (DUWL)-associated bacteria and yeast. Methods and Results: The in vitro effect of SB, SMP and SDS alone and in combination on biofilm formation and dispersal in Pseudomonas aeruginosa, Klebsiella pneumoniae, Actinomyces naeslundii, and Candida albicans was investigated using a 96-well microtitre plate biofilm assay. The combination showed a broad-spectrum inhibitory effect on growth as well as biofilm formation of both gram-negative and gram-positive bacteria, and yeast. In addition, the SB + SMP + SDS combination was significantly more effective in dispersing biofilm than the individual compounds. The combination dispersed more than 90% of P. aeruginosa biofilm whereas the commercial products, Oxygenal 6, Sterilex Ultra, and PeraSafe showed no biofilm dispersal activity. Conclusion: The composition comprising SB, SMP, and SDS was effective in inhibiting as well as dispersing biofilms in DUWL-associated bacteria and yeast. Significance and Impact of the Study: This study shows that a composition comprising environmentally friendly and biologically safe compounds such as SB, SMP, and SDS has a potential application in reducing DUWL-associated acquired infections in dental clinics. [ABSTRACT FROM AUTHOR]

Objective:  To evaluate by means of Petrifilm™ system (3M, St Paul, MN, USA) the level of bacterial contamination in water from old and new dental units (air–water syringes and high-speed turbines) before and after flushing water through waterlines. The old dental units had been used for 13 years and the new dental units for 1 year. A fast method named Petrifilm™ AC (3M) was employed to evaluate the level of water contamination with total aerobic bacteria and Petrifilm™ EC for Escherichia coli and coliforms. Methods:  Dental unit water were collected before and after flushing of 4 (air–water syringes) and 2 min (high-speed turbines) from 24 old and new dental units. Thereafter, samples were diluted, inoculated onto Petrifilm™ plates and incubated. Results:  The filtered tap water that filled up dental unit reservoirs showed a low level of bacterial contamination (4 and 15 CFU ml−1). However, all water samples from old and new dental units were highly contaminated. The flushing of dental unit waterlines reduced the bacterial count in all dental unit water, but the reduction was better in water from new dental units than from old dental units. E. coli and coliforms were not detected in any water samples analysed. Conclusion:  Flushing water is a simple measure that should do part of dental routine, because it was able to reduce the level of total aerobic bacteria in water from old and new dental units. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Summary: 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. [Copyright &y& Elsevier]

The purpose of this study was to evaluate how time-dependent waterline flushing affects the presence of biofilm in otherwise-untreated dental unit waterlines (DUWLs). Water samples were obtained from twelve highspeed handpiece DUWLs located in the undergraduate treatment clinic at the University of Missouri-Kansas City, School of Dentistry. Baseline water samples (50 cc) were collected prior to the start of continuous flushing. Additional 50 cc samples were collected after two-, three-, and four-minute flushing intervals from the baseline. The levels of planktonic bacteria in DUWLs were quantified by counting colony forming units (CFUs). In addition, segments of water tubing from each of the highspeed handpiece waterlines were examined by scanning electron microscopy, which confirmed the presence of a residual biofilm in the lumen of each dental unit waterline. A one-factor repeated measures ANOVA showed a statistically significant (p< 0.01) reduction in CFUs at all intervals compared to baseline and between each successive time interval. Indeed, after four minutes of continuous flushing, all waterlines still harbored CFU levels that exceed current American Dental Association (ADA) recommendations. It was concluded that water flushing of DUWLs produced a statistically significant reduction in planktonic bacteria at each time interval compared to the baseline and between each successive time interval. However, the level of CFUs after four minutes of continuous water flushing still exceeds the current ADA recommendations for acceptable levels of microorganisms. [ABSTRACT FROM AUTHOR]

The highly structured biofilms on the surface of internal tubing are regarded as the most important source of water pollution in the dental unit waterline (DUWL). Herein, the study aimed to evaluate the anti-biofilm effect of combined application of chlorine-containing disinfectant with multi-enzyme detergent in the dental unit waterline. Six dental units were included and randomly divided into two groups - Group A was treated with chlorine-containing disinfectant and multi-enzyme detergent; Group B was treated only with chlorine-containing disinfectant as control. All groups were treated once a day for four weeks. The anti-biofilm effect was evaluated by heterotrophic plate counts in output water, structure of biofilms, and fluorescence density of biofilms before and after treatment. Abundant opportunistic bacteria forming dense biofilms were observed before treatment. After one week, scanning electron microscopy showed the extracellular polymeric substance of biofilms in Group A was partially destroyed. The biofilms of Group A were completely removed in the third week, while the biofilms of Group B were still present. The combined application of chlorine-containing disinfectant and multi-enzyme detergent achieved a satisfactory effect on biofilms removal, demonstrating this strategy may play a significant role in reducing contamination in the dental clinic.

Aims: The aim of this research is to verify the presence of Legionella in human dental plaque., Methods: 65 adult patients not treated with systemic or local antibiotics at least 2 months before the time of sample collection were enrolled for plaque collection between September 2015 and December 2016. A brief questionnaire about lifestyle and health risks was administered. Legionella spp. detection has been executed by semi- nested PCR., Results: 8 out of 65 plaque samples (12.3%) were positive for Legionella spp. As regards health risks and lifestyle aspects, no relevant difference was observed between patients involved in our study, except for two positive patients who have reported a COPD ongoing and a pneumonia in the past., Conclusions: This study represents a step forward in the knowledge of reservoirs of the microorganism and richness of oral microbiota.