Comparative evaluation of effect of sodium hypochlorite and chlorhexidine in dental unit waterline on aerosolized bacteria generated during dental treatment.

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.

The long-term effect of sub-boiling water on dental unit waterlines and its ability to control cross-contamination in dentistry.

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.

Impact of Chlorine Dioxide on Pathogenic Waterborne Microorganisms Occurring in Dental Chair Units.

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.

Bacterial biofilm prevalence in dental unit waterlines: a systematic review and meta-analysis.

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.

Effect of Sodium Hypochlorite in Dental Unit Waterline on Aerosolized Bacteria Generated from Endodontic Procedures.

INTRODUCTION: 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. METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.

Disinfection methods of dental unit waterlines contamination: a systematic review.

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

Legionnaires' disease in dental offices: Quantifying aerosol risks to dental workers and patients.

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.

Anti biofilm effect of low concentration chlorine containing disinfectant assisted by multi enzyme detergent in dental unit waterlines.

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.

Odontogenic cutaneous sinus tracts due to infection with nontuberculous mycobacteria: a report of three cases.

BACKGROUND: Soft tissue or skin infections due to nontuberculous mycobacteria (NTM) have been reported frequently and are mostly associated with trauma or cosmetic interventions like plastic surgery. However, infection with NTM as a result of a dental procedure have rarely been described and the lack of clinical suspicion and a clear clinical manifestation makes diagnosis challenging. CASE PRESENTATION: We report on three patients with a facial cutaneous sinus tract of dental origin, due to an infection with respectively Mycobacterium fortuitum, M. abscessus and M. peregrinum. The infection source was the dental unit waterlines (DUWLs), which were colonized with NTM. CONCLUSIONS: Water of the DUWL can pose a health risk. This report emphasizes the need for quality control and certification of water flowing through DUWLs, including the absence of NTM. Our report also shows the need for a rapid recognition of NTM infections and accurate laboratory diagnosis in order to avoid long-term ineffective antibiotic treatment.

Dental Unit Waterlines in Quito and Caracas Contaminated with Nontuberculous Mycobacteria: A Potential Health Risk in Dental Practice.

Three cases of severe odontogenic infections due to nontuberculous mycobacteria (NTM) in Venezuela that were directly associated with dental procedures and the finding of dental unit waterlines (DUWLs) in dental offices that were colonized with mycobacteria species was the reason for assessing the water quality of DUWLs in dental offices in two capital cities in South America, namely, Quito and Caracas. The main water supplies and the water from 143 DUWLs in both cities were sampled and especially checked for contamination with NTM. To measure the overall bacteriological quality of the water also the presence of heterotrophic bacteria, coliform bacteria, and Pseudomonas was determined. Results showed that respectively 3% and 56% of the DUWLs in Quito and Caracas yielded NTM species (up to 1000 colony-forming units (CFU)/mL). Furthermore, high and unacceptable total viable counts of heterotrophic bacteria and/or coliform bacteria and Pseudomonas were detected in 73% of the samples. We conclude that, in both cities, the water in the majority of DUWLs was contaminated with NTM and other potential pathogens, presenting a risk to human health. The detection of NTM in DUWL water with acceptable heterotrophic bacteria counts shows the need to include NTM in water quality testing. Mycobacteria are more resistant to disinfection procedures than other types of vegetative bacteria, and most testing protocols for DUWLs do not assess mycobacteria and thus do not guarantee risk-free water.

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.

Água em elevada temperatura: é viável a sua aplicabilidade no controle do biofilme de equipo odontológico? / Water at high temperature: is its applicability for biofilm control of dental unit viable?

Na Odontologia, as linhas d'água de equipos odontológicos são substratos para a formação de biofilme e, consequentemente, dispersão dessa contaminação microbiana para água destinada ao tratamento odontológico. O objetivo desta pesquisa foi investigar a atividade antibiofilme da água em elevada temperatura contra Pseudomonas aeruginosa, visando à sua aplicabilidade em linhas d'água de equipos odontológicos para o controle dessa problemática. Trata-se de um estudo do tipo experimental/laboratorial in vitro. Alíquotas de 2mL de Tryptic Soy Broth com 1% do inóculo bacteriano padronizado (106UFC/mL) de P. aeruginosa (ATCC 27853) foram inoculadas em cada um dos poços de placas de poliestireno de 24 poços. Em seguida, fragmentos de linha d'água (FL) de 1cm (n=48) foram transferidos para os poços das placas. A incubação foi efetuada em estufa de agitação a 37°C por 24h em 80rpm. Decorrido o período de incubação, os FL foram enxaguados com 5mL de solução salina a 0,85% por três vezes para retirada das células planctônicas. Posteriormente, as amostras foram transferidas para duas placas de 24 poços contendo 2mL de água purificada do tipo II (osmose reversa) esterilizada em cada poço. Grupos experimentais com temperaturas e tempos de exposição diferentes foram avaliados: temperatura ambiente (controle) - (n=24) e a 60°C (n=24), e 30s (n=12) e 60s (n=12). As amostras dos FL foram transferidas para microtubos contendo 1mL de Tryptic Soy Broth e pérolas de vidro. Os tubos foram homogeneizados em agitador de tubos por 2min e, em seguida, alíquotas de 50µL in natura e diluídas (diluição decimal seriada até 10-5) foram semeadas em placas de Petri (60x15mm) com Cetrimide Agar. Após o período de incubação em estufa a 37°C por 24h, os números de unidades formadoras de colônia expressas por FL (UFC/FL) foram determinados. Além disso, as amostras dos FL foram fixadas, desidratadas, metalizadas e submetidas à análise por meio de microscopia eletrônica de varredura (MEV). Os dados coletados foram submetidos à análise estatística empregando-se os testes de Shapiro-Wilk e U de Mann-Whitney por meio do software BioEstat® (versão 5.3) e nível de significância a=5%. Houve diferença entre a comparação das medianas das cargas bacterianas expostas à água à temperatura ambiente (335.000UFC/FL) e a 60°C (2.030UFC/FL) por 30s (p=0,0005), com redução de 3logUFC/FL. Ainda, a comparação entre as medianas das cargas bacterianas expostas à água à temperatura ambiente (173.000UFC/FL) e a 60°C (1.780UFC/FL) por 60s mostrou diferença (p=0,0047), com redução de 2logUFC/FL. A MEV demonstrou a presença de biofilme em todas as amostras analisadas, entretanto nos FL expostos à água a 60°C, os bastonetes (P. aeruginosa) foram evidenciados em menor quantidade e com características morfológicas atípicas. Em conclusão, a exposição do biofilme de P. aeruginosa formado nos FL de equipo odontológico à água em elevada temperatura reduziu a carga e alterou a morfologia bacteriana, demonstrando possível aplicabilidade na biossegurança: controle de contaminação/infecção na Odontologia

In dentistry, dental unit waterlines were substrates for biofilm formation and, consequently, dispersion of this microbial contamination for distilled water to dental treatment. The objective of this study was to investigate water antibiofilm activity at high temperature against Pseudomonas aeruginosa, aiming at its applicability in dental unit waterlines for controlling this problem. It is an in vitro experimental/laboratory study. 2mL aliquots of Tryptic Soy Broth with 1% of standardized bacterial inoculum (106CFU/mL) of P. aeruginosa (ATCC 27853) were inoculated on each one of 24-well polystyrene plates. Next, fragments of waterline (FW) of 1cm (n=48) were transferred for plates wells. The incubation was carried out in an incubator shaker at 37°C for 24h at 80rpm. After the incubation period elapsed, the FW were flushed with 5mL of saline solution at 0.85% by three times for removing planktonic cells. Subsequently, the samples were transferred to two 24-well plates containing 2mL of type II purified water (reverse osmosis) sterilized in each well. Experimental groups with different temperatures and exposition times were evaluated: room temperature (control) - (n=24) and at 60°C (n=24), and 30s (n=12) and 60s (n=12). The FW samples were transferred to microtubes containing 1mL of Tryptic Soy Broth and glass beads. The tubes were homogenized in an orbital shaker for 2min and, following this, diluted in natura 50µL aliquots (serial decimal dilution up to 10-5) were seeded in Petri plates (60x15mm) with Cetrimide Agar. After the incubation period in chamber at 37°C for 24h, the numbers of colony-forming units expressed per FW (CFU/FW) were determined. Furthermore, the FW samples were fixed, dehydrated, metalized and submitted to analysis through scanning electron microscopy (SEM). The data collected were submitted to statistical analysis using Shapiro-Wilk and Mann-Whitney U tests through BioEstat® (version 5.3) software and a=5% significance level. There was a difference between the comparison of medians of bacterial loads exposed to water at room temperature (335,000CFU/FW) and at 60°C (2,030CFU/FW) for 30s (p=0.0005), with reduction of 3logCFU/FW. Moreover, the comparison between the medians of bacterial loads exposed to water at room temperature (173,000CFU/FW) and at 60°C (1,780CFU/FW) for 60s showed difference (p=0.0047), with a reduction of 2logCFU/FW. The SEM demonstrated biofilm presence on all analyzed samples, but on FW exposed to water at 60°C, the rods (P. aeruginosa) were evidenced in less quantity and with atypical morphological characteristics. In conclusion, the exposition of P. aeruginosa biofilm formed in dental unit FW to water at high temperature reduced the load and changed the bacterial morphology, demonstrating a possible applicability in biosafety: contamination/infection control in dentistry

Presence of Legionella spp. in human dental plaque.

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.

Evaluation of the Antimicrobial Functions of N-halamine Dental Unit Waterline Tubing for One Year.

OBJECTIVES: The objective of this study was to test the biofilm-controlling properties of N-halamine antimicrobial dental unit waterline (DUWL) tubing (T) tubing, without recharging over one year, compared to a control line (C). METHODS: A simulated clinical model was used to pump ultrapure water through T and C lines at a rate of 1.4 mL/min, five minutes on, 15 minutes off, eight hours/day, five days a week. Samples of source water, effluent from T and C, and from the stagnant water in the carboy (liquid container) after bench work was completed (S2), were collected aseptically, serially diluted, and cultured on R2A agar for seven days every six weeks. SEM images of the inside surfaces of detached tubing sections were also taken. The carboy was rinsed with a 1:10 dilution of sodium hypochlorite after six months. Means of log transformed CFU values obtained in triplicate were paired by T and C lines across months for comparison by paired Student's t-tests. RESULTS: An increase in effluent and carboy bacterial counts were noted after six months, but decreased after bleach rinse of the carboy. No significant difference (p > 0.25) between T and C lines were observed; similarly, T and carboy were not significantly different (p > 0.30). SEM images showed biofilm attachment on the inside surface of C after two months, but not on T. Organisms identified in the effluent reflected those in the source carboy. CONCLUSIONS: No biofilm attachment was detected on the N-halamine test line after 12 months, indicating its antimicrobial properties were retained. Further evaluation is recommended to determine the optimal recharge interval for N-halamine DUWL tubing when ultrapure source water is used.

Retraction of dental unit waterlines in Tianjin City / 中国感染控制杂志

Objective To survey the retraction of dental unit waterlines (DUWLs)in medical institutions,and evaluate the influencing factors for retraction of DUWLs.Methods In May-November 2014,dental chair units (DCUs)in medical institutions in Tianjin City were sampled through systematic random sampling method,retrac-tion volume of DUWLs was detected by independently made detector,the relevant influencing factors were investi-gated.Results A total of 58 DCUs in 30 medical institutions in 10 districts(counties)of Tianjin were investigated, the average retraction volume of DUWLs was (103.60 ±117.85 )mm3 ,the qualified rate of retraction volume of DUWLs was 48.28 %(28/58);length of utilization of DCUs was positively correlated with DUWLs retraction (r=0.52,P 0.05 ).Conclusion The qualified rate of retraction volume of DUWLs is low,routine maintenance of DUCs needs to be intensified,especially the long-term used DUCs,contaminatin of DUWLs due to the invalidity of retraction valve should be prevented.

Contamination status of dental unit waterlines in three general hospitals / 中国感染控制杂志

Objective To realize the contamination status of dental unit waterlines (DUWL)in general hospitals, and provide scientific evidence for making preventive measures.Methods Three hospitals were selected for study, water source adopted by hospital A,B and C was running water,reservoir water,and filtered water through reverse osmosis filtration system respectively,specimens of dental handpiece spray water and flushing water of dental chair units were collected quarterly,total bacterial colony in water were detected.Results The qualified rate of source wa-ter,handpiece spray water,and flushing water in hospital A was 75.00%(3/4),0 (0/40)and 0 (0/40)respectively,col-ony count of handpiece spray water and flushing water was (1.20×103 -5.53×104 )CFU/mL(M=3.80×104 CFU/mL) and (2.11×104 -1.66×105 )CFU/mL(M=4.80×104 CFU/mL)respectively.The qualified rate of source water,hand-piece spray water,and flushing water in hospital B was 50.00%(2/4),60.00%(24/40)and 72.50%(29/40)respectively, colony count of handpiece spray water and flushing water was (0.00 -3.71 ×106 )CFU/mL(M=83.00 CFU/mL)and (0.00-2.39×106 )CFU/mL(M=72.00 CFU/mL)respectively.The qualified rate of source water,handpiece spray wa-ter,and flushing water in hospital C was 100.00%(4/4),55.00%(22/40)and 65.00%(26/40)respectively,colony count of handpiece spray water and flushing water was (0.00-6.20×103 )CFU/mL(M=96.00 CFU/mL)and(0.00-1.63×103 )CFU/mL(M=87.50 CFU/mL)respectively.Conclusion Water of DUWL in general hospitals is seriously con-taminated,disinfection and standardized management of source water and DUWL must be strengthened.

A comparison of 2 laboratory methods to test dental unit waterline water quality.

The performance of 2 American Public Health Association standard laboratory methods, the R2A spread plate and the SimPlate(TM) for heterotrophic plate count, for quantifying heterotrophic microorganisms in dental waterline samples was evaluated. Microbial counts were underestimated on SimPlate(TM) compared with R2A, and the results indicated a poor correlation between the 2 methods.

Evaluation of A Chlorine Dioxide Disinfectant for Dental Unit Waterlines / 中华医院感染学杂志

OBJECTIVE To investigate the use of a chlorine dioxide-based dental unit waterline(DUWL) treatment to reduce the colonization and growth of heterotrophic bacteria.METHODS Twenty-two dental units with self-contained water systems were randomly selected.Three of the units and tap water served as controls.Twenty-three water samples were taken at baseline and once a week for five weeks.They were serially diluted,spread-plated in duplicate onto R2A agar plates and incubated at 37 ℃ for 7 days.RESULTS At baseline,the 3 control DUWLs had a median count of 8440 colony-forming units/milliliter(CFU/ml) and the 19 treated DUWLs had a median count of 9160 CFU/ml.By week 1,18 of the 19 treated DUWLs had counts of less than 200 CFU/ml,and by week 4,the median count for all of the treated DUWLs was 0 CFU/ml.The measurement at week 5 showed that the reduction to below 200 CFU/ml had been maintained.Scanning electron examination revealed a similar results,with biofilm accumulation more evident in the untreated control specimens.CONCLUSIONS Using a chlorine dioxide-based disinfectant in DUWLs can achieve the American Dental Association(ADA) goal of less than 200 CFU/ml of heterotrophic bacteria per milliliter of unfiltered output water.