Dental Unit Waterlines Research Articles

Effect of Inhibition of Bacterial Proliferation by Neutral Electrolytic Water inDental Unit Waterlines

Background: Microbial contamination in dental unit waterlines (DUWLs) has recently become an important issue in the field of dental infection control. Using neutral electrolytic water as a new disinfecting method has attracted considerable attention. However, long term data about the effect of using neutral electrolytic water in clinical settings are scarce. This is the first study to evaluate the long term effectiveness of inhibition of bacterial proliferation using the purification system to supply neutral electrolytic water to refine the waterworks in DUWLs. Methods: Before the study, we investigated the actual levels of bacterial contamination in DUWLs. Then we did thorough cleaning of DUWLs and water samples were collected 6 dental units. Three dental units assigned as Group A had purification systems that used neutral electrolytic water, and the other 3 units were the Control group. Water samples were collected from the gargle water, high-speed handpieces and the three-way syringe. We utilized the equipment in Group A, and both groups were maintained for daily clinic work for 14 months. We counted the bacterial colony forming units (cfu) for each sample and identified the pathogenic bacterial species. Results: 3 and 14 months later, no microbes were detected during the study period in Group A whereas numbers of cfu which grew from the Control group increased and glucose non-fermenting gram-negative rod of possible pathogenic organisms to human were identified in the control groups. Conclusions: The water purification system using neutral electrolytic water was effective to control the proliferation of bacteria and could maintain a hygienic environment in DUWLs.

Optimization of Ozonation Process for Disinfection of Dental Unit Waterlines Using Response Surface Methodology

ABSTRACTThe reduction of microbial contamination in dental unit waterlines (DUWLs) appears to be necessary because of a potential risk of infections in immunocompromised patients and medical staff, which are regularly exposed to water and aerosols generated from DUWLs. In the present study, the qualitative and quantitative microbial contamination of water in DUWLs were determined and the conventional biomedical diagnostic tests were applied to identify microorganisms. A 3-level, 2-factor central composite design was utilized to investigate the effects of chief operating parameters and optimize ozone disinfection conditions. Also, the activity of three disinfectant (ozone, NaOCl, and peracetic acid) in microbial decontamination of DUWLs were compared. The results indicated that Microbacterium laevaniformans were the most prevalent genera (21%) among both Gram-negative and positive species in all samples. Regression analysis illustrated the good fit of the experimental data to the predicted model with R2 and R2adj correlation coefficients of 0.988 and 0.980, respectively. Moreover, under the optimal circumstances (Ozone concentration = 1.2 ppm and reaction time = 13.5 min) the disinfection efficiency was 97.52%. The results also revealed that ozone was effective disinfectant to reduce prevalent genera (with the removal of 93.75%, 92.57% and 96.15% of Pseudomonas aeruginosa, Microbacterium ‎laevaniformans, and Alcaligenes faecalis, respectively) and already formed biofilms under optimum conditions. Based on achieved results, ozone was highly effective on microbial decontamination compared to peracetic acid and NaOCl disinfectant and can be used for disinfection of DUWLs.

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

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. 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. 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. 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. 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.

Occurrence and biofilm forming ability of Pseudomonas aeruginosa in the water output of dental unit waterlines in a dental center in Alexandria, Egypt.

Dental unit waterlines (DUWLs) are notorious for being contaminated with different bacterial species including the opportunistic pathogen Pseudomonas aeruginosa which poses a risk to patients and professionals. This work aimed at studying the occurrence and biofilm-forming ability (BFA) of P. aeruginosa in the output of DUWLs in a dental center in Egypt. Water samples were collected from the outlets of the high-speed hand piece, the air/water syringe and the cup filler waterlines. Bacteriological analysis included heterotrophic plate count (HPC), isolation and identification of P. aeruginosa and determination of the antimicrobial susceptibility and the BFA of the isolates by tissue culture plate (TCP) method and tube method (TM). The average concentration of HPC bacteria in the output of the 3 DUWLs was 2.9×104 CFU/μL where 88.3% of the samples exceeded the Egyptian standards for drinking water (<50 CFU L). P. aeruginosa was isolated from nine cup filler samples (which had a water source different from the other waterlines). The isolates were sensitive to all tested antimicrobials. Of these nine isolates, 6, 5 and 4 were positive for BFA by TCP, modified TCP and TM, respectively. More stringent measures are required to ensure safer dental water; as the majority of studied samples exceeded the required HPC bacterial limit and P. aeruginosa isolates were detected. P. aeruginosa isolates from DUWLs may not be as resistant to antibiotics as what is reported in the literature about clinical isolates. Some P. aeruginosa isolates can colonize DUWLs despite their inability to form biofilms in experimental testing.

Colonization by Pseudomonas aeruginosa of dental unit waterlines and its relationship with other bacteria: suggestions for microbiological monitoring.

Pseudomonas aeruginosa is an environmental bacterium, ubiquitous in aquatic habitats and water distribution systems, including dental unit waterlines (DUWLs). We investigated the prevalence of P. aeruginosa in DUWLs from private dental settings. We also analyzed the relationship between P. aeruginosa contamination and the presence of Legionella spp. and total viable count (TVC) in order to suggest a simple and inexpensive protocol to test the quality of water from DUWLs. We detected and quantified P. aeruginosa both by culture and by a PMA (propidium monoazide)-qPCR method. Overall, we detected P. aeruginosa in 17 samples using the PMA-qPCR and in 11 samples using the culture. All culture-positive samples were positive with the PMA-qPCR too, with an agreement between the two methods of 93% and a Cohen's kappa coefficient of κ = 0.747 (good concordance). Comparing results with results of our previous study, we noted that (a) P. aeruginosa was isolated only from DUWLs with high TVC and (b) five out of six Legionella-positive samples were negative for Pseudomonas spp. Our final suggestion is that the cleanliness of DUWLs should be assessed by TVC because it is a good indicator of the presence of pathogens such as Legionella spp. and P. aeruginosa.

DUWL infection control protocols in force? Check

Peter Bacon has a tried and tested protocol for maintaining the water quality of dental unit waterlines that should at least tick that off your list.

Efficacy of acoustic waves in preventing Streptococcus mutans adhesion on dental unit water line.

The quality and health safety of water used for refrigeration and flushing of the handpieces, water-syringes and other components of dental units is of considerable importance. Water crosses these devices by a system of intersected small plastic tubes (about 2 mm of diameter), named dental unit water lines (DUWLs). DUWLs may be heavily colonized by many bacterial species in a planktonic phase, adherent or in biofilm lifestyle, resulting in a potential risk of infection, not only for all professionals who routinely use these devices, but also for occasional-patients, especially immunocompromised patients. Contamination of DUWLs can be prevented or reduced with the use of disinfectants, but the eradication of microorganisms, especially which those are adherent or living in biofilm lifestyle on the inner surfaces of DUWLs is challenging and often, the normal methods of water disinfection are not effective. Moreover, disinfectants routinely used to disinfect DUWLs may alter the bond strength of the dentine bonding agent used for restorative practice in dentistry. To identify an innovative and alternative strategy, able to prevent bacterial adhesion to DUWL surfaces through a physical approach, which is more effective in overcoming the problem of DUWL contamination and the risk of infection compared to the standard methods already in use. In this pilot study we tested a member of the oral streptococci family, that is not a component of the biofilm detected on the walls of DUWL, but is frequently detected in water samples from DUWL, due to human fluid retraction during dental therapy. Namely, the pathogenic bacterial species Streptococcus mutans. We employ elastic acoustic waves at high-energy in preventing S. mutans adhesion to the inner walls of an experimental water circuit reproducing a DUWLs. To stress the capability of acoustic waves to interfere with bacterial adhesion also in extreme conditions, a high S. mutans contamination load was adopted. We observe a significant decrease of adherent bacteria exposed to acoustic waves treatment respect to control. This study demonstrates the effectiveness of acoustic waves in counteracting the adhesion of S. mutans to the inner walls of an experimental water circuit reproducing a DUWL, opening up new prospects for future practical applications. The interesting results, so far obtained, require an in-depth analysis of the methods regarding both the various bacterial species involved and the infective charges to be used.

An Assessment of the Bacterial Diversity found in Dental Unit Waterlines using the Illumina MiSeq.

Water from the waterlines of dental units is often contaminated with bacteria but there have been few studies accurately assessing the diversity of these bacterial populations. The aim of our study was to assess the bacterial diversity present in water collected from dental unit waterlines using the Illumina MiSeq. Water was collected from two separate dental units located in a dental hospital and two units found in two separate private clinics in Gangneung-si, Korea. From the four water samples that were analyzed, a total of 233 bacterial genera were identified. The most abundant genera were Sphingomonas (25%), Halomonas (20%), Reyranella (8%), and Novosphingobium (6%). Halomonas was more prevalent in the two dental units located at the dental hospital, while Reyranella and Sphingomonas were more commonly found in the private dental clinics. Only 19 of the 233 identified genera were common between water samples from all dental units. Opportunistic pathogens were shown to account for 7.7% of the total bacterial genera identified. Our results have demonstrated that there is a wide assortment of bacterial genera present in dental unit waterlines.

Comparative evaluation of the chlorhexidine and cinnamon extract as ultrasonic coolant for reduction of bacterial load in dental aerosols.

Background:Ultrasonic instruments generate aerosols with significantly greater number of bacteria. Preprocedural mouthrinses or chemotherapeutic coolants are used for the reduction of bacterial load in dental aerosols. The use of chlorhexidine as an ultrasonic coolant has been well established. However, this application has not yet been investigated for cinnamon extract which is known to have antibacterial and anti-inflammatory properties in vivo.Aim:The aim of this study is to compare and evaluate the efficacy of chlorhexidine and cinnamon extract as an ultrasonic coolant in reduction of aerosol contamination and biofilm formation during ultrasonic scaling in comparison with the distilled water (DW).Materials and Methods:Sixty patients diagnosed with moderate-to-severe gingivitis were randomly divided into three groups of twenty patients each undergoing ultrasonic scaling. For Group I, chlorhexidine was used as an ultrasonic coolant; for Group II, cinnamon extract was used; and Group III was served as control where DW was used. The aerosols from ultrasonic units were collected on two blood agar plates at three different positions. Both the plates from each position were incubated aerobically for 48 h. The total number of colony-forming units were counted as mean ± standard deviation and statistically analyzed. In addition, biofilm sampling of dental unit waterlines (DUWLs) was also done to evaluate the effect of these antimicrobials. Apart from microbial examination, clinical parameters such as plaque index and gingival index were also evaluated at baseline and 1-month follow-up.Results:Chlorhexidine and cinnamon both were equally effective (P > 0.05) in reducing the bacterial count in aerosols and biofilm in DUWL as compared to DW when used as ultrasonic cooling agent.Conclusion:Both cinnamon and chlorhexidine used as an ultrasonic device coolant through DUWLs effectively helped in the reduction of bacterial count in dental aerosols.

Risk assessment for the spread of Candida sp. in dental chair unit waterlines using molecular techniques

The aim of this study was to evaluate the presence of yeasts in dental chair unit waterlines (DCUWLs) and to test their ability to form biofilms. Eighteen dental waterlines were analysed by culture in liquid Sabouraud in order to allow the quantification and the purification of isolated yeasts from their internal surfaces. All isolates were identified by standard laboratory procedures, including CHROMagar Candida medium for orientation, commercial yeast identification system Api Candida, MALDI-TOF MS and DNA sequencing. To evaluate their kinetics of antifungal susceptibility during different phases of biofilm formation, these yeasts were subjected to three antifungal agents. From the 18 DCUWLs studied, 10 were altered (55.56%). Eleven strains of Candida sp. [Candida albicans (2), Candida guilliermondii (5) and Candida glabrata (4)] and two species of non-Candida; Rhodotorula spp. (1) and Trichosporon spp. (2) were identified. The majority of yeasts in planktonic form were susceptible to amphotericin B, caspofungin and voriconazole, except C. albicans was resistant to voriconazole. In the biofilm form, caspofungin was the most effective antifungal agent for all isolated strains. For the other antifungal agents, sessile cells were resistant. Several types of yeasts were identified; the most frequently isolated genus was Candida. The majority of these yeasts had the ability to form biofilms and resisted antifungal agents used in this study.

Microbial water quality management of dental unit water lines at a dental school

Contaminated dental unit water lines (DUWLs) are a possible source for spreading micro-organisms in dental practices. This study reports the microbial load of the water from DUWLs of a large dental school over time. The water quality of 231 dental chairs was tested three times over 1.5 years; 175 DUWLs at student clinics and 56 DUWLs at staff clinics. DUWLs at the staff clinics met the Dutch requirement of 100colony-forming units/mL. An increasing number of DUWLs at the student clinics complied with this requirement, indicating that the local protocols are adequate but that compliance can be improved.

Detection of Legionella Anisa in Water from Hospital Dental Chair Units and Molecular Characterization by Whole-Genome Sequencing.

This study aims to assess contamination with Legionella spp. in water from dental chair units (DCUs) of a hospital dental ward and to perform its molecular characterization by whole-genome sequencing (WGS). We collect eight water samples (250 mL) from four DCUs (sink and water-syringe). Samples are tested for the presence of Legionella spp. (CFUs/mL) by culturing according to the Nederland Norm (NEN) 6265. Three DCUs are found positive for Legionella anisa, and four isolates are cultured (sink n = 2, water-syringe n = 1; two isolates from the same chair) with 1 × 102 CFU/mL. Whole-genome multi-locus sequence typing (wgMLST) results indicate that all strains belong to the same cluster with two to four allele differences. Classical culture combined with WGS allows the identification of a unique clone of L. anisa in several DCUs in the same hospital dental ward. This may indicate a common contamination source in the dental unit waterlines, which was fixed by replacing the chairs and main pipeline of the unit. Our results reveal tap water contamination in direct contact with patients and the usefulness of WGS to investigate bacterial molecular epidemiology.

Disinfection effects of intelligent water treatment system on dental unit waterlines

Objective To investigate the disinfection effect and cytotoxicity of intelligent water treatment system on dental unit waterlines (DUWLs) , so as to provide basis for the safe and intelligent treatment of DUWLs. Methods From September to October 2017, 4 dental units with intelligent water treatment system were selected as the experimental group, and 4 dental units with municipal water as the source of water supply were used as the control group. The microbiological quality of water samples collected from DUWLs was assessed before and after installation of the intelligent water disinfection system in terms of the total viable counts of microorganisms. Student t was used to detect the inhibitory effect of water samples on oral microorganism and its toxicity on human oral normal clone. Results After thoroughly disinfecting the waterlines of the dental unit, the bacteria of dental unit in the control group could rapidly grow up to (3.2±1.02) ×103 CFU/ml within 1 weeks, and the experimental group could be maintained at <100 CFU/ml, the difference was statistically significant (P<0.05) ; In the control group, Pseudomonas aeruginosa, non tuberculous mycobacteria and Acinetobacter baumannii could be detected in the water samples of the control group, while the above pathogens were not be detected in the experimental group. The water samples in the experimental group had significant inhibitory effects on the common bacteria in the dental unit waterlines and in the human oral cavity (P< 0.05) , but only a lower cytotoxicity was shown to the epithelial cells of the human oral cavity. Conclusions The intelligent water treatment system can effectively reduce microbial contamination in dental waterlines and provide safe water for patients. Key words: Disinfection; Dental unit waterlines; Bacterial contamination; Cytotoxicity

Biofilm formation

Peter Bacon discusses the problem of biofilm formation and the best management strategies to control its growth in dental unit waterlines

Adhesion and Biofilm Formation Abilities of Bacteria Isolated from Dental Unit Waterlines

Adhesion and Biofilm Formation Abilities of Bacteria Isolated from Dental Unit Waterlines

Unexpected diversity in the mobilome of aPseudomonas aeruginosastrain isolated from a dental unit waterline revealed by SMRT Sequencing

The Gram-negative bacterium Pseudomonas aeruginosa is found in several habitats, both natural and human-made, and is particularly known for its recurrent presence as a pathogen in the lungs of patients suffering from cystic fibrosis, a genetic disease. Given its clinical importance, several major studies have investigated the genomic adaptation of P. aeruginosa in lungs and its transition as acute infections become chronic. However, our knowledge about the diversity and adaptation of the P. aeruginosa genome to non-clinical environments is still fragmentary, in part due to the lack of accurate reference genomes of strains from the numerous environments colonized by the bacterium. Here, we used PacBio long-read technology to sequence the genome of PPF-1, a strain of P. aeruginosa isolated from a dental unit waterline. Generating this closed genome was an opportunity to investigate genomic features that are difficult to accurately study in a draft genome (contigs state). It was possible to shed light on putative genomic islands, some shared with other reference genomes, new prophages, and the complete content of insertion sequences. In addition, four different group II introns were also found, including two characterized here and not listed in the specialized group II intron database.

Susceptibility of bacteria isolated from dental unit waterlines to disinfecting chemical agents.

Susceptibility testing of bacteria to disinfecting chemical agents isolated from dental unit waterlines (DUWL) is necessary for the development of effective disinfectant products. However, until now, susceptibility tests for chemical agents, which are components of DUWL disinfectant products, have not been conducted on bacteria isolated from DUWL water. The aim of this study was to evaluate and compare the susceptibilities of DUWL isolates in planktonic and biofilm states to cetylpyridinium chloride, as well as to the four chemical agents currently used for DUWL management. A total of 56 isolates, including 12 genera, were identified by 16S rDNA sequencing, and one strain of each genus was selected for susceptibility testing. A total of 12 isolates were used for the susceptibility tests. We determined the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) for the planktonic state and the minimum biofilm inhibitory concentration (MBIC) and minimum biofilm eradication concentration (MBEC) for the biofilm state using microtiter plates. MIC, MBC, MBIC, and MBEC of the 12 isolates for ethanol were the highest, followed by sodium hypochlorite, hydrogen peroxide, and chlorhexidine. Similar to chlorhexidine, the lowest MIC, MBC, MBIC, and MBEC were found in cetylpyridinium chloride. The susceptibilities of the isolates for sodium hypochlorite and ethanol were similar in the planktonic and biofilm states. For hydrogen peroxide and chlorhexidine, the MBIC and MIC were similar, but MBEC was 256 times higher than MBC. The MBIC and MBEC of isolates for cetylpyridinium chloride were 128 and 256 times higher than the MIC and MBC, respectively. As far as we know, this was the first study reporting the susceptibility of DUWL isolates to cetylpyridinium chloride and chemical agents used for disinfecting DUWLs. Cetylpyridinium chloride, for which the DUWL isolates showed the highest susceptibility, could be used for disinfecting DUWLs.

Application of D-Amino Acids as Biofilm Dispersing Agent in Dental Unit Waterlines.

Aim and Purpose Biofilms in dental unit waterlines (DUWLs) are extremely difficult to eliminate. Aim of this study is to evaluate the efficacy of a mixture of four D-amino acids on biofilm dispersion in DUWLs. Materials and Methods A mixture of four D-amino acids (D-methionine, D-tryptophan, D-leucine, and D-tyrosine, 10 mM each), distilled water (control), and 0.1 M hydrochloric acid (HCl) was used in the experiment. In laboratory, pieces of DUWLs covered with biofilms were submerged in different solutions for 5 days, flushed, and measured OD600 of the dispersed biofilms. Remnants of biofilms on the DUWLs were evaluated by SEM. In clinic, fifteen DCUs were incubated with test and control solutions, flushed, and measured OD600 of the dispersed biofilms. Microbial count of DUWL output water was enumerated twice a week for four weeks. Results There was a slight, but not significant, increase in OD600 of flushing water in D-amino acids group. D-amino acids effectively reduced bacterial plaque as demonstrated by SEM. Incubation with D-amino acids significantly reduced biofilms especially after the first day of flushing. Bacterial count in DUWL output water was significantly reduced after treatment with D-amino acids. Conclusion D-amino acids are applicable as biofilm dispersing agents in DUWLs.

Study the Effects of Two Types of Microbial Disinfectants on Contamination of Dental Unit Water Lines

The main aim of this study is study the effects of alcohol and hydrogen peroxide in determination the extent of microbial contamination in dental unit water lines. The study included one hundred twenty water samples were collected from dental unit water lines at the clinics of the college of Dentistry/University of Babylon located in the center of the province of Babylon during the period from October 2016 to April 2017. The water samples were subjected to different methods for identification bacteria using traditional bacteriological method. After obtaining baseline water samples, the dental unit waterlines were treated with alcohol 96% and hydrogen peroxide 1% where the two disinfectants were used in treatment and their inhibiting effect was compared. The highest contamination rate of all water samples were found in the bottle in both disinfectants alcohol and hydrogen peroxide. There weresignificant difference in Mean ± SD when treated with disinfectants.hydrogen peroxide was found to be the most effective in reducing the microbial contamination. Improving the water quality from dental unit water lines are of considerable importance. It were stated highest contamination rate of dental unit chair was found in the bottle and hydrogen peroxide disinfectant was more effective than alcohol.

Establishing a laboratory model of dental unit waterlines bacterial biofilms using a CDC biofilm reactor

In this study, a laboratory model to reproduce dental unit waterline (DUWL) biofilms was developed using a CDC biofilm reactor (CBR). Bacteria obtained from DUWLs were filtered and cultured in Reasoner’s 2A (R2A) for 10 days, and were subsequently stored at −70°C. This stock was cultivated on R2A in batch mode. After culturing for five days, the bacteria were inoculated into the CBR. Biofilms were grown on polyurethane tubing for four days. Biofilm accumulation and thickness was 1.3 × 105 CFU cm−2 and 10–14 μm respectively, after four days. Bacteria in the biofilms included cocci and rods of short and medium lengths. In addition, 38 bacterial genera were detected in biofilms. In this study, the suitability and reproducibility of the CBR model for DUWL biofilm formation were demonstrated. The model provides a foundation for the development of bacterial control methods for DUWLs.