The effect of disinfectant agents in eliminating the contamination of dental unit water

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

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

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

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

Risk of Fungal Infection to Dental Patients

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

Breaking the Chain of Infection: Dental Unit Water Quality Control

INTRODUCTION

The air-water syringes, ultrasonic scalers, high speed air turbine handpieces are connected to dental units by a network of small-bore plastic tubes through which water and air travel to activate or cool the instruments and it had been shown that this system is extensively contaminated with microbial biofilms and pose a potential risk of infection for patients as well as dental professionals.

AIM

To evaluate and compare the efficacy of various disinfectants in reducing the microbial colony count in water derived from Dental Unit Waterlines.

MATERIALS AND METHODS

Five random dental units were selected and samples were collected before and after intervention with 5 disinfectants (0.02% H2O2 continuously, 0.02% H2O2 continuously with shock treatment with 0.25% H2O2 weekly, 0.12% Chlorohexidine and 12% Ethanol overnight, 1:50 Original Listerine overnight, 2% Sodium Perborate and 2% EDTA 5 minutes in morning) using different disinfection methods for 4 weeks. Samples were cultured on Reasoner's 2A (R2A) agar for microbial counting.

RESULTS

Results were recorded as Colony forming units/ml (cfu/ml) and were evaluated statistically. Results showed that all the dental unit waterlines were heavily contaminated with microbes before any intervention. After 1 day of disinfection regime the counts reduced significantly and showed progressive reduction in consecutive weeks. Goals set by ADA & CDC were ultimately achieved at the end of 4 weeks.

CONCLUSION

All the disinfectants were equally effective in reducing the microbial colony count of DUWLs, irrespective of their concentration and method of disinfection.

Antiseptic effect of slightly acidic electrolyzed water on dental unit water systems

Biofilm formation in dental unit water systems (DUWSs) can contaminate water from three-in-one syringes, air rotors, and low-speed handpieces. This may serve as a potential source of infection for dentists, dental staff, and patients, so these systems must be sterilized. Because slightly acidic electrolyzed water (SAEW) is often used as a disinfectant for food, the aim of this study was to investigate the possibility of using SAEW as a DUWS disinfectant. Slightly acidic electrolyzed water was injected into a dental unit and its effects evaluated. Chemical properties such as chlorine ion and potential hydrogen in the SAEW were measured. Detection of both ordinary and heterotrophic bacteria from the DUWS was performed by culture, and biofilm formation of the bacteria in the DUWS evaluated. Polymerase chain reaction (PCR) was used to detected contamination by nosocomial pathogens. Almost all the chlorine ions in the SAEW were exhausted during the two-day trials, and the pH value of the SAEW fell from 5 to 4. No viable cells were detected in the SAEW collected. Biofilm formation in the water from the DUWS with SAEW was almost at a baseline level, whereas that without SAEW was 4 times higher. The PCR analysis showed that no nosocomial infecting pathogens were detected in the SAEW. The present study demonstrated the antiseptic effect of SAEW in DUWS.

Disinfection of dental unit water line using aloe vera: in vitro study

Context. Dental unit waterlines may be heavily contaminated with microorganisms and are a potential source of infection for both practicing staff and immunocompromised patients particularly. Contamination of dental unit water lines could be inhibited with the use of disinfectants. The present study investigates the effect of aloe-vera-based disinfectant in reducing the microbial growth in dental unit water lines (DUWLs). Aims. To compare the efficacy of aloe vera, hydrogen peroxide (H₂O₂), and 5% sodium hypochlorite (NaOCl) in controlling microbial contamination of DUWLs. Materials and Methods. After obtaining baseline water samples, the dental unit waterlines were treated with aloe vera, 10% hydrogen peroxide, and 5% sodium hypochlorite. Each of the three disinfectants was used in increasing concentrations and their inhibiting effect was compared. Water samples were analyzed for microbiological quality by the total viable count (TVC) method. Statistical Analysis Used. SPSS 16. Results. There was significant reduction in mean CFU/ml when treated with disinfectants each for a period of one week. Aloe-vera solution was found to be the most effective in reducing the microbial colonies. Conclusions. Improving the water quality from dental unit water lines is of considerable importance; chemical-based disinfectants can be replaced with herbal disinfectants for treating microbial contamination in dental unit waterlines.

Management of dental unit waterline biofilms in the 21st century

Dental chair units (DCUs) use water to cool and irrigate DCU-supplied instruments and tooth surfaces, and provide rinsewater during dental treatment. A complex network of interconnected plastic dental unit waterlines (DUWLs) supply water to these instruments. DUWLs are universally prone to microbial biofilm contamination seeded predominantly from microorganisms in supply water. Consequently, DUWL output water invariably becomes contaminated by high densities of microorganisms, principally Gram-negative environmental bacteria including Pseudomonas aeruginosa and Legionella species, but sometimes contain human-derived pathogens such as Staphylococcus aureus. Patients and staff are exposed to microorganisms from DUWL output water and to contaminated aerosols generated by DCU instruments. A wide variety of approaches, many unsuccessful, have been proposed to control DUWL biofilm. More recently, advances in biofilm science, chemical DUWL biofilm treatment agents, DCU design, supply water treatment and development of automated DUWL biofilm control systems have provided effective long-term solutions to DUWL biofilm control.

Rechargeable biofilm-controlling tubing materials for use in dental unit water lines

A simple and practical surface grafting approach was developed to introduce rechargeable N-halamine-based antimicrobial functionality onto the inner surfaces of continuous small-bore polyurethane (PU) dental unit waterline (DUWL) tubing. In this approach, tetrahydrofuran (THF) solution of a free-radical initiator, dicumyl peroxide (DCP), flowed through the PU tubing (inner diameter of 1/16 in., or 1.6 mm) to diffuse DCP into the tubing's inner walls, which was used as initiator in the subsequent grafting polymerization of methacrylamide (MAA) onto the tubing. Upon chlorine bleach treatment, the amide groups of the grafted MAA side chains were transformed into acyclic N-halamines. The reactions were confirmed with attenuated total reflectance infrared (ATR) spectra and iodometric titration. The mechanical properties of the tubing were not significantly affected by the grafting reactions. The biofilm-controlling function of the new N-halamine-based PU tubing was evaluated with Pseudomonas aeruginosa (P. aeruginosa), one of the most isolated water bacteria from DUWLs, in a continuous bacterial flow model. Bacteria culturing and SEM studies showed that the inner surfaces of the new N-halamine-based PU tubing completely prevented bacterial biofilm formation for at least three to four weeks. After that, bacteria began to colonize the tubing surface. However, the lost function was fully regenerated by exposing the tubing inner surfaces to diluted chlorine bleach. The recharging process could be repeated periodically to further extend the biofilm-controlling duration for long-term applications.

Evaluation of antimicrobial-antibiofilm activity of a hydrogen peroxide decontaminating system used in dental unit water lines

A dental unit water line (DUWL) equipped with a device designed to automatically and continually flush a bacteriostatic solution of hydrogen peroxide (WHE) and a discontinuous disinfecting system (BIOSTER) was evaluated. In the first instance a preliminary sensitivity test on a large number of microorganisms (bacteria and fungi) was tried with a H₂O₂ range from 100 to 800 ppm. The bacteria frequently reported in DUWL (including Pseudomonas spp, Streptococcus spp., Staphylococcus spp., E. coli) and some periodontal pathogens showed a minimum inhibitory concentration from 100 to 300 H₂O₂ ppm (also including M. marinum and C. albicans). However, H₂O₂ did not show any inhibitory effects against: A. actinomycetemcomitans, C. glabrata C. parapsilos, F. nucleatum, M. micros. In a second step, the DUWL was experimentally infected with S. faecalis, E. coli, P. aeruginosa, S. aureus. After disinfection steps with 3% H₂O₂, the inhibitory effect on planktonic forms and on sessile biofilm was measured. In a third step, the count of 16S rRNA gene copies by real time PCR at different points of the DUWL described an accrue of bacterial slime in “hot spot” regions characterized by irregular/slow water flux (valves, elbows). However these results suggest that hydrogen peroxide is not only able to inhibit bursts of planktonic bacteria inside the DUWL, but that it could also be effective against sessile biofilm containing heterotrophic microorganisms derived from domestic water line contamination. In addition some oral pathogens could be contaminating and surviving in DUWL.

AcyclicN-halamine-based biocidal tubing: Preparation, characterization, and rechargeable biofilm-controlling functions

In this study, the surfaces of polypropylene tubing were hydroxylated with potassium persulfate. The resultant tubing surfaces were grafted with methacrylamide (MAA) using ceric(IV) ammonium nitrate as an initiator. Upon chlorination treatment with diluted chlorine bleach, some of the amide groups in the grafted MAA side chains were transformed into stable acyclic N-halamines. The reactions were confirmed with attenuated total reflectance infrared, X-ray photoelectron spectra, and iodimetric titration. The resultant tubing was challenged with Pseudomonas aeruginosa (P. aeruginosa) in a continuous flowing model. Bacteria culturing and scanning electron microscope studies showed that the chlorinated MAA-grafted tubing could provide potent and rechargeable biofilm-controlling functions against the test microorganisms.

Microbial biofilm formation in DUWS and their control using disinfectants

OBJECTIVES

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

STUDY SELECTION

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

SOURCES

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

DATA

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

CONCLUSIONS

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

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

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

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

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