Microbiological Water Evaluation from Biofilm Adhered to Dental Unit Waterlines / Evaluación Microbiológica del Agua de Biofilm Adherido a Líneas de Agua de la Unidad Dental

ABSTRACT: The contamination of the dental units' waterlines is a reality, which can develop individual and collective disorders. The aim of this study was to evaluate the prevalence and resistance profile of bacteria on the internal surfaces of waterlines in a dental clinic from a Dentistry school of a Brazilian university. The design was an exploratory, descriptive study with quantitative and qualitative approach. Samples (n=4) were collected for analysis at different points: the portion closest to the water reservoir of the chair, and the portion closest to the triple syringe. After collection the samples were cultured in BHI medium in an oven for 24-48 h at 37 °C. For the quantitative analysis 1 ml of each sample was used for serial dilution up to the dilution value seven. The colonies were counted after pour plate and the results expressed in UFC/cm2. The qualitative analysis was initiated with the cultivation of Agar Blood, EMB-Levine and Cetrimide Agar for 24 h, and the identification of bacteria was performed by microscopic analyses. The resistance profile was verified by classical antibiogram. The internal surfaces of unit waterlines units exhibited a mean of 2.44 x 109 CFU / cm2. Bacillus subtilis and Pseudomonas aeruginosa were identified. The resistance profile of Pseudomonas aeruginosa indicated sensitivity to all tested antibiotics. A large number of microorganisms was quantified from biofilm accumulated in the dental units' waterlines. However, they were not resistant to classic antibiogram. Better management and application of decontamination protocols for waterlines need to be applied since opportunistic infections may be associated with Pseudomonas aeruginosa.

RESUMEN: La contaminación de líneas de agua en las unidades dentarias es una realidad, generando enfermedades individuales y colectivas. El objetivo de este estudio fue evaluar la prevalencia y resistencia de las bacterias en las zonas internas de las líneas de agua de la Facultad de Odontología de una universidad brasileña. El diseño del estudio fue exploratorio, descriptivo con enfoques cuantitativos y cualitativos. Las muestras para análisis (n=4) fueron selecionadas de distintos lugares: el punto más cercano al sistema de agua del sillón odontológico y el punto más cercano a la jeringa tríplice. Las muestras obtenidas fueron cultivadas en un médio BHI por 24-48 h, en un horno a 37 ºC. Para el análisis cuantitativo, se utilizó 1 ml de cada muestra para dilución hasta el valor siete. Las colonias fueran contadas y los resultados fueron expresados en UFC/cm2. El análisis cualitativo fue iniciado con el cultivo de Agar Sangre, EBM-Levine y Agar Cetrimide por 24 h y la identificación de la bacteria fue realizada por análisis microscópicos. El perfil de resistencia fue verificado por el antibiograma clásico. Las zonas internas de las unidades de líneas de agua mostraron un promédio de 2,44 x 109 UFC/cm2. Bacillus subtilis y Pseudomonas aeruginosa fueron encontrados. El perfil de resistencia de Pseudomonas aeruginosa indicó sensibilidad a todos los antibióticos testados. Un gran número de microorganismos fue cuantificado desde la biopelícula acumulada en las líneas de agua de unidades dentales. Sin embargo, no resistieron al antibiograma clásico. Se requiere una mejor gestión y aplicación de protocolos de decontaminación en las líneas de agua debido a que las infecciones oportunistas puedan estar asociadas a Pseudomonas aeruginosa.

Importancia del proceso de limpieza y desinfección de superficies críticas en un servicio dental: impacto de un programa de intervención / Importance of cleaning and disinfection of critical surfaces in dental health services: impact of an intervention program

Resumen Introducción La atención odontológica se ha transformado en un desafío para los programas de prevención y control de infecciones asociadas a la atención de salud (IAAS), dado que el ambiente, entre otros factores, juega un rol importante en la cadena de transmisión. Método Se realizó un programa de intervención en el Servicio de Dental del Hospital Militar de Santiago, entre los años 2014-2015, que contempló tres etapas: etapa diagnóstica, de intervención y de evaluación. Objetivo Mejorar la seguridad de las superficies críticas involucradas en la atención dental. Resultados Durante la etapa diagnóstica se constató que el proceso de limpieza y desinfección era deficiente. La superficie crítica más contaminada fue la unidad porta-instrumental, luego el área limpia y la manilla de la lámpara. Las superficies que redujeron significativamente su contaminación, posterior a la intervención, fueron el área limpia y la unidad porta-instrumental. Conclusiones La capacitación en relación a los procesos de limpieza y desinfección de superficies y del equipamiento dental es una de las estrategias costo-eficientes en la prevención de las IAAS, sencilla y fácil de aplicar.

Introduction Dental care has become a challenge for healthcare associated infection prevention programs, since the environment, within other factors, plays an important role in the transmission chain. Materials and Methods An intervention program was designed for the Dental Unit of Hospital Militar de Santiago, between years 2014 and 2015. The program contemplated 3 stages: diagnostic, intervention and evaluation stage. Objective To improve the safety of critical surfaces involved in dental healthcare. Results During the diagnostic stage, the cleaning and disinfection process was found to be deficient. The most contaminated critical surface was the instrument holder unit, then the clean area and lamp handle. The surfaces that significantly reduced their contamination, after the intervention, were the clean area and the instrument carrier unit. Conclusion Training in the processes of cleaning and disinfecting surfaces and dental equipment is one of the cost-effective strategies in preventing healthcare-associated infections (HCAI), with simple and easy-to-apply methods.

Qualidade da água em clínica odontológica na perspectiva microbiológica: uma proposta de intervenção / Water quality in a dental clinic in the microbiological perspective: a proposal of intervention

Na odontologia, o biofilme formado nas linhas d'água de equipos odontológicos pode disseminar a contaminação microbiana na água. O objetivo desta pesquisa foi investigar a contaminação microbiana da água de abastecimento e de equipos odontológicos antes e após a implementação de um protocolo para melhoria e manutenção da qualidade microbiológica da água de equipos odontológicos, bem como desenvolver produtos antibiofilme com possível aplicabilidade nas linhas d'água. A carga microbiana da água de 27 torneiras e equipos (reservatórios, seringas tríplice e alta rotação) de uma clínica odontológica foi avaliada por meio do sistema Petrifilm(TM) (bactérias aeróbias totais e fungos) e meios de cultura convencionais (enterobactérias e Legionella spp.) em duas etapas distintas, sendo a segunda análise realizada após a implementação de um protocolo para melhoria e manutenção da qualidade microbiológica da água dos equipos. Ainda, as atividades antibacteriana (concentração inibitória mínima - hipoclorito de sódio, ácido cítrico, bicarbonato de sódio, cloreto de sódio, dodecil sulfato de sódio, peróxido de hidrogênio, polissorbato 20 e quitosana) e antibiofilme (biomassa total e viabilidade celular) foram determinadas in vitro a partir de substâncias e produtos com possível aplicabilidade na desinfecção de linhas d'água de equipos. As amostras de água das torneiras apresentaram carga bacteriana dentro do parâmetro estabelecido pela legislação brasileira, no entanto, as seringas tríplices e os alta rotação não. A implementação do protocolo para manutenção da qualidade microbiológica da água dos equipos demonstrou uma redução nas cargas bacteriana e fúngica apenas nos alta rotação. Enterobactérias e Legionella spp. não foram isoladas das amostras de água das torneiras e dos equipos. De acordo com a concentração inibitória mínima, o ácido cítrico, bicarbonato de sódio, cloreto de sódio, hipoclorito de sódio e peróxido de hidrogênio demonstraram as melhores atividades antibacterianas. As melhores atividades antibiofilme (biomassa total) foram do peróxido de hidrogênio a 5% (E. coli e P. aeruginosa), ácido cítrico a 30% (P. aeruginosa) e bicarbonato de sódio a 30% (S. aureus). Os produtos (Wanitox A e Wanitox B) desenvolvidos apresentaram atividade antibiofilme (viabilidade celular) contra a E. coli e S. aureus. Assim, os produtos desenvolvidos nesta pesquisa apresentaram possível aplicabilidade no enfrentamento do biofilme nas linhas d'água de equipos odontológicos, que permanece como um dos grandes desafios na odontologia. Ainda, pesquisas adicionais são necessárias para o aperfeiçoamento e aplicabilidade destes produtos

In dentistry, biofilm formed on dental unit waterlines can disseminate microbial contamination in water. The objective of this research was to determine the microbial contamination of water from supplies and dental units before and after the implementation of a protocol for improvement and maintenance of microbiological water quality of water from dental units as well as to develop antibiofilm products with possible applicability in waterlines. The microbial load of water from 27 taps and dental units (reservoirs, air-water syringes and high-speed turbines) in a dental clinic was evaluated through a Petrifilm(TM) system (total aerobic bacteria and fungi) and conventional culture mediums (enterobacteria and Legionella spp.) in two distinct stages, being the second analysis performed after the implementation of a protocol for improvement and maintenance of microbiological water quality of water from dental units. Moreover, the antibacterial (minimum inhibitory concentration - sodium hypochlorite, citric acid, sodium bicarbonate, sodium chloride, sodium dodecyl sulfate, hydrogen peroxide, polysorbate 20 and chitosan) and antibiofilm (total biomass and cell viability) activities were determined in vitro from substances and products with possible applicability in disinfection of dental unit waterlines. The water samples from taps presented bacterial load within the parameter established by Brazilian legislation; however, air-water syringes and high-speed turbines did not. The protocol implementation for maintenance of microbiological water quality of water from dental units showed a decrease on bacterial and fungal loads only on high-speed turbines. Enterobacteria and Legionella spp. were not isolated from water samples from taps and dental units. According to minimum inhibitory concentration, citric acid, sodium bicarbonate, sodium chloride, sodium hypochlorite and hydrogen peroxide showed the best antibacterial activities. The best antibiofilm activities (total biomass) were from 5% hydrogen peroxide (E. coli and P. aeruginosa), 30% citric acid (P. aeruginosa) and 30% sodium bicarbonate (S. aureus). The developed products (Wanitox A and Wanitox B) showed antibiofilm activity (cell viability) against E. coli and S. aureus. Thus, the products developed in this research presented a possible applicability in confrontation with biofilm on dental unit waterlines, and this remains as a major challenge in dentistry. Besides, additional researches are necessary for enhancement and applicability of these products

Study of the antimicrobial efficacy of chlorhexidine in dental unit water: evaluation of microbial contamination in the dental office / Estudo da capacidade antimicrobiana da clorexidina na água do equipamento odontológico: avaliação de contaminação microbiana em ambiente odontológico

Objective: The aim of this study to count anaerobic bacteria before and after the use of dental equipment and to study the influence of chlorhexidine on the dental unit reservoir water. Methods: Sterile swabs were used to collect bacterial samples from the cuspidor, lights, syringes, low-and high speed handpieces and dental chairs (arms and backrest) before and after the placement of barriers. Blood agar plates were placed on the patient's and dentist's forehead and by the patient's nose and shoulder and exposed to aerosoils without (group 1) and with 0,5% (group 2) and 1,0% (group 3) chlorhexidine generated by the high speed handpiece. Ten aerosol samples were collected for each group. A sample of 1mL of the dental unit reservoir water was collected before and after the use of the high speed handpiece. The anaerobic bacterial counts were compared by the Wilcoxon and Kruskal-Wallis tests. Results: The contamination of the high speed handpiece (p=0,0431) and cuspidor (p=0,0117) increased significantly after use. Contamination in the dental unit reservoir water also increased significantly after use of the high speed handpiece. The most contaminated area was the patient's nose. Conclusion: The addition of 0,5% and 1,0% chlorhexidine in the dental office sifnificantly.

ObjetivoO objetivo deste estudo foi quantificar as bactérias anaeróbicas, antes e após o uso deequipamentos odontológicos e estudar a influência da clorexidina na água doreservatório.MétodosOs seguintes itens foram avaliados: cuspideira, luzes, seringas, baixa e alta rotação,braço da cadeira e do encosto com coleções realizadas antes e após a colocação debarreiras. A contaminação microbiana causada pelos aerossóis de alta rotação tambémfoi avaliada: Grupo 1 (controle): (100%) de água no reservatório; Grupo 2: água noreservatório contendo 0,5% de clorexidina, Grupo 3: água no reservatório contendo1,0% de clorexidina. Dez amostras de aerossol foram recolhidos a partir de cadagrupo: placas de ágar-sangue foram colocadas na testa do paciente e do dentista e nonariz e ombro do paciente. Amostra de 1mL a partir do conteúdo da água no reservatóriofoi medida antes e após a utilização de alta rotação. Comparações entre bactériasanaeróbias foram feitas com o uso de Wilcoxon e Kruskal-Wallis teste estatístico.ResultadosVerificou-se um aumento significativo na contaminação antes e após o procedimentoutilizando alta rotação (p=0,0431) e na cuspideira (p=0,0117). Foi possível observarum aumento significativo de contaminação microbiana na água do reservatório, apósa sua utilização. O nariz do paciente era a área mais afetada.ConclusãoA adição de 0,5% e 1,0% de clorexidina no reservatório representa uma reduçãosignificativa de contaminação microbiana gerado no ambiente de um consultório odontológico.

Microbial Biofilm: Contamination in Dental Chair Unit.

This short review focuses on biofilms in the dental clinic environment. Microbial biofilms are potentially a significant source of contamination and cross-infection in the dental clinic. Biofilms in dental chair unit waterlines (DUWLs), suction hoses and fittings pose the most significant risk as these may come into contact with the patient during treatment. These can be managed effectively by regular disinfection using chemical and other methods to minimize reservoirs and disseminators of potentially pathogenic bacteria from these areas.

Contaminación microbiana en las líneas de agua de las unidades odontológicas / Microbial contamination in the water lines of dental inits

Los microorganismos son responsables de múltiples patologías e infecciones. De esta manera, es fundamental controlar la microbiota que se encuentra en el agua que sale de la jeringa triple y que es usada para la irrigación en diferentes procedimientos odontológicos como en cirugía, periodoncia, endodoncia, entre otros, para producir el éxito a largo plazo. El objetivo de éste estudio fue identificar las especies microbianas (bacterianas y micóticas) cultivables, presentes en las líneas de agua de las unidades odontológicas en una clínica privada en la ciudad de Medellín, Colombia. Se evaluaron por conveniencia y al azar 11 unidades odontológicas de 89, de cada una se recolectó una muestra de agua de 500 ml expulsada por la jeringa triple. El análisis consistió en búsqueda de coliformes totales y recuento de microorganismos cultivables como también recuento de hongos filamentosos y levaduras. El recuento de microorganismos mesófilos osciló entre 40 UFC y más de 200 UFC. Se aislaron microorganismos como Aeromona Salmonicida, Actinobacilus sp y Speudomona maltophil. No se encontraron coliformes totales ni fecales. La alta contaminación indica formación de una biopelícula madura, pero la ausencia de coliformes totales y fecales señala que el agua está bien tratada, pero en algún sitio de la línea de agua hay formación de biopelículas.

Microorganisms are responsible for multiple infections and pathologies; this is why it is important to control microbes that can be found in the triple syringe used for irrigation in different dental procedures. The aim of this study was to identify cultivable species of microbes (fungus and bacteria) found in some dental units water lines of a private dental clinic from Medellín, Colombia. Random samples were taken from 11 chairs from a total of 89; a sample of water of 500ml was collected from the triple syringe of each selected chair. The study aim to search for the presence of total coliforms, filamentous fungi and leavened. The average presence of microorganisms was between 40CFU and more of 200 CFU. Microorganisms such as Aeromona salmonicida, Actinobacilus sp and Pseudomona maltophil were isolated. No total coliforms neither fecal coliforms were found. The high levels of contamination suggest that there is a mature biofilm in somewhere of the dental unit water line, but the absence of total and fecalis coliforms suggest that the water had been treated.

Evaluación microbiológica de la desinfección en unidades odontológicas (estudio piloto) / Microbiological evaluation of the disinfection in dental units (pilot study)

La presente investigación, de interés en salud pública en el área de Odontología, evaluó la acción de tres desinfectantes (glutaraldehído, hipoclorito de sodio y cloruro de benzalconio) frente a superficies susceptibles con mayor contaminación bacteriana en unidades dentales de uso continuo, comparando la población bacteriana antes y después de la desinfección. Se seleccionaron tres superficies (jeringa triple, testera de la silla, escupidera) por medio de cuestionarios al personal de las clínicas odontológicas de la Universidad Antonio Nariño - Sede Sur. Los microorganismos encontrados fueron similares para todas las unidades dentales, con prevalencia de Gram negativos no fermentadores en mayor proporción, seguido de fermentadores, Gram positivos y esporulados. Se logró la mayor eliminación de microorganismos por el protocolo de desinfección con glutaraldehído al 2%, seguido de hipoclorito de sodio al 0,5% y cloruro de benzalconio al 1%.

The present research evaluated the action of three disinfectants (glutaraldehyde, sodium hypochlorite and benzalconic chloride) in front of susceptible surfaces with more bacterial contamination in dental units of continuous use, comparing the bacterial population before and after the disinfection, of interest in health publishes in the area of Dentistry. Three surfaces were selected (it squirts triple, front of the seat, spittoon) by means of questionnaires to the personnel of the clinical dentistry of the University Antonio Nariño South Headquarters. The microorganisms found were similar for all dental units, with prevalence of Gram negative not fermentadors in greater proportion, followed by fermentadors, Gram positive and sporulade. There was the largest removal of microorganisms by the protocol of disinfection with glutaraldehyde to 2%, followed by sodium hipochloride to 0.5% and benzalconic chloride to 1%.

Evaluation of the effectiveness of peracetic acid in the sterilization of dental equipment.

PURPOSE: To evaluate the effectiveness of peracetic acid in the microbiological sterilisation of dental materials. METHODS: Peracetic acid solution was evaluated at concentrations of 800, 1500 and 2500 ppm. At these concentrations, it was determined whether peracetic acid caused corrosion to dental instruments and induced cellular mutagenicity and cytotoxicity. In addition, the minimum inhibitory concentration (MIC), the minimum bactericidal concentration (MBC), agar diffusion and diffusion by well method, were also verified. RESULTS: The corrosion rate, calculated from potentiodynamic assays was 10(-6) cm/year, indicating that the product does not damage equipment. The sterilisation capacity of peracetic acid at 2500 ppm was the best. The comet assay indicated genotoxic activity at 2500 ppm. CONCLUSIONS: This study demonstrated the effectiveness of peracetic acid for sterilizing dental equipment, providing another alternative for the prevention of infections in clinics.

Survival of Staphylococcus aureus on fomites

El objetivo de este estudio fue evaluar la viabilidad del Staphylococcusaureus en el tiempo.Se contaminaron los siguientes fomites estandarizados: Papel de uso médico (T1) y poliester(T2) esterilizados en autoclave de vapor de agua, y comprobar los posibles efectos inhibitorios del soporte (telas usadas en indumentaria odontológica y papel de envoltorio) medianteprotocolo de relación test de bacteriostasis. Se evaluaron dos tipos de muestras estandarizadas y esterilizadas (T1 y T2) previa validación con controles biológicos segúnprotocolo Cátedra de Microbiología. Se contaminaron con 50μl. de una suspensión microbiana calibrada de Staphylococcus aureus (cepa de referencia ATCC 25923) en una concentración de 107 ufc/ml y 106 ufc/ml en fase de crecimiento exponencial. Dichos materiales se incubaron a 27ºC y se testearon la viabilidad y la concentración adheridas superficialmente en las mismasdel mencionado microorganismo cumplidos los siguientes tiempos: recién contaminadas, 3 horas, 24 horas, 3 días y 7 días. Se calculó el porcentaje de recuperación del mismo y se realizóel test de bacteriostasis que resultó negativo. Los resultados sugirieron que la cantidad de microorganismosrecuperada varia de acuerdo al tipo de soporte analizado y la viabilidad del microorganismo está en relación con eltiempo de incubación del soporte inoculado que actuaría de nicho artificial.

Bacterial, fungal and yeast contamination in six brands of irreversible hydrocolloid impression materials

This study assessed the level of contamination of six commercially available irreversible hydrocolloids (two containing chlorhexidine) and identified the contamination present in the materials. Petri dishes containing selective and enriched culture media were inoculated with alginate powder (0.06 g), in triplicate. After incubation (37°C/7 days), the colony-forming units (CFU) were counted and Gram stained. Biochemical identification of the different morphotypes was also performed. The contamination levels for the materials were: Jeltrate - 389 CFU/g; Jeltrate Plus - 516 CFU/g; Jeltrate Chromatic - 135 CFU/g; Hydrogum - 1,455 CFU/g; Kromopan - 840 CFU/g; and Greengel - 59 CFU/g. Gram staining revealed the presence of Gram-positive bacillus and Gram-positive cocci. The bacteria Staphylococcus epidermidis, Bacillus subtilis, Bacillus sp., Bacillus coagulans, Bacillus licheniformis, Bacillus cereus, Micrococcus luteus, and Nocardia sp.; the filamentous fungi Aspergillus niger, Aspergillus flavus, Rhizopus sp., Neurospora sp.; and the yeast Candida sp. were isolated. The contamination detected in the impression materials points out the need for adopting measures to improve the microbiological quality of these materials. The use of contaminated materials in the oral cavity goes against the basic principles for controlling cross-contamination and may represent a risk for debilitated or immunocompromised patients.

Este estudo avaliou o nível de contaminação de seis marcas comerciais de alginato (duas contendo clorexidina) e identificou a contaminação presente nesses materiais. Alíquotas de alginato (0,06 g) foram semeadas em meios de cultura seletivos e enriquecidos, em triplicata. Após incubação (37°C/7 dias), as unidades formadoras de colônia (UFC) foram contadas e foram realizadas as identificações morfotintorial (Gram) e bioquímica. Os níveis de contaminação dos materiais foram: Jeltrate - 389 UFC/g; Jeltrate Plus - 516 UFC/g; Jeltrate Chromatic - 135 UFC/g; Hydrogum - 1.455 UFC/g; Kromopan - 840 UFC/g; e Greengel - 59 UFC/g. A coloração de Gram revelou a presença de bacilos Gram-positivos e cocos Gram-positivos. As bactérias Staphylococcus epidermidis, Bacillus subtilis, Bacillus sp., Bacillus coagulans, Bacillus licheniformis, Bacillus cereus, Micrococcus luteus e Nocardia sp.; os fungos filamentosos Aspergillus niger, Aspergillus flavus, Rhizopus sp., Neurospora sp.; e a levedura Candida sp. foram isolados. A contaminação detectada nos materiais aponta a necessidade de adoção de medidas para melhorar seu controle de qualidade microbiológica. O uso de materiais contaminados na boca contradiz os princípios básicos de controle de infecção-cruzada e pode representar um risco para pacientes debilitados ou imunocomprometidos.

Microbial contamination of samples of dental unit water systems in Saudi Arabia

The purpoe of this study was to investigate contamination of the dental unit water systems in a sample of dental clinics in Saudi Arabia. A total of 270 water samples [200mL/sample] was collected from the handpieces line, air-water spray and tap water sources of the dental clinics. Microorganisms were identified using established culturing techniques [Analytab Products Inc.] The prevalence of bacterial contamination was 84% in dental unit water lines of handpieces and 64% in air-water spray, while it was 10% in tap water samples. Bacillus and Pseuodmonas were found to be the predominant [52%] pathogenic microorganisms. The results indicated that dental unit water systems tested were contaminated. Therefore, more effort should be directed to reduce [if not totally eliminate] the number of pathogens in the dental unit water systems

Contamination of dental unit water and air outlets following use of clean head system and conventional handpieces

Dental handpiece is a source of contamination because it is in constant touch with the oral cavity. Sterilization does not seem to be sufficient to prevent penetration of microorganisms into air and water lines of the unit, because negative pressure developed by valves [which are placed in water outlets] and post shut-off inertial rotation of handpiece result in water and debris being sucked into air and water outlets of dental unit. The aim of this study was to compare dental unit contamination following use of clean head system handpieces and conventional handpieces. Twenty-two dental units in the Department of Pediatric Dentistry in Shahid Beheshti Faculty of Dentistry were used for the purpose of this study. A 1.5x10[8] cfu/mm[3] concentration of Staphylococcus epidermis [SE] was used to contaminate the air and water outlets of dental units. Ten clean head system handpieces and 10 conventional handpieces were used for 30 seconds in the above-mentioned suspension. Microbial samples were collected from the air and water lines. Culturing and colony counting procedures were carried out. Data was analyzed by t-test; a value of p < 0.01 was considered significant. demonstrated a significantly lower SE contamination in water outlets following the use of clean head system [p < 0.01]. A lower tendency of clean head system handpieces to transmit SE compared to conventional system makes them a better choice for infection control

Microbial contamination in dental unit waterlines

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 32ºC. 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 percent; 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