Análisis bacteriológico de piezas de mano de alta velocidad utilizadas en la práctica clínica / Bacteriological analysis of high speed handpieces used in clinical practice

Los profesionales de la salud están expuestos a una gran variedad de microorganismos desde esporas, bacterias, hongos, virus y protozoarios que pueden encontrarse en la sangre y/o saliva de los pacientes. Cualquiera de estos microorganismos puede causar una enfermedad infectocontagiosa a través de pinchazos y/o salpicaduras producidas por el aerosol durante la práctica dental. Objetivo: Determinar la presencia bacteriana en las piezas de alta velocidad utilizadas en la práctica clínica. Material y métodos: Es un estudio experimental, observacional y transversal en el que se evaluó la contaminación de 30 piezas de alta velocidad utilizadas en la práctica clínica. Previo al estudio se efectuó una estandarización obteniendo una kappa del 0.85. Se realizó una base de datos en el programa SPSS versión 22, con el que se llevó a cabo el análisis descriptivo para determinar medidas de tendencia central. Resultados: 73.3% de las muestras analizadas tuvieron crecimiento bacteriano, entre las bacterias que se encontraron resultó que 54.5% de ellas fueron bacterias Gram positivas y el resto Gram negativas. La bacteria con mayor presencia en la muestra fue el Bacillus en 45.5% seguida del Streptococcus en 27.3%, el restante 27.2% fue Staphylococcus, Coccus y Streptobacillus. Conclusiones: El uso correcto de las piezas de alta, así como su desinfección en la consulta dental es de suma importancia, ya que nos ayudan a evitar contaminaciones cruzadas y a prevenir que dentro del área de trabajo se formen focos de infección (AU)

Health professionals are exposed to a wide variety of microorganisms from spores, bacteria, fungi, viruses and protozoa that can be found in the blood and/or saliva of patients. Any of these microorganisms can cause an infectious disease through punctures and / or splashes produced by the aerosol during dental practice.1,2 Objective: To determine the bacterial presence in the high-speed pieces used in clinical practice. Material and methods: It are an experimental, observational and transversal study; where the contamination of 30 high-speed pieces used in clinical practice was evaluated. Prior to the study, a standardization was made obtaining a kappa of 0.85. A database was made in the program SPSS version 22, with which the descriptive analysis was carried out to determine measures of central tendency. Results: 73.3% of the analyzed samples showed bacterial growth, among the bacteria that were found, 54.5% of them were gram-positive bacteria and the rest were gram-negative. The bacterium with the highest presence in the sample was for Bacillus in 45.5% followed by Streptococcus in 27.3%, the remaining 27.2% was for Staphylococcus, Coccus and Streptobacillus. Conclusions: The correct use of the discharging parts, as well as their disinfection in the dental practice is of the utmost importance as they help us to avoid cross contamination and to prevent foci of infection from forming within the work area (AU)

Comparación bacteriana de 30 piezas de alta velocidad antes y después de ser utilizadas en la facultad de odontología, Región Veracruz / Bacterial comparison of 30 high speed handpieces before and after being used at the school of dentistry, Veracruz Region

Introducción: en los procedimientos odontológicos se está expuestoa gran cantidad de microorganismos y las intervenciones clínicas provocan un contacto directo o indirecto con éstos, ya sea a través del instrumental, equipo odontológico contaminado con saliva, sangre, exudados, etcétera. Por esta razón debe tomarse en cuenta el tipo de contaminación de las piezas de mano por ser parte del equipo de uso cotidiano para realizar tratamientos odontológicos. Objetivos generales:Determinar la carga bacteriana en las piezas de alta velocidad antes y después de su uso en diferentes clínicas de la Facultad de Odontologíade la UV Región Veracruz. Metodología: Investigación transversal, descriptiva y observacional. Material y métodos: Se seleccionaron al azar 30 piezas de mano de los estudiantes de la Universidad Veracruzana Facultad de Odontología Región Veracruz, a las cuales se tomó una muestra con un hisopo de algodón antes y después de su uso en la práctica dental. Se realizaron cultivos con las muestras obtenidas que se observaron durante tres días seguidos bajo microscopio para comprobar la presencia de colonias bacterianas. Resultados: De las30 piezas antes de ser utilizadas se detectó Bacillus grampositivos en24 por ciento de las muestras; en 20 por ciento Bacillus gramnegativos, en 6 por ciento Streptobacillus gram-positivos; en 20 por ciento Staphylococcus grampositivos; en 3 por ciento Cocobacillus gramnegativos y en 22 por ciento Actinomyces gramnegativos. El restante 2 por ciento no reveló unidades formadoras de colonias (UFC). En un segundo muestreo, 33 por ciento desarrolló Bacillus grampositivos, 10 por cientoBacillus gramnegativos, 20 por ciento adquirió Sthapylococcus grampositivos, 3 por ciento Sthapylococcus gramnegativo y 34 por ciento no reveló UFC. Conclusión:En el primer muestreo se detectaron microorganismos en 98% de laspiezas de mano, mientras que en el segundo muestreo 66% se contaminócon microorganismos y en 34% no se observó contaminación.

Introduction: dental activity is exposed to a lot of microorganisms,and clinical interventions have a direct or indirect contact with them.Whether through the instruments, dental equipment contaminatedwith saliva, blood, etc; so you should take into account the type ofcontamination of handpieces for being the most widely used equipmentfor dental treatment. General Objectives: Determine the bacterialload in high-speed parts before and after being used in diff erentclinical uses in Dentistry School at UV, Veracruz. Methodology:Cross-sectional, descriptive and observational research. Materialand methods: 30 pieces of students from the Universidad VeracruzanaSchool of Dentistry, Veracruz region, which a sample was takenwith a swab to pieces before and after use in dental practice wererandomly selected. Cultures with samples obtained observedduring three days in a row microscope to determine the presenceof bacterial colonies were made. Results: Of the 30 pieces beforebeing used 24% of Bacillus Gram-positive samples were found; 20%Bacillus Gram-negative, Gram-positive Streptobacillus 6%; 20%Gram-positive Staphylococcus, 3% developed Coccobacillus Gramnegativeand 22% Gram negative Actinomyces. The remaining 2%no colony forming units development (UFC). In a second sampling;33% developed Bacillus Gram-positive, Gram-negative Bacillus10%, 20% obtained Sthapylococcus Gram-positive, Gram-negativeSthapylococcus 3% and 34% did not develop colony forming unit(CFU). Conclusion: In the first sampling 98% of the pieces were microorganism growth, while in the second 66% and the presence ofmicroorganisms obtained 34% no development.

[Monitoring steam sterilisation processes in the dental office]. / Het monitoren van stoomsterilisatieprocessen in de mondzorgpraktijk.

In dental offices, steam sterilisation is used to sterilise instruments and in that way to prevent the cross-contamination of patients and the dental team. In order to ensure that the sterilisation process has been executed successfully, every sterilisation process has to be monitored. The monitoring of every load in the steam steriliser is necessary and often even required, either directly (by legislation) or indirectly (by harmonised standards). The complete monitoring protocol consists of controls of the installation, the exposure, the loading, the packaging and, finally, the 'track and trace' of the instruments. For examining the installation, a steam penetration test, such as the Bowie and Dick test, can be carried out.

Contaminación bacteriana generada por aerosoles en ambiente odontológico / Analysis of bacterial contamination produced by aerosols in dental clinic environments

En odontología estamos expuestos a muchos microorganismos por la producción de aerosoles. Por ello es esencial conocer la naturaleza de éstos y su potencial patogénico. El objetivo de esta investigación es determinar contaminación bacteriana, generada por aerosoles durante procedimientos odontológicos, con uso de pieza de mano de alta velocidad, realizados por alumnos de la carrera, en Clínica Odontológica Docente Asistencial (CODA), Universidad de La Frontera, Temuco, Chile. Estudio con muestra aleatoria, de 16 de un total de 32 unidades dentales, estratificado por box, con 40 muestras, ocho placas control y 32 placas prueba. El medio de cultivo, se mantuvo por diez minutos, donde se realizaron acciones de operatoria con turbina, bajo aislamiento absoluto, ubicadas en frente del operador y pechera del paciente. Las muestras fueron analizadas microscópicamente, incubadas a 37°C en atmósfera de oxígeno por 24 horas y dióxido de carbono a las 48 horas. Treinta y dos placas prueba fueron positivas, registrándose diversidad de crecimiento bacteriano, promedio 58,874 Unidad Formadora de Colonias (UFC) por unidad dental. El mayor porcentaje de microorganismos fueron: Bacillus spp. (28,56%) y Bacilos Gram positivos (24,31%). Siete placas control resultaron negativas y una con 3 UFC de Micrococcus spp. La mayoría de los microorganismos encontrados son comensales potencialmente patógenos. Al comprobar que los aerosoles constituyen una fuente importante de emisión de microorganismos, se hace imprescindible cumplir con todas las normas de bioseguridad que protegen tanto al operador como al paciente

In dental practice we are exposed to many microorganisms due to aerosol production. It is essential to be aware of the nature of these elements and their pathogenic potential. The purpose of this research is to determine the presence of bacterial contamination in aerosols produced during dental procedures that require the use of a high speed dental handpiece. These dental procedures were carried out by dentistry students at the dental clinic of the Universidad de La Frontera. In order to determine the presence of bacteria in aerosols, cultivation plates were used. A total of 40 samples were taken from 16 dentistry students while performing dental procedures that required the use of a high speed dental handpiece in conditions of complete isolation. Eight control plates and 32 test plates were used. Two selected areas were examined: operator´s front andpatient´s chest protector, during 10 minutes. The samples were then taken to the laboratory and incubated in an oxygen atmosphere for 24 hours and subsequently in carbon dioxide for another 24 hours at a temperature of 37 degrees Celsius. Finally the samples were microscopically analyzed. Seven control plates showed no bacterial contaminants and one showed 3UFC of Micrococcus spp. The 32 test plates were found to be positive showing diverse bacterial growth (58.874 UFC average per subject). The highest percentage of microorganisms was constituted by Bacillus spp. (28.56 %) and Bacillus Grampositivos (24.31 %), representing more than 50% of the total. The majority of the microorganisms found belong to the commensal family, although they can change into opportunistic pathogen microorganisms. Verifying that aerosols are an important source of emission of microorganisms, it is essential to comply with all biosecurity standards in order to protect the operator as well as the patient

Microbial diversity in dental unit waterlines.

Dental health care providers and patients are exposed during ongoing work to contamination by the water used in the dental units, due to accidental swallowing or aspiration of the sprays generated by the high-speed handpiece and the threeway syringe. This study evaluated the quality of water in dental units in the public dental care system of Maceio, Alagoas, Brazil, by conducting analyses of contamination by total coliforms, E.Coli, heterotrophic bacteria and filamentous fungi. We collected 200 mL of water at 5 sites in 6 dental offices of the Department of Health located in different parts of the city. A total 212 isolates and 16 genera of filamentous fungi were identified in the water collected from the dental units. Total coliforms indicated that the water used in dental units was not appropriate for human consumption. The high levels of contamination found in this study showed that water was a potential source of cross-infection.

Can oil lubricated dental handpieces be sterilized?: part 1. The problem.

UNLABELLED: HTM 01-05 guidelines state that decontamination of handpieces remains a challenge, in particular the lumen, due to oil impeding access for steam sterilization. This paper discusses important aspects of cleaning and sterilization of the handpiece lumen and critically appraises the literature found on this topic. The paper is not intended to cover precleaning methods in detail. CLINICAL RELEVANCE: The complex structure of handpiece lumens makes them difficult to sterilize. Current knowledge of this subject is necessary for general dental practitioners to decide on investment in new equipment correctly, which has been validated by the manufacturer, in order to comply with HTM 01-05 guidelines.

Survey of the decontamination and maintenance of dental handpieces in general dental practice.

OBJECTIVES: To determine how dental handpieces are decontaminated and maintained in general dental practice. DESIGN: Observational survey. SETTING: The survey was carried out in general dental practice in Scotland. Survey visits ran from January 2003 until the end of March 2004. METHODS: Data were collected by interview and observation in 179 dental surgeries in Scotland. RESULTS: In virtually all surgeries, handpieces were cleaned before disinfection or autoclaving (99%; n = 177), most commonly by wiping the external surface with a cloth impregnated with disinfectant. Most surgeries lubricated their handpieces after cleaning and before sterilisation (91%; n = 162), although a number of surgeries (24%; n = 42) also lubricated their handpieces after sterilisation. In the majority (97%; n = 174) of dental surgeries, all handpieces were autoclaved after use, most frequently (89%; n = 160) in a bowl and instrument steriliser. In 38 surgeries (21%), handpieces were being wrapped (paper pouches) before sterilisation in bowl and instrument sterilisers. A minority of surgeries (20%; n = 36) had a dedicated handpiece for surgical procedures. CONCLUSIONS: The majority of dental handpieces are manually cleaned externally with a disinfectant impregnated cloth and processed in a type N (bowl and instrument) bench top steam steriliser. Handpieces are lubricated with non-water soluble lubricants at different stages of reprocessing, indicating clarification is required in this area. More work is required by manufacturers to establish a validated cleaning and lubrication process to facilitate the sterilisation of handpieces.

The effect of frequent clinical use of dental unit waterlines on contamination.

Three dental units with self-contained water systems in an outpatient teaching dental clinic were treated with a proprietary chlorine dioxide waterline cleaner. Three similar units were used as controls. After four weeks, test and control units were crossed over. Water samples were taken from each line on each unit and from the sink faucets at six time periods; and the frequency of use of each line was recorded. Statistical analysis showed that increased frequency of use of waterlines did not affect lines that were chemically treated, but was associated with less contamination of untreated lines.

The in vivo contamination of air-driven low-speed handpieces with prophylaxis angles.

BACKGROUND: The authors conducted an in vivo study to determine if low-speed handpiece motors can become contaminated with oral flora when used with prophylaxis angles. METHODS: This crossover study involved 20 subjects, two types of handpieces and three prophylaxis angles. The authors used each handpiece/prophylaxis angle system to polish teeth. They then collected samples, spiral-plated the specimens and incubated them at 37 degrees C anaerobically and aerobically (with 5 percent carbon dioxide). After incubation, the authors examined the plates for the presence of bacterial colonies. RESULTS: At least 75 percent of the handpiece/prophylaxis angle systems used on the 20 subjects had bacterial contamination for at least one cultured area. Of the 420 specimens, 258 (61.4 percent) produced bacterial growth. Contamination varied from zero to 6,300 colony-forming units per milliliter. CONCLUSIONS: These data suggest that the internal surfaces of low-speed handpieces can become microbially contaminated during use with prophylaxis angles. CLINICAL IMPLICATIONS: Unless low-speed handpieces are sterilized properly after each use, they pose a risk for crossinfection.

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.

Internal contamination of air-driven low-speed handpieces and attached prophy angles.

BACKGROUND: In an in vitro crossover study, the authors investigated whether the interior of low-speed handpiece/prophy-angle systems becomes contaminated during operation and submersion into Geobacillus stearothermophilus. METHODS: This study involved two types of handpieces attached to eight brands of prophy angles. The researchers operated angles attached to sterile handpieces for 60 seconds. They then analyzed the inside surfaces of the angle, nosecone and motor. They tested each prophy angle and handpiece 10 times. RESULTS: In the 160 tests of handpieces contaminated at the prophy cup end, the spores traveled into the motor gears 32 times (20 percent). In the other 160 tests in which the motor gears were contaminated, the test bacterium traveled through the prophy cup in 75 instances (47 percent). CONCLUSIONS: The in vitro data suggest that low-speed handpiece motors can become contaminated internally during use with prophy angles. Also, internal contaminants appear to have been released from the handpiece. CLINICAL IMPLICATIONS: The results suggest that low-speed hand-pieces can become contaminated internally during use. Unless low-speed handpieces are sterilized properly between patients, they may become cross-contaminated.

The sterility of dental burs directly from the manufacturer.

BACKGROUND: The purpose of this research was to assess the sterility of burs directly from manufacturers. The authors wished to determine the types of bacteria, if any, found on nonsterilized burs. METHODS: The authors used burs from a major manufacturer. Sterilized and nonsterilized burs were cultured for bacteria. Any burs found to be contaminated were further cultured on agar plates. The bacteria on the plates were identified by a commercial laboratory. RESULTS: Of the 100 sterilized and nonsterilized burs, the authors found none of the sterilized burs to be contaminated. Eight of the nonsterilized burs showed growth of bacteria after 24 hours. Seven of the eight bacteria identified on the burs belonged to the genus Bacillus. CONCLUSIONS: The Bacillus genus is encountered in daily living and is not considered to be pathogenic; however, there have been documented cases of infection in humans in which these bacteria dominate. They should never be introduced into the bloodstream. CLINICAL SIGNIFICANCE The dentist must consider that soft tissue exposure may be unavoidable with subgingival restorations or even those close to the gingiva. Therefore, it is imperative that the dentist use sterile burs during dental procedures. This article will prove the necessity for sterile burs and leave the rest to the manufacturers.

Microbial contamination in dental unit waterlines: comparison between Er:YAG laser and turbine lines.

The investigation was carried out by evaluating the microbiological characteristics of the water before and after treatment with Er:YAG laser and turbine. The study was carried out in 2 dental surgeries. In both cases the laser and dental units were served by two independent circuits, fed by the same potable tap water. Samples were taken from the water supplying and the water leaving the turbine and laser before and after treatment on the same patient. Total heterotrophic plate count was measured at 36 degrees C and at 22 degrees C, and the presence of Staphylococcus species and non-fermenting Gram negative bacteria was investigated. Bacterial contamination was found within the circuit, especially in the laser device. Pseudomonas aeruginosa was detected in only 1 sample of supply water, in 11.1 % and in 19.4 % of the samples from the turbine and the laser respectively. No evidence of Staphylococcus aureus was found. The contamination of supply water was low, whereas that of the water leaving the handpieces of the 2 devices was high, especially in the laser. Attention should be paid to the control of the water leaving laser devices, given the increasingly wide use of such instruments in dental treatment exposed to risk of infection.

Exposure to bacterial endotoxin during conservative dental treatment.

The aim of the study was to determine bacterial endotoxin concentration in the water flowing from a high-speed handpiece of a dental unit and in the air contained in the bioaerosol formed during dental conservative treatment. The air was collected in the space between the patient and dentist. The study was conducted on 25 operative sites (units) and had two stages: before application of a dental unit waterline (DUWL) disinfectant and after a 2-week application of disinfection procedure. The research showed that the mean concentration of bacterial endotoxin in the water flowing from high-speed handpieces was significantly reduced after the use of a disinfectant. The mean concentration of bacterial endotoxin in the air was similar at both stages - before and after application of waterline decontamination procedure. The study showed that in dental air-water aerosol, water is the main source of bacterial endotoxin contaminating the aerosol during the work with dental handpieces. Application of a user-friendly water disinfectant to significantly decrease endotoxin concentration in the DUWL water and in the aerosol, is one of recommended methods to reduce health risk.

Endotoxin level as a potential marker of concentration of Gram-negative bacteria in water effluent from dental units and in dental aerosols.

Gram-negative bacteria concentration in water effluent from a dental unit, and in dental aerosol forming during the work of a dental handpiece, was assessed. The study was conducted on 25 dental units before and after a 2-week period of using a disinfecntant for water in dental units waterlines (DUWL). The contamination of water with Gram-negative bacteria before disinfection was 18-398 x 10(3) cfu/ml, and after disinfection, bacteria were not found. The concentration of Gram-negative bacteria in the air before disinfection was 0-23 x 10(1) cfu/m(3), and after disinfection - 0-8 x 10(1) cfu/m(3). Simultaneously, the water and air were sampled to determine bacterial endotoxin. The statistical analysis did not show correlation between endotoxin concentration and Gram-negative bacteria concentration for the water before disinfection, and for the air before and after disinfection of DUWL water. Because the number of bacteria in the water after disinfection dropped to zero, statistical methods could not be used. The performed analysis suggests that bacterial endotoxin concentration is not indicative of Gram-negative bacteria contamination. Thus, bacterial endotoxin determination is not recommended as a method of monitoring the microbiological quality of DUWL water and dental aerosols.

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

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 32 degrees C. Analysis was based on the number of colony forming units (CFU). The Wilcoxon non-parametric test indicated that the levels of water contamination were highest in the triple-syringe (13 of 15) and in the high-speed (11 of 15); both levels were higher than those of the water reservoir. There was no significant statistical difference between the level of contamination in the triple-syringe and the high-speed as determined by the Mann-Whitney test [p(H0) = 40.98%; Z = - 0.2281]. Because biofilm forms on solid surfaces constantly bathed by liquid where microorganisms are present, these results indicate that the water in the dental unit may be contaminated by biofilm that forms in these tubules.

Waterline biofilm and the dental treatment facility: a review.

Biofilms are well-organized communities of cooperating microorganisms that can include bacteria, protozoa, diatoms, and fungi. Surveys of dental unit waterlines (DUWLs) indicate that biofilm formation is a universal problem and that environmental and human-derived opportunistic pathogens can be cultured consistently from biofilms retrieved from DUWLs and other dental devices. Although the health risks presented by waterline bacterial colonization have yet to be adequately addressed, professional and ethical considerations indicate that steps should be taken to improve the quality of DUWLs. To address these concerns, the Council on Scientific Affairs of the ADA recently published a list of products cleared by the FDA to control dental waterline contamination. The goal of this article is to increase the awareness of potential health risks posed by biofilm formation and provide information on techniques and devices designed to control the microbial contamination of DUWLs.

Dental unit waterline contamination and its possible implications during periodontal surgery.

BACKGROUND: Dental unit waterline contamination has become a concern to clinical dentistry. This concern arises from the fact that bacteria sloughed from established biofilms in dental unit waterlines increase heterotrophic bacteria counts in water exiting these units. METHODS: Scanning microscopy and bacterial viability staining were used to examine the sessile and planktonic biofilm present in dental unit waterlines and water samples, respectively. In addition, the limulus amebocyte assay was used to measure the lipopolysaccharide (LPS) levels in water samples. RESULTS: All dental unit waterlines were coated with a well-established biofilm made up of filamentous and bacillus-like microorganisms. Water samples collected from these dental units contained high numbers of individual bacteria and bacterial aggregates. A viability staining technique identified significantly more bacteria in water than could be cultured, and 64% of the total bacterial population stained as nonvital. Since the bacterial load (viable and nonviable) was high, we examined the LPS in dental unit water samples. The mean LPS levels in water collected from high-speed and air/water lines in use were 480 and 1,008 endotoxin units (EU)/ml. This was significantly higher than the mean level of 66 EU/ml found in water samples collected from adjacent clinic sinks. The LPS level at the start of the day (2,560 EU/ml) was reduced by 70% with 1 minute of flushing (800 EU/ml). Flushing times of 5 and 10 minutes were not able to reduce LPS levels to zero. CONCLUSION: The presence of high heterotrophic bacterial counts, sloughing biofilm, and high LPS levels are discussed in relation to patient risk and periodontal wound healing biology.