Dental Unit Water Asepsis Lecture 1-12-2024 PDF

Dental unit water asepsis 1-12-2024 First semester 2024-2025 Dr.Lama Rafieh,DDS,MPH. Week 8  DENTAL UNIT WATER Water enters the dental office from municipal supplies or from wells. As in homes, water then is routed to various sites including sink f...

Dental unit water asepsis 1-12-2024 First semester 2024-2025 Dr.Lama Rafieh,DDS,MPH. Week 8  DENTAL UNIT WATER Water enters the dental office from municipal supplies or from wells. As in homes, water then is routed to various sites including sink faucets, toilets, water heaters, air conditioners, humidifiers, washers, and, in dental offices, dental units. At the dental unit, water enters plastic water lines that pass through a multichannel control box that allows the water to be distributed to the hoses that feed various attachments, such as high-speed handpieces, air/water syringes, and sometimes an ultrasonic scaler. 2  DENTAL UNIT WATER The water lines in dental units have a small bore (about 1/16-inch inside diameter), and in the standard four-hole handpiece hose, the water line is one of the two smaller lines. Thus the water that enters the dental unit is the same water that supplies the entire office. 3 4  PRESENCE OF MICROORGANISMS IN DENTAL UNIT WATER potable water : it is the EPA standard for the microbial quality of drinking water, and it is no more than a total of 500 colony-forming units per milliliter (CFU/mL) of non-coliform bacteria. A colony-forming unit : is considered to be one bacterial cell or a small number of bacterial cells, and a milliliter is approximately one-fourth of a tea spoon. Municipal water that enters the dental unit is not sterile and does have a low number of waterborne microbes present. 5  PRESENCE OF MICROORGANISMS IN DENTAL UNIT WATER So the water that enters the dental unit usually contains just a few microorganisms (e.g., 0–500 CFU/mL). However, water exiting the dental handpiece, air/water syringe, and ultrasonic scalers may contain more than 100,000 CFU/mL. 6 7 8 9  TYPES AND IMPORTANCE OF MICROORGANISMS IN DENTAL UNIT WATER Although human oral microorganisms have been found in dental unit water, the vast majority of those present are waterborne microorganisms. Most of the waterborne microorganisms are of low pathogenicity or are opportunistic pathogens causing harmful infections only under special conditions or in immunocompromised persons. Microorganisms of main concern are species of Pseudomonas, Legionella, and Mycobacterium. 10  Pseudomonas Pseudomonas aeruginosa and Pseudomonas cepacia are common inhabitants of the environment, existing in soil and natural waters. Many strains can survive and even multiply in water of low nutrient content, such as distilled water. Thus it is not unusual to find Pseudomonas species in almost any type of domestic water supply, storage tanks, and drain lines. 11  P. Cepacia and P. aeruginosa P. cepacia is an important respiratory pathogen in patients with cystic fibrosis. P. aeruginosa is usually opportunistic in causing urinary tract infections, wound infections, pneumonia, and septicemia in burn patients and, along with P. cepacia, usually has a higher degree of resistance than many bacteria to killing by disinfecting chemicals and by antibiotics. 12  Example A report from England implicated P. aeruginosa from dental unit water as the cause of oral infections in two medically compromised dental patients. 13  Legionella Legionella pneumophila and other Legionella species are gram- negative bacteria that naturally occur in water and may gain some protection against the chlorine present in domestic water because they can exist inside certain free-living amebae also present in the water. L. pneumophila is the causative agent of a type of pneumonia called Legionnaires disease. The bacterium is usually transmitted by inhalation of aerosolized contaminated water or by aspiration of organisms that have colonized the oropharynx. 14  Legionella Specific examples of how L. pneumophila have been transmitted to human beings from various sources of water involve cooling towers, heat exchange apparatuses, a mist machine spraying produce in a grocery store, humidifiers, shower heads, hot-water faucets, decorative fountains, tap water used to clean medical equipment. L. pneumophila and other Legionella species have been detected in dental unit water. 15  Example L. pneumophila was found in the water in approximately 10% of 42 units in 35 practices in Austria, in three of five units in a hospital dental clinic in London, in 4% of 194 dental units at levels greater than 100 CFU/mL in a London teaching hospital, and in several dental units at the University of Dresden in Germany. In the United States, L. pneumophila has been detected in dental unit water in an Ohio dental school clinic and in 8% of the water samples taken from 28 dental facilities in California, Massachusetts, Michigan, Minnesota, Oregon, and Washington. 16  As of this writing, no scientific documentation exists for spread of Legionnaires disease from dental offices in the United States, but some dental offices have Legionella in untreated dental unit water used for patient care. Thus some dental patients may be exposed to this bacterium and, if such patients are compromised somehow, may acquire the disease. 17  Case In 2011 a woman died in Rome, Italy, from Legionnaires disease contracted from a dental office. Indirect evidence that dental team members may have occupational exposure to Legionellae comes from two studies that showed higher rates of seroconversion with antibodies to Legionellae in dental personnel than in nondental personnel. One of the studies also showed that seroconversion rates increased as the years of experience in dentistry increased. 18  This information suggests that dental workers at least are exposed to Legionella through contact with aerosols from dental unit water coming out of high-speed handpieces, ultrasonic scalers, and air/water syringes. 19  Nontuberculous Mycobacterium Nontuberculous mycobacteria (e.g., Mycobacterium chelonae) have been detected in some domestic water supplies. These bacteria are somewhat resistant to chemical killing, have caused infections in dialysis patients, and have been detected in the water used to process dialyzers. 20  Cases Dental unit water from a pediatric dental practice in Georgia has been confirmed as the source of infection with M. abscessus in at least 11 children receiving pulpotomies. Dental unit water also is suspected as the source of M. abscessus in oral infections of at least 20 children who underwent pulpotomies at a dental office in Anaheim, CA in 2016. 21  Other Bacteria Acinetobacter, Alcaligenes, Klebsiella, and Serratia are gram-negative opportunistic pathogens that may cause harmful infections in compromised hosts. No specific documentation exists that these bacteria from dental unit water have caused any infections in patients or in dental team members. 22  Endotoxins Endotoxin is a component of the cell walls of gram-negative bacteria, also known as lipopolysaccharide. One study showed that the dental unit water tested contained 1000 units of endotoxin per milliliter. Endotoxin can cause inflammation and shock. Although no endotoxin standard for drinking water exists, United States Pharmacopeia sterile water cannot have more than 0.25 units of endotoxin per milliliter. 23  BIOFILM IN DENTAL WATER LINES Water entering dental units usually has a low number of microorganisms present, but the water that passes out of the dental unit through handpieces, scalers, and air/water syringes is highly contaminated. Thus the incoming water becomes highly contaminated when inside the dental unit. This contamination comes from biofilm that forms on the inside of the dental unit water lines. 24  General Nature of Biofilm Microorganisms exist in dental unit water lines in two types of communities: Planktonic : bacterial community exists in the water itself (free- floating) microorganisms. The other exists in a sessile form attached to the inside walls of the water lines called biofilm. Biofilm : is defined as a mass of microorganisms attached to a surface exposed to moisture. 25  Biofilm Biofilms are common; they form just about anywhere one finds a moist nonsterile environment. including the surfaces of rocks, plants. The best example of biofilm in dentistry is dental plaque, also referred to as oral biofilm. 26  Mechanisms of Biofilm Formation Biofilm forms when bacterial cells adhere to a surface using cell surface polymers. Many of these polymers are highly hydrated exopolysaccharides, referred to as glycocalyx polymers, that give the biofilm a “slimy” nature. As the attached cells multiply within the glycocalyx, the new cells remain embedded and form microcolonies on the surface. 27  Mechanisms of Biofilm Formation Continued multiplication results in the joining of microcolonies, and this, with the continual recruitment of additional bacteria from the planktonic phase, can result in a covering of the surface. Biofilm forms on the inside of the dental unit water lines as the water is flowing through the unit. 28  Factors allowing biofilm to be formed The water in the dental unit water lines moves at normal line pressures, which is slower than one might imagine. The water is not pressurized into the form of the handpiece spray until the water and air mix inside the handpiece. Intermittent stagnation of the water inside the units commonly occurs between patients, overnight, and over the weekend( This facilitates attachment of bacteria from the planktonic community.) 29  Factors allowing biofilm to be formed The dynamics of fluid flowing through a line are such that the maximum flow rate occurs in the center of the stream of fluid and the minimum flow rate occurs near the surfaces of the wall of the tubing. (Thus the water is moving more slowly near the surface of the walls, facilitating attachment of bacteria.) key factor in water line biofilm formation is that most waterborne bacteria have developed the ability to attach to surfaces more efficiently than most nonwaterborne bacteria. The small diameter of dental unit water lines causes a large amount of biofilm to form. 30  Factors allowing biofilm to be formed As the diameter of pipes or tubings decreases, the surface-to-volume ratio increases.(So the smaller the diameter, the more surface relative to volume there is for biofilm to form.) 31 32  Rate of Biofilm Formation The rate at which biofilm forms depends on the aforementioned factors. As we all know, the biofilm on our teeth (dental plaque) begins to reform immediately after we brush them. Dental unit water line biofilm forms more slowly but begins in a new dental unit within hours. 33 shows what mature biofilm in dental handpiece water lines looks like under the scanning electron microscope. 34 shows scanning electron microscope photomicrographs of biofilm that formed in an air/water syringe water line of a new dental unit that was in operation for just 5.3 months. 35  Biofilm can serve as a continuous source of contamination of the flowing water as cells or chunks dislodge naturally or from physical stress placed on the line. No evidence indicates the occurrence of any widespread public health problem from exposure to dental unit water. However, the sources of the microorganisms causing low levels of infectious diseases in the community are not always identified, and the presence of potential pathogens in dental unit water is of concern. 36  Also the goal of infection control is to eliminate or reduce exposure to microorganisms. Using dental unit water contaminated heavily with microorganisms of any kind for dental treatment is contrary to the goals of infection control. Thus improving the quality of dental unit water as means become available is a natural part of maintaining the high quality of patient care and staff protection. 37  CURRENT INFECTION CONTROL RECOMMENDATIONS Current (2003) recommendations from the Centers for Disease Control and Prevention (CDC) related to microorganisms in dental unit water are as follows: Dental offices use water that meets regulatory standards setby the EPA for drinking water (