Environmental Infection Control

Dental operatory environmental surfaces are those surfaces or objects that do not come in contact with. They can become contaminated during patient care and can become a reservoir of microbial contamination. These may in turn be transferred to the DHCP, instruments or the patient. Although hand hygiene is key to minimizing this transferal, barrier protection or cleaning and disinfecting of environmental surfaces also protects against healthcare–associated infections.

Environmental surfaces can be divided into clinical contact surfaces (eg, light handles, unit switches and drawer knobs) and housekeeping surfaces (eg, floors, walls and sinks). Because housekeeping surfaces have limited risk of disease transmission, they can be decontaminated with less rigorous methods than those used on dental patient-care items and clinical contact surfaces. Strategies for cleaning and disinfecting surfaces in patient-care areas should consider the 1) potential for direct patient contact; 2) degree and frequency of hand contact; and 3) potential contamination of the surface with body substances or environmental sources of microorganisms (eg, soil, dust or water).

Cleaning is the necessary first step of any disinfection process. Cleaning is a form of decontamination that renders the environmental surface safe by removing organic matter, salts and visible soils, all of which interfere with microbial inactivation. The physical action of scrubbing with detergents and surfactants and rinsing with water removes substantial numbers of microorganisms. If a surface is not cleaned first, the success of the disinfection process can be compromised. Removal of all visible blood and inorganic and organic matter can be as critical as the germicidal activity of the disinfecting agent.

General Recommendations:
• Follow the manufacturers’ instructions for correct use of cleaning and EPA-registered hospital disinfecting products.
• Do not use liquid chemical sterilants/high-level disinfectants for disinfection of environmental surfaces (clinical contact or housekeeping).
• Use PPE, as appropriate, when cleaning and disinfecting environmental surfaces.

Such equipment might include gloves (eg, puncture- and chemical-resistant utility), protective clothing (eg, gown, jackets or lab coat), and protective eyewear/face shield, and mask
• Areas when they are visibly dusty or soiled
• When a surface cannot be cleaned adequately, it should be protected with barriers


Clinical contact surfaces can be directly contaminated from patient materials either by direct spray or spatter generated during dental procedures or by contact with DHCP’s gloved hands. These surfaces can subsequently contaminate other instruments, devices, hands, or gloves.
Examples of such surfaces include:
• Light handles,
• Switches,
• Dental radiograph equipment,
• Dental chairside computers,
• Reusable containers of dental materials,
• Drawer handles,
• Faucet handles,
• Countertops,
• Pens,
• Telephones, and
• Doorknobs.

Barrier protection of surfaces and equipment can prevent contamination of clinical contact surfaces, but is particularly effective for those that are difficult to clean. Barriers include clear plastic wrap, bags, sheets, tubing, and plastic-backed paper or other materials impervious to moisture. Because such coverings can become contaminated, they should be removed and discarded between patients, while DHCP are still gloved. The surface needs to be cleaned and disinfected only if contamination is evident. Otherwise, after removing gloves and performing hand hygiene, DHCP should place clean barriers on these surfaces before the next patient.

Also, general cleaning and disinfection are recommended for clinical contact surfaces, dental unit surfaces and countertops at the end of daily work activities and are required if surfaces have become contaminated since their last cleaning. To facilitate daily cleaning, treatment areas should be kept free of unnecessary equipment and supplies.

Manufacturers of dental devices and equipment should provide information regarding material compatibility with liquid chemical germicides, whether equipment can be safely immersed for cleaning, and how it should be decontaminated if servicing is required.


Clinical Contact Surfaces
1. Use surface barriers to protect clinical contact surfaces, particularly those that are difficult,to clean (eg, switches on dental chairs) and change surface barriers between patients.
2. After removing the barrier, examine the surface to make sure it did not become soiled inadvertently. Clean and disinfect areas that are visibly contaminated.
3. Clean and disinfect clinical contact surfaces that are not barrier-protected, by using an EPA-registered hospital disinfectant with a low- (ie, HIV and HBV label claims) to intermediate-level (ie, tuberculocidal claim) activity after each patient. Use an intermediate-level disinfectant if visibly contaminated with blood.


Evidence does not support that housekeeping surfaces (eg, floors, walls and sinks) pose a risk for disease transmission in dental healthcare settings. Actual, physical removal of microorganisms and soil by wiping or scrubbing is probably more critical than disinfection.

The majority of housekeeping surfaces need to be cleaned only with a detergent and water or an EPA-registered hospital disinfectant/detergent, depending on the nature of the surface and the type and degree of contamination.

Floors should be cleaned regularly, and spills should be cleaned up promptly with detergent. An EPA-registered hospital disinfectant/detergent designed for general housekeeping purposes should be used in patient-care areas if uncertainty exists regarding the nature of the soil on the surface (eg, blood or body fluid contamination versus routine dust or dirt). Unless contamination is reasonably anticipated or apparent, cleaning or disinfecting walls, window drapes and other vertical surfaces is unnecessary. However, when housekeeping surfaces are visibly contaminated by blood or OPIM, prompt removal and surface disinfection is appropriate infection-control practice and required by OSHA.

Part of the cleaning strategy is to minimize contamination of cleaning solutions and cleaning tools (eg, mop heads or cleaning cloths). Cost, safety, product-surface compatibility and acceptability by housekeepers can be key criteria for selecting a cleaning agent or an EPAregistered hospital disinfectant/detergent. In the cleaning process, another reservoir for microorganisms can be dilute solutions of detergents or disinfectants, especially if prepared in dirty containers, stored for long periods of time, or prepared incorrectly. Preferred cleaning methods produce minimal mists and aerosols or dispersion of dust in patient care areas.


Housekeeping Surfaces
1. Clean housekeeping surfaces (eg, floors, walls and sinks) with a detergent and water or an EPA-registered hospital disinfectant/detergent on a routine basis, depending on the nature of the surface and type and degree of contamination, and as appropriate, based on the location in the facility, and when visibly soiled.
2. Clean mops and cloths after use and allow to dry before reuse, or use single-use, disposable mop heads or cloths.
3. Prepare fresh cleaning or EPA-registered disinfecting solutions daily and as instructed by the manufacturer.
4. Clean walls, blinds and window curtains in patient-care areas when they are visibly dusty or soiled.


The majority of blood contamination events in dentistry result from spatter during dental procedures using rotary or ultrasonic instrumentation, although no evidence supports that HBV, HCV or HIV has been transmitted from a housekeeping surface. Prompt removal and surface disinfection of an area contaminated by either blood or OPIM are appropriate infection-control practices and required by OSHA.

Strategies for decontaminating spills of blood and other body fluids differ by setting and volume of the spill. Blood spills on either clinical contact or housekeeping surfaces should be contained and managed as quickly as possible to reduce the risk of contact by patients and DHCP. Visible organic material should be removed with absorbent material (eg, disposable paper towels discarded in a leak-proof, appropriately labeled container). Nonporous surfaces should be cleaned and then decontaminated with either an EPA-registered hospital disinfectant effective against HBV and HIV, or an EPA-registered hospital disinfectant with a tuberculocidal claim (ie, intermediate-level disinfectant). If sodium hypochlorite is chosen, an EPA-registered sodium hypochlorite product is preferred. However, if such products are unavailable, a 1:100 dilution of sodium hypochlorite (eg, approximately ¼ cup of 5.25% household chlorine bleach to 1 gallon of water) is an inexpensive and effective disinfecting agent.


Spills of Blood and Body Substances
Clean spills of blood or OPIM and decontaminate nonporous surface with an EPAregistered
hospital disinfectant with low- (ie, HBV and HIV label claims) to intermediatelevel
(ie, tuberculocidal claim) activity, depending on size of spill and surface porosity.

Carpeting and Cloth Furnishings

Carpeting is more difficult to clean than nonporous hard surface flooring, and it cannot be reliably disinfected, especially after spills of blood and body substances. Studies have documented the presence of diverse microbial populations, primarily bacteria and fungi, in carpeting. Cloth furnishings pose similar contamination risks in areas of direct patient care and places where contaminated materials are managed (eg, dental operatory, laboratory or instrument processing areas). For these reasons, use of carpeted flooring and fabricupholstered furnishings in these areas should be avoided.


Carpet and Cloth Furnishings
1. Avoid using carpeting and cloth-upholstered furnishings in dental operatories, laboratories and instrument processing areas.

Nonregulated and Regulated Medical Waste

Studies have compared microbial load and diversity of microorganisms in residential waste with waste from multiple healthcare settings. It was shown that general waste (gloves, masks, gowns, lightly soiled gauze or cotton and environmental barriers) are not more infective than residential waste. These are considered non-regulated medical waste. Although any item that has had contact with blood, exudates or secretions might be infective, treating all such waste as infective is neither necessary nor practical. Infectious waste that carries a substantial risk of causing infection during handling and disposal is regulated medical waste. A complete definition of regulated waste is included in OSHA’s blood-borne pathogens standard.

Spills of Blood and Body Substances

Clean spills of blood or OPIM and decontaminate nonporous surface with an EPA registered hospital disinfectant with low- (ie, HBV and HIV label claims) to intermediatelevel (ie, tuberculocidal claim) activity, depending on size of spill and surface porosity.

Regulated medical waste is only a limited subset of waste: 1% to 2% of total waste in dental offices. Regulated medical waste requires special storage, handling, neutralization and disposal, and is covered by national or local rules and regulations. Examples of regulated waste found in dental-practice settings are solid waste soaked or saturated with blood or saliva (eg, gauze saturated with blood after surgery), extracted teeth, surgically removed hard and soft tissues, and contaminated sharp items (eg, needles, scalpel blades and wires). Regulated medical waste requires careful containment for treatment or disposal. A single leakresistant biohazard bag is usually adequate for containment of non sharp regulated medical waste, provided the bag is sturdy and the waste can be discarded without contaminating the bag’s exterior. Exterior contamination or puncturing of the bag requires placement in a second biohazard bag. All bags should be securely closed for disposal. Puncture-resistant containers with a biohazard label, located at the point of use (ie, sharps containers), are used as containment for scalpel blades, needles, syringes and unused sterile sharps. Dental healthcare facilities should dispose of medical waste regularly to avoid accumulation. Any facility generating regulated medical waste should have a plan for its management that complies with national and local regulations to ensure health and environmental safety.


Regulated Medical Waste
1. General Recommendations:
a. Develop a medical waste management program. Disposal of regulated medical waste must follow national or local regulations.
b. Ensure that DHCP who handle and dispose of regulated medical waste are trained in appropriate handling and disposal methods and informed of the possible health and safety hazards.
2. Management of Regulated Medical Waste in Dental Healthcare Facilities:
a. Use a color-coded or labeled container that prevents leakage (eg, biohazard bag) to contain non sharp regulated medical waste.
b. Place sharp items (eg, needles, scalpel blades, orthodontic bands, broken metal instruments and burs) in an appropriate sharps container (eg, puncture resistant, color-coded and leak proof). Close container immediately before removal or replacement to prevent spillage or protrusion of contents during handling, storage, transport, or shipping.
c. Pour blood, suctioned fluids or other liquid waste carefully into a drain connected to a sanitary sewer system, if local sewage discharge requirements are met and the state has declared this an acceptable method of disposal. Wear appropriate PPE while performing this task.

Discharging Blood or Other Body Fluids to Sanitary Sewers or Septic Tanks

All containers with blood or saliva (eg, suctioned fluids) can be inactivated in accordance with state-approved treatment technologies, or the contents can be carefully poured down a utility sink, drain or toilet. Appropriate PPE (eg, gloves, gown, mask and protective eyewear) should be worn when performing this task. No evidence exists that blood-borne diseases have been transmitted from contact with raw or treated sewage. Multiple bloodborne pathogens, particularly viruses, are not stable in the environment for long periods, and the discharge of limited quantities of blood and other body fluids into the sanitary sewer is considered a safe method for disposing of these waste materials. State and local regulations vary and dictate whether blood or other body fluids require pretreatment or if they can be discharged into the sanitary sewer and in what volume.

Dental Unit Waterlines, Biofilm and Water Quality

Studies have demonstrated that dental unit waterlines (ie, narrow-bore plastic tubing that carries water to the high-speed handpiece, air/water syringe and ultrasonic scaler) can become colonized with microorganisms, including bacteria, fungi and protozoa. Protected by a polysaccharide slime layer known as a glycocalyx, these microorganisms colonize and replicate on the interior surfaces of the waterline tubing and form a biofilm, which serves as a reservoir that can amplify the number of free-floating (ie, planktonic) microorganisms in water used for dental treatment. Although oral flora and human pathogens (eg, Pseudomonas aeruginosa, Legionella species and nontuberculous Mycobacterium species) have been isolated from dental water systems, the majority of organisms recovered from dental waterlines are common heterotrophic water bacteria. These exhibit limited pathogenic potential for immunocompetent persons.

Clinical Implications

Certain reports associate waterborne infections with dental water systems, and scientific evidence verifies the potential for transmission of waterborne infections and disease in hospital settings and in the community. Infection or colonization caused by Pseudomonas species or nontuberculous mycobacteria can occur among susceptible patients through direct contact with water or after exposure to residual waterborne contamination of inadequately reprocessed medical instruments. Nontuberculous mycobacteria can also be transmitted to patients from tap water aerosols. Healthcare–associated transmission of pathogenic agents (eg, Legionella species) occurs primarily through inhalation of infectious aerosols generated from potable water sources or through use of tap water in respiratory therapy equipment. Disease outbreaks in the community have also been reported from diverse environmental aerosol producing sources, including whirlpool spas, swimming pools and a grocery store mist machine. Although the majority of these outbreaks are associated with species of Legionella and Pseudomonas, the fungus Cladosporium has also been implicated.

Researchers have not demonstrated a measurable risk of adverse health effects among DHCP or patients from exposure to dental water. Certain studies determined DHCP had altered nasal flora or substantially greater titers of Legionella antibodies in comparisons with control populations; however, no cases of legionellosis were identified among exposed DHCP. Contaminated dental water might have been the source for localized Pseudomonas aeruginosa infections in two immunocompromised patients. Although transient carriage of P aeruginosa was observed in 78 healthy patients treated with contaminated dental treatment water, no illness was reported among the group. In this same study, a retrospective review of dental records also failed to identify infections.

Concentrations of bacterial endotoxin (<1,000 endotoxin units/mL) from gram-negative water bacteria have been detected in water from colonized dental units. No standards exist for an acceptable level of endotoxin in drinking water, but the maximum level permissible in United States Pharmacopeia (USP) sterile water for irrigation is only 0.25 endotoxin units/ mL. Although the consequences of acute and chronic exposure to aerosolized endotoxin in dental healthcare settings have not been investigated, endotoxin has been associated with exacerbation of asthma and onset of hypersensitivity pneumonitis in other occupational settings. Dental Unit Water Quality

Research has demonstrated that microbial counts can reach <200,000 colony-forming units (CFU)/mL within 5 days after installation of new dental unit waterlines, and levels of microbial contamination <106 CFU/mL of dental unit water have been documented. These counts can occur because dental unit waterline factors (eg, system design, flow rates and materials promote both bacterial growth and development of biofilm. Although no epidemiologic evidence indicates a public health problem, the presence of substantial numbers of pathogens in dental unit waterlines generates concern. Exposing patients or DHCP to water of uncertain microbiological quality, despite the lack of documented adverse health effects, is inconsistent with accepted infection-control principles. Thus in 1995, ADA addressed the dental water concern by asking manufacturers to provide equipment with the ability to deliver treatment water with <200 CFU/mL of unfiltered output from waterlines. This threshold was based on the quality assurance standard established for dialysate fluid, to ensure that fluid delivery systems in hemodialysis units have not been colonized by indigenous waterborne organisms. Standards also exist for safe drinking water quality as established by EPA, the American Public Health Association (APHA), and the American Water Works Association (AWWA); they have set limits for heterotrophic bacteria of <500 CFU/mL of drinking water. Thus, the number of bacteria in water used as a coolant/irrigant for nonsurgical dental procedures should be as low as reasonably achievable and, at a minimum, <500 CFU/mL, the regulatory standard for safe drinking water established by EPA and APHA/AWWA. Strategies to Improve Dental Unit Water Quality

It was previously recommended that dental waterlines be flushed at the beginning of the clinic day to reduce the microbial load. However, studies have demonstrated this practice does not affect biofilm in the waterlines or reliably improve the quality of water used during dental treatment. Because the recommended value of <500 CFU/mL cannot be achieved by using this method, other strategies should be employed. Dental unit water that remains untreated or unfiltered is unlikely to meet drinking water standards. Commercial devices and procedures designed to improve the quality of water used in dental treatment are available; methods demonstrated to be effective include self-contained water systems combined with chemical treatment, in-line microfilters and combinations of these treatments. Simply using source water containing <500 CFU/mL of bacteria (eg, tap, distilled or sterile water) in a self-contained water system will not eliminate bacterial contamination in treatment water if biofilms in the water system are not controlled. Removal or inactivation of dental waterline biofilms requires use of chemical germicides. Patient material (eg, oral microorganisms, blood and saliva) can enter the dental water system during patient treatment. Dental devices that are connected to the dental water system and that enter the patient’s mouth (eg, handpieces, ultrasonic scalers or air/water syringes) should be operated to discharge water and air for a minimum of 20 to 30 seconds after each patient. This procedure is intended to physically flush out patient material that might have entered the turbine, air or waterlines. The majority of recently manufactured dental units are engineered to prevent retraction of oral fluids, but some older dental units are equipped with anti-retraction valves that require periodic maintenance. Users should consult the owner’s manual or contact the manufacturer to determine whether testing or maintenance of anti-retraction valves or other devices is required. Even with anti-retraction valves, flushing devices for a minimum of 20 to 30 seconds after each patient is recommended. Maintenance and Monitoring of Dental Unit Water

DHCP should be trained regarding water quality, biofilm formation, water treatment methods and appropriate maintenance protocols for water delivery systems. Water treatment and monitoring products require strict adherence to maintenance protocols, and noncompliance with treatment regimens has been associated with persistence of microbial contamination in treated systems. Clinical monitoring of water quality can ensure that procedures are correctly performed and that devices are working in accordance with the manufacturer’s previously validated protocol.

Dentists should consult with the manufacturer of their dental unit or water delivery system to determine the best method for maintaining acceptable water quality (ie, <500 CFU/mL) and the recommended frequency of monitoring. Monitoring of dental water quality can be performed by using commercial self-contained test kits or commercial water-testing laboratories. Because methods used to treat dental water systems target the entire biofilm, no rationale exists for routine testing for such specific organisms as Legionella or Pseudomonas, except when investigating a suspected waterborne disease outbreak. Delivery of Sterile Surgical Irrigation

Sterile solutions (eg, sterile saline or sterile water) should be used as a coolant/irrigation in the performance of oral surgical procedures where a greater opportunity exists for entry of microorganisms, exogenous and endogenous, into the vascular system and other normally sterile areas that support the oral cavity (eg, bone or subcutaneous tissue) and increased potential exists for localized or systemic infection (see Oral Surgical Procedures). Conventional dental units cannot reliably deliver sterile water even when equipped with independent water reservoirs because the water-bearing pathway cannot be reliably sterilized. Delivery devices (eg, bulb syringe or sterile, single-use disposable products) should be used to deliver sterile water. Oral surgery and implant handpieces, as well as ultrasonic scalers, are commercially available that bypass the dental unit to deliver sterile water or other solutions by using singleuse disposable or sterilizable tubing.


Dental Unit Waterlines, Biofilm, and Water Quality
General Recommendations:
1. Use water that meets EPA regulatory standards for drinking water (ie, <500 CFU/mL of heterotrophic water bacteria) for routine dental treatment output water. 2. Consult with the dental unit manufacturer for appropriate methods and equipment to maintain the recommended quality of dental water. 3. Follow recommendations for monitoring water quality provided by the manufacturer of the unit or waterline treatment product. 4. Discharge water and air for a minimum of 20 to 30 seconds after each patient from any device connected to the dental water system that enters the patient’s mouth (eg, handpieces, ultrasonic scalers and air/water syringes). 5. Consult with the dental unit manufacturer on the need for periodic maintenance of anti-retraction mechanisms.

Boil-Water Advisories

A boil-water advisory is a public health announcement that the public should boil tap water before drinking it. When issued, the public should assume the water is unsafe to drink. Advisories can be issued after:
• Failure of or substantial interruption in water treatment processes that result in increased
turbidity levels or particle counts and mechanical or equipment failure
• Positive test results for pathogens (eg, Cryptosporidium, Giardia or Shigella) in water
• Violations of the total coliform rule or the turbidity standard of the surface water treatment rule
• Circumstances that compromise the distribution system (eg, watermain break)
coupled with an indication of a health hazard
• A natural disaster (eg, flood, hurricane or earthquake)


Boil-Water Advisories
1. The following apply while a boil-water advisory is in effect:
a) Do not deliver water from the public water system to the patient through the dental operative unit, ultrasonic scaler or other dental equipment that uses the public water system.
b) Do not use water from the public water system for dental treatment, patient rinsing or handwashing.
c) For handwashing, use antimicrobial containing products that do not require water for use (eg, alcohol-based hand rubs). If hands are visibly contaminated, use bottled water, if available, and soap for handwashing or an antiseptic towelette.
2. The following apply when the boil-water advisory is cancelled:
a) Follow guidance given by the local water utility regarding adequate flushing of waterlines. If no guidance is provided, flush dental waterlines and faucets for 1 to 5 minutes before using for patient care.
b) Disinfect dental waterlines as recommended by the dental unit manufacturer.

Special Considerations: Dental Handpieces and Other Devices Attached to Air and Waterlines

Handpieces and other semi-critical devices such as scalers and air/water syringes are probably one of the most neglected instruments and devices in the dental office. Dye expulsions have confirmed the potential for retracting oral fluids into the internal components of handpieces. Laboratory models suggest the retention of viral DNA and viable virus inside both handpieces and prohylaxis angles. For this reason dental devices attached to air and water should run from 20 to 30 seconds to physically flush patient material that might have entered the turbine or water lines.

Disinfection and immersion in germicides is not an accepted method for handpieces and similar devices. In clinical evaluations of high-speed handpieces, cleaning and lubrication were the most critical factors in determining performance and durability (361–363). Manufacturer’s instructions for cleaning, lubrication, and sterilization should be followed closely to ensure both the effectiveness of the process and the longevity of handpieces.

Components or instruments that are permanently attached to the dental unit such as suction hoses, light handle and the like are likely to become contaminated and should therefore be considered as a possible source of disease transmission.

Saliva Ejectors

Backflow from low-volume saliva ejectors occurs when the pressure in the patient’s mouth is less than that in the evacuator. This occurs when a patient closes the lips around the suction tip. This of course can be a source of potential contamination of the patient. Such backflow can also occur if the hose of the suction tip is positioned higher than the patient. Although
no adverse health effects associated with the saliva ejector have been reported, practitioners should be aware that in certain situations, backflow could occur when using a saliva ejector and is a potential source of contamination.


Special Considerations: Dental Handpieces and Other Devices Attached
to Air and Waterlines
1. Clean and heat-sterilize handpieces and other intra-oral instruments that can be removed from the air and waterlines of dental units between patients.
2. Follow the manufacturer’s instructions for cleaning, lubrication and sterilization of handpieces and other intra-oral instruments that can be removed from the air and waterlines of dental units.
3. Do not surface-disinfect, use liquid chemical sterilants or ethylene oxide on handpieces and other intra-oral instruments that can be removed from the air and waterlines of dental units.
4. Permanently attached devices should be covered with barriers such as plastic wrappings and should be replaced after every patient. If they are visibly soiled the DHCP should disinfect these devices with an acceptable disinfectant.
5. Do not advise patients to close their lips tightly around the tip of the saliva ejector to evacuate oral fluids.

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