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Putting a Stop to Cross-Contamination

Disposable barriers and surface disinfectants—when properly used—are important tools in the dental office’s plan to prevent cross-contamination.

Since the publication of the American Dental Association’s (ADA) infection control recommendations in 1978,1 dental health care workers (DHCW) have confronted numerous infection control challenges, from the onset of HIV to the re-emergence of tuberculosis. The most recent Centers for Disease Control and Prevention (CDC) Guidelines for Infection Control in Dental Health-care Settings, released in 2003, refined and recommended a number of practices aimed at reducing occupational risks, including routine aseptic techniques, immunization with available vaccines, protective barriers to physically reduce microbial exposures, work practice and engineering controls, and effective heat sterilization and disinfection procedures.2


Cross-contamination and cross-infection can occur by direct contact with microorganisms, indirect contact with contaminated objects, droplet transmission, and inhalation of airborne pathogens. In dentistry, operatory surfaces can routinely become contaminated with patient saliva, blood, and other fluids during treatment. In contrast to a number of reports implicating environmental surfaces in microbial infections in medical facilities,3-5 data are not available to confirm cross-infection to DHCW or dental patients. As a result, the data on medical facilities should be used as the basis for cross-contamination protection in the dental office environment. Limiting environmental surface cross-contamination from blood and body fluid is a fundamental principle of dental infection control. Thus using chemical disinfectants and disposable barriers is appropriate when sterilizing all items and surfaces contaminated during patient treatment is not possible.2,6 To prevent this type of environmental cross-contamination, the following precautions should be taken: (1) preventing contamination by using barriers, (2) cleaning and disinfecting contaminated surfaces, (3) aseptic protocol, (4) removing unnecessary items, and (5) a dental facility design that is conducive to promoting asepsis. These practices are effective if they reduce the chances of disease transmission through indirect contact with contaminated surfaces or objects.2

Environmental Surfaces

Contaminated patient care items and surfaces pose different degrees of risk for infection transmission based on their location and potential to transmit pathogens. With regard to environmental surfaces, the latest precautionary dental guidelines also provide a better understanding of how to discriminate between the two categories of environmental surfaces: clinical contact surfaces and housekeeping surfaces. These require different infection control practices based on the potential for direct patient contact, degree and frequency of hand contact, and potential contamination of the surface with body substances or pathogens.
Clinical contact surfaces are defined as surfaces that can act as reservoirs for microbial contaminants with the potential to transmit infection because they can be directly contaminated from patient materials either by direct spray or spatter or by (gloved) hand or instrument contact. Examples are light handles, switches, dental chairside computers, telephones, and countertops. These surfaces should be covered with disposable single-use barriers to prevent contamination or cleaned and disinfected with a low to intermediate level disinfectant. In contrast, housekeeping surfaces, eg, floors, walls, and sinks, have limited risk of disease transmission and can be decontaminated with less rigorous methods. These processes are summarized in Table 1.

Disposable Barriers

Clinicians shoulder the responsibility of selecting appropriate products and protocols to maintain environmental asepsis.1,2,7One significant change from previous CDC guidelines is the primary importance given to single-use, impermeable surface barriers to prevent contamination of selected clinical contact surfaces rather than cleaning and disinfecting every surface after each use.2 Any surface that is difficult to clean and disinfect due to surface irregularity or complexity may be covered to more efficiently and reliably promote environmental asepsis between patients. Examples of surfaces suitable for barrier coverage are switches, light handles, computers and keyboards, radiograph equipment, countertops, pens, telephones, and other knobs and handles. Given the time limitations and many demands on dental workers, the potential for inadequate decontamination increases when a surface is difficult to clean and/or disinfect. Using barriers correctly is more reliable, saves time, reduces exposure to chemicals, and is visible to the patient, thereby demonstrating the clinician’s commitment to professional safety standards.

Key points for successful use of environmental surface barriers are:

  1. Cover surfaces that are most used and/or most difficult to clean.
  2. Select impermeable disposable materials such as plastic.
  3. Consider adhesive materials, shapes designed for specific equipment or items, or universal shapes with multiple uses.
  4. Train workers to place and remove barriers after each use aseptically, without contaminating surfaces or themselves with contaminated sides of used barriers. Gloves should be worn to remove contaminated barriers.
  5. Establish a reasonable and consistent protocol for cleaning and disinfecting contaminated clinical, barrier-covered, and exposed surfaces.

Selecting Surface Disinfectants

Much of the epidemiologic rationale for preventing cross-infection through environmental surface disinfectants is derived from health care-associated infections originating from hospitals, such as outbreaks involving antibiotic-resistant strains of Staphylococcus aureus and enterococci.8,9 Surface disinfectants should be selected to provide reliable protection against these and other pathogens in dental environments with minimal negative impact on dental clinic materials, practices, and workers.

When evaluating the available surface sprays and wipes, DHCW should compare their efficacy with criteria for an ideal disinfectant. Desirable features include: cleaning capability, penetration and activity in the presence of bioburden, spectrum of activity, residual antimicrobial activity, toxicity, and compatibility with the surfaces to be treated. As historical as these characteristics appear, they continue to remain important concerns for DHCW with the rapidly expanding selection of commercially available disinfectant sprays, wipes, and foams. When the above criteria are used as a guide, the application and limitations of various chemical disinfectant classes can be best evaluated.10-13

While cleaning may remove all or most viable pathogens, effective disinfectants should be chosen to deactivate or kill any remaining organisms. Low-level disinfectants are recommended for housekeeping surfaces and some clinical contact surfaces, while intermediate-level disinfectants are effective against vegetative bacteria and most fungi and viruses and inactivate Mycobacterium bovis (a genus of bacteria that causes tuberculosis) if used correctly.2,4 Many offices use intermediate level disinfectants on all clinical contact surfaces rather than trying to determine which surfaces might also be appropriately treated with low-level disinfectants.

Where surfaces are contaminated, and at least daily if surfaces are covered during use, the CDC recommends that visible soil and bioburden are first removed by mechanical cleaning followed by surface disinfection using either low-level (hospital disinfectants with an HIV or HBV claim) or intermediate-level (hospital disinfectants with a tuberculocidal claim).2Environmental Protection Agency-approved products offer the best assurance that clinical asepsis efforts will be effective.

Misuse of Environmental Barriers and Surface Disinfectants

Recognizing and avoiding mistakes involving the misuse of barriers and disinfectant products are important for successful clinic asepsis. Examples of misuses include:

  1. Not understanding the basic principal of cleaning prior to disinfection. Removing physical debris is the necessary first step to disinfection and the presence of physical matter or bioburden compromises the effectiveness of surface disinfectants.
  2. Failure to read and follow the label on disinfectants. Each product has been tested and approved according to specific protocol. If the label is not followed, results are not predictable. An example is applying an intermediate level disinfectant for less than stated tuberculocidal contact time.
  3. Use of inappropriate products. For example, high level disinfectants, such as gluteraldehyde, are not effective surface disinfectants. They pose health risks to personnel and should not be sprayed or used on surfaces. Hand-hygiene towelettes also should not be used to disinfect a surface.
  4. Use of household cleaners and sanitizers. Only products tested and approved for the dental setting should be used to insure predictable patient and operator safety.
  5. Combining different chemical cleaners and disinfectants, either in solution or on a surface. Professional products may have unpredictable and possibly hazardous effects if used in combinations not recommended on labels.
  6. Overuse or application of sprays. Excessive pooling and dripping of disinfectants can corrode, damage, discolor, or alter the texture or feel of clinic materials. Chemical penetration into equipment joints and connections can damage internal wiring or mechanisms. Inhaling aerosolized disinfectants can cause irritation and sensitivity in workers. Sprays should not be excessively applied. Alternatively, disinfectant wipes reduce chemical pooling and overspray.
  7. Use of high alcohol products for initial cleaning. Products with alcohol content higher than 40% are not effective cleaners of organic materials and should only be used on precleaned surfaces.
  8. Use of absorbent or permeable barriers. Only environmental barriers that have been tested and shown to be impermeable can predictably protect a surface or item.
  9. Re-use of barriers. They are advertised and sold as single-use and should be replaced after one use.
  10. Cross-contamination of surfaces by contact during removal of used barriers. Aseptic protocol should be practiced when placing and removing barriers to avoid the need to clean and disinfect covered surfaces after each use.


Every dental office or clinic must review and update their policies, practices, and procedures yearly and when changes are made to existing guidelines. The 2003 CDC Infection Control Guidelines address the relatively low infection risk from environmental surfaces and provide reasonable barrier, cleaning, and disinfectant approaches for minimizing cross-contamination. Preventing contamination by the use of barriers in key areas, using surface disinfectants correctly and sparingly, and performing personnel training and practice evaluations are vital to meet professional standards of patient and employee infection protection.

 Table 1. Categories of Contaminated Environmental Surfaces
Category Definition Examples Appropriate Asepsis Products
Clinical contact
Surfaces that are directly contacted by contaminated instruments, devices, hands, or gloves Dental unit surfaces, laboratory equipment, reusable containers of dental materials, drawer handles, heavily used countertops, pens,telephone handles, doorknobs Radiology equipment barriers, EPAregistered hospital disinfectant with tuberculocidal activity, CDC intermediate-level disinfectant, or CDC low-level disinfectant
 Housekeeping  Surfaces that require regular cleaning to remove soil and dust but that rarely contact dental personnel or patients Floors, walls, lightly used countertops EPA-registered hospital disinfectant with no tuberculocidal activity, CDC low-level disinfectant/detergent, or intermediate-level if blood is visible

infection chart


    1. Infection control in the dental office. Council on Dental Materials and Devices. J Amer Dent Assoc. 1978;97:673-677.
    2. Kohn WG, Collins AS, Cleveland JL, Harte JA, Eklund KJ, Malvitz DM, Centers for Disease Control and Prevention. Guidelines for infection control in dental health-care settings—2003. MMWR Recomm Rep. 2003;52(RR-17):1-61.
    3. Fekety R, Kim KH, Brown D, Batts DH, Cudmore M, Silva J Jr. Epidemiology of antibiotic-associated colitis; isolation of Clostridium difficile from the hospital environment. Am J Med. 1981;70:906-908.
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    8. Beard-Pegler MA, Stubbs E, Vickery AM. Observations on the resistance to drying of staphylococcal strains. J Med Microbiol. 1988;26:251-255.
    9. Moore EP, Williams EW. A maternity hospital outbreak of methicillin-resistant Staphylococcus aureus. J Hosp Infect. 1991;19:15-16.
    10. Molinari JA, Campbell MD, York J. Minimizing potential infections in dental practice. Journal of the Michigan Dental Association. 1982:64:411-416.
    11. Runnels RR. Identifying and Treating Risk Patients In the Wet Finger Environment. North Salt Lake, Utah: Infection Control Publications; 1985:110.
    12. Molinari JA, Gleason MJ, Cottone JA, Barrett ED. Cleaning and disinfectant properties of dental surface disinfectants. J Am Dent Assoc. 1988:117:179-182.
    13. Rutala WA. APIC guideline for selection and use of disinfectants. 1994, 1995, and 1996 APIC Guidelines Committee. Association for Professionals in Infection Control and Epidemiology, Inc. Am J Infect Control. 1996;24:313-342.

From Dimensions of Dental Hygiene. October 2004;2(10):24-26.

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