Environmental Surface Asepsis

Dental practitioners may be exposed to a variety of pathogenic microorganisms when providing dental treatment. Exposure can occur via direct contact with saliva and blood or indirectly through contact with contaminated instruments, equipment, and environmental work surfaces.^1-3

This article reviews environmental surface asepsis, including the materials and methods used for surface disinfection.

ENVIRONMENTAL SURFACES

There are 2 types of dental environmental surfaces: clinical contact surfaces and housekeeping surfaces. Clinical contact surfaces are touched frequently with gloved hands during patient care, or may become contaminated with blood, saliva, or other potentially infectious material and then come in contact with instruments, devices, hands, or gloves. Housekeeping surfaces (eg, floors, walls, and sinks) do not come in contact with hands or devices used in dental procedures. Proper treatment of clinical contact surfaces is required before they become involved in the care of the next patient. Treatment of housekeeping surfaces can occur at the end of the day.^1-3

There are 2 general approaches to environmental surface asepsis (Table 1). One way to prevent contamination is with the use of surface covers. The other approach is to preclean and disinfect surfaces after contamination and before reuse. Each approach has advantages and disadvantages. Dental practices usually employ a combination of both.^1-3

Surface covers take little time to place, cover surfaces difficult or impossible to disinfect, and reduce the exposure of workers to chemicals. Covers can be demanding, as a variety of sizes and shapes may be required, and may be aesthetically unattractive.^1-3

Disinfection may be less expensive than covering, involves processes familiar to practitioners, and produces less waste material. Disinfection increases practitioner exposure to chemicals and requires that personal protective equipment (PPE) such as masks and protective eyewear be worn. Some chemicals need to be mixed in a specific manner and prepared daily. All chemicals have to be stored correctly with proper labeling, and material safety data sheets should be easily accessible for reference.^1-4

MICROORGANISMS

Because Mycobacterium tuberculosis is more difficult to kill than most other microorganisms, disinfectants with tuberculocidal activity are acceptable for use in most situations in dentistry. Tuberculocidal agents are usually effective against nonenveloped (hydrophilic, such as poliovirus) and enveloped (lipophilic, such as herpes virus, influenza, and HIV) viruses.^1-4

Different microorganisms survive on environmental surfaces for widely varying amounts of time. Factors influencing survival include temperature, humidity, inoculating dose, and the presence of blood and saliva. Thus, predicting the number and types of microorganisms present on a contaminated surface is impossible. The safest approach is to assume that any contamination contains viable microorganisms. Removal and/or killing of microorganisms before treatment of the next patient are thus required.

PRECLEANING

Precleaning and disinfection best occur on smooth, easily accessible, nonporous surfaces. These types of surfaces best afford good contact with decontaminating chemicals. Proper precleaning (predisinfection) is essential to reduce the bioburden present initially, so that disinfection will have a better chance to kill a reduced number of residual microorganisms.

The practitioner should always check the surface-cleaning ability of an agent. Water-based agents solubilize organic materials such as blood and saliva. Precleaning agents are often the same chemical used for disinfection.

Not all contaminated surfaces in dental practices can be precleaned and/or disinfected well or easily. Buttons, control switches, and drawer pulls are examples of difficult-to-clean items and are best covered with a barrier.

The practitioner should always wear PPE when disinfecting surfaces and equipment. This includes utility gloves (not clinical-use gloves), masks, protective eyewear, and protective clothing. Proper use will minimize worker contact with both contaminants and chemicals.

SURFACE DISINFECTION

After properly precleaning, surfaces are ready for disinfection. The most frequently used method of disinfection is the spray-wipe-spray technique, but wiping surfaces with disinfectant wipes or towelettes is equally effective. Spray-wipe is the precleaning step, while the second spray is disinfection. Complete coverage of surfaces is required. Sur-faces need to remain moist for the longest contact time (usually 5 to 10 minutes) indicated by the manufacturer. Removal of residual moisture is accomplished with a paper towel. Alternatively, premoistened disinfectant wipes can be used.

Intermediate-level disinfection is required to treat clinical contact surfaces in dentistry. Such agents can destroy vegetative bacteria, which include most fungi and viruses. They can also inactivate Mycobacterium bovis (tuberculocidal) in 10 minutes of exposure or less. Disinfectant containers must have an EPA registration number. Examples of these agents include chlorine-based products, phenolics, iodophors, quaternary ammonium compounds with alcohol, and bromides.

Antimicrobial chemicals come in 4 general types: (1) antibiotics (for killing microorganisms in or on the body); (2) antiseptics (for killing microorganisms on the skin or other body surfaces); (3) disinfectants (for killing microorganisms on environmental/inanimate surfaces or objects), and (4) sterilants (for killing all microorganisms on inanimate objects).¹

The Centers for Disease Control and Prevention have categorized disinfectants based on their microbial spectrum of activity (Table 2). The categories include the following: sterilant/high-level disinfectant (for killing all microorganisms on submerged inanimate objects that are heat sensitive); intermediate-level disinfectant (for killing vegetative bacteria, most fungi, and M. tuberculosis); and low-level disinfectant (for killing most vegetative bacteria, some fungi, and some viruses).^1,2

SUMMARY

Environmental surface disinfection is easily accomplished with precleaning and disinfection techniques, and prepared surfaces or difficult-to-clean items can be covered with impermeable barriers. When carried out effectively, both practitioners and patients are protected from exposure to microorganisms that transmit disease and cause illness.

References

1. Miller CH, Palenik CJ. Infection Control & Management of Hazardous Materials for the Dental Team. 3rd ed. St Louis, Mo: Mosby-Year Book; 2004:260-275.

2. Kohn WG, Collins AS, Cleveland JL, et al. 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. Organization for Safety & Asepsis Procedures. From Policy to Practice: OSAP’s Guide to the Guidelines. Annapolis, Md: OSAP; 2004:45-62.

4. Organization for Safety & Asepsis Procedures. Surface disinfectants for dentistry: tools for selecting and using surface disinfectants in dental settings. Infection Control In Practice. May 2005; Vol 4:1-4.

Dr. Palenik has held over the last 25 years a number of academic and administrative positions at Indiana University School of Dentistry. These include professor of oral microbiology, director of human health and safety, director of central sterilization services, and chairman of infection control and hazardous materials management committees. Currently he is director of infection control research and services. Dr. Palenik has published 175 articles, more than 305 monographs, 3 books, and 7 book chapters, the majority of which involve infection control and human safety and health. Also, he has provided more than 100 continuing education courses throughout the United States and 8 foreign countries. All questions should be directed to OSAP at office@osap.org.