Disinfection in the Dental Office

During most dental procedures, equipment, materials, and surfaces may become contaminated with patient blood or other potentially infectious materials (OPIM) such as saliva. This occurs when dental healthcare personnel (DHCP) members touch objects or surfaces with gloved hands, when contaminated instruments or devices are placed on surfaces, and from contact with spray and spatter that are created during the use of dental devices such as handpieces, air/water syringes, and ultrasonic scalers.¹ For dental instruments or other equipment that touch the oral mucosa, thorough cleaning followed by heat sterilization is the appropriate method for processing for reuse. For items that do not contact the patient’s oral tissues and cannot be heat sterilized, either decontamination with a chemical disinfectant, the use of impervious barrier covers, or a combination of these is necessary to prevent the transfer of blood or OPIM from patient to patient or patient to DHCP.

Disinfection of Instruments and Devices

Devices and instruments used for patient care can be divided into three broad categories, called Spaulding’s classification: noncritical, semi-critical, and critical. Items are categorized according to the risk from contamination on a device to patient safety² (Table 1). The Centers for Disease Control and Prevention (CDC) provides guidance regarding the appropriate process or level of processing for each classification.³ For example, all dental instruments or devices that enter the patient’s mouth are either critical or semi-critical and should be heat sterilized. If the heat sterilization process would destroy the item, then high-level disinfection or sterilization by immersion in a liquid high-level disinfectant/sterilant should be used. These types of disinfectants are for immersion of items only and should never be used on clinical surfaces. All items must be free of debris before disinfection or sterilization. The use of an ultrasonic cleaner, instrument washer, or hand scrubber should be selected based on compatibility with the item being cleaned, and how effective the method is in removing the debris that is present on the instrument or device. The DHCP member performing the procedure should wear appropriate personal protective equipment (PPE) sufficient to prevent contact with any spray, splash, or spatter that may contain body fluids and to protect against accidental injury with a contaminated sharp instrument. These include gown, eye protection, mask, and heavy-duty utility gloves.⁴ When instruments are sterilized using chemical sterilant, they should be rinsed with sterile water, handled with sterile gloves, and dried with sterile towels. The item should then be delivered directly to the patient-care area using aseptic technique. If the item is stored before use, it will no longer considered sterile and will need to be sterilized again just before use.³

The limitations of liquid chemical sterilants include the inability to maintain items in sterile packaging, lack of a biological test to validate sterility, the effect of dilution and evaporation on potency, and the sensitizing nature of the chemicals. Because of these limitations, these products are rarely used for sterilization of instruments and are most commonly utilized for high-level disinfection of heat-sensitive semi-critical items, requiring only limited immersion time (12 to 90 minutes).

In today’s dental clinical environment, very few critical and semi-critical items cannot be detached and heat sterilized. Also, there should be very limited need to use liquid-chemical high-level disinfection or sterilization as the means of processing reusable critical and semi-critical items.

High-, Intermediate-. and Low-Level of Disinfectants

Disinfectants are divided into three categories depending on the types of resistant organisms they are able to inactivate (Table 2). Bacterial spores are the most difficult organisms to inactivate; therefore, heat sterilization processes or chemicals capable of sterilization of instruments and devices are necessary to inactivate large numbers of spores. Germicides that can kill spores are considered high-level disinfectants. Mycobacterium, although not as difficult to inactivate as spores, is also highly resistant to chemical disinfection. Germicides able to demonstrate tuberculocidal activity are designated as intermediate-level disinfectants and are appropriate for use on blood-contaminated surfaces. Disinfectants that kill bacterial spores, which are the most resistant to germicidal activity, are considered high-level disinfectants. Low-level disinfectants destroy many organisms but do not have the potency necessary to kill Mycobacterium or bacterial spores and are therefore suitable for housekeeping surfaces in a clinical environment, or those surfaces that are not contaminated with blood.³

Regulations

Two agencies within the US government regulate the manufacture of disinfectants used in healthcare settings. The Environmental Protection Agency (EPA) regulates disinfectants for use on environmental surfaces. The Food and Drug Administration (FDA) regulates the manufacture of liquid chemical sterilants and high-level disinfectants. Liquid chemical sterilants/high-level disinfectants are not appropriate for use on environmental surfaces and should be used for immersion of heat-sensitive items only. Products registered with the EPA are classified as hospital-level disinfectants and carry the EPA registration number on the label. All claims for germicidal activity must be reviewed by the EPA and supported through testing by the manufacturer. The EPA does not recognize the distinction between low- and intermediate-level disinfectants in its registration procedures, so this will not be reflected on the EPA registration label. The way to determine if a product is intermediate-level is by whether it has a claim as a tuberculocidal disinfectant on the product label. Disinfectants that are EPA-registered as a hospital-level disinfectant, but do not kill tubercle bacillus, are categorized as low-level disinfectants.

The Occupational Safety and Health Administration (OSHA) also regulates the use of disinfectants as they relate to healthcare in the Bloodborne Pathogens Rule. OSHA requires that contaminated work surfaces be decontaminated at the end of procedures, after blood spills, as soon as feasible after becoming overtly contaminated, and then at the end of the work shift if contamination has occurred since the last decontamination.⁴ OSHA does not specify the type or level of disinfection, but it does indicate that impervious barriers are an acceptable alternative to chemical disinfection.

Disinfection of Environmental Surfaces

The management of environmental surfaces in the dental clinical environment includes both cleaning and disinfection. Cleaning removes debris such as dental materials, blood, or other organic material and soil from surfaces. All of these could interfere with the antimicrobial action of disinfectants, making cleaning a critical and essential part of decontamination. All surfaces should be cleaned with a product containing a detergent, followed by application of the disinfectant. Selecting a product that has both disinfection and cleaning claims may be the easiest approach. Cleaning reduces the number of microorganisms through physical removal. Applying the disinfectant then destroys the remaining organisms for which the product is effective. DHCP members should read the manufacturer’s instructions for use and follow them precisely, especially when using a concentrated product that requires mixing with water. Some equipment may contain more complex surfaces that are difficult to clean. These types of surfaces should be protected with barriers that are impervious to fluids and are changed between each patient.⁵

Surfaces in the dental operatory may be divided into two categories: clinical contact surfaces and housekeeping surfaces.³ Each requires a different level of management due both to the likelihood of contamination being greater on clinical contact surfaces and the lower risk for disease transmission on housekeeping surfaces.

Housekeeping surfaces include floors, walls, and sinks. These surfaces generally only require cleaning with detergent or water. If desired, an EPA-registered hospital disinfectant may be used. If these surfaces become visibly contaminated with blood, they should be cleaned and then disinfected. The DHCP member performing the cleaning and disinfection should wear PPE appropriate to prevent exposure to the blood and chemical germicide. Reusable mops and cloths used for cleaning housekeeping surfaces should be washed and allowed to dry between uses.³

Clinical contact surfaces are either touched by the DHCP member’s gloved hands or come into contact with the spray or spatter generated during dental procedures by devices, such as handpieces, ultrasonic scalers, and air/water syringes. Clinical contact surfaces include light handles and switches, chairside computers, drawer handles, countertops, endodontic microscopes, and x-ray equipment. Because these surfaces come into contact with the DHCP member’s gloved hands and instruments, they provide a potential source for cross-contamination if not managed properly.

Clinical contact surfaces should either be protected with fluid-impervious barriers that are changed between each patient or cleaned and disinfected using an EPA-registered low- to intermediate-level disinfectant. A low-level disinfectant has a human immunodeficiency virus and hepatitis B kill claim and is appropriate if no visible blood contamination is apparent. When visible blood is present, an intermediate-level disinfectant with a tuberculosis kill claim should be used. For practical purposes, it may simplify the disinfection process to use one product for all clinical contact surface applications. In that case, an intermediate-level disinfectant would be the product of choice because it is appropriate both for nonblood- and blood-contaminated surfaces.

Conclusion

Disinfection of operatory surfaces is part of the overall infection-control program for any dental setting. Distinguishing between the levels of disinfectants and having an understanding as to when to use various applications is essential for providing a safe environment for patients and dental staff. The use of barriers and product selection are important considerations for dental staff.

About the Author

Eve Cuny, MS
Associate Professor, Dental Practice
Director, Environmental Health and Safety
University of the Pacific
Arthur A. Dugoni School of Dentistry
San Francisco, California