Effective Asepsis for Clinical Surfaces and Equipment

The dental profession relies heavily upon disinfectants to manage clinical contact surfaces (i.e., those that do not come into direct contact with patients’ oral tissues) that may become contaminated with bodily fluids during dental treatment. Contamination may occur from contact with oral health professionals’ gloved hands, or through contact with spray, spatter, or droplets containing a patient’s oral fluids. As technology has advanced, oral health professionals have also come to rely on impervious barriers for management of sensitive semi-critical equipment, such as cordless handpiece components, scanners, intraoral cameras, digital X-ray sensors and endodontic microscopes, among others. The proper use and application of disinfectants and barriers are essential to patient safety, and preventing occupational injury or illness due to unsafe exposure.

Hospital disinfectants may be divided into three broad categories; low-level, intermediate-level, and high-level disinfectants (Table 1).¹ All of these products have claims for killing human immunodeficiency virus and hepatitis B virus, but only intermediate-level disinfectants can claim to inactivate Mycobacterium tuberculosis. Low-level disinfectants are appropriate for contaminated surfaces that do not have visible blood.² Intermediate-level disinfectants with a tuberculocidal claim should be used on surfaces visibly contaminated with blood.² Some high-level disinfectants are capable of eliminating all microorganisms under specific circumstances, and are therefore considered sterilants.¹ The use of liquid chemical sterilants usually requires a contact time ranging from 20 minutes to several hours.¹ High-level disinfectants or liquid chemical sterilants are intended for immersion of heat-sensitive items that have contacted oral tissues and should never be used for environmental or clinical contact surfaces.

In the United States, disinfectants are regulated by two agencies. The U.S. Environmental Protection Agency (EPA) regulates antimicrobial products as pesticides.³ Manufacturers of disinfectants must demonstrate to the EPA that their products are effective against the organisms listed on the product label.³ The EPA also tests products that have been submitted for approval as hospital disinfectants, and provides a list of products the agency has tested.⁴ Disinfectants that make a claim for high-level disinfection or sterilization must be registered with the U.S. Food and Drug Administration (FDA).⁵ These products are used for immersion of critical and semi-critical devices or instruments that cannot be heat sterilized. The active ingredients in these solutions include glutaraldehyde, ortho-phthaldehyde, hydrogen peroxide, hydrogen peroxide, peracetic acid and hypochlorous acid/hypochlorite.

DISINFECTION OF SURFACES, EQUIPMENT AND REUSABLE DEVICES

The use of liquid chemical disinfectants should be limited to clinical contact surfaces, and devices or equipment that cannot be heat sterilized.² Dental devices, instruments, and equipment that can be detached from power sources and are heat stable should be heat sterilized.² Whenever possible, dental teams should use either heat stable or disposable critical or semi-critical instruments and devices. Disinfection is an inferior process to sterilization for several reasons, including the inability to monitor the success of the chemical process, lack of packaging for instruments and devices, and the hazards associated with chemical products. The disinfection process may be compromised by human error and the limitations of disinfectant products. Some of the issues that may result in inadequate disinfection include the level of prior cleaning of the object or surface, presence of organic or inorganic debris, type and level of microbial contamination, concentration of the germicide, exposure time, presence of biofilm, and the temperature and pH of the disinfectant.² The use of high-level disinfectants and liquid chemical sterilants should be limited in dental practice because most critical and semi-critical dental instruments and devices are available in either heat stable or disposable versions.¹

Following manufacturer instructions for use of disinfectant products is critical to effective asepsis. The need to preclean surfaces, contact time for all microorganisms to be inactivated, storage, shelf life, and use of personal protective equipment (PPE) should be reviewed before using a product. All dental health care personnel (DHCP) should receive training in the proper use of disinfectants, including the need for personal protective equipment (PPE).⁶ Surfaces that may contain debris, such as blood, saliva or dental materials, should be precleaned prior to disinfection. Dental teams should not use a disinfectant for precleaning surfaces unless the manufacturer has indicated the product is suitable for this purpose.⁷ While some disinfectants are also cleaners, it may be necessary to use a different product for precleaning surfaces. The manufacturer’s label should indicate whether the product can be used as both a cleaner and disinfectant.

Surface disinfectants are available as liquid sprays or premoistened towelettes. Once applied, the surface should remain wet with the disinfectant for the contact time indicated on the label.⁸ Generally, either a spray-wipe-spray technique or wipe-discard-wipe technique should be used. When using disinfectant sprays, DHCP should first spray the surface and wipe to clean, followed by application of the spray disinfectant. When using premoistened wipes, clinicians should use wipes to clean surfaces, then discard the wipes and use fresh wipes to apply the disinfectant.

The antimicrobial effectiveness of some disinfectant products may be affected by contact with certain fabrics or cloths used with spray disinfectants. For example, quaternary ammonium compounds interact with cotton and microfiber cloths, resulting in reduced concentrations of the active ingredient delivered to the surface.⁸ When using spray disinfectants, DHCP should consult the manufacturer’s instructions for limitations on the types of wipes that may be used with that product.

Most disinfectants are intended for use on hard, nonporous surfaces, and are not suitable for managing contamination of areas, such as upholstered chairs in dental waiting rooms. Some products also stain or discolor surfaces, making them impractical for some uses. Recently, approved products containing 30% ethanol are available that feature a label claim to kill bacteria and viruses on soft surfaces (such as upholstery) in a single application; these may also be used on hard surfaces in a manner similar to other surface disinfectants. These products do not require precleaning of surfaces and are applied as a spray. Previous ethanol-based disinfectants have had a higher concentration of ethanol, which, in some cases, is less effective in killing microorganisms — and also raises concerns regarding flammability and evaporation.⁹

IMPERVIOUS BARRIERS

Impervious barriers may be used to protect clinical contact surfaces and semi-critical devices that cannot be heat sterilized, such as digital X-ray sensors, heat sensitive components of cordless handpieces, and multiple-use dental dispensers (e.g., syringes) for etchants, sealants and similar materials.² Multiple-use dispensers usually have disposable tips, but the dispenser itself is considered a semi-critical device and should be either heat sterilized or high-level disinfected between uses. The FDA issued an alert advising DHCP that dispensers that have become contaminated with bodily fluids due to contact with the patient’s lips or cheeks should be discarded.¹⁰ The FDA provides a number of strategies to reduce the risk of cross-contamination between patients when using multiple-use dental dispensers, including the use of barriers (Table 2).

Barrier products are cleared by the FDA as medical devices and should have specific instructions for use from the manufacturer. The barrier should be adequate to cover the entire surface, and must be changed between patients. If it is possible that the underlying surface has become contaminated because the barrier has been compromised or the surface was touched with contaminated gloves, it should be cleaned and disinfected before a new barrier is placed.

Barriers, like disinfectants, have limitations. The integrity of impervious barriers may be compromised by how they are handled, the length of time they remain on surfaces or equipment, and barrier material and thinkness.¹¹ A study by MacDonald and Waterfield¹² demonstrated that — even under carefully controlled circumstances — digital sensors often became contaminated during extraction from barrier envelopes. In addition, several studies have shown that contamination of barrier-encased digital sensors occurred either through perforation of barriers or for unexplained reasons.^11–13 Due to evidence that barriers may provide incomplete protection, the application of a liquid disinfectant between patients has been recommended; this is in addition to placing a new barrier for each patient. One study also found that using double barriers reduced the likelihood of contamination of barrier-protected sensors.¹¹

Cordless handpieces are semi-critical devices with components that cannot be heat sterilized. Existing recommendations state that all devices, such as handpieces attached to an air supply or waterline, should be heat sterilized between uses.² Even though a battery-driven handpiece may not be attached to an air line, it is still a semi-critical device that preferably should be reprocessed using heat sterilization. Some manufacturers have designed cordless handpieces with autoclavable outer sheaths and handpiece holders. This provides a mechanism for sterilizing the parts that may come into contact with oral fluids or patient tissues, while protecting the heat-sensitive components.

OCCUPATIONAL SAFETY

With the widespread use of disinfectants in the dental setting, it may be easy to overlook that chemical germicides may carry risks if improperly applied. The use of some high-level disinfectants has been associated with skin irritation and sensitization, as well as respiratory problems, including dermatitis and asthma.^14–18 Glutaraldehyde has long been known to present a risk for dermatitis and asthma in workers exposed to the vapors in hospital settings.¹⁴ Little information exists regarding occupational risks associated with the use of newer high-level disinfectants, although limited reports have associated other high-level disinfectants’ active ingredients with asthma and skin irritation.^19,20

The Occupational Safety and Health Administration has released guidelines on the use of glutaraldehyde in health care settings.²¹ The recommendations include the use of local exhaust or ductless exhaust hood containment of glutaraldehyde. A local exhaust hood removes vapors, which pass through a system of ducts to be exhausted outside. Since this is impractical in many dental settings, a ductless fume hood may be used. Ductless fume hoods collect vapors, which pass through a charcoal filter to cleanse the air, which is then returned to the room (Figure 1). Additionally, it is recommended that rooms in which glutaraldehyde is being use have rates of at least 10 air exchanges per hour — an unlikely high number of air exchanges for a typical dental office.

In addition to control of vapors, it is important for DHCP to avoid bare-handed contact with high-level disinfectant/sterilants. Consequently, PPE — including fluid-resistant gowns, eye and face protection, and protective gloves — should be worn when handling high-level disinfectants. It may be necessary to wear chemical-resistant gloves, such as those made of nitrile, when handling some chemical germicides. Each manufacturer’s instructions for use should be reviewed directions regarding which specific PPE is appropriate.⁶

High-level disinfectants should be thoroughly rinsed from the surface of equipment or devices to avoid irritation of the patient’s mucosa. One of the problematic areas of using high-level disinfectants as sterilants is the inability to package the item prior to processing. This prevents DHCP from storing such items in a sterile pack. Limiting the use of high-level disinfectants by selecting devices that are either heat stable (i.e., can be sterilized) or disposable, single-use items is recommended to reduce reliance on liquid chemical disinfectant/sterilants.² There may be some devices for which no other option is available, however — in which case appropriate precautions should be consistently followed and the least hazardous product selected.

CONCLUSION

Before a chemical product is used, DHCP must review the information found on the safety data sheet (SDS) included with the product.⁶ If the manufacturer does not provide an SDS with the product, it should be requested and the product should not be used until the SDS is reviewed. It will contain important information for safe use, such as necessary PPE, proper disposal, and any hazards or risks associated with the product. The manufacturer’s label will contain additional information, such as the active ingredient, proper application, storage, use, and efficacy of the product.

Liquid chemical disinfectants and impervious barriers are important tools for infection prevention in dental settings — however, disinfectants and barriers have risks and limitations that should be considered when making decisions regarding clinical asepsis. Manufacturers of reusable products and devices should provide information regarding how to safely reprocess items. If a manufacturer cannot provide written instructions, the product should not be used and a suitable alternative is needed. As dental devices become increasingly complex — with components that are difficult to clean and disinfect, or are sensitive to heat sterilization — manufacturers must provide adequate reprocessing instructions, and clinicians must follow instructions diligently. At times, this will require multiple products or processes in order to safely and effectively manage the devices and clinical surfaces in a fashion that ensures safe care.

KEY TAKEAWAYS

• Clinical contact surfaces (i.e., those that do not come into direct contact with patients’ oral tissues) may become contaminated with bodily fluids during dental treatment.
• The use of liquid chemical disinfectants should be limited to clinical contact surfaces and devices or equipment that cannot be heat sterilized.²
• Clinicians have come to rely on impervious barriers for management of sensitive semi-critical equipment, such intraoral cameras and digital X-ray sensors, among others.
• Hospital disinfectants are divided into three broad categories: low-level, intermediate-level, and high-level disinfectants.
• Low-level disinfectants are appropriate for contaminated surfaces that do not have visible blood.² Intermediate level disinfectants with a tuberculocidal claim should be used on surfaces visibly contaminated with blood.²
• High-level disinfectants are considered sterilants;¹ they are used for immersion of critical and semi-critical devices or instruments that cannot be heat sterilized.
• Following manufacturer instructions for use of disinfectant products is critical to effective asepsis.

REFERENCES

1. 1. U.S. Centers for Disease Control and Prevention. Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008. Available at: cdc.gov/infectioncontrol/pdf/guidelines/disinfection-guidelines.pdf. Accessed December 22, 2017.
   2. U.S. Centers for Disease Control and Prevention. Guidelines for infection control in dental health-care settings — 2003. MMWR. 2003;52:1–61.
   3. U.S. Environmental Protection Agency. Pesticide Registration. Selected EPA-Registered Disinfectants. Available at: epa.gov/pesticide-registration/selected-epa-registered-disinfectants. Accessed December 22, 2017.
   4. U.S. Environmental Protection Agency. The Antimicrobial Testing Program — Hospital Disinfectant and Tuberculocidal Products Tested or Pending Testing. Available at: epa.gov/pesticide-registration/hospital-disinfectant-and-tuberculocidal-products-tested-or-pending-testing. Accessed December 22, 2017.
   5. U.S. Food and Drug Administration. FDA Guidance Information. FDA-Cleared Sterilants and High Level Disinfectants. Available at: fdaguidance.net/2014/04/fda-cleared-sterilants-and-high-level-disinfectants/. Accessed December 22, 2017.
   6. Occupational Safety and Health Administration. Hazard Communication Standard. CFR 1910.1200. Federal Register. March 26, 2012.
   7. U.S. Centers for Disease Control and Prevention. Summary of Infection Prevention Practices in Dental Settings: Basic Expectations for Safe Care. Available at: cdc.gov/oralhealth/infectioncontrol/pdf/safe-care.pdf. Accessed December 22, 2017.
   8. Rutala WA, Weber DJ. Monitoring and improving the effectiveness of surface cleaning and disinfection. Am J Infect Cont. 2016;44:e69–e76.
   9. Alhmidi H, Koganti S, Cadnum JL, Rai H, Lenscon AL, Donskey CJ. Evaluation of a novel alcohol-based surface disinfectant for disinfection of hard and soft surfaces in healthcare facilities. Open Forum Infect Dis. 2017;25:4.
   10. U.S. Food and Drug Administration. Multiple-Use Dental Dispenser Devices. Available at: fda.gov/MedicalDevices/ProductsandMedicalProcedures/DentalProducts/ucm404472.htm. Accessed December 22, 2017.
   11. Choi JW. Perforation rate of intraoral barriers for direct digital radiography. Dentomaxillo Radiol. 2015;44:20140245.
   12. MacDonald DS, Waterfield JD. Infection control in digital intraoral radiography: evaluation of microbiological contamination of photostimulable phosphor plates in barrier envelopes. J Can Dent Assoc. 2011;77:93.
   13. Hokett SD, Honey JR, Ruiz F, Baisden MK, Hoen MM. Assessing the effectiveness of direct digital radiography barrier sheaths and finger cots. J Am Dent Assoc. 2000;131: 463–467.
   14. Henn SA, Boiano JM, Steege AL. Precautionary practices of healthcare workers who disinfect medical and dental devices using high-level disinfectants. Infect Control Hosp Epidemiol. 2015;36:180–185.
   15. U.S. Centers for Disease Control and Prevention. Glutaraldehyde — Occupational Hazards in Hospitals. Available at: cdc.gov/niosh/docs/2001-115/default.html. Accessed December 22, 2017.
   16. Fowler JF Jr. Allergic contact dermatitis from glutaraldehyde exposure. J Occup Med. 1989 ;31:852–853.
   17. Nethercott JR, Holness DL, Page E. Occupational contact dermatitis due to glutaraldehyde in health care workers. Contact Dermatitis. 1988 ;18:193–196.
   18. Waters A, Beach J, Abramson M. Symptoms and lung function in health care personnel exposed to glutaraldehyde. Am J Ind Med. 2003;43:196–203.
   19. Fujita H, Ogawa M, Endo Y. A case of occupational bronchial asthma and contact dermatitis caused by ortho-phthalaldehyde exposure in a medical worker. J Occup Health. 2006;48:413–416.
   20. Cristofari-Marquand E, Kacel M, Milhe F, Magnan A, Lehucher-Michel MP. Asthma caused by peracetic acid-hydrogen peroxide mixture. J Occup Health. 2007;49:155–158.
   21. Occupational Safety and Health Administration. Best Practices for the Safe Use of Glutarladehyde in Health Care. Available at: osha.gov/Publications/glutaraldehyde.pdf. Accessed December 22, 2017.

The author has no commercial conflicts of interest to disclose.

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From Decisions in Dentistry. February 2018;4(2):24-26,28.