Sterilization and High-Level Disinfection for Today’s Dental Office

Over the past 20 years the dental profession has experienced the most rapid advances in treatments and techniques than perhaps ever before. Some of the newer devices, equipment, instruments, and ancillary reusable materials used in dentistry may present challenges to properly cleaning them, and then disinfecting or sterilizing them. This may be due to the device design, which could incorporate crevices, grooves, or connections that may be difficult to fully access, or it could be that the items are sensitive to heat or chemical germicides. It is important for clinicians to review manufacturer’s instructions for use (IFUs) and consider the steps necessary to reprocess reusable devices before using them on patients.

Classification of Medical Devices and Instruments

First introduced in 1968, Spaulding’s classification is a tool that can be used to determine the appropriate method for reprocessing a used dental instrument or device.¹ This practical and helpful classification system divides medical devices into three broad categories: critical, semicritical, and noncritical.¹ Although the system has been updated and modified slightly over the years, today it remains the standard for identifying the appropriate reprocessing method for devices and instruments.

In its guidance for infection control in dental healthcare settings, the Centers for Disease Control and Prevention (CDC) recommends the use of Spaulding’s classification and provides examples of dental devices that fall into the three aforementioned categories (Table 1).² This classification system is designed to help clinicians make guided decisions regarding how to manage the processing of all reusable devices and instruments. Depending on which classification the device falls within, it may require sterilization, high-level disinfection, or low- to intermediate-level disinfection.² Table 2 provides an overview of the methods available for sterilization and disinfection of medical and dental instruments and devices.² According to Spaulding’s classification, all dental instruments and devices that enter the patient’s mouth will be either critical or semicritical and will need to be either sterilized or high-level disinfected.

Critical devices such as surgical instruments or any reusable item penetrating bone or tissue should be heat sterilized.² Single-use devices (SUDs) used in surgical procedures should either be purchased sterile or be sterilized before use.³ If heat sterilization is not feasible due to the item being heat-sensitive, one of various low-temperature sterilization processes may be used. Medical facilities have addressed some of these challenges by adopting the use of low-temperature sterilization technologies. These devices use vaporized hydrogen peroxide, hydrogen peroxide gas plasma, or hydrogen peroxide ozone to slowly sterilize devices, materials, and instruments that cannot withstand the high temperatures of dry heat or steam autoclave sterilization, or that would be damaged if immersed in a high-level chemical disinfectant/sterilant.

Most low-temperature sterilization devices are sizeable and are unlikely to be used outside of larger institutional settings. Sterilization in dental offices by means other than heat is more likely to be accomplished through the use of liquid chemical sterilants, such as glutaraldehyde- or hydrogen peroxide-based formulations.³

The CDC dental infection control recommendations discourage the use of semicritical and critical dental devices that require liquid chemical sterilization because such items necessitate a myriad of special considerations after processing. These include rinsing with sterile water, handling while wearing sterile gloves, drying with sterile towels, and using an aseptic technique for delivery to the treatment area.² Because items cannot be packaged for sterilization and storage when using chemical germicides, instruments must also be used immediately, or resterilized immediately before use if they have been stored.²

Exposure to glutaraldehyde has been linked to occupational asthma and other adverse health effects.^4,5 When using glutaraldehyde it is important to ensure proper ventilation, which often requires either modifications to the number of air exchanges per hour in the room of use or the installation of a ventilation hood or similar device (Figure 1).⁶

Semicritical items include dental handpieces and dental instruments and devices that contact mucous membranes. These should also be heat sterilized; a chemical germicide can be used for high-level disinfection only if the heat-sterilization process is not feasible because it would damage or destroy the device.² With specific regard to handpieces, most handpieces today can be heat sterilized safely, and should be so treated in keeping with the CDC guidelines. For other semicritical instruments, in addition to the liquid chemical germicides used as sterilants, additional products such as orthopthaldehyde may be used for high-level disinfection. Intermediate- to low-level disinfectants intended for surface disinfection should not be used to reprocess semicritical devices. These disinfectants include sprays and wipes intended for use on environmental and clinical contact surfaces.

Issues With Spaulding’s Classification

Spaulding’s classification is highly useful in identifying the appropriate reprocessing method for reusable dental instruments and devices. However, this classification is somewhat limited due to its simplification and assumption that all critical and semicritical medical and dental devices can either be heat sterilized or disinfected using an immersion liquid germicide. In modern dental practices, numerous semicritical devices may be sensitive to heat-sterilization processes and could be damaged by exposure to chemical germicides used for disinfection. Unless a non-liquid, low-temperature sterilization process such as gas plasma or vaporized hydrogen peroxide is available, ensuring proper reprocessing of the item becomes a difficult task for the clinician.

Heat-Sensitive Equipment

Some of the electronic and technical equipment used in many dental offices today cannot be heat sterilized because it cannot tolerate high temperatures. Also, some items may be damaged by exposure to liquid chemical germicides. In determining the appropriate sterilization/disinfection process for a device or instrument, the clinician should first review the device manufacturer’s IFUs. The US Food and Drug Administration (FDA) regulates the labeling of medical and dental devices. Manufacturers must validate their label claims, including the IFUs for reprocessing, and submit those validation studies to the FDA for clearance.⁷ The IFUs must be provided to the user of the device and include a description of the validated steps for disassembly, lubrication, cleaning, disinfecting, packaging, and sterilization.⁸ It is important to note that all of these steps need to be completed, not just the sterilization or disinfection steps. Improper cleaning of reusable semicritical devices has been associated with patient infections and resulted in mass patient notifications of breaches in sterilization.³

If the manufacturer does not provide IFUs for reprocessing, the FDA considers the item a SUD.⁹ Although the FDA does not regulate users of medical devices, attempting to reprocess SUDs in the dental office should be avoided. Examples of SUDs in dental settings include some types of dental burs, plastic saliva ejectors, disposable air/water syringe tips, disposable prophy angles, disposable prophy brushes and cups, and some sterile irrigating syringes, among many others. If the manufacturer has not provided instructions for reprocessing, or the item is labeled for single patient use, it should be used for one patient only and then discarded.

Reusable electronic devices such as digital x-ray sensors, digital imaging scanners, and some cordless handpieces, among others, present an infection control challenge because these items may not be tolerant to heat-sterilization processes or high-level liquid chemical germicides. In addition, some dental materials are delivered directly to the patient’s mouth using a multidose dispenser, sometimes referred to as a syringe. The syringe tips are often disposable, but the dispenser itself may contact oral tissues and is not considered single-use. If the device contacts mucous membranes, simply wiping it with a surface disinfectant is not appropriate because it is semicritical and should be either sterilized or high-level disinfected.² Some of these devices may tolerate immersion in a high-level disinfectant such as orthopthaldehyde- or hydrogen peroxide-based products. Manufacturers of these devices should include in their IFUs the types of liquid chemical germicides that have been validated as safe and effective for the device. Some manufacturers may include the brand names of the products that have been tested on their device. It is important to follow the instructions provided by the liquid chemical germicide manufacturer for storage, use, and disposal of the product, as well as any instructions regarding personal protective equipment that the user should wear.

For semicritical devices that cannot be sterilized or immersed in a high-level disinfectant, the use of fluid-impervious barriers offers another option.² Several digital imaging scanners now provide a barrier to protect the portion of the device that contacts oral tissues. Digital x-ray sensors may also be barrier-protected during use. If the surface underlying the barrier becomes contaminated, that surface must be cleaned and high-level disinfected before a new barrier is placed for subsequent patients. Because the reason for the barrier is that the device cannot be high-level disinfected, this presents an infection control challenge for the practitioner, often resulting in a breach of accepted practice when the item is disinfected with an intermediate-level surface disinfectant. If a question arises regarding the safe high-level disinfection of a device, the user should consult the manufacturer.

Multiple-use dental dispensers or prefilled syringes of dental materials may also be barrier-protected. Some manufacturers of these dispensers offer barriers that are specifically intended for this purpose. The FDA issued an advisory to practitioners regarding these dispensers advising that: the dispensers should be barrier-protected during use and handled with clean gloves; dental assistants should dispense the material for the dentist; contact between the dispenser body and the patient’s oral tissues should be avoided; and a new tip should be used for each patient.¹⁰ Single-use dispensers are available for many of these types of dental products. If the product is not sensitive to light or air it may also be dispensed onto a disposable pad or other transfer surface to be taken to the treatment area for use; this eliminates the need for a barrier if the dispenser is handled with clean gloves only.

Summary

Advances in dental materials, techniques, and devices have revolutionized dental care. Dental clinicians and researchers will likely continue to develop innovations for better outcomes for patients, and manufacturers will improve upon existing technology, producing devices that are increasingly complex, small, and sensitive to traditional reprocessing methods. Clinicians will need to guard against compromising patient safety as an unintended consequence of these advances. Some of these needs have already been met through innovations such as low-temperature sterilization processes that pose no occupational risk, barriers that can be removed and heat sterilized to protect delicate surfaces of imaging devices, and unit-dose dental materials. Manufacturers must consider infection control requirements throughout the research and development process, and clinicians must insist that IFUs are complete and conform to the existing guidelines and regulations that govern dental practice.

ABOUT THE AUTHOR

Eve Cuny, MS

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

REFERENCES

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2. Centers for Disease Control and Prevention. Guidelines for Infection Control in Dental Health-Care Settings–2003. MMWR. 2003;52(RR17):1-61. https://www.cdc.gov/MMWR/preview/mmwrhtml/rr5217a1.htm. Accessed January 3, 2017.

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9. Vukelich DJ. Lessons Learned from FDA’s Regulation of ‘Single-Use’ Device Reprocessing. Biomed Instrum Technol. 2016 Spring;suppl:32-34.

10. Multiple-use Dental Dispenser Devices. Food and Drug Administration website. May 16, 2016. www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/DentalProducts/ucm404472.htm. Accessed January 3, 2017.