Chain of Events

Successful infection control is, in essence, a chain of events that disrupts the microbial chain of events that would otherwise lead to cross-contamination. We discuss current strategies for sterilization, disinfection, and reprocessing of instruments and devices used in dental practices.

In a winter season that some experts are predicting may be a particularly bad one for influenza, infection control in dental practices may be especially top of mind. But while infection control for dental practitioners doesn’t involve Hazmat suits or gas masks, it does embrace a protocol that involves personal protection equipment, as well as disinfection and sterilization procedures recommended by the Centers for Disease Control and Prevention (CDC).

Due to constantly evolving dentistry practices, technologies and pathogens, the CDC frequently updates its guidelines — which is considered the gold standard for infection control. Likewise, the agency advises continual evaluation on the part of clinicians to ensure that infection control principles are met. In fact, Kandis V. Garland, RDH, MS, an associate professor in the Department of Dental Hygiene at Idaho State University in Pocatello, explains to Mentor the most recent update to the agency’s 2003 guidelines. “The CDC put out companion documents in March 2016 called Summary of Infection Prevention Practices in Dental Settings: Basic Expectations for Safe Care that include helpful checklists for offices to use to self-audit how they are doing,” she explains. Garland notes that the Organization for Safety, Asepsis and Prevention (OSAP) also offers beneficial infection control resources that can help offices ensure compliancy with best practices.

Such resources can go a long way toward protecting dental practitioners and their patients from the havoc that assorted microbes can wreak. This is especially true in light of emerging and resistant pathogens. “The transmission of any infectious disease is problematic in dentistry,” says Louis G. DePaola, DDS, MS, a professor and associate dean of clinical affairs in the Department of Oncology and Diagnostic Sciences in the School of Dentistry at the University of Maryland in Baltimore. “However,” he adds, “while the most worrisome infections are the human immunodeficiency virus, hepatitis B, hepatitis C, human papillomavirus and herpes, the emergence of highly resistant bacterial and fungal infections is also problematic.”

While the CDC reports that infectious disease transmission in dental settings is rare, the agency has made documentation of such instances between 2003 and 2015. These included patient-to-patient transmissions. Much of the failure was found to be linked to lapses in infection control and prevention related to procedural breakdowns, which included failure to heat sterilize handpieces between patients, and failure to conduct spore testing on autoclaves.1

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  • While the Centers for Disease Control and Prevention (CDC) Guidelines for Infection Control in Dental Health Care Settings, 2003 are recommendations, not requirements, they are adopted as such by numerous states and organizations.
  • Resources offered by the CDC, Organization for Safety, Asepsis and Prevention, and other agencies can help ensure practices are protected from infection control lapses.
  • Lapses in infection control and prevention in the past few years have often been linked to procedural breakdowns.
  • Helpful measures practices can take toward infection control and prevention include keeping current on staff training and designating one person to be the infection control coordinator.
  • While manufacturer’s recommendations should always be followed, all instruments and devices should be properly cleaned, and disinfected or sterilized, according to their level on the Spaulding scale, between patients. In some cases, automated devices can make these chores a snap.
  • Steam autoclaves can sterilize at lower temperatures than dry heat autoclaves. This makes them ideal for sterilizing many of today’s low-speed handpieces.
  • Increasingly, low-speed handpieces that are designed to allow steam heat autoclaving are becoming available.


Other factors are also at work that can lead to infection control failures. “The biggest mistakes I see include being complacent, meaning sticking to ‘the way it’s always been done here,’” says Garland. In this regard, she says offices are not staying as current as they could be in regard to infection control. “They feel like they learned it in school and nothing has changed,” she explains.

This attitude, Garland observes, can lead to offices not keeping up with annual infection control training, misinterpretation of the CDC guidelines, and continuation of sloppy practices. For instance, she says, “I see a lot of offices still storing loose instruments in drawers instead of bagging or pouching them; lack of utility glove use when handling chemicals and contaminated instruments; failure to routinely offer patients eye protection; and the absence of a designated infection control coordinator.”

This last point, in Garland’s opinion, is where the most significant development in infection control lies. “The CDC recommends that all offices have a designated infection control coordinator,” she says.

Designating one person on the oral health care team who has training in infection prevention as a coordinator helps ensure that the appropriate supplies and equipment are on hand. This is the go-to person on all infection control matters. Responsibilities outlined by the CDC typically include developing written infection prevention policies and procedures; establishing policies and protocols to deal with infectious patients; and coordinating ongoing training and education for practice staff.


According to the CDC, the processing of instruments should be performed in a designated central processing area that’s divided into separate sections: one for receiving, cleaning and decontamination; a second for preparation and packaging; a third for sterilization; and a fourth for storage. To limit risk of contamination by pathogens, instruments and devices must be properly cleaned via scrubbing with a brush by hand using neutral or near-neutral pH detergent and water, with the occasional addition of an enzyme.

Alternately, automated cleaning systems such as ultrasonic cleaners and washer/disinfectors may be used to remove debris prior to disinfection or sterilization. Such equipment also limits the staff’s exposure to contaminants or injury while processing. Cleaning is a critical step, as blood, saliva or tissue left on an instrument from a previous patient can prevent thorough sterilization and lead to infectious transmission.2,3

After cleaning, items to be sterilized may be packaged and labeled for processing. Whether they are disinfected or sterilized depends on which category they fit into in the Spaulding classification system. Developed by Earle H. Spaulding more than three decades ago, the system categorizes instrument and device processing by degrees of risk, which depend on how items are used.

In the Spaulding system, instruments and devices are divided into three categories indicating the level of decontamination required. “Noncritical” refers to items that will only contact intact skin, such as blood pressure cuffs, and environmental surfaces, such as patient furniture and floors. According to the CDC, these may be disinfected with low-level disinfectants, simply cleaned with soap and water, or protected with disposable barriers.1,3,4



Considered semicritical devices, handpieces do a significant chunk of the work in modern dentistry and can easily become contaminated with tooth and tissue debris, blood and saliva inside and out. This is especially true of low-speed handpieces, whose designs feature venting portals that allow microbial infiltration. Therefore, simple disinfection won’t cut it. The entire handpiece must be carefully flushed, cleaned, lubricated and heat sterilized between patients. This especially makes sense in light of studies showing that oral fluids can be retracted into air and waterlines and then spit back out — into a patient’s mouth.6–8

For such reasons, the Centers for Disease Control and Prevention (CDC), the Organization for Safety, Asepsis and Prevention, the American Dental Association, and numerous organizations and licensing boards, along with manufacturers agree that handpieces must be sterilized via heat between patients after cleaning and lubrication. Further, a number of states now require it. In fact, according to the CDC’s Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008 (last updated in February 2017), “Handpieces that cannot be heat sterilized should not be used.”4

In the case of high-speed handpieces, heat sterilization has been an uncomplicated matter. But traditionally, it has not been possible to separate low-speed handpieces from their heat intolerant motors, or from air and water lines. But that is changing.

Thanks to the efforts of manufacturers who have been working to address this problem, cordless low-speed handpieces with sealed motors and internal features designed to prevent suck back, and that can tolerate temperatures up to 275º F in steam autoclaves are proliferating. In fact, heat tolerance appears now to be a major consideration in handpiece purchasing decisions. Seamless housings and lube-free designs are also surfacing.

The “semicritical” designation pertains to instruments and devices, such as mouth mirrors, impression trays and radiography sensors (even though used with barrier sleeves) that come into contact with mucous membranes or nonintact skin. “Semicritical” items call for heat sterilization.1 However, if an item is heat sensitive, the CDC advocates replacing it with a heat-tolerant or disposable version, or at the very least, processing it with a high-level disinfectant. Such disinfection, according to the CDC, results in “complete elimination of all microorganisms in or on an instrument, except for small numbers of spores.” 1 Disinfectants used for reusable semicritical items that cannot be heat sterilized include glutaraldehyde, hydrogen peroxide, ortho-phthalaldehyde, and peracetic acid with hydrogen peroxide.1

Dental handpieces fall into the “semicritical” category. When it comes to processing and maintenance, it’s important with any handpiece to follow manufacturer recommendations. They commonly recommend germicidal detergents or dedicated handpiece cleaners over chemical disinfectants, as the latter can cause corrosion. Small brushes can be used to scrub off debris from external and recessed surfaces and components.

Because this can be an exacting, time-consuming chore, at least one system has been developed to ease reprocessing of handpieces. Designed to thoroughly clean and lubricate multiple handpieces of any brand in just one minute, it not only offers time savings but ensures that handpieces are correctly maintained and prepared for sterilization.

While handpieces are regarded as “semicritical,” because they accumulate debris internally via retraction, the CDC stresses that they should be heat sterilized. In the event the handpiece is heat sensitive, the recommendation is that it should be replaced with heat-tolerant or single-use alternatives.1 “Disinfecting nonautoclavable devices and equipment can be problematic, especially in the age of digital dentistry,” explains DePaola, adding, “The best approach to these types of devices is to follow the manufacturer’s recommendations for cleaning and disinfection. If there are no cleaning and disinfection recommendations, that device probably should not be used; unless it is a single-use, disposable device.”

The top tier of this classification listing, “critical,” refers to items, such as surgical instruments and periodontal scalers, that penetrate tissue or bone. These items are typically purchased in a sterile state and, as they carry the greatest risk of cross contamination, they should always be sterilized with heat.1


Disinfection obliterates many of the microbes that contaminate surfaces. But not all of them. In that sense, disinfection merely reduces the load of viable microorganisms. In addition, most disinfectants do not kill bacterial spores. Disinfection is accomplished with the application of disinfectants on surfaces that cannot be sterilized.

There are three levels of chemical disinfection. High-level refers to sterilant/disinfectant formulations that can kill spores. These are used on medical devices. Intermediate-level disinfection is used to kill vegetative microorganisms, fungi, and to deactivate most viruses. These disinfectants are used to disinfect housekeeping surfaces. Low-level disinfectants kill most vegetative bacteria, some fungi and deactivate some viruses. They are used in general sanitation.5

Some germicides are more capable than others of killing certain pathogens, such as staphylococci, streptococci, fungi and viruses. Those used for disinfection include glutaraldehyde, ortho-phthalaldehyde, hy­dro­gen peroxide, sodium hypochlorite, formaldehyde, chlorine dioxide, peracetic acids, chlorine compounds, alcohols, phenolic compounds, io­dophor compounds and quaternary ammonium compounds.5

Unlike disinfection, sterilization is a process that kills all or most microorganisms, including spores. Methods of sterilization that can be used for critical or semicritical dental instruments and materials that are heat-stable include steam under pressure (autoclave), chemical (formaldehyde) vapor, and dry heat. Other sterilization methods include ethylene oxide gas, hydrogen peroxide gas, plasma, ozone and radiation.5

Although dry heat sterilization does not promote corrosion in some metals as can steam heat autoclaving, the latter is common in dental practices. Available in countertop-size units, these devices sterilize via pressurized steam and heat. In fact, steam autoclaves are the recommended way to sterilize low-speed handpieces. This is because they can sterilize at lower temperatures of 275º F than can their dry-heat counterparts, which sterilize at 320ºF.


Antiseptic: A germicide used on skin to inhibit or kill microorganisms; includes alcohols, chlorhexidine, chlorine, iodine, triclosan, etc.
Decontamination: The removal of living pathogens.
Disinfectant: A chemical formulation used to kill almost all pathogens on inanimate objects.
Germicide: A formulation that kills pathogenic microorganisms.
Microbe: A microorganism; often refers to pathogens.
Pathogen: An infectious agent such as a bacterium or virus.
Spore: A single-celled reproductive entity produced by various types of microorganisms.
Sterilization: Procedure to kill all microorganisms, including most spores.


Both DePaola and Garland believe that the greatest stress points in the infection control linkage are located in training and organization. Says DePaola, “The greatest challenges for infection control are making sure that the entire dental team is properly trained and everyone follows the CDC recommendations inclusive of the use of standard precautions and cleaning, disinfection and sterilization of dental instruments and devices.”

Garland agrees. “Clinicians and their staffs should know the 2003 CDC Guidelines inside and out — as well as the 2016 new companion documents,” she recommends, again stressing the importance of employing an infection control coordinator. “They should attend the OSAP Bootcamp and annual conference, and utilize its website for the latest updates. The CDC checklist should be used to audit offices, assess compliance and note deficiencies, so that improvements can be made where needed.”

There are many links in the infection control chain. But there are also numerous resources available to oral health care practitioners to help them forge a chain of events will keep their practices cross-contamination-free.




  1. Centers for Disease Control and Prevention. Summary of infection prevention practices in dental settings: basic expectations for safe care. Available at: Accessed November 2, 2017.
  2. Kohn WG, Collins AS, Cleveland JL, et al. Guidelines for infection control in dental health-care settings — 2003. Centers for Disease Control and Prevention. Available at: Accessed November 2, 2017.
  3. Rutala WA, Weber DJ, Healthcare Infection Control Practices Advisory Committee. Guideline for disinfection and sterilization in healthcare facilities, 2008. Centers for Disease Control and Prevention. Available at: Accessed November 2, 2017.
  4. Hendricks LG. Simple strategies for surface disinfection. Dimensions of Dental Hygiene. 2015;13(6):42.
  5. Centers for Disease Control and Prevention. Apendix B — Decontamination and disinfection. Available at: Accessed November 2, 2017.
  6. Centers for Disease Control and Prevention. Recommended infection control practices for dentistry. MMWR Morbid Mortal Weekly Rep. 1993;42(RR-8):1–14.
  7. Herd S, Chin J, Palenik CJ, Ofner S. The in vivo contamination of air-driven low-speed handpieces with prophylaxis angles. J Am Dent Assoc. 2007;138:1360–1365.
  8. Chin JR, Miller CH, Palenik CJ. Internal contamination of air-driven low-speed handpieces and attached prophy angles. J Am Dent Assoc. 2006;137:1275–1280.
  9. Organization for Safety, Asepsis and Prevention. Dental unit waterline toolkit. Available at: Accessed November 2, 2017.
  10. Occupational Safety and Health Administration. Latex allergy. Available at: Accessed November 5, 2017.
  11. Centers for Disease Control and Prevention: National Institute for Occupational Safety and Health. Latex allergy: a prevention guide. Available at: Accessed November 5, 2017.
  12. Newswise. Malaysian SMG-certified latex gloves already meet or exceed FDA’s new barrier quality standards. Available at: Accessed November 5, 2017.


From MENTOR. December 2017;8(12): 20-22, 24-25.

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