Infection Control and Sterilization

In the 1980s, the ADA Foundation’s Health Screening Program helped identify hepatitis B virus as an occupational hazard in dentistry. The ADA responded by being the first entity to recommend that dentists and dental offices follow standard infection control procedures. The ADA subsequently worked with the Centers for Disease Control and Prevention (CDC) to develop CDC’s own infection control recommendations for dentistry, which were originally issued in 1993. 1 Since then, the CDC has updated and supplemented their recommendations to reflect new scientific knowledge and growing understanding of the principles of infection control. 2, 3

In addition to the standard infection control procedures discussed on this page, the CDC recommends the following nonpharmaceutical interventions (NPIs) to help limit the spread of influenza, 4 urging dental staff and patients to always:

• Stay home when ill.
• Practice good respiratory etiquette: cough or sneeze into a tissue or a shirt sleeve and immediately wash your hands with soap and water or use an alcohol-based hand sanitizer (at least 60% ethanol or isopropanol) to disinfect them.
• Routinely clean all frequently touched surfaces, using standard infection control procedures as directed in the CDC 2003 guidelines on infection control2 where appropriate.

During influenza pandemics, CDC recommends more stringent NPIs: 4

• People living with a person who has influenza should stay home for up to three days after their initial contact with the ill person.
• Persons who are ill should wear a face mask if they must go out of the house.

While the CDC provides recommendations for infection control in healthcare and dental settings, the Occupational Safety and Health Administration (OSHA) regulates and enforces infection control measures among staff and employers, including within dental offices. The Bloodborne Pathogens standard (CFR 1910.1030) protects workers who may be exposed to infectious materials in their workplace. Please see the Oral Health Topics page on OSHA for more information.

In December 2003, the CDC published a major consolidation and update of its infection control recommendations for dentistry. 2 The 2003 document incorporated relevant recommendations that were previously published in several other CDC documents and contained an extensive review of the science related to dental infection control. In March 2016, the CDC issued the new “CDC Summary of Infection Prevention Practices in Dental Settings: Basic Expectations for Safe Care.” 3 Although not intended as a replacement for the 2003 Guidelines document, the new CDC Summary is targeted to “anyone who seeks information about basic infection control in dental settings and includes several new recommendations as well as an assessment checklist.” Although the primary content is essentially unchanged, the new Summary document brings together recommendations from the 2003 CDC guidelines as well as other recommendations published in CDC guidance documents since 2003.

The 2003 CDC Guidelines and 2016 Summary are comprehensive and evidence-based sources for infection control practices relevant to the dental office that have been developed for the protection of dental care workers and their patients. The new resource includes tools to help dental health care personnel follow infection prevention guidelines, including:

• a summary of basic infection prevention principles and recommendations for dental settings;
• a checklist to help evaluate dental staff compliance with administrative and clinical practice infection prevention recommendations; and
• key references and resources for each area of focus including sterilization, safe injection practices and hand hygiene in dental settings.

The updated recommendations 3 emphasize the importance of having one person in every dental practice assigned to be the infection prevention coordinator. The coordinator would develop written infection prevention policies based on evidence-based guidance outlined in the new resource. The coordinator can help ensure that dental health care personnel are aware of the equipment and supplies necessary to address infection prevention issues with all staff members.

The ADA has long advocated the use of infection control procedures in dental practice and provided dentists with resources to help them understand and implement them. The ADA urges all practicing dentists, dental auxiliaries and dental laboratories to employ appropriate infection control procedures as described in the 2003 CDC guidelines and 2016 CDC Summary and to keep up to date as scientific information leads to improvements in infection control, risk assessment, and disease management in oral health care.

The CDC distinguishes several levels of sterilization and disinfection of patient-care items according to the level of risk based on intended use. Items must be cleaned prior to disinfection or sterilization.

Manufacturer’s instructions must be followed for the use of EPA-registered disinfectants and FDA-cleared sterilants and high-level disinfectants, and intended use must be clearly stated on the label; if not, do not use the product. Similarly, reusable devices must provide clear instructions for reprocessing and should not be reused. For more detailed information please see the 2003 CDC recommendations, the 2016 CDC update, or the ADA Practical Guide to Effective Infection Prevention and Control.

• Noncritical environmental (housekeeping) surfaces include surfaces that are not typically contacted during patient care, such as floors and walls, but also higher-contact items like pens and door handles. Such surfaces should be cleaned and disinfected with a low-level disinfectant. See the CDC's Best Practices for Environmental Infection Prevention and Control for more detailed information.
• Noncritical patient-care items are not expected to break skin or touch mucous membranes, and present the lowest risk of infection. Noncritical items include light handles, protective eyewear, and extraoral radiographic equipment; these items may be barrier-protected, and should be disinfected using an intermediate-level tuberculocidal hospital disinfectant between patients.
• Semicritical patient care items may contact mucous membranes and exposed or broken skin, presenting a higher risk than noncritical items. Semicritical items include reusable instruments and devices that enter the oral cavity and should be heat-sterilized whenever possible, or high-level disinfected. Dental handpieces and attachments are semicritical items that must be heat sterilized between patients according to the manufacturer’s instructions and CDC recommendations as describe in the section below.
• Critical patient care items penetrate skin or mucous membranes and have the highest risk of transmitting infection. Critical patient care items include periodontal probes and scalers, forceps and rotary cutting instruments, scalpels and other instruments that break tissue or contact bone. Such critical items, after being thoroughly cleaned, should always be heat sterilized or immersed in chemical sterilant according to manufacturer’s instructions.

In April, 2018, the CDC released a Statement on Reprocessing Dental Handpieces stressing that handpieces (both low-speed and high-speed) and other intraoral instruments that can be removed from the air lines and waterlines need to be heat sterilized between patients, 5, 6 and that reusable devices made prior to 2015 6 may not meet current FDA reprocessing guidance. 7 The CDC Statement reaffirmed and clarified 2003 CDC recommendations 2 and emphasized three key points: 6

1. Clean and heat sterilize handpieces and other intraoral instruments that can be removed from the air lines and waterlines of dental units.
2. For handpieces that do not attach to air lines and waterlines, use FDA-cleared devices and follow the validated manufacturer’s instructions for reprocessing these devices.
3. If a dental handpiece cannot be heat sterilized and does not have FDA clearance with validated instructions for reprocessing, do not use that device.

If a dentist is concerned about the validity of the manufacturer’s reprocessing instructions, or believes that the instructions are not consistent with basic infection prevention and control principles, they can contact the manufacturer to request documentation of FDA clearance of the device in question. If the manufacturer is not able to provide sufficient information, dentists can contact FDA’s Office of Compliance for assistance, at OCMedicalDeviceCo@fda.hhs.gov or 1-240-402-7675.

Along with the proper sterilization of instruments and materials, sterilizer monitoring is an essential part of any in-office infection control program.

Many factors can cause sterilization to fail—from procedural errors that are easily remedied, like overloading, to mechanical problems that can take a sterilizer out of service until repairs can be made. Since this variety of factors can influence successful sterilization, the ADA and CDC encourage dentists to regularly assess the efficiency of their in-office sterilizers. 2, 8, 9 In addition, state or local regulations may exist regarding frequency and record-keeping issues related to sterilizer monitoring. Check with your state dental board for regulatory information.

Sterilization is best monitored using a combination of mechanical, chemical, and biological indicators.8 The CDC has provided the following recommendations: 2, 3, 9

Mechanical Indicators

• Record cycle time, temperature, and pressure as displayed on the sterilizer gauges for each instrument load.

Chemical Indicators

• Use chemical indicators, such as indicator tapes, with each instrument load. These indicators change color after exposure to the proper sterilization environment.
• Failure of the indicator to change color indicates that it was not exposed to the proper sterilization environment (e.g., proper pressure or temperature). In such cases, the instrument load should be re-sterilized.
• Indicator tapes are sterilizer-specific (i.e., tapes for steam sterilizers cannot be used to test chemical vapor sterilizers).
• Chemical indicators should not replace biological indicators, as only a biological indicator consisting of bacterial endospores can measure the microbial killing power of the sterilization process.

Biological Indicators

• The CDC recommends monitoring sterilizers at least weekly with biological indicators. 2, 3 Check to see whether your state dental board has different requirements.
• Biological monitoring can be done in two ways:

1. In-office incubator and spore monitoring strips (contact your dental supplier for a list of products). This method usually gives results in 24-48 hours.
2. Mail-in spore monitoring programs. This process usually takes a week. Although it takes longer to get results using a service, third-party monitoring programs may

provide more accuracy than in-house monitoring.

• A positive spore test result indicates that sterilization failed. According to CDC recommendations: 1, 3
• Take the sterilizer out of service.
• Review the sterilization process being followed in the office to rule out operator error as the cause of failure.
• Correct any identified procedural problems, and retest the sterilizer using biological, mechanical, and chemical indicators.
• If the repeat biological indicator test is negative and the other test results fall within normal limits, the sterilizer can be returned to service.
• Maintain a log of spore test results. Check with your state dental board to determine how long you need to keep spore testing records.

What to Do When Results Confirm Sterilization Failure

If the biological indicator test is positive, or the mechanical or chemical test results indicate failure, the sterilizer should not be used until the reason for failure has been identified and corrected.

• If no procedural errors are identified or failures persist after procedural errors are corrected, the sterilizer should not be used until the reason for failure has been identified and corrected.

Before the sterilizer can be returned to service, the biological indicator should return negative results for tests conducted during three consecutive empty-chamber sterilization cycles to ensure that the problem has been corrected.

• To the extent possible, reprocess all instruments that were sterilized since the last negative spore test.
• Record the positive test results and all actions taken to help ensure proper functioning of the sterilizer in the monitoring log.