Concepts and first steps of reprocessing dental devices
March 24, 2021
Dr. Nita Mazurat, DMD, MSc

Taking the Mystery out of Reprocessing: Concepts and First Steps of Reprocessing

Reprocessing dental devices can be complex and confusing – and starts long before sterilization. Take a closer look at this critical process and the importance of knowing your equipment inside and out.

Reprocessing is the science and practice of preparing instruments and devices for use and reuse in patient care. To many dental personnel, reprocessing of instruments when they were students was a magical, if not mysterious process. This mysterious component about reprocessing still remains for many clinicians since they do not (nor have time to) participate in reprocessing activities in their practices. Fortunately, oral healthcare knowledge of reprocessing, both what to do and how to do it (theoretical and clinical) has advanced through awareness and adoption of established Reprocessing Standards: AAMI ST:79 in the Unites States and Canadian Standards Association (CSA) Z314-18 in Canada. Both of these standards that have been developed for use in all healthcare settings and provide guidance to State and Provincial Dental Associations when developing their infection prevention and control guidelines.

This is the first in a series of articles that has been developed to assist oral healthcare and other community-based healthcare services with reprocessing. The objective for this first article is to describe background information with rationale for these practices as well as introducing terminology used in reprocessing that may be unfamiliar for oral healthcare.

Reprocessing is a great deal more than a ‘sterilizer in a room’ and is comprised of many steps.

Steps for reprocessing

  • Cleaning at chairside, also known as ‘cleaning at point of care’
  • Transport to the central sterilization area
  • Pre-cleaning and disassembly of devices (e.g. mirrors, composite guns, syringes)
  • Cleaning, rinsing
  • Drying
  • Inspection
  • Testing for functionality
  • Packaging
  • Monitoring
  • Sterilization (loading and unloading)
  • Storage
  • Traceability
  • Aseptic presentation
    Aseptic presentation is not part of reprocessing, however, because it includes removal of sterile devices from their packaging for patient care, contamination during operatory set up can negate the careful work of the previous steps. For this reason, discussion about aseptic presentation will be included in this series.

Manufacturers instructions for use

During reprocessing, critical decision making is a skill that has to be accompanied by strict adherence to instructions from the manufacturer for products and procedures to achieve cleanliness, functionality, and sterility. Let’s examine some of these hallmark concepts surrounding manufacturers’ instructions for use. Please note that these concepts are not in any particular order and they are all important! All of our activities are driven by the need for patient safety.

  • ‘Do no harm’ is the overlying umbrella for patient care.
  • Only devices, (in these articles, both instruments and devices are together simply referred to as ‘devices’), manufactured with the intent of use and licensed for use in healthcare should be used in healthcare as these have had to be demonstrated to be safe for use during patient care.
  • Devices developed for use in healthcare are ‘labelled’, meaning that the manufacturer has to provide instructions for their reprocessing.
  1. Obtain and follow manufacturers’ instructions for use, known as MIFIs in Canada and IFUs in the United States.
    Assumptions about how to reprocess or assumptions that all devices can be sterilized using the same parameters for time, temperature, and pressure can result in devices that are not sterile and therefore, are not safe for patient care. Only the manufacturer knows the composition of the device and how it should optimally be reprocessed to prevent premature degradation of the device while providing instructions to achieve sterility. Manufacturers are required to provide instructions for reprocessing for all classes of instruments and the type of information provided should conform to an International Standards Organization (ISO) directive which has been adopted by the FDA (Unites States) and Health Canada (Canada)1 from preparation at point of care to storage.

    In the excitement of purchasing new devices, it is easy to forget that the first question to ask is ‘how will this be reprocessed?’ and it will take a team effort to remind each other to develop this change in purchasing practices. Requesting manufacturers’ instructions for use prior to purchasing any devices is done to ensure that:

    1. The written reprocessing instructions provided by the manufacturer adhere to ISO directives. Preferably these instructions are ‘validated’. Validated instructions are instructions that have been shown by an independent testing company to verify that when the reprocessing instructions provided by the manufacturer are followed, this will result in a sterile device.
    2. Equipment required for reprocessing is available in your office.
      For example, your hygienists recommend purchasing a new type of highspeed suctioning device that would be more effective during ultrasonic scaling. Upon checking the instructions for reprocessing, it was found that the manufacturer had only provided instructions for use of a gravity sterilizer. Even after contacting the company, no instructions were provided for use with a dynamic sterilizer. Since your office uses a steam flush pressure pulse (SFPP) sterilizer (dynamic sterilization), your office would not be able to sterilize the device because the device has only been tested (validated) for gravity, not for use in a dynamic sterilizer.

    Reprocessing is a tailored process and is not a ‘one set of sterilization parameters fits all’ process. Until the manufacturer is able to provide instructions for the type of sterilizer that you have in your office, you are not able to reprocess the device, and therefore should not buy it. Only buy what can be cleaned and sterilized because clear instructions have been provided for both!

    One further comment. Often a manufacturer’s representative will try to be helpful by providing their assurance that the device can be sterilized using ‘a standard cycle’. Until assurances are provided by the manufacturer using validated written instructions, place the purchases on your wishlist.

  2. Devices that do not have MIFUs, cannot be reprocessed and are considered single use items.
    Some single use items such as burs, may come with MIFUs for reprocessing prior to use only. Many disposable cotton products such as gauze, rolls, pellets, and tipped applicators should not be reprocessed prior to use because they do not have instructions for reprocessing. Sterilization only is not ‘reprocessing’. This is a practice so commonly performed in healthcare, especially for providing ‘sterile’ cotton gauze following surgery, that it has become normalized; however, if the office is unable to purchase cotton items with validated MIFUs and sterile materials are required, then these disposable products need to be purchased sterile.
  3. Surfaces must be clean prior to sterilization or disinfection.
    Cleaning is the most important step in reprocessing because a soiled instrument cannot be effectively sterilized as the soil shields the bacteria and viruses from the sterilizing agent.2 The first cleaning that occurs is done at chairside or ‘point of care’ when dental materials are removed from devices before they set or dry. Performing this cleaning will save valuable time in trying to remove these materials after they dry and unless appropriate solvents are used, devices can be damaged when attempting to remove these materials. Whenever possible, follow instructions from the dental material manufacturers.

    Once devices are transported to the reprocessing area, if cleaning will not be performed before blood and saliva dry, they should be disassembled (mirrors, composite guns, syringes) and hinges opened and kept moist with a towel moistened with water or, with an enzyme pre-clean which will need to be thoroughly rinsed before cleaning begins. (High level disinfectants are not appropriate for this purpose.)

    • Cleaning is very important – but what is clean? “Clean” is described as: ‘visually clean’, ‘microscopically clean’ and ‘verified clean’.
    • ‘Visually clean’ means that when the device is examined after cleaning, preferably under magnification and good lighting, no remaining soil can be seen. Devices are considered ‘visually clean’ when they have been cleaned manually, in an ultrasonic cleaner, or through the use of an automated washer.
    • ‘Microscopically clean’ is the result after devices are successfully cleaned in a washer/disinfector and are also known as thermally disinfected. This final result is very different that the final result of devices cleaned in a washer.
    • ‘Verified clean’ means that a special product is used following visual or microscopic cleaning to ensure that certain organic soils such as protein or blood have been removed from the device. These products can be provided as a specially-wetted swab that is swiped over the device being tested and then placed into an activated indicator where a colour change indicates presence or absence of the material being tested. In other systems the swab is placed into a mechanical read-out device that provides quantified results for the residual amount of organic soil that is being tested.

    Clean is very important for patient safety whereas visually clean or microscopically clean determine how devices are handled in the reprocessing area after cleaning is performed and will be discussed in the next article.

  4. Cleaning should be directed by the MIFUs and MIFUs for cleaning need to be followed.
    All cleaning requires the use of specified cleaning agents; specified water, including temperature and type, especially for the final rinse to remove residual detergent and minerals that are present in tap water; and specific equipment. Water hardness, the concentration of certain minerals, will reduce the efficiency of cleaning agents because the minerals bind with detergents and enzymes. Knowing the water hardness in your facility and receiving guidance with purchasing cleaning agents based on this important variable can be very useful in preventing staining and premature degradation of devices.

    1. Manual cleaning
      Manual cleaning includes the use of appropriate brushes3, designed and purchased for this purpose. Because toothbrushes and denture brushes are often readily available in dental offices, these are convenient and often used for cleaning devices. However, these brushes have been carefully designed to be used for oral hygiene and since the oral hygiene brushes do not come with MIFUs, they may not achieve optimal results for cleaning devices.

      Devices that have lumens, present their own unique challenges. There are open ended lumens, such as hygiene handpieces that are open at both ends, that require open ended brushes, and closed ended lumens for areas such as the lumen in the handle of mirrors when mirrors (with replaceable mirrors) are disassembled. Brushes used for cleaning lumens need to be large enough to be effective on the inner walls without being difficult to brush back and forth. Open ended brushes need to be long enough to extrude from the distal end of the lumen. End cleaning brushes have a round fan brush at one end for cleaning the solid wall at the end of the closed ended lumen. Because the cleaning of lumens is a resource intense step, many offices have switched to disposable items when they are readily available, including air/water syringe tips and high-volume suction tips.

      All devices should be fully immersed for cleaning and rinsing to reduce the production of spatter and aerosols, especially that which occurs if performing these in running water.

    2. Ultrasonic cleaning
      Ultrasonic cleaning occurs when the bubbles caused by high frequency sound waves in the cleaning solution implode causing a vacuum (cavitation) which draws debris from the surfaces of the devices. Ultrasonic cleaners can be a single tank or multiple tank device and various sizes can be purchased.

      Ultrasonic cleaning works because all surfaces of the devices are exposed to the solution and overcrowding will reduce the effectiveness of cleaning. Other factors that affect the efficiency of ultrasonic cleaning are:

      • Using the correct cleaning agent and maintaining the required level of solution to ensure that devices being cleaned can always be submerged. Follow manufacturers’ instructions for the solution specified as these remove debris in the way that the ultrasonic cleaner was designed to work. Know the target soil. Enzymatics assist in removing dried blood and in offices where the majority of procedures performed are surgical, this would be the preferred cleaning agent. In practices that are mostly restorative or orthodontic, a cleaning agent that targets inorganic materials such as luting cements and restorative materials will be more applicable. Follow the MIFUs for correct dilution, correct volume of diluted agent in the ultrasonic tank, and correct water temperature. Cleaning and disinfecting the tank when changing the solution helps to reduce the microscopic bioburden4.
      • Removing gas bubbles caused largely by trapped air when fresh cleaning agent is placed into the tank. The bubbles need to be expelled by running or ‘degassing’ the ultrasonic without instruments in the tank for the time specified by the manufacturer so these gas bubbles do not interfere cleaning.
      • Placing the devices being cleaned in a tray or basket designed for use in the tank to allow more accessibility to cavitation and prevents the devices from touching the walls and floor of the ultrasonic tank. Stainless steel instruments should not be mixed with aluminum, brass or copper instruments in a sonic cycle as this may cause galvanic reactions that result in corrosion5.
      • Removing gross soil from the devices prior to ultrasonic cleaning. When the ultrasonic cleaning solution has less debris its cleaning action is more effective. Rinsing is more effective when devices are immersed using the basket designed to be used in the ultrasonic in water and allowing this to drain prior to placement into the cleaner to remove excess water and gross debris. Lumens should be manually cleaned prior to placement into the ultrasonic washer.
      • Following the ultrasonic cleaner instructions for use for loading. A single layer of instruments should only be cleaned at a time so that cavitation can reach every surface. When instruments are stacked, cavitation may be unattainable to every surface. Many dental offices use ultrasonic cleaners that are too small for the volume of instruments and devices that are used in the office which in turn results in overfilled ultrasonic cleaners with poor cleaning results. Ensure that all items are submerged and that hinged devices are open to allow cleaning.
      • Rinsing following cleaning removes residual solution and soil which need to be removed before the next steps in reprocessing. Fully immerse the instruments into clean rinse water and allow to drain before drying.

      Ultrasonic cleaners should be run with the lid on to prevent escape of microorganisms into the ambient office air.

      Cleaning efficacy or a function test is required at least once weekly, preferably daily either using a foil test or using a commercial ultrasonic cleaner test.

    3. Automated washers
      The key here is the word ‘automated’. As long as MIFUs exist regarding detergents, water including type of water used and water temperature, and office personnel allow complete cycles to run, there is less human error to intervene in the cleaning process surrounding washers. Just as with ultrasonic cleaners, stainless steel instruments should not be mixed with aluminum, brass or copper instruments during cleaning in a washer or washer/disinfector. It is worth repeating that the final level of clean is visual when using a washer, whereas it is microscopically clean using a washer/disinfector. The consequences of this are substantial in how devices are able to be handled in the remaining steps of reprocessing.

In summary, this article was designed to introduce and review some of the underlying concepts for reprocessing. Most notable are the role of obtaining and following validated manufacturers instructions for use and the role of cleaning in reprocessing.

Article takeaways

  1. Users should request validated instructions for reprocessing before purchase of devices as well as requesting clarification for instructions for existing devices in the office inventory that are unclear, incomplete, or require parameters of sterilization that vary from the normal expected cycles.
  2. Users must assemble and follow the instructions for the entire office inventory of devices.
  3. Practice using the new terms used in this article to better describe reprocessing in oral healthcare offices.

The next article will continue to discuss the infrastructure required for safe, effective reprocessing in the dental setting. This will include office design and the use of personal protective equipment as we continue to describe steps in reprocessing.

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