Instrument washers not dishwashers

June 1, 2009
The cleaning of reusable instruments prior to heat sterilization is a crucial, yet sometimes misunderstood, infection-control procedure.

The cleaning of reusable instruments prior to heat sterilization is a crucial, yet sometimes misunderstood, infection-control procedure. If biological contamination and other debris are not removed properly, the remaining matter can interfere with microbial inactivation during a sterilization cycle. This compromises the process.

Similarly, as seen with other infection-control areas, there are acceptable approaches when dental care providers select cleaning methods and equipment for their practices.

The most recent Centers for Disease Control and Prevention infection-control guidelines for dentistry recognize these choices in their recommendations: “Use automated cleaning equipment (ultrasonic cleaner or washer-disinfector) to remove debris to increase cleaning effectiveness and decrease worker exposure to blood …. Use work practice controls that minimize contact with sharp instruments if manual cleaning is necessary (i.e., long-handled brush).“

Fortunately, scrubbing contaminated instruments by hand is no longer performed in the overwhelming majority of dental facilities because of the documented risk of accidental sharps exposures. Use of automated cleaning equipment, such as ultrasonic cleaners or instrument washers, does not require presoaking or scrubbing of instruments. This can increase productivity, improve cleaning effectiveness, and decrease personnel sharps risks.

Although most dental practices use ultrasonic units as the primary method for cleaning instruments prior to sterilization, instrument washers are being installed in more schools, clinics, and practice settings. A common comment heard after personnel use them for a while is that these units substantially streamline the instrument-cleaning process.

They generally accommodate more instruments than ultrasonic units and use automated washing cycles, which compare to intervals for ultrasonic cleaners. Washers also eliminate the need for manual presoaking, hand scrubbing, rinsing, and drying. Some instrument washers, or washer-disinfectors, have a high-temperature cycle. This setting allows the unit to achieve thermal disinfection in addition to cleaning.

It is important to remember that, while these washers may appear to be similar to home dishwashers, instrument washing equipment is considered medical equipment and is regulated by the Food and Drug Administration. Commercially available household dishwashers are not designed to process medical instruments and have not met FDA requirements for safety and effectiveness. As such, use of a household dishwasher in clinical settings is not a substitute for using a tested and approved instrument washer.

Despite this caution, dental health-care professionals continue to hear recommendations for use of commercial dishwashers in certain infection control seminars. Numerous problems can develop from this practice, including issues with unit cycles, instrument cleaning, and cleaning solutions.

Instrument washers are designed, tested, and FDA-approved as medical instrument cleaners to operate many cycles per day in order to facilitate efficient reprocessing of a practice's limited number of instruments. Dishwashers have neither any data supporting use in health-care facilities nor warranties that allow such use.

Most instrument washers are used to clean contaminated instruments held in cassettes. Newer generations of cassettes contain vents to allow adequate cleaning solutions to reach instruments within; however, older style cassettes have solid edges. When loaded into an instrument washer, cassettes are set at an angle to facilitate maximum penetration of solution jetting from rotating washer arms.

Home dishwashers are designed to stack dishes vertically. When instrument cassettes are loaded in this way, the forced cleaning spray has only limited access to bioburden-laden instruments since the majority of cassette holes will not be used efficiently. The result is that much of the water-based cleaning solution does not penetrate the cassette's interior. This increases the potential for inadequate removal of debris.

Cleaning solutions designed for use on contaminated medical instruments have been tested for their a) ability to remove biological and other debris, and b) compatability with expensive, delicate items. Many of the available cleaners contain proteolytic enzymes that degrade contaminating proteins and can accomplish a “medical grade“ instrument wash.

These preparations also can contain anti-rust and anti-corrosion chemicals to reduce damage to processed instruments. In contrast, dishwasher soaps can irreversibly harm medical and dental instruments and are not recommended by any instrument manufacturers.

Consider these areas when you evaluate and purchase new cleaning equipment. Your initial cost may be higher but the long-term efficiency benefits and savings can be greater.

Dr. John A. Molinari is professor and chairman of the Department of Biomedical Sciences at the University of Detroit Mercy School of Dentistry. Contact him at [email protected].

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