Instrument sterilization

Oct. 1, 2006
I was privileged to attend the Annual OSAP (Organization for Safety and Asepsis Procedures) Symposium recently...

I was privileged to attend the Annual OSAP (Organization for Safety and Asepsis Procedures) Symposium recently and to participate in a summit meeting on instrument sterilization. My thanks go to Barnstead/Harvey and my good friends, Eve Cuny, Dr. Shannon Mills, and Dr. John Molinari for their dedication to dentistry and infection control, and for their inspiration. Their presentations focused on many of the common questions that I hear from hygienists, so I thought it might be helpful to share this information with you. Without further adieu, here are the answers to your questions.

Do instruments have to be packaged for sterilization and why?

According to the CDC Guidelines for Infection Control in Dental Health Care Settings - 2003, instruments that are sterilized and not used immediately should be packaged for sterilization. This CDC guideline is a widely accepted standard of care, although many dental professionals don’t believe it carries much weight since it is not an OSHA rule. Keep in mind that OSHA does not have jurisdiction over patient safety issues, only employee safety. Since this is a patient safety issue - potential contamination of stored, loose instruments - it falls under the purview of your state dental board.

Many state dental boards have accepted or adopted the CDC guidelines as their standards for patient safety. Some boards, such as the Ohio State Dental Board, have their own infection-control rules written into the dental practice act.

Should instruments be dried before placing them in the sterilizer?

When instruments are cleaned, they are typically rinsed with tap water after the cleaning process. Tap water contains minerals that, in many cases, can be transferred to the sterilization chamber on the instruments, causing a buildup of minerals in the chamber as well as on the instruments. This buildup can lead to discoloration and pitting of the instrument. In chemical vapor sterilizers, moisture on the instruments can dilute the solution and interfere with the sterilization process.

In addition, wet instruments can cause tears or breaks in the instruments’ packaging material. When the instruments are removed from the sterilizer, the packages are compromised.

How can I dry the instruments?

There are several ways to dry instruments after cleaning. The instruments can be rinsed and placed on a surface to air dry. This may take longer than would be desirable, since most practices need to turn around instruments rather quickly for reuse. Another option is to use an instrument dryer with a fan and heated air. If your practice uses a thermal washer/disinfector for instrument cleaning, this process is completed for you.

Yet another option is to dip the cleaned instruments into a container with 90 percent isopropyl alcohol. The alcohol is a desiccating or drying agent that will evaporate very quickly from the instruments, along with the water from rinsing.

Does it matter how the instrument packages are placed in the sterilizer?

First, consult the manual to learn about the manufacturer’s recommendations for loading your sterilizer. It is best to follow the recommendations.

Remember that for sterilization to be effective, the steam or chemical vapor in an autoclave or chemical vapor sterilizer must be able to contact the instrument surfaces. Therefore, it is very important to avoid placing too many instrument packages in a load. If you use sterilization pouches, keep in mind that the steam or chemical vapor penetrates through the paper side of the package, not through the clear “plastic” side of the package. Thus, placing instrument packages with the paper sides together may affect the sterilization of those instruments.

Several sterilizer manufacturers provide racks that fit inside the chamber, allowing instrument packages to be placed on their sides, rather than flat, and to be separated for maximum exposure to steam or chemical vapor. Keeping the instrument packages separated also maximizes the drying process.

Do the instrument packages really need to be dried before they are removed from the sterilizer?

It is very important to let the drying cycle finish before you remove the packages from the sterilizer. If the packages are handled when they are wet, the material can tear and the instruments can become contaminated.

Wet packaging material can also act as a wick, drawing in contaminants from the air.

The packages are wet even after the drying cycle is completed. What should I do?

Again, be careful not to overload the sterilizer, which can interfere with the drying process. Use racks for the packages if possible. If you lay your packages on the trays in the sterilizer, place the paper sides up so that moisture can escape.

Also, have your sterilizer checked to make sure that the heating element for the dryer is working properly.

Is it true that autoclaving instruments and burs makes them dull?

A number of years ago several studies were conducted which demonstrated that steam under pressure (autoclaving) caused some cutting surfaces to become dull. But the dullness caused by this process is not as great as that caused by using the instruments or burs.

Because burs and instruments such as scalers and curettes fall into the category of critical items, CDC guidelines advocate heat sterilization for these items. Since they are difficult to clean, disposable burs may be a better choice.

Do instrument packages have to be dated?

Studies demonstrate that instruments remain sterile inside packages unless tearing or puncture compromises the package, or it becomes wet. At this time there are no studies that demonstrate that the packaging material degrades (in the absence of tear, puncture, or moisture) over a specific time and compromises the sterility of the instruments.

Dating packages serves several purposes that may be applicable in your practice setting. One reason is to rotate the instrument stock. This may be important with hygiene instruments to prolong their life from use and sharpening. The other reason for dating packages is to track instruments to a specific load should there be a sterilizer failure.

In most dental practices, however, once sterilizer failure has been identified, the instruments in question most likely will have already been used on patients.

Does the sterilizer have to be tested regularly for effectiveness?

CDC guidelines recommend weekly monitoring of heat sterilizers with biological monitors. A biological monitor is commonly called a spore test. It may be a strip or a glass vial containing microbial spores. The strip or vial is placed inside an instrument package and run through a sterilization cycle to validate that the sterilizer has destroyed all microbes.

There are many sterilizer-monitoring services that can provide these tests, as well as several in-office systems if you choose to test and validate the results that way.

What about the indicators on the instrument packages? Don’t they show that the sterilizer is working?

The color-change indicators on sterilization pouches and autoclave tape are process indicators that show that the packages have been exposed to the proper temperature in the sterilizer. Remember that temperature is only one of three parameters necessary for sterilization to occur. The others are time and pressure.

Another device that the CDC recommends is a chemical indicator/integrator that is placed inside the instrument package. This small strip indicates that the instruments have been exposed to all of the sterilization parameters. Place the strip so that it is visible from the outside of the package.

In some cases, manufacturers have begun to integrate this into the package. If the strip indicates a failure, the instruments should be repackaged and reprocessed before use. Integrator strips are an inexpensive and excellent quality-control measure.

Many sterilizer failures can occur from improper loading (overloading) of the sterilizer. These failures may be limited to individual packages and may not occur on the day that the biological monitor is run, therefore posing a possible risk to patients.

Does steam sterilization damage hinged instruments?

It was commonly believed that dry heat was the most appropriate method of sterilization for hinged instruments, since it would not cause rusting or corrosion.

A recent study, however, suggests that there is not a significant difference between dry heat and steam sterilization on hinged instruments.

Can I place curing-light tips in a heat sterilizer?

Again, always follow the manufacturer’s instructions for your equipment; however, studies show that heat sterilization is less damaging to curing-light tips than chemical sterilants and disinfectants.

Trivia question: Why is a steam sterilizer called an autoclave?

The term autoclave is French, and is derived from the Greek word auto, or automatic, and the Latin word clavis, which means key - hence the term “automatic lock,” an important feature of an autoclave. As the cycle begins, the sterilizer automatically locks shut to prevent the door from opening accidentally when the pressure rises.

I hope that you find these questions and answers helpful in your practice. If you have questions that have not been addressed here, please send them to me for future columns: [email protected].

Mary Govoni, CDA, RDH, MBA, is the owner of Clinical Dynamics, a consulting company based in Michigan. She is a member of the Organization for Safety and Asepsis Procedures and is a featured speaker on the ADA Seminar Series. She also writes a column for Dental Equipment & Materials magazine. She can be contacted at [email protected].