Chris Miller, PHD
The goal of instrument processing is to deliver sterile instruments to chairside for patient care. The various steps involved are holding, cleaning, rinsing, corrosion reduction, drying, packaging, heat-processing, cooling/drying, storage, and delivery. In addition to being rendered sterile, they must be maintained in a sterile state after heat-processing until used at chairside.
Sterilization failure occurs when the instruments do not become sterile during processing or when sterility is breached after heat-processing before use at chairside. Although a variety of events can cause sterilization failure, it is not always possible to determine in the office when sterilization failure has occurred.
For example, the sterilization process inside the sterilizer can be monitored with chemical indicators and spore tests. But we can`t actually test each instrument for the absence of all living microbes, which is what sterility really means.
Therefore, sterility assurance must be practiced. This means that instrument processing must be performed correctly by well-controlled, proven procedures. Remember that we`re seeking the very best chances for achieving and maintaining sterility for the highest level of patient protection.
The purpose of instrument cleaning is to remove as much bioburden as possible. The heat-processing step, as a result, will have the best chance of killing all remaining microbes. If tissue, blood, saliva, or dental materials are not removed, they may insulate underlying microbes from direct contact with the sterilizing agents. A holding (presoaking) solution can prevent instrument debris from drying, and it may facilitate subsequent cleaning. Ultrasonic cleaning can be very effective in removing debris. It is also much safer than hand-scrubbing since direct handling of sharps is greatly reduced.
Packaging instruments for sterilizer
Cleaned instruments are placed in functional groups or setups and packaged before being placed in the sterilizer. This eliminates direct handling after heat processing. Contamination can easily occur if the instruments are inadvertently handled when preparing setups, during storage, and distribution to chairside. So packaging provides sterility assurance by helping maintain sterility of the instruments after heat-processing.
Unpackaged instruments removed from the sterilizer have no shelf-life. Not packaging instruments before heat-processing automatically results in sterilization failure after the sterilizer door is opened.
Improperly packaged material also causes sterilization failure. The sterilizing agent (for example, steam or unsaturated chemical vapor) is prevented from penetrating and reaching the instruments inside. It is important to use packaging materials manufactured for the type of sterilizer in your office.
Do not use more than two layers of wrapping material. But cotton rolls to cover sharp points should be avoided, since this prevents contact with the sterilizing agent during heat-processing.
In addition, avoid thick cloth as a wrap. Such materials absorb water or chemical sterilants, reducing the amounts available for generation of steam or chemical vapors. Cloth tends to retain moisture after steam processing, extending the needed drying time.
Appropriate heat-sensitive chemical indicators and spore-tests are added during the packaging procedures for sterility assurance. Seal wraps and pouches securely with heat-resistant tape (autoclave tape, for example), heat sealing, or with self-sealing materials. Solid, closed containers of instruments (such as metal boxes, capped glass vials, and items wrapped with aluminum foil or water-impervious plastics) prevent the steam or chemical vapors from reaching the items inside.
Sterilization failure will also occur if the sterilizing agent (steam, hot air, or chemical vapor) does not contact all surfaces of all instruments in the chamber within the set time. With that in mind, sterility assurance demands that the sterilizing agent have access to all instrument packages. Leave a small amount of space (one-quarter inch, for example) around each package or cassette. Avoid layering packages by stacking one package upon another. Rather place them on their edges, and do not overload the chamber.
Sterility should be maintained until the heat-processed instruments are used at chairside. Sterile packages must be handled carefully (and as little as possible to avoid tearing the package). The instruments should be stored in a clean, low-dust area away from moisture and heat.
Check the integrity of each package and see if the chemical indicator on the package has changed to the proper color before use at chairside.
Chris Miller is director of Infection Control Research and Services and professor of oral biology at Indiana University.