Chris Miller, PHD
Sterilization is a process designed to kill all microbes. In the dental office, sterilization mainly in-volves the heat processing of cleaned and packaged instruments through a steam autoclave, dry-heat sterilizer or unsaturated, chemical-vapor sterilizer. Also, sterilization procedures are used in some parts of the country to process certain kinds of regulated waste generated in the office before the waste is discarded.
Sterilization monitoring involves assessing the effectiveness of the sterilization process so that problems with the use or functioning of the sterilizer can be detected and corrected. This helps assure patient safety.
The three forms of sterilization monitoring are physical monitoring, chemical monitoring and biological monitoring. All three types of monitoring should be used because each provides different information.
Physical monitoring includes periodically observing sterilizers as they are being operated to see if the gauges are indicating the proper temperatures and/or pressure. It also may estimate if the cycle times appear to be correct and listen for unusual sounds that may detect a problem (hissing from a steam autoclave, for example, may suggest that it needs a new door gasket).
Biological monitoring involves demonstrating the effect of the sterilization process on live bacterial spores that are more difficult to kill than all the common disease-producing microbes. The spores are in the form of spore strips or spore vials, called spore tests or biological indicators. They are analyzed for live spores after being processed through the sterilizer.
Even though these spores are highly kill-resistant, they commonly are killed very quickly in a properly functioning sterilizer. While spore testing provides the main guarantee of sterilization, it is performed only periodically (usually weekly or monthly). And it takes from one to seven days to analyze a spore test. Thus, it is important to continue with routine physical and chemical monitoring that provide immediate results.
Chemical monitoring in dentistry involves using heat-sensitive chemicals that indicate exposure to a certain temperature, a combination of temperature and time, or the presence of steam. These chemicals change color or form after the appropriate exposure. Their reaction to the exposure can be determined (observed visually) immediately after removing the items from the sterilizer.
Process indicators - Process indicators (also referred to as through-put indicators) change color very quickly after being exposed to a certain temperature (250 degrees F, for example). Examples of process indictors include the dots, arrows or other special markings on sterilization pouches, tubing and wrap. Other examples are autoclave tape used to seal packages and strips or tabs that can be placed inside packages or cassettes being processed.
Since process indicators change color rapidly, they can indicate only that an item has been exposed to a sterilizing temperature (such as 250 degrees F) for some unknown time. They cannot indicate that the processed items are sterile.
When process indicators are on the outside of a package or wrapped cassette, they can show if the item has been processed through the sterilizer. Packages ready to be processed through a sterilizer can look just like those that already have been processed. Thus, external process indicators may be the only way to identify instrument packages that are ready to use on patients and prevent the intermingling of sterile items with nonsterile items.
In the sterilizing room, these indicators confirm to the sterilization staff which packages have been processed. They also show other staff entering the room which packages are ready for patient use.
This may be especially important if the person who normally distributes sterilized items to chairside is not available and others must retrieve these items from the instrument processing room. A mere glance at instrument packages or cassettes containing external process indicators gives dentists, hygienists, and assistants quick assurance at chairside that the setup is appropriate and that the instruments delivered have indeed been heat-processed.
Integrators - A chemical integrator (also referred to as a multi-parameter indicator) requires more than just temperature to give a color change. The temperature must be sustained for a period of time or steam must be present in addition to the appropriate temperature for the chemical change to occur.
So these indicators provide a little more information than the process indicators do. They show if combinations of time and temperature, or time, temperature, and steam have been achieved.
External chemical indicators identify the packages that have been processed and are ready for use with patients. Chemical indicators placed inside packages or cassettes (internal chemical indicators) show that the proper temperature or the sterilizing agent has penetrated the packaging material and reached the instruments.
The current ADA infection-control recommendations state that "process indicators should be used with each load." The current CDC recommendations state, "A simple and inexpensive method to confirm heat penetration to all instruments during each cycle is the use of a chemical indicator inside and in the center of either a load of unwrapped instruments or in each multiple-instrument pack; this procedure is recommended for use in all dental practices." The Office Safety and Asepsis Procedures Research Foundation recommends that "chemical indicators should be used inside of each package during every sterilizer load."
In summary, the use of chemical indicators in conjunction with physical and biological monitoring is an important part of quality control for patient safety, assuming other aspects of sterility assurance are performed.
Chris Miller is director of Infection Control Research and Services and professor of oral biology at Indiana University.