Biological indicators (BIs) are the only definitive method of demonstrating sterilization as they show if actual microbial life has been destroyed. Biological indicators are either strips or ampoules that contain a large, known quantity of the highly resistant spore Geobacillus stearothermophilus for steam and chemical vapor sterilization or Bacillus atrophaues for dry heat and ethylene oxide sterilization. Biological monitoring of a sterilizer should be performed at least weekly. The BIs should be placed in the center of the largest, most difficult pack to be sterilized. The pack is placed horizontally in the lower front portion of the sterilizer chamber to create the greatest challenge.
After being subjected to the sterilization process, BIs must be incubated or processed according to the BI manufacturer’s instructions. If a processed BI shows a positive result, the sterilizer should be retested and products should be recalled if possible. The sterilizer in question should not be used until the cause of the sterilization failure is determined, corrected, and testing has been performed to validate the sterilizer efficacy.
Chemical indicators show that the package has been exposed to the physical conditions within a sterilizer; they do not prove that sterilization has taken place. There are several types of chemical indicators available. Each type is meant to monitor specific parameters such as time, temperature, and/or the presence of steam or gas. There are external chemical indicators which are placed on the outside of the package and should be checked after the sterilization process.
There are internal chemical indicators which are placed within the package in an area that is least accessible to the sterilant and should be checked at point-of-use. If parameters are not met, the product should NOT be considered sterile and should be reprocessed before use. A special type of chemical indicator, called a chemical integrator measures time, steam, and temperature. Chemical indicators are best when used with every load or at least once daily. Follow the chemical indicator manufacturer’s instructions for interpretation of results.
Mechanical monitoring includes temperature gauges, pressure gauges, and recording charts (i.e., round charts and computer driven printouts found on larger and newer sterilizing units). Checking temperature and pressure will help determine if the proper cycle parameters are being met, and will alert the operator if a malfunction occurs. Mechanical monitoring measures specific parameters at certain points in the sterilizer chamber and does not indicate that actual sterilization has taken place.
It is vital to the safety of your employees and patients that you properly monitor the sterilization process in your practice. It is imperative to monitor your sterilizer to reduce the risk of cross contamination. It is important to mechanically monitor your sterilizer during every cycle, paying close attention to all gauges and printouts and following the manufacturer’s recommendations.
At least once daily (preferably with every sterilizer cycle), it is recommended that chemical indicators/integrators are used to monitor the main parameters of the sterilization cycle including time, steam, and temperature. Biological monitoring should also be performed to determine sterilization. Biological indicators are the only method of demonstrating sterilization, as the results show if actual microbial life has been destroyed.
Biological monitoring is recommended on a weekly basis by the CDC, ADA, OSAP, and AAMI. A majority of state dental boards require weekly biological monitoring (see our regulations map). Chemical and mechanical monitoring should be done with each load.
The most frequent reason for sterilization failure is operator error. It is critical that specific procedures and techniques be clearly defined and followed to aid the overall quality assurance program. The proper training of employees in sterilizer operation and sterilization procedures can result in more effective sterilization.
It is recommended to review all sterilization protocol and follow procedures recommended by the CDC. Please send us another test immediately.
Another necessary step to reduce your exposure to liability is accurate record keeping. It is important to keep accurate records regarding the phases of sterilizer monitoring. Inspectors may request to see your records to see that mechanical, chemical and biological monitoring is being properly performed and recorded. Should a situation arise and litigation become necessary, accurate records will protect you and your practice.
Maintenance recording should include:
- Date of service
- Reason for maintenance
- Model and serial number of sterilizer
- Name of person requesting service
- Description of service
- Types and parts replaced
- Signature of service technician
- Date for retesting
- Retesting results
Sterilization is the process of destroying forms of microbial life including infectious bacteria, viruses, yeasts, molds and bacterial spores. The efficacy of sterilization processes can be easily monitored to assure that medical devices are free from pathogenic organisms and are safe for use in the medical and dental office. Sterilization is a statistical process which can provide a high level of confidence that all infectious organisms have been destroyed. Sterilization should not be confused with disinfection, which does not kill spores.
Disinfection is the process of destroying disease-causing microorganisms. It does not assure destruction of bacterial spores. Disinfection is usually achieved through the use of a chemical agent. There are a variety of chemical disinfectants available and each is designed to destroy a specific group of microorganisms. The product label of the chemical disinfecting agents should be consulted and strictly followed regarding range of microbial efficacy, concentration required, contact time and temperature, storage conditions, and shelf life.
Sterilization provides the greatest margin of safety and therefore, must be used in conjunction with disinfection. The disinfection process should be performed with strict controls and only when it is impossible to sterilize. The CDC and ADA guidelines specify that surgical and other instruments that normally penetrate soft tissue and/or bone should be sterilized before each use. They also specify that dental hand pieces should be sterilized after use with each patient. Follow the manufacturer’s instructions for cleaning and rinsing methods prior to sterilization or disinfection.
There are four primary sterilization methods used in healthcare settings:
- Steam (autoclave) sterilization
- Chemical vapor sterilization
- Dry heat sterilization
- Ethylene oxide gas sterilization
Each of these methods, when used properly, will achieve sterilization. Effective sterilization is dependent upon the ability of the sterilant (e.g., saturated steam, heat or gas) to have direct contact with all surfaces of the device or product being sterilized, for a specified time at a set temperature. Proper techniques in cleaning, preparation, packaging, and placement of supplies in the sterilizer chamber are critical for successful sterilant contact.
Moist heat in the form of saturated steam under pressure is the sterilant used in the steam sterilizer (autoclave). Steam sterilization is the least time consuming, and the preferred, method of sterilization for heat and moisture stable medical devices. In steam sterilization it is important that the ambient air in the chamber and contents be completely removed at the beginning of the cycle so that the saturated steam can have direct contact with the items being sterilized. There are three main types of steam sterilization cycles: gravity, pre-vacuum, and flash.
In the gravity cycle, air is displaced by steam entering the chamber. In the pre-vacuum cycle, air is removed very quickly by mechanical means. The flash cycle is for quickly sterilizing unwrapped medical devices that are to be used immediately after sterilization. The flash cycle can use either gravity or prevacuum air removal. Flash sterilization is intended only for emergencies where an instrument is needed immediately (e.g. dropped instrument). It is not intended as a primary method of sterilization.
Unsaturated chemical vapor (a mixture of alcohol, water, ketones, and formaldehyde heated under pressure) is a typical sterilant used in this method of sterilization. Because of the low moisture content of unsaturated chemical vapor, it will not cause rust and corrosion on carbon steel instruments. Chemical vapor sterilization requires proper ventilation for post-cycling fumes. Formaldehyde has been shown to be a carcinogen; therefore, as with all chemicals employed in your practice, users must follow strict OSHA standards to protect employees and patients from exposure.
Hot air is the sterilant used in the dry heat sterilizer (hot air oven). It is a slow process because it depends upon higher temperatures to incinerate microorganisms. This method of sterilization is used for heat-stable, moisture-sensitive, or steam impermeable medical devices and products. The Cox dry heat sterilizer is a rapid cycle dry heat sterilizer and is typically run for six minutes at 375°