MadgeTech Blog — Steam Sterilization

3 Factors to Consider when Sterilizing Dental Instruments

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Just like any other branch in the health care industry, dentistry is held to strict guidelines set forth by the Centers for Disease Control and Prevention (CDC) and the American Dental Association (ADA). Ensuring the highest level of patient and personnel safety relies on the implementation of an infection control program.

At the center of an infection control program, outlined by the CDC, is the proper sterilization and disinfection of patient-care items and devices. This step is critical to ensure all instruments are free of hazardous bodily fluids and materials. A staple at any dental facility, an autoclave, is utilized to validate sterilization cycles are carried out according to government regulations.

As one might expect, this is a process that must be executed with enormous care, as even a slight procedural lapse can compromise patient health. This includes the regular monitoring of the autoclave to ensure it is operating as expected. According to the CDC and ADA, dental professionals should carefully check three types of indicators when validating the effectiveness of the sterilization process.


The use of indicator tapes and other types of chemical indicators can help the technician determine whether the autoclave has reached proper sterilization temperatures. An indicator tape works by changing color if sterilization conditions reach a certain threshold. If the indicator does not respond, it should be assumed that any item being sterilized during that cycle is not sterile. The use of this indicator alone is not a guarantee that sterilization was effective.


It’s important to monitor temperature, pressure, and cycle duration while validating or using an autoclave. To accomplish this, technicians typically use high-quality data loggers. In fact, there are data loggers that are specifically designed for use with autoclaves and provide reporting tools for easy data analysis and confirmation.


Finally, biological monitoring is important to root out problems with the autoclave and ensure successful sterilization cycles. According to the CDC, an autoclave used in a dental setting should be examined for biological indicators at least once a week. The technician may elect to use spore monitoring strips or resort to a “mail-in” service to check for the presence of harmful microbes.

It’s worth pointing out that, in addition to the above, a dental practice may be subject to state and local regulations that might impose further regulatory obligations. Dental professionals have a responsibility to stay current with any applicable guidelines.

Top 5 Causes of Steam Sterilization Failure

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Autoclaves are valuable tools that benefit a wide range of industries. In healthcare settings, autoclaves protect patients by eliminating pathogens from tools and equipment. In the laboratory, autoclaves provide scientists with assurance that they have eliminated biological factors that may interfere with their results. In manufacturing facilities, autoclaves are used in a variety of innovative ways to create new products and materials such as aerated concrete.  

When autoclaves don’t work properly, however, they’re not benefiting anybody. Here are some of the most common reasons that steam autoclave sterilization cycles fail:  

Choosing the Wrong Cycle for Autoclave Contents  

Nobody wants to hear that they’re the problem, but human error is at the root of many cases of sterilization failure.  

While a steam autoclave can process a variety of different objects, not all materials can be sterilized in the same manner. For example, if you are sterilizing wrapped medical tools using your autoclave’s gravity cycle, sterilizing steam may not be reaching every part of your instruments.  

If you experience a sterilization failure, begin by looking back at where you started and consider if you chose the correct cycle for the autoclave’s contents. You can learn more about which sterilization cycles are appropriate for different materials by checking out our “What Kind of Autoclave Cycle Do I Need for My Work?” post.  

Inappropriate Packing or Loading  

While some objects, such as large glassware, may go into the autoclave completely uncovered, many smaller objects must be packed or wrapped prior to sterilization. Wrapping ensures that sterilizing steam reaches all materials in an even manner.  

When a packet of materials is not wrapped correctly, though, it may interfere with your autoclave’s ability to sterilize. This is another example of how human error may be interfering with your sterilization cycle.  

Additionally, when loading the autoclave chamber, technicians should place materials based on the equipment manufacturer’s guidance. If your autoclave is not loaded the way the manufacturer intended, it may not work properly.  

Proper wrapping and loading protocols should be part of training for medical and dental assistants, sterilization engineers, laboratory technicians or any other professionals who may be responsible for preparing materials to be placed into an autoclave.  

Poor Steam Quality  

If you’re seeing wet packets and materials after a sterilization cycle, your autoclave may be suffering from poor steam quality.  

Low steam quality can be created by a variety of factors. If the “weight” (water content) of the steam is outside of desired parameters, it may interfere with the autoclave’s ability to function as designed. Superheated steam – steam heated above the point at which all liquid has vaporized – is also considered low quality for sterilization.  

To understand your steam production, it’s important to have a clear picture of both temperature and pressure within the autoclave chamber. Measurement devices, such as data loggers, are useful in creating these profiles.  

Vacuum Failure  

If you’re sterilizing small, porous or irregularly-shaped materials, you need to be using a vacuum sterilization cycle. In a vacuum cycle, all air is forcibly removed from the autoclave during preconditioning. This allows sterilizing steam to reach every nook and cranny of your contents.  

If your autoclave is not able to create adequate vacuum conditions, your sterilization cycle will fail.   The most straightforward way to learn if you have a vacuum failure is to use a Bowie-Dick test. The Bowie-Dick test is a specialized test sheet that uses steam and air barriers to validate that your autoclave is producing the proper vacuum environment for steam production and sterilization.  

To learn more about how the Bowie-Dick test is beneficial to autoclave owners, download a free copy of our Autoclave Validation Guide!

Inadequate Temperatures  

Steam sterilization simply doesn’t work without high temperatures. The specific temperature at which you will be sterilizing will depend on a variety of factors such as the materials you’re sterilizing, the nature of your work and good manufacturing or laboratory practices.  

Temperatures within the autoclave can be double-checked or validated using a temperature data logger or similar device. If your autoclave isn’t reaching 100 °C, it can’t produce steam at all! If it’s not reaching 121 °C, it isn’t reaching the threshold required for sterilization.  

Create a study of autoclave temperatures throughout your sterilization cycle to determine if you’re reaching adequate conditions for sterilization.  

Whether it’s human error or equipment malfunction, sterilization failures can cost businesses and laboratories valuable time and money. To keep this from happening to you, make sure you have an autoclave validation plan in place and train any autoclave users in proper preparation and use of the device.  

To learn more, download the free guide!

What Kind of Autoclave Cycles Does My Work Require?

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It is easy for first-time autoclave shoppers to become overwhelmed with all of the technical jargon they have to decipher and consider before purchasing a steam sterilizer. One of the most common points of confusion is how to determine which sterilization cycle is best for different applications.

Typically, there are three main types of steam sterilization cycles: gravity, vacuum and liquid. All three use high heat and pressure to sterilize, however, each cycle uses a slightly different tailored process to maximize the conditions for sterilization of certain items.


Gravity is the simplest and most common of the autoclave cycles. Like the name suggests, the cycle relies on gravity to replace air with steam. When steam is pumped into the chamber, it rises to the top because it has a lower density than air. This in turn forces the air to the bottom of the chamber, where it is completely displaced from the chamber through a drain port. Once the cycle is complete, the steam is released through the drain vent and cooling begins.

This cycle is ideal for sterilizing biohazardous waste, glassware, and certain unwrapped goods.


An autoclave designed for vacuum cycles will be configured with a vacuum system. This system begins each cycle with alternating steam injections and vacuum pulls, which work together to completely remove air from the chamber. By performing vacuum draws, air can be completely obliterated from even the hardest to reach places. The absence of air also allows the steam to penetrate the entire load rapidly, leading to a faster overall sterilization cycle.

Because of the vacuum, this cycle is ideal for bagged or wrapped loads, porous materials and packets such as pipettes or surgical instruments.


Contrary to the first two types of sterilization, the liquid cycle does not involve sterilizing with liquid, but rather,the sterilization of the liquid itself. Professionals familiar with sterilizing liquids know the dreaded phenomenon of the boil-over. This means that when a liquid is being sterilized and heated, it boils over the container, in the same way spaghetti will boil-over if not watched during cooking.

Unlike cooking spaghetti, a wooden spoon cannot be used to prevent boil-over in the chamber. During sterilization cycles, boil-over can occur if pressure is released too quickly during the exhaust phase. To help combat the risk of boil-over, the chamber pressure must be released slowly. Because of this, the cycle is sometimes referred to as the ‘slow exhaust’ method. By slowing the release of pressure, the liquid’s temperature will slowly cool off as the pressure is decreased.

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