Importance of Autoclave in the field of Dentistry

The autoclave was invented by ancient greeks who used boiling water to sterilize the medical tools. The modern autoclave was invented by Pasteur’s collaborator Charles Chamberland in the 1880s. However, the process had started early in 1679.


Autoclave carries out the function of sterilizing dental instruments with the help of steam and pressure with a very high temperature which makes it impossible for any microorganism to survive. It breaks the proteins of the cell wall of the microorganisms.


Autoclave works on the principle of “Pressure is directly proportional to temperature.”


When the autoclave is switched on the steam is pushed into the chamber containing the items to be sterilized. Autoclaves generally increase the temperature until 121° C. The temperature and pressure remain the same for almost 15 minutes. This temperature is long enough to kill the micro-organisms.

Mechanism of Autoclave:

When the autoclave is locked or sealed all the air is taken out with a vacuum pump. Then the steam is pumped in with high pressure so it reaches the temperature of 121-141° C. Once the desired temperature is reached the thermostats start the timer. The steam pumping continues for 3 minutes minimum and 15-20 minutes maximum. Generally, high temperature means a shorter time. Sterilization depends on various factors like how much contaminated the equipment is and how much the autoclave is loaded. It also depends upon whether the steam is able to move and circulate freely or not as it makes autoclaving quicker and effective.

Types of Autoclave:

There are two types of autoclave, N Class, and B Class


N Class Autoclave is also known as Gravity Autoclave i.e. gravity displacement autoclaving. Gravity Autoclave is the most commonly used autoclaves because of its simplicity and lack of dependency on peripheral mechanisms to displace ambient air with steam prior to the beginning of the cycle. “N” in N Class Autoclave stands for Naked or Unwrapped solid instruments. The sterilization point of the autoclave is 121°C - 134°C. The autoclave lasts for fifteen minutes at 121°C for delicate instruments like plastics, for other hard items the autoclave temperature is 134°C.


In N class autoclave, when sterilization is done, the pressure has to be released physically after the exhaustion stage followed by the drying stage. 


B Class/Pre-Vacuum Autoclave also known as Vacuum Autoclaves allows deeper sterilization of the content as it evacuates air completely by using a vacuum pump to almost 99% before the temperature and pressure reaches to the necessary point. It allows the high temperature to penetrate and sterilize that are normally occupied by ambient air. These autoclaves are more efficient in sterilizing equipment or parts of equipment where it is hard to reach. The sterilization occurs with moist air known as “dry cycle”. While using a B class autoclave, packed items can be sterilized and porous instruments and hollow items can be sterilized as well.


B Class Autoclave is chosen above the N Class Autoclave mostly.   


B Class Autoclaves have 3 dry cycles of the time span between 1min-6mins. Although B Class Autoclaves are smaller in sizes as compared to others but have high efficiency, flexibility, and better safety standards. With B Class Autoclaves the sterilization can be done when with the pouches, textiles or fabrics.


Working of Autoclave:

The working procedure of the autoclave is the same for all sizes. However, there are various steps involved in between the locking of the chamber to the displacement of air with the replacement of steam. The autoclave starts sterilization once the temperature, time and pressure shoot up to the desired level. The following procedure involved in between is as follows:


  • When the steam flows between the sterilizer while displacing the air as the temperature, the pressure reaches for the desired flow is known as Purge Phase.


  • After the purge phase is successfully attained, there comes the Exposure Phase, where the exhaust valve is closed in order to reach the desired point of temperature and pressure until the desired time.


  • Once the sterilization point is attained and the desired time is taken, the pressure is released from the chamber known as Exhaustion Phase. However, the contents of the chamber are hot and one has to be careful about it.


The following is the sterilization process that makes everything disinfected and safe for use. We never know where and how we would have sterilized instruments if science would have not reached this level of expertise. 


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