The key difference between dry heat sterilization and moist heat sterilization is that in moist heat sterilization, the process of sterilization is carried out through moist heat (steam) at high pressure while in dry heat sterilization, the sterilization process is undertaken in a dry condition at high temperature.
Heat is the best method for killing microorganisms because it denatures the proteins and the enzymes of the microorganisms. So sterilization is carried out by applying heat to microorganisms. The applied heat can be dry heat or moist heat. There are many differences between both methods. During moist heat sterilization, high pressure and high temperature are applied
through steam (moist heat). During dry heat sterilization, dry air which has a very high temperature is applied for a longer period of time. There is no use of water or steam in this process.
Moist heat sterilization is completed in comparatively less time because latent heat of evaporation is also present in the steam. On the contrary, dry heat sterilization is completed in comparatively longer time because dry heat is used and there is no role of water vapors. During moist heat sterilization, coagulation of the enzymes and other proteins of microorganisms takes place while during the process of dry heat sterilization, oxidation of chemical bonds and proteins takes place.
Moist heat sterilization is undertaken at high pressure while dry heat sterilization is undertaken directly at the flame. Further types of moist heat sterilization include boiling and autoclaving. While the typed of dry heat sterilization include Incarnation, hot air oven, Bunsen burner, and microwave. Advantages of moist heat sterilization are, it needs low temperature and less time. It has low cost, non-toxic and easy to control and monitor. Advantages of dry heat sterilization are, it is a nontoxic and reliable method. It has a low cost. There are no chances of rusting of instruments because they remain dry. It is not harmful to the environment.
Disadvantages of moist heat sterilization are, it cannot be performed for heat-sensitive instruments. Instruments may be rusted because they remain wet. If instruments are sterilized again and again by this method, they may be rusted. Disadvantages of dry heat sterilization include, it needs more time for sterilization. Since instruments are exposed to very high temperature, they may be damaged.
|Basis||Moist heat sterilization||Dry heat sterilization|
|Definition||It is the process of killing the microbes by steam|
|It is the process of killing the microbes by dry|
heat (directly via flame or through hot air).
|Time took||This process takes less time because latent heat of|
evaporation is also present in steam which helps in killing microbes early.
|This process takes comparatively more time.|
|The process of killing microbes||During this process, coagulation of enzymes and|
other microorganisms takes place.
|During this process, the oxidation of chemical bonds and proteins of microbes takes place.|
|Pressure required||This process is undertaken at high pressure.||This process is undertaken directly on flame or via|
|Types||Further types of moist heat sterilization are|
autoclaving and boiling.
|Further types of dry heat sterilization are Bunsen|
burner, Incineration, hot air oven, and microwave,
|Advantages||It requires low temperature. It has a low cost. It is easy to control. It is nontoxic.||It is easy to control and less expensive. No harm to the environment.|
No chances of rusting of instruments because they are not exposed to
|Disadvantages||There are chances of rusting of instruments because|
they are exposed to moisture. It cannot be performed for heat-sensitive instruments. Instruments may
be damaged if they are sterilized again and again by this process.
|It needs more time for the complete sterilization.|
Instruments may be damaged.
What is Moist Heat Sterilization?
Moist heat sterilization is a process of sterilization (killing microbes) via applying dry heat in the form of a flame or hot air. This process is carried out at high pressure, and it is completed in comparatively less time. High pressure is required for moist heat sterilization. Coagulation of the enzymes and other proteins of microbes takes place, and thus they are killed. The autoclave is an example of such type of sterilization in which high pressure in combination with a temperature less than that for dry heat sterilization is used for killing microorganisms. Usually, a temperature of 121-degree Celsius is applied while the time required is 15 minutes.
Dry heat sterilization is less expensive and easy to control. It is a nontoxic method and easy to control. Its disadvantages can be explained as heat sensitive instruments are not able to be sterilized by this method. Since instruments become wet after sterilization, they may be rusted. Beside this, instruments may be damaged due to repeated heat exposure.
What is Dry Heat Sterilization?
It is an old method to sterilize the instruments. It takes more time that moist heat sterilization. Heat can be applied in the form of hot air or direct flame. Oxidation of the chemical bonds and proteins of microorganisms takes place, and thus they are killed by applying dry heat. The temperature required is 160 to 170-degree Celsius while the time required is 1 to 2 hours. Incineration is also a type of dry heat sterilization. It is a nontoxic and reliable method. It is an economical method and easy to install. There are no chances of rusting or corrosion of the instruments because they remain dry throughout the procedure. This method is not harmful to the environment. The disadvantages of this method can be explained as; it takes more time for the sterilization process. Repeated exposure to high temperatures is not good enough for instruments.
- In the moist heat sterilization, steam (moist heat) is used for the sterilization purpose while in dry heat sterilization, dry heat in the form of a flame or hot air is used.
- Moist heat sterilization takes less time while dry heat sterilization takes more time.
- High pressure is also required for moist heat sterilization while not required for the dry type.
- In moist type sterilization, microorganisms are killed by coagulation of proteins and
enzymes while in dry type, they are killed by oxidation of bonds and proteins.
- Rusting of instruments can take place in moist sterilization while no rusting occur in dry
Moist heat sterilization and dry heat sterilization are two major types of making instruments microbes free. It is mandatory for science students to learn differences between both types. In the
above article, we learned the clear differences between moist heat sterilization and dry heat sterilization.