Low-temperature sterilization technologies

1.Low-temperature sterilization technologies
 The most prominent low temperature sterilization methods is ethylene oxide (ETO) and hydrogen peroxide (H2O2) . Low temperature sterilization methods are very useful in dental clinic because many critical reusable medical devices are made of materials and components that cannot withstand the tortuous high temperature and residual moisture prevalent in today’s steam sterilization processes.


(1)Ethylene oxide:
Ethylene oxide is one of the oldest low-temperature sterilization methods. It can be used in  a wide range of equipment, such as porous materials and lumens, without the risk of corrosion. Ethylene oxide destroys microorganisms including their spores by interfering with the metabolic and reproductive processes of the cell. The process in enhance with moisture. The gas chamber is maintained at 20-40% humidity with temperature ranging from 49-60⁰. Timing of the goods depends on the following factors: concentration of ethylene oxide, temperature, humidity and the density and type of materials to be sterilized.

Fig 1:Ethylene Oxide Sterilizer 
 



(2)Hydrogen peroxide gas plasma or vapor
A hydrogen peroxide gas plasma cycle can take as few as 28 minutes, while vapor cycles run about 55 minutes. It can be used in material that cannot tolerate higt temperature and humidity including some plastic, electrical devices and corrosin-susceptible metel alloys.

Fig 2:Hydrogen peroxide Sterilizer 

More information:
1. Healthcare Infection Control Practices Advisory Committee (HICPAC)
2.WHO - Infection Control Guidelines for Transmissible Spongiform Encephalopathies
                                                                    Writte by Chang,yi-chu (Blythe)

Cleaning the dental chairs and instruments

The cleanliness of the dental unit not only leaves a good impression to the patients but also provides a hygienic ambience. Dental instruments must be cleaned and sterilized after used. Because  instruments can collect bacteria and other contaminants that could be spread to a patient if they are used without proper cleaning and treatment. They must be properly cleaned, sterilized and stored in order to prepare them for future use.




The cleanliness of the dental unit not only leaves a good impression to the patients but also provides a hygienic ambience. In a dental cabinet, the basic equipments are dental instruments, dental unit, dentist chair, and the working desk.

fig1 Cleaning dental chair

 

fig2 Use of chemical disinfectants

 

 Hygiene and safety for the patients are guaranteed thanks to thorough cleaning and sterilization activities and procedures of all equipment, instruments and devices used during patient care .All non-disposable dental instruments should be cleaned and sterilized between patients.Before any patient enters the examining room, all surfaces, such as the dental chair, dental light, instrument tray, drawer handles and countertops, are cleaned and decontaminated.

More information:
1. Healthcare Infection Control Practices Advisory Committee (HICPAC)
2.WHO - Infection Control Guidelines for Transmissible Spongiform Encephalopathies
                                                                  Writte by Chang,yi-chu (Blythe)

Steam sterilization

  Sterilization is a process that eliminates or kills all forms of microbiology includind fungi, bacteria, viruses and spore. Sterilization can be used by different method such as heat, irradiation,chemical,pressure or filtration.

1.Steam sterilization basic principle:
   Steam sterilization has been used for more than a century to destroy microbiology. Steam sterilization destroy microbiology by misture and high temperature. The basic principle of steam sterilization is to expose item to direct steam contact at the high temperature and pressure for the specified time.







2.Autoclave
   Autoclaves are widely used in microbiology , medicine , podiatry , tattooing , body piercing , veterinary science , mycology , dentistry , and prosthetics fabrication. Autoclave is a sterilizes tool through a process of heated and pressurized steam. Means to create absolute condition of total destruction of elimination of all living microorganisms.

Fig 1 Autoclave is the process design to produce a sterile state.

 

 

 

 

 

 



3.How to use autoclave


  



 
 
4.Uses of steam sterilization
   Steam sterilization can be used on all ctitical and semi-critical items that are heat and moisture stable.


More information:
1.Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008
2.WHO - Infection Control Guidelines for Transmissible Spongiform Encephalopathies
                                                    
               Writte by Chang,yi-chu (Blythe)

Factor affect the Efficacy of disinfection and sterilization?

    (1)Type of microbiology
         Sterilization is a process that eliminates all forms of microorganisms, including bacterial spores. And disinfection is a process that eliminates many kind of microorganisms, but except bacterial spores. In addition, some type of  bacteria may resistance some sterilization process or disinfection process. For example, spore-forming organisms are most resistant to sterilization.
   (2)Number of microbiology
        It is an exponential relationship between the number of microorganisms and the time taken to eliminate them. It means that the larger number of microorganisms need the more time to destroy all of them.
   (3)Location of microbiology
       If the microorganisms are in a place that the germicide cannot attend then the efficacy of the disinfection and sterilization will be compromised.
   (4) Innate resistance of microorganisms
        For example some bacterial can secrete beta-lactamase to inhibit  beta-lactam and break the  beta-lactam ring, it cause bacterial resistant  beta-lactam of antibiotic such as penicillin.
 

Fig 1 .Penicillinase:

 Beta-lactamase break the  beta-lactam ring and inhibit pencillin active.

  
(5)Biofilm
        Biofilm accumulation reduces efficacy of sterilization by impairing exposure of the sterilant to the microbial cell.

Fig 2 Biofilm resistance to antibacterial agents

   (6)Organic and inorganic matter
        Organic matter includes serum, blood, fecal and pus. Those can interfere with antimicrobial activity.  The organic matter have chemical reaction between germicide, forming a non-germicidal complex. And the organic matter protect the microorganism from germicide, acting as a physical barrier.

More information:
More information:
1. Healthcare Infection Control Practices Advisory Committee (HICPAC)
2.WHO - Infection Control Guidelines for Transmissible Spongiform Encephalopathies



                                                              Writte by Chang,yi-chu (Blythe)

Approach to Disinfection and Sterilization

1. why is this important?
Early civilizations practiced salting, smoking, pickling, drying, and exposure of food and clothing to sunlight to control microbial growth.And use of spices in cooking was to mask taste of spoiled food.  Some spices prevented spoilage.In 1804,the first steps toward sterilization was made by Nicolas Appertaining who placed the food in glass jars, sealed them with cork and sealing wax and placed them in boiling water. It has helped to reduce food borne illness and prevent food decay. In mid 1800s Semmelweiss and Lister helped developed aseptic techniques to prevent contamination of surgical wounds.Before then nosocomial infections caused death in 10% of surgeries.And up to 25% mothers delivering in hospitals died due to infection.

 Food cans use method of preserving food using heat-processing to remove microorgaisms in glass jars.

 

2. Difinition:

    (1)Sterilization: Killing or removing all forms of microbial life including endospores  in a material or an object by physical or chemical methods.
    (2)Disinfection: Decreasing the number of pathogenic microorganisms ,except bacterial spores, to the point where they no longer cause diseases. Applied to inanimate objects.
    (3)Germicide: it is an agent that kills certain microorganisms,usually pathogenic organisms. The term germicide includes both antiseptics and disinfectants.
    (4)Antiseptics: "sepsis" comes from Greek for decay or putrid,indicates bacterial contamination. Antiseptics are a type of germicide, usually  applied to living tissue.
    (5) Disinfectants: it similar antiseptics. But disinfectants are not used for skin antisepsis because they can injure skin and other tissues.

More information:
More information:
1. Healthcare Infection Control Practices Advisory Committee (HICPAC)
2.WHO - Infection Control Guidelines for Transmissible Spongiform Encephalopathies




                                                                      write by Chang,yi-chu (Blythe)