Synopsis of Oral and Maxillofacial Surgery (An Update Overview) Pradip K Ghosh
INDEX
×
Chapter Notes

Save Clear


Sterilization and DisinfectionONE

 
 
Sterilization and Disinfection Play Very Important Role of Any Surgical Modality
Sterilization means complete killing or removal of all living forms including endospores from an object or a location. It is an absolute term, i.e. an object is either sterile or not sterile.
Disinfection means destruction of pathogenic microorganisms only and does not necessarily include endospores or viruses.
Antiseptics means chemical disinfection of the skin, mucous membranes, or other living tissues. The agents with which this state is achieved are called antimicrobial agents.
Asepsis is the avoidance of pathogenic microorganisms. In practice, ‘aseptic technique’ is one, which aims to exclude all microorganisms. Surgical technique is aseptic in the use of sterile instruments, clothing and the ‘no touch’ technique.
Antisepsis is the procedure or application of an antiseptic solution, or an agent, which inhibits the growth of microorganisms. Examples are, scrubbing and preparation of operative site.
  1. Pattern of microbial death: A population of microorganism treated with antimicrobial agent does not die all at once; instead, they die at a constant rate. The total time required is dependent upon the initial microbial concentration (as well as the temperature and/or concentration of the chemical agent). Endospores are the most resistant forms of life.
  2. Sterilization frees an object of all forms of life. It can be achieved by using heat, radiation, filtration and chemicals.
  3. The heat used in sterilization is either moist heat such as in an autoclave or dry heat in a hot air oven.
    Autoclaves are mechanized versions of home pressure cookers. Water is boiled and the air inside the vessel is expelled by the steam. The vessel is then sealed; and, the pressure is allowed to build up. The rise of pressure causes the temperature of steam to exceed that of boiling water. Safety release valves prevent excess pressure from building up. Autoclaves are usually operated at 15 psi at 121°C for 15 minutes or at 20 psi at 134°C for 3 minutes. Boiling is not a method of sterilization because a temperature of 100°C is not high enough to kill all organisms. Autoclaves are available in many sizes, with various automatic features. Autoclaves are the best and most dependable method of sterilization and used for surgical packs, rubber materials, metallic instruments, glasswares, culture media, and any heat-resistant contaminated material. Moist heat cannot be used for sterilization of substances in sealed containers or hydrophobic substances like oils and waxes. The major drawback of moist heat is rusting of non-stainless steel instruments. Hot air ovens are usually operated at 160 to 170°C for 1 to 2 hours. Dry heat requires higher temperatures and longer times than to do usual steam sterilization, because proteins are denatured less-readily when dehydrated. Hot air ovens are used to sterilize glassware, metallic instruments, and hydrophobic substances. Microwave is not a reliable method of sterilization.
  4. Radiation: Ionizing radiation such as X-rays and gamma-rays inactivate microorganisms by reacting with their DNA. Radiation is used to sterilize pharmaceutical and disposable medical supplies.
  5. Filtration is used to sterilize heat-sensitive material in solution and gases. Membrane filters with varying pore sizes have replaced the earlier filters such as Seitz (asbestos) and Chamberland (ceramic).
  1. Ethylene oxide is an example of a chemical sterilizing agent; it is used to sterilize heat-sensitive materials such as plastic catheters, prosthetic devices and disposable medical supplies.
  2. The effectiveness of a sterilizing technique is assessed by its ability to kill the most resistant life-forms such as bacterial spores (e.g., Bacillus stearrothermophilus spores). Records of temperature, pressure and time are regularly made. Autoclave tape such as Bowie-Dick is routinely used to ensure that the autoclave is functioning properly.
  3. Disinfection is defined as removal or killing of infectious microorganisms. Disinfectants are antimicrobial agent applied to inanimate objects for disinfection. Antiseptics are chemical disinfectants used on living tissues. Disinfection is achieved by physical or chemical agents.
  4. Moist heat is the best method of disinfection. Boiling for 5 to 10 minutes kills most pathogens. Pasteurization involves heating to 60 to 80°C for 30 minutes to 30 seconds; it kills most vegetative forms of bacteria but not spores.
  5. Ultraviolet light is a form of non-ionizing radiation that is lethal to microorganism. However, it has very little penetrability, and therefore used on flat surfaces and air.
  6. There are many chemical disinfectants and antiseptics. Before we can use them properly, it is important to know about them. In general their activity is affected by the following factors:
    1. Concentration of the chemical.
    2. Length of exposure time.
    3. Temperature and pH.
    4. Number, nature and types of microorganisms.
    5. Amount of organic material present.
  7. Alcohols: Ethyl alcohol, isopropyl alcohol and methylated spirits are bactericidal but not sporicidal. They act by denaturing protein. Because proteins are not hot denatured in the absence of water, a 70 percent solution of alcohol in water better than absolute alcohol. Alcohols are often used with other disinfectants such as chlorhexidine and povidone iodine.
  8. Aldehydes: Formaldehyde and glutaraldehyde act by denaturing protein and nucleic acids. Formaldehyde is used as a 37 percent solution in water (called formalin). Glutaraldehyde is effective against bacteria, viruses and fungi. It is used to sterilize instruments such as endoscopes that cannot be autoclaved. Both are skin and eye irritant.
  9. Chlorhexidine is a bisguanide that affects bacterial cell membrane permeability, leading to leakage of intracellular materials. It is less effective against gram-negatives. It is used in combination with alcohol or detergent for antiseptic use, and is a good antiplaqe agent when used as mouthwash. It has low toxicity. Long-term oral use causes tooth staining.
  10. Halogens used as disinfectants and antiseptics include chlorine and iodine.
    Sterilization or disinfection of dental equipment
    Equipment
    Suggested treatment
    Dental hand piece
    Autoclave, ethylene oxide
    Hand instruments
    Hot air oven, autoclave
    Mirrors
    Hot air oven, autoclave
    Forceps, elevators, scalpel handles, retractors and other surgical items
    Autoclave
    Endodontic instruments
    Hot air oven, autoclave
    Gauzes, cotton wool and paper points
    Autoclave after wrapping
    Linen
    Autoclave after wrapping
    Surgery floors
    Wash daily with detergent and dry
    General working surfaces
    Wash daily with detergent and dry
    Bracket table
    Wipe with chlorhexidine in alcohol or 70 percent isopropyl alcohol between patients
    Bullk disposable syringe, gloves, mask and dressing
    Gamma radiation
    Purification of air in the operating room
    Ultraviolet rays
    3
  11. Hypochlorites act by releasing chlorine that is an oxidizing agent killing most bacteria and viruses including hepatitis B virus. It is a very effective disinfectant in hospitals and home. The main disadvantages are corrosion of metals and inactivation in the presence of organic matter.
  12. Iodine, like chlorine, it is a strong oxidizing agent and an effective antiseptic. Its drawbacks are staining, hypersensitivity and corrosion. Iodine is used either as tincture of iodine (i.e., iodine in alcohol) or as povidone iodine (i.e., iodine complex with polyvinyl-pyrrolidone).
  13. Phenols are very toxic and so only the less toxic derivatives are used. They act by damaging the cell membrane and denaturing proteins. Some well-known phenol derivatives are: Dettol (chloroxyphenols), hexachlorophene (bis-phenol), and cresol (methyl phenol).
  14. Detergents or surface-active agents act by damaging microbial cell membrances. They are generally used as cleaning agents. Benzalkonium chloride (a quaternary ammonium compound) is used as a skin antiseptic.
  15. Hydrogen peroxide is a strong oxidizing agent and used as an antiseptic to clean wounds.
  16. Tests for effectiveness of disinfectants and antiseptics. The in-use test is one of many widely-used tests. In this test, sample of the diluted disinfectant in use is examined for viable bacteria.
  17. The choice of antimicrobial agent to be used depends on many factors:
    1. Nature of the item and its intended use.
    2. The kind of microbe to be treated.
    3. The risk of cross-infection.