sterlisation and disinfection

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STERILISATION AND DISINFECTION :

STERILISATION AND DISINFECTION

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Objective of sterilization –Removal of microorganisms or destroy them from materials or from areas since they cause contamination, infection and decay. In microbiology - to prevent contamination Surgery - to maintain asepsis Drug & food -for ensuring the safety

Definitions :

Definitions Sterilization – T he process by which an article, surface, or medium is freed of all living microorganisms either in the vegetative or spore state Disinfection – The destruction or removal of all pathogenic organisms, or organisms capable of giving rise to infection Sanitization - This term is sometimes used as a synonym for disinfection, particularly used with reference to food processing & catering

Definitions :

Definitions Antisepsis – used to indicate the prevention of infection, usually by inhibiting the growth of bacteria in wounds or tissues Bactericidal agents Bacteriostatic agents Cleaning Degerming

HISTORY:

HISTORY The science of microbiology has shed much light on the nature of disease. In the nineteenth century the work of Pasteur ,Lister and Koch did much to explain the role of bacteria in disease and to indicate possible methods of practicing safer medicine. LOUIS PASTEUR (1822-95) was the first scientist to show clearly that bacteria never generate spontaneously and that no growth of any kind occurs in the sterilized media. One of his many achievements was the development of the technique of controlled heating known as ‘PASTEURISATION’ for the preservation of beverages and food stuffs.

Dr. Joseph Lister (1827-1912) :

Dr. Joseph Lister ( 1827-1912) Discovered the effectiveness of 'carbolic acid,‘ which was used in controlling typhoid. Using carbolic acid, Lister was able to keep his hospital ward in Glasgow free of infection for nine months.

Carbolic acid spray being used at the time of a surgery:

Carbolic acid spray being used at the time of a surgery

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“ The Golden Age of MICROBIOLOGY” Louis Pasteur (France) Robert Koch (Germany) Oliver Wendell Holmes (USA) Lord Joseph Lister (England)

WHY STERILIZATION IS IMPORTANT IN DENTISTRY:

WHY STERILIZATION IS IMPORTANT IN DENTISTRY

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Diseases Pathogen Herpes infections Herpesvirus hominis (herpes simplex virus) Syphilis Treponema pallidum Hand-foot-mouth disease Coxsackievirus Herpangina Coxsackievirus Gonococcal pharyngitis Neisseria gonorrhoeae Candidiasis Candida albicans ORAL DISEASES

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HERPES INFECTIONS : In this disease, vesicle-type lesions can occur in the mouth. -Vesicles during active herpes simplex infections at any site of the body contain the virus which may be spread to others by direct contact with these lesions. -Also, the herpes simplex virus may be present in saliva in those with oral or lip lesions and possibly in a small percent of those who are infected but have no active lesions. -In such instances, sprays or aeorosols of the saliva may result in spread of the virus to unprotected eyes of the dental team.

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I I) HERPANGINA AND HAND-FOOT-MOUTH DISEASE : Herpangina appears as vesicles on the soft palate or elsewhere in the posterior part of the mouth that break down to ulcers that last for about a week. -Fever, sore throat and headache frequently accompany the vesicular stage. -The lesions are caused by specific types of coxackie virus .

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III) ORAL SYPHILIS . Treponema pallidum is a spirochete bacterium and is the causative agent of syphilis. About 5-10% of the cases of syphilis first occur in the mouth in the form of a lesion called a primary chancre, an open ulcer frequently on the tongue or lips. These lesions do contain the live spirochetes and may be spread by direct contact. The possibility of the spirochete entering small cuts or breaks in the skin of unprotected hands and can cause syphilis of the finger.

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IV) ORAL CANDIDIASIS : Candida albicans is a yeast that occurs in the mouth asymptomatically in about one third of adults. Such circumstances that may result in oral disease called thrush or oral candidiasis might include conditions that disturb our body defense mechanisms such as the systemic diseases of HIV infection, and leukemia; -Spread of C. albicans from a patient’s mouth to the dental team is theoretically possible through direct contact with lesions or sprays or aerosols of infected saliva.

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PREREQUISITES FOR AN IDEAL DISINFECTANT AND ROLE PLAYING FACTORS

Selection of antiseptics & disinfectants :

Selection of antiseptics & disinfectants Prerequisites It should have a wide spectrum of activity Fast acting Active in the presence of organic matter Nontoxic to animals or humans ( antiseptic ) Soluble in water It should not separate on standing Should have high penetrating power Surface compatibility Relatively inexpensive

METHODS OF MICROBIAL CONTROL:

METHODS OF MICROBIAL CONTROL Physical Agents Chemical Agents Chemotherapeutic Agents

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Physical Agents Heat Freezing Radiation Filtration Ultrasonic and SonicVibration

PHYSICAL CONTROL WITH HEAT:

PHYSICAL CONTROL WITH HEAT SUNLIGHT – Ultraviolet rays Typhoid bacilli exposed to sun on pieces of cloth were killed in 2 hours, where the controls kept in dark were alive after 6 days DRYING - 4/5 th of the bacterial cell is made-up of water

Dry heat :

Dry heat DIRECT FLAME Bunsen burner

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Incineration

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HOT AIR OVEN Radiating dry heat 160 0 C ( 320 0 F) & 2 Hours useful for sterilizing dry powders, water free oily substances, many types of glass ware such as pipettes, flasks, and syringes. Advantage – non corrosive method

Hot air oven :

Hot air oven

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Moist heat Temperatures below 100 0 C/ pasteurization Temperatures at 100 0 C/ boiling Steam at atmospheric pressure

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Pasteurization ( below 100 0 C ) Purpose – To reduce the bacterial population of a liquid such as milk Spores are not affected by pasteurization Holding method 62.9 0 C for 30 minutes Flash pasteurization – 71.6 0 C for 15sec Ultra pasteurization – 82 0 C for 3sec

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BOILING WATER (100 0 C) Less time of exposure are required Denaturation of proteins . Minimum exposure time – 30 minutes Less reliable Washing soda ( 2% conc.) may be added

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Fractional sterilization ( steam at atmospheric pressure ) Tyndallization ( John Tyndall ) Intermittent sterilization

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Free flowing steam at 100 0 C for 30 minutes on each of 3 successive days. First day - steam kills all organisms except spores, and it stimulates spores to germinate vegetative cells Second day –vegetative cells are killed Third day – kills the remaining cells

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AUTOCLAVE Moist heat In the form of pressurized steam increase in the pressure of the gas increase in the temperature As the water molecules in steam becomes more energized, their penetration increases

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Used for glassware, metal ware, blankets, intravenous solutions and a broad variety of other objects Pressure in autoclave - 15pds/sq. inch Temperature – 121.5 0 C Time – 3 to 30 min

AUTOCLAVE:

AUTOCLAVE

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Limitations Plastic ware melts in high heat sharp instruments become dull Oily substances cannot be treated Prevacuum autoclave Temperature - 132 0 C to 134 0 C Pressure – 28 to 30 lb/1n 2 Time – 4minutes Advantage – minimal exposure time for sterilization

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HOT OIL 160 0 C for 1 hour Advantages – no rusting of instruments minimal corrosion SILICON

Physical control by other methods :

Physical control by other methods

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FILTRATION ( 1980s ) filter technology – Charles Chamberland Julius petri Filter – a mechanical device used to remove microorganisms from a solution Ex; IV solutions,bacteriological media, toxoids, pharmaceuticals etc.

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Types of filters Candle filters 1.Unglazed ceramic filters Ex; Chamberland filter 2.Diatomaceous earth filters Ex; Berkefeld filter Asbestos filters Sintered glass filters Membrane filters

Membrane filter technique :

Membrane filter technique

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ULTRASONIC LIGHT Wave length Visible light is between 400 & 800nm Ultraviolet light is between 100 & 400 nm

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Mechanism of action When microorganisms are subjected to UV light linking of thymine molecules occurs Demerits; It is not effective against bacterial spores Does not penetrate liquids or solids It may cause damage to human cells

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Other types of radiation Ionizing radiation X-rays & gamma rays Both have wavelengths shorter than the UV light They force electrons out of their shells, thereby creating ions

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Microwave - Wave length is longer than that of UV light - Molecules are set into a high speed motion Laser beam L ight A mplification by S timulated E mission of R adiation

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ULTRASONIC VIBRATIONS High frequency sound waves beyond the range of the human ear ‘Cold boiling’ They cause the formation of bubbles or cavities and the water appears to boil - cavitation Demerits Not very effective Liquid is required

Chemical control of microorganisms:

Chemical control of microorganisms

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Chemical Agents Agents that damage cell membrane Agents that denatures protein Agents that modify the functional group of protein & nucleic acid

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Destroys structural integrity of cell membrane (protein & lipids). Net effect is the release of small metabolites from the cell that interferes with the active transport and energy metabolism. Agents that damage cell membrane

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Agents: Surface active agents Cationic – most effective Anionic Non-ionic – not effective Amphoteric Phenolic compound Alcohol

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Cationic Agents Quarternary ammonium compound Bactericidal for a wide range of organisms, gram (+) species are more susceptible Used primarily in hand or face washes Acts on phospholipids, changes cell permeability. Include in disinfecting instruments and preserving drugs in low concentration form.

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Anionic Agents Soaps and fatty acid dissociate to yield negatively charged ions (active at acid Ph). Causes gross disruption of the lipoprotein framework of the cell wall. Displays rapid bactericidal action (within 30secs) . Effective against gram (+) organisms.

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Biguanides - Antimicrobial activity against vegetative bacteria, yeasts, and enveloped viruses . - Disrupts cytoplasmic membrane. - It may be used together with surface active agents.

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Chlorhexidine which is more effective at pH 7 – 8 Used as a safe antiseptic to prevent body infection , in oral rinses for treating sore gums, mouth ulcers and preventing plaque on teeth.

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II Phenolic compound - At low concentration, causes leakage of cell contents and irreversible inactivation of membrane-bound oxidases and dehydrogenases . - Parent compound : Carbolic acid ( phenol ) Excellent for disinfecting faeces , blood, pus, sputum & other proteinaceous material.

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Primarily used for testing new bactericidal agent Cresols Xylenols Phenolics are effective against bacteria, fungi and viruses.

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Kills 99.9% of germs in 30 seconds Hospital disinfectant deodorant is highly effective against TB, and HIV-1 It is tuberculocidal , virucidal, fungicidal, bactericidal

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Diphenyl compound Exhibits unique antibacterial property. Hexachlorophene Topical anti-infective, anti-bacterial agent, often used in soaps, toothpaste and antiperspirant . Used as a preservative in cosmetic products.

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III. Alcohol Disorganizes lipid structure by penetrating into the hydrocarbon region, denatures proteins. Optimal activity best at 70% - 75% .

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Effective against vegetative bacteria, fungi and viruses . Sporicidal activity Disinfects work surfaces and, as antiseptics on skin.

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Ethanol / Ethyl alcohol - Used as skin disinfectant. Uses: Sterilizes skin before cutaneous injections. Disinfects thermometers. Most effective at 50-70% Effective against gram (+) , gram (-) bacteria.

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Isopropyl alcohol - Most effective at 50-70% Recommended as replacement for the sterilization of thermometers Necrosis may result from absorption of vapours through the lungs during alcohol sponge bath.

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Acid & alkalies – Benzoic acid Lactic acid Acetic acid Propionic acid 2. Alcohol 3. Acetone Agents that denature Proteins

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Agents: Heavy metals Oxidizing agents Dyes Alkylating agents Agents that Modify the Functional Group of Proteins and Nucleic Acid

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Heavy Metals Mercurials Mercuric chloride – very toxic disinfectant, not used today. Metaphen , Merthiolate , Mercuchrome . Silver compounds Soluble silver salts or as colloidal preparations. Silver nitrate – highly bactericidal for gonococci. Silver sulfadiazine – topical cream for burn patients .

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Oxidizing agent Halogens (1) Iodine - As I 2 at pH value below 6 where maximal bactericidal action takes place. - D estroys many microorganisms and viruses within 3-5 minutes . - S trong smell and can stain skin and clothing. - Skin irritant .

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Betadine Solution - Iod o phores - E nhance s stability - Povidone –iodine Available in "Swab Aid" pads, Swab Sticks and as a Surgical Scrub. It is a fast-acting, broad-spectrum antiseptic . Indicated for degerming skin, wounds and mucous membranes. - wide ly use in hospitals, sanitation and water purifi cation .

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(2) chlorine - Hypochlorite, inorganic ,inorganic chloramines. - The active moiety of hypochlorites and chlorine is hypochlorous acid. - Water disinfectant Hypochlorites - most useful of the chlorine compound

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Hydrogen peroxide It is a weak acid. Used in the cleansing of wounds. It has strong oxidizing properties and is therefore a powerful bleaching agent that is mostly used for bleaching paper.

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Dyes Triphenyl methane dyes Crystal violet, Malachite green, Brilliant green Highly selective for gram (+) organisms Used in the laboratory in the formulation of selective culture media Acidine dyes Often referred as Flavines ( proflavine , acriflavine ) . Exerts a bactericidal and bacteriostatic effect. Used in wound antisepsis.

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Alkylating agent Glutaraldehydes and formaldehydes . Active against bacteria and their spores, viruses, fungi and protozoa. These effects are mediated predominantly via amine, sulfurhydryl and carboxyl groups on microbial surface proteins.

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Formaldehyde:- Aqueous solution containing 37% formaldehyde (Formalin) Paraformaldehyde a poymer (contain 91-99% formaldehde ) Formalin - used for preserving fresh tissues when used in high concentration, it destroys all organisms, including spores.

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Used to inactivate virus in the preparation of vaccines. As a gas – used to decontaminate rooms, buildings, fabrics, and instruments..

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Glutaraldehyde used as “cold sterilant” for surgical instruments 10x more effective than formaldehyde as a bactericidal and sporocidal agent and less toxic. Ethylene oxide Employed in gaseous sterilization, especially on materials that would be damaged by heat (polyethylene tubings, drugs). Active against all types of bacteria, including spores & TB bacilli. f

Causes of sterilization failure :

Causes of sterilization failure Improper loading of sterilization chamber Improper packing Improper timing improper temperature Improper cleaning of items to be sterilized.

CONCLUSION:

CONCLUSION IT IS OUR MOST IMPORTANT DUTY TO PRESERVE AND MAINTAIN THE HEALTH OF OUR PATIENTS AND OURSELVES. WE AND OUR PATIENTS ARE AT ALARMINGLY HIGH RISK OF GETTING INFECTED BY DANGEROUS DISEASES LIKE Hepatitis-B, TB, Herpes, HIV ETC. TO PREVENT ALL THESE DEADLY DISEASES AND TO PROTECT OURSELF WE SHOULD TAKE ATMOST PRECAUTION BY FOLLOWING STRICT STERILISATION AND DISINFECTION PROCEDURES.

References :

References Text book of microbiology -R.Ananthnarayan & C.K.J.Paniker Infection control & office safety - DCNA ( 1991 April ) Infection control - C.H.Miller Fundamentals of microbiology - Edward Alcamo Microbiology - W.K.Joklik & H.P.Willett

References :

References Robert.G.cash.- Trends in sterilization procedures and disinfection procedures in orthodontic offices – AJODO ;1990.Vol.98 Gerald.E.Smith -Glass bead sterilization of orthodontic bands –AJODO; Sept 1986 W.F.Hohlt, C.H. Miller - Sterilization of orthodontic instruments in cassettes - AJODO; Nov 1990 G.M.Mccarthy A.H.Mamandras - Infection control in the orthodontic office in Canada - AJODO Sept.1997

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Thank you

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