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  2. 2. Microorganisms are present all around us may be in active. Suppressive from since they cause contamination, infection and decay. H became necessary to remove or destroy them from the materials or the related areas. So this is the main objective of sterilization. In our daily routine practice we are paying very less attention towards sterilization and disinfection as a result of which treatment provided to the patient can be a failure. So in a country like India with a huge population and demand for health service it is important to follow strict sterilization and disinfection procedures in dentistry to prevent spread of infections. II. DEFINITION : Sterilization is a process by which actives surface or medium are freed of all microorganisms of both in vegetative or spore state. Disinfection : Destruction of pathogenic organism but not necessarily resistant spores. Antiseptic : Chemical disinfectant which are safely applied to the skin or mucous membrane and used to prevent infection. Disinfectant : Reserved – Gr. germicides which are too corrosive or toxic to be applied on tissues but which are suitable for application on objects or articles by inhibitions the growth. III. CLASSIFICATION OF INSTRUMENTS TO BE STERILIZED :
  3. 3. A) CRITICAL : • Surgical and other instruments used to penetrate soft tissue and bone. eg: Surgical burs, elevators forceps, scalpel scaling instruments sutures, needles. B) SEMI CRITICAL : • Instruments that do not penetrate soft tissue or bone but contact oral tissue. Eg: mirror, amalgam carries, plastic instruments tweezer. C) NON CRITICAL : • Do not come in contact with body fluids. Eg: medicament tars, cavity liners, restorative material light switches, drawer pulls on cabinets. IV. PROCEDURE BEFORE STERILIZATION : 1) Grouping and presoaking of contaminated instruments. 2) Pre sterilization cleaning. 3) Packing and sealing of instruments. • Grouping and presoaking of contaminated instruments. Instruments should be grouped according to their use, (eg: amalgam set, composite set) banded together and presoaked together. Presoaking prevents blood to adverse into instrument surface and easily removed by cleaning process. • Pre sterilization cleaning - After soaking, instruments should be cleaned. Cleaning is performed by scrubbing with soap and H2O or ultrasonic cleaning.
  4. 4. • Packing and sealing of instruments. Instruments should be properly packed and before sterilization packing protects the instruments after sterilization and before use at chair side. Packing materials used are sealing paper, plastic pouches, bags and tubing. Selection of packaging materials for various sterilization methods : Packaging material Moist heat Paper, plastic pouches paper thin cloth, nylon type Dry heat Nylon plastic tubes some sterilization paper. Chemiclave Plastic pouches of some sterilization paper. V. Rate of killing of microorganisms : Rate of killing is defined by relationship. N  no. of survivors is inversely proportional to the conc. and time of the sterilizing agent. CT  referred as dose. Relationship is usually stated in turns of survivors because they are reassured by colony formation. VI. Classification : A) Moist heat sterilization. B) Dry heat sterilization C) Chemical sterilization. Sterilization is also classified as N α 1 CT Chemical agents Alcohols Aldehydes Malogens Phenols Gases Ethylene oxide BPL beta propio lactone Physical agents Sunlight Drying Dry heat (flaming, incineration hot air oven) Moist heat (pasteurization, boiling, steam under normal pressure, steam under pressure) Filtration (candles, asbestos filters membranes) Radiation Ultrasonic and sonic vibrations.
  5. 5. Sunlight : • Bactericidal activity. • Germicidal activity because of U V rays + heat. Studies have shown that in India, typed bacilli exposed to sun on pieces of white drill cloth were killed in 2 hours where as controls kept in dark room were still alive after 6 days. Drying : • Moisture is essential for the growth of bacteria 4/5th by wt of bacterial cell consists of H2O drying in air is ∴deleterious effects on many bacteria. • Un reliable method. • Spores are unaffected by drying. Heat : • Dry • Moist
  6. 6. • Heat is the most reliable method of sterilization and should be method of choice unless contraindicated. Killing by dry heat is due to • Protein denaturation • Oxidative damage • Toxic effects of elevated of electrolytes. Dry heat (Flaming) : Inoculated loops wires point of forceps and scaring spatulas are held in Bunsen flame till they become red hot in order to be sterilized. • If the loops contain infective proteinacious material they should be first dipped in chemical disinfectant before flaming to prevent spattering. • Scalpel, needles, mouth of cultures tubes, glass slides cover slips etc are passel few times over the flame without allowing them to become red hot. • Bacteria are destroyed by this method. Incineration : Excellent method for destroying materials such as soiled dressings, animal carcasses, bedding and pathological material. Hot air oven : Dry heat sterilization at 1600 C. • Have heated members that allows air to circulate by gravity flow. • Hot air is bad conductor of heat and penetrating power is low. Individual instrument must be heated at 1600 C for 1 hour for effective sterilization. Time reavised depends upon  o Oven size o Size of load
  7. 7. o How instruments are packed. • Instruments packets must be placed atleast 1 cm apart to allow heated air to circulate. If packed together without spacing  ineffective sterilization. Disadvantage : • Time consuming procedure. • High temp may damage rubber and plastic goods. • Heavy load, crowding of packs can easily defect sterilization. Advantages : Carbon steel instruments and burs do not rust, collude, or lose their tamper or witting edge if they are died before procedure. To over come this lengthy time procedure, RHTS Cox manufacturing has introduced rapid heat transfer sterilizer (short cyclic high temp dry heat over). Operated at 1900 C  packed instruments 12min un wrapped instruments 6min. MOIST HEAT : Action is by • Protein denaturation. • Coagulation of protein. Advantage of steam lies in the blatant heat liberated when it condenses on a cooler surface raising the temp of that surfaces. • In cases of spores  steam condenses on the spores and kill them by hydrolysis and breakdown of bacterial protein. Temp below 1000 C :
  8. 8. Pasteurization  630 C for 30min (holder method) or 720 C for 15-20 sec (flash forces) following by cooling quickly to 130 C by this process all non spacing pathogens such as mycobacterium brucella and salmonella are destroyed. Vaccine bath  bacterial vaccine  are sterilized at 600 C for 1 hour. Inspissator  80 – 850 C for 30min Iowenstein Jensens and coeffies serum are rendered sterile for 3 successive days in an inspissator. Most heat resistant cells are the spore of clostridium botulinum – require 1200 C for 4min. Temperature at 1000 C (Boiling)  (10 – 30 min) • Vegetative bacteria are killed almost at 900 C – 1000 C but sporing bacteria require considerable periods of boiling. • Boiling is not recommended for surgical instruments. • Hard water should not be used Hard water soft water • Lid should not be opened during this period. Steam at atmospheric pressure 1000 C : • Used for sterilize culture media which may decompose if subjected to increase temperature. • Koch or Arnol steamer is usually used. Steam at normal atmosphericpressure 1000 C  90 min. For media containing sugar or gelatin on exposure of 1000 C for 20 min for 3 successive days is used – this is known as. Tyndallization or intermittent sterilization : adding 2% NaH CO3
  9. 9. The principle is first exposure kills all gram –ve bacteria and spares present will germinate in favourable medium and are killed in subsequent occasion. STEAM UNDER PRESSURE (AUTOCLAVE) : Temp. 12,0c. Pressure - 15-16 per square, inch. Time - 15 – 20 min Disadvantage : • Carbon steel instruments cannot be sterilized results in rusting corrodes or dulling. • Certain plastics and rubber are sensitive to heat and moisture cannot be placed in autoclave. • Steam appears to corrode steel neck and shank portion of diamond instruments and carbide burs. Advantages : Most rapid and effective method for sterilizing cloth surgical packs and towel packs. Sterilization of burs in autoclaves : For autoclave sterilization burs can be protected by keeping them submerged in a small amount of 2% sodium nitrite 50% preparation – Rotagerm of sodium nitrite crystals to 1 litre of H2O). After ultrasonic cleaning burs can be rinsed and placed in metal or glass beaker with a perforated lid. Fill the beaker with sufficient fresh nitrite sol. to have it above the burs approx. 1cm place the container of burs and fluid into the sterilizer and operate a normal sterilization cycle. Then discord the fluid from the container through perforated lid. Use store forcep to place
  10. 10. the burs into bur holder. Store the burs dry. Any nitrite residue can be wiped or rinsed off with clean or sterile H2O if desired. Advantages of moist heat over dry heat : • Moist heat kills organisms and spores at lower temp and lower time. • Penetrating power is more for moist heat than dry heat. Filtration : Useful for antibiotic solutions, sera, carbohydrate solution,etc. Draw back: viruses and mycoplasma may pass through Types used: • Earthen-ware candles, ex: berkfeld, chamberland. • Asbestos disc filter, ex: seitz. • Sintered glass filters. • Collodion or membranous filter. RADIATION : • Ionizing radiation (x-rays, x-rays cosmic rays). • Non – ionizing radiation (infra red, U.V rays). Ionizing rays : • Lethal to DNA high penetration power. • Used to sterilize plastic syringes latherers rubbers. Nonionizing : • Infra red rapid moss sterilization of syringes. • UV-rays  Operation rooms entry way virus laboratories hospital wards. ULTRASONIC AND SONIC VIBRATION :
  11. 11. • Results are not good because microorganisms still survive after the ultrasonic and sonic vibration sterilization procedures. CHEMICAL VAPOUR STERILIZATION (CHEMICLAVE ): This method is based on the factors of heat, water and chemical synergism. • Chemicals include alcohols, formaldehyde. • The water content is below the 15% level, above which rust, corrosion dullness of metal occur. Composition of heat + chemicals is much kinder to metal surfaces than other tech. Temperature 1310 C and 20 pounds pressure for 20min. Advantages : Carbon steel and corrosion sensitive burs, instruments, and pliers are sterilized. Disadvantages : Odor is released when chemical are heated. Periodontal, Restorative and Endodontic Instruments Carbon steel Instruments and Burs VII. STERILIZATION MONITORING : Autoclave (OR) Chemical vapor pressure sterilizer Dry heat (OR) Chemical vapor pressure
  12. 12. A) Physical monitoring : Refers to periodic observation of displays or gauges on the sterilizer during cycle o ensure sterilization process. A) Chemical monitoring B) Biologic monitoring Chemical monitoring  Heat sensitive chemical indicators (those that change color after exposure to heat). Two types of chemical used. Biologic monitoring  is the only dependent method to determine sterility. Those monitors are composed of strips of paper with live, resistant spore which should be killed if properly sterilized. • Should be done weekly. • Spore types used for evaluating sterilization spore type used. Autoclave Chemical vapor Dry heat Etox IX. PROCEDURE AFTER STERILIZATION : Process indicator paper T.S, T strips (time, steam temp.) Bacillus Staerothermophilus Bacillus Subtilis
  13. 13. Drying and cooling of instrument : Instrument sterilized by moist heat are allowed to dry before handling. Cooling of warm packages must be done slowly and warm packs should not be transferred to cool surfaces or placed under air conditioning units. • Use of fans to cool down the warm instrument is not recommended because it can cause undue circulation of potentially contaminated air around the packs. Storage : After sterilization – they should be kept in a cool dry protected area, above the floor a few inches away from walls and ceilings , away from sinks and heat sources. X. DISINFECTION : It is a lethal process to kill disease producing microorganisms but not bacterial spores. • Process of disinfecting instruments, equipments by using a liquid chemical germicides is called cold sterilization. Time period according to environmental protection agency (EPA) is 10 hours. • After immuring the instruments for a holding period than they should be rinsed with sterile water and thin drying should be done. Mechanism of action : • Protoplasmic poision. • Damages the microbial cell membrane resulting in loss of vital cell constituents. • Glutaraldehyde and formaldehyde appear to seal or fix cell membrane and thereby block the progress of cellular component thus killing of organisms.
  14. 14. • Halogens by oxidizing agents. Ideal properties : - Should have wide spectrum of action. - Speedy action - High penetrating power should be stable. - Not corrode metals. - Not to toxic if absorbed in the circulating system. - Not to interfere with healing. Alcohols : Not accepted by ADA for disinfection of instruments. Aldehydes : Disinfection occurs in 10-30min various types of preparations are capable of sterilization. 2% acidic  600 C for 1 hour. 2% alkaline  room temp for 10 hours. 2% alkaline with phenolic buffer  room temp for 6.7 5 hours. 2% neutral  room temp for 10 hours. Glutasaldehydes are generally not recommended for sterilization because of instability of activated solutions. Disadvantage by the use of glutaraldehyde • Vaportoxicity • Hand and eye irritation • Expense Chlorinedioxide : • Used to disinfect instruments and operatory surfaces in 1-3 min.
  15. 15. • Solution reavires no rinsing and leaves no reside after use. • Solution can sterilize items in 6 hours at rooms temp. Advantages  non toxic disadvantages – corrosion non sensitive non irritating NaOCl : • Suitable surface disinfection other than instrument sterilization. Divtions 1:1 to 1:5 are recommended disinfection time 3-3.0 minutes • Virucidal, bactericidal, tubercolocidal. Disadvantage, corrosive un pleasant older Iodophors : broad spectrum disinfectant including HBV, M tuberculosis, Poliovirus, Herpes Simplex virus. Advantage : slow release of elemental iodine to enhance bactericidal activity. • Hard H2O inactivates iodophor. • Biocidal activity occurs within 30 min. when iodophor solution is fresh it will be amber color as age of solution advances it changes to light yellow indicating loss of lodophor molecule. • Iodophor solely disinfectant Sporicidal capabilities absent. Disinfection techniques : A) Immersion disinfection B) Surface disinfection C) Decontamination of dental unit – Check values have been recommended to fervent aspiration of infective materials into hand pieces of H2O lines. • The center for disease control recommends that hand pieces be flushed 20 – 30 sec. Between patient and several minutes at the
  16. 16. beginning of each day to redvice and over night bacterial accumulation in the units. GASES : Formaldehyde gases : • Used for fumigation of operation theaters after sealing the windows and other outlets formaldehyde gas is generated by adding 150 gm of kmno4 to 280 ml of formation. The reaction produces heat. There heat resistant vessels should be used. • After fumigation door are left unopened for 48 hours. • Surfaces which have been disinfected by this agent may release on irritant vapor for sometime after disinfection and this can be nullified by exposure to NH3 vapor after disinfection. Ethylene oxide : Colorless liquid, boiling point 1070 C • At normal temp and pressure it is highly penetrating pas with sweet small. • Highly inflammable and explosive so other gases are added CO2 or N2 • Used for disinfection of heart lung machines respirators. Sutures, books and clothing. INFECTION CONTROL FOR IMPRESSIONS AND RELATED REGISTRATIONS : Concepts for transporting impressions and associated registrations to a remote laboratory. • Potentially infectious material shall be placed in a container which prevents leakage during collection, handlings, processing, transport.
  17. 17. Controversy regarding transport of potentially infectious item. i) Sent it cleaned (rinsed) and undisinfected in a biohazard- labeled, heat-sealed, plastic bag or ii) Debride, clean (rinse) and adequately disinfect it place sealed transport bag. In either case most laboratories will disinfect the item to ensure protection of lab. Personal disinfecting twice is time wasted and multiple exposure to disinfectant should be avoided. The simplest and best approach is 1st one. Procedures for handing and transporting poly vinyl siloxane or rubber based impression material and any associated registrations to a remote laboratory : I.C. procedures regarding nanaqueous rubber impression and any associated registration are as follows : 1) Before the patient appointment, prepare one or more clean, strong, clear, heat sealable, bionazard labeled plastic bags of appropriate size. One for containing the scheduled impression and a separate one for any inter occlusal registration. Place bag into an open canister of suitable size so that the bags open end extends above the rim of the canister, allowing a slight folding downward outward of the bags open edge. This helps keep it open and also prevents contamination of the bags outer surface during insertion of item. 2) Remove impression from mouth were still wearing gloves. Remove any attached debris and rinse the item well with running tap H2O for 15 sec. to remove saliva and blood. 3) After rinsing and while still wearing barriers place impression into bag without touching the bags outer surface.
  18. 18. 4) Now remove gloves because they are contamina with clean hands, close the bag while touching only. The bags clean outer surface and heat seal it. 5) Tape the prescription to bag 6) Attach a note appropriately lettered to alert the laboratory that the item in the bag was debrided and rinsed but not disinfected send the bag to remote lab. Procedures for handling and transporting items for an aqueous impression material tech usually irreversible, reversible hydrocolloids and poly ether impressions : 1) Thoroughly rinse the impression under top H2O (15 sec) to remove any saliva or blood. 2) Disinfect the impression by spraying unit thoroughly soaked with a hospital level disinfectant. The product with the shortest time allows less distortion. 3) With clean hands thoroughly rinse the disinfected impression under top H2O to avoid prolonged exposure to the disinfectant % any residual disinfectant can adversely affect surface hardness or stone cast. 4) Shake excess H2O from impression and pour cast immediately. One reversible hydrocolloid manufactures [VANR] offers two alternatives to immediate pouring of impression after disinfection. i) Submerge impression into 2% potassium sulfate solution for 20 min and then remove shake off excess and pour the impression. ii) Place the impression into a humidor for upto 4 hours with no temp change remove and submerge into 2% potassium sulfate 50% for 20 min remove, shake of excess and pour the impression. 5) The cast from a disinfected impression does not need to disinfected,
  19. 19. 6) Pack the cast for shipment to remote lab. Irreversible hydrocolloid  Chlorine compounds or lodophors Poly sulfide silicone  Glutaraldehyde chlorine compounds lodophors phenolies Polyether  Chlorine compounds iodophors Reversible hydrocolloid  2% potassium sulfate XII. Handpiece surface contamination control and sterilization : Blood and saliva contaminate the surfaces of handpieces during various dental treatments irregular surfaces and especially crevices around the bur chuck are difficult to clean and disinfect. • Submersion of high speed handpiece in a high level disinfectant has not been an option by manufuact. • Scrubbing and applying disinfectant will reduce the no of bacteria but did not completely eliminate them. Only sterilization can completely bring infection control of handpiece surface. • Handpieces are semicritical instruments. • Autoclave sterilization of handpiece is one of the most rapid method. • Fiber optic dim with repeated heat sterilization apparently due to oil residue and debris baked on the ends of optical fibers. Cleaning with detergent sol and wiping ends of optics with alcohol will prolong use. Procedures for handpiece with a metal bearing turbine : • Scrub metal bearing high speed handpieces and sheath or cone of low speed handpiece at the sink with running water and detergent. • Because the handpiece and autoclave them. Procedure for handpiece with a lube free ceramic bearing turbine : • For this type of handpiece avoid using chemicals because they damage internal parts. • Fiber optics are cleaned by isopropyl alcohols.
  20. 20. • Bag and autoclave the handpiece. Chemical vapor pressure sterilization recommended for ceramic bearing handpieces. Ex: ETOX (ethylene oxide) gas is used. • Oil left in handpiece can impair sterilization in some ETOX sterilizers gas appears to penetrate high speed handpieces. Dry heat sterilization of handpiece is generally not recommended. XIII. STERILIZATION IN ENDODONTICS : • Rubber dam sterilized by – 2% benzalkonivm chloride in 50% isoprophylalcohol (OR) swabbing with H2O2 followed by tincture of iodine. • Cold sterilization of instruments is not recommended for 2 reasons. i) Process is ineffective against all variety of microorganitions. ii) Lengthy procedure. Cold sterilizing 50% is sporicidin – composition Phenol – 7.05% Sodium tetraborate Glutaraldehyde Sodium phenate • Absorbent points, broaches, files and other root canal instruments – sterilized in Hot salt sterilizer. It consists of metal cup in which table salt is kept at temp 4250 F and 4750 F silver cones broaches, reamer, files  5 sec. Absorbent point and cotton pellets  10 sec. Bring disinfection in 10min at room temp and sterilization in 6.75 hours
  21. 21. Hot salt sterilizer has superseded glass bead sterilizer and molten – metal sterilizer because metal and glass beads occasionally clung to a wet instrument, escaped detection and then clogged the root canal as instrument was instated. Advantages of Hot salt sterilizers is 1) Use of ordinary table salt. 2) Eliminates the risk of clogging the canal. Usual commercial table salt, contains a small amount (1%) of sod. Silicoaluminate, magnesium, carbonate, sod carbonate. Pure NaCl should not be used without these additives because high heat may cause fusion of the granules of salt. Glass beads may be effectively substituted for a salt in a hot salt sterilizer provided the beads are less than 1mm in diameter. Larger beads are not so effective in transfer of heat to endo instruments because larger air spaces between the beads reduce the efficacy of sterilizer. Operating temperature 4200 F to 4750 F • Hottest part of salt bath in sterilizer is along its outer rim, starting at the bottom layer of salt. Temperature is lowest in the center of the surface layer of salt. To sterilize on instrument one should immerse it at least a greater inch below the salt surface and in peripheral area of the sterilizer. Root canal instruments are immersed in not salt or gloss bead sterilized for 5 sec. (Recovers, files breaches) and for 10 sec. (absorbent points and cotton pellets). • Dappen dishes  sterilized by swabbing with tincture of thimersol followed by alcohol.
  22. 22. • Long handle instruments, tips of cotton plier blades of scissors  sterilized by dipping the working point in alcohol and flaming twice. • Root canal instruments may be sterilized by autoclave – 15,6 pressure at 120 C for 15 min. • Dry heat autoclave  may ie. Used to sterilize root canal instruments but this is time consuming because it requires an elapsed time of 2 hours for sterilization at 3200 F 1 hours for sterilization at 3400 F 30 min for sterilization at 3800 F Gutta-percha sterilized by immersion it in 5.25% NaOCl for 1min than rinse the cone with H2O2 and dry it between 2 layers of sterile gauge. • Silver cones  passing them over bunsen flame for 3 – 4 times.  Also sterilized by hot salt sterilizer 5 sec. • Pyrex glass ware  can with stand high temperature can be sterilized by autoclave or dry heat sterilization. XIV. ADVANCES IN STERILIZATION : Lasers : Sterilization of root canal by CO2, Nd:YAG, XeCl, Er:YAG is being tried. Nd:YAG is more popular because thin fiber optic delivery system is available for entering narrow root canal. • Sterilization time – 2 sec. • Lasers have bactericidal effect. MGP Gutta-percha : Medicated gutta-percha has been developed by martin and martin. • Iodoform is centrally located within gutta-percha and takes about 24 hours to leach to the surface. • Iodoform inhibit microbial growth.
  23. 23. • Iodoform remains inert until it comes in contact with tissue fluids that activates the free iodine. REFERENCES 1. EFFICACY OF CHEMICAL STERILIATION AND STORAGE CONDITIONS OF GUTTA PERCHA CONES. a. ( IEJ,34;6;SEP:2001.) 2. THE STERILIZATION OF ENDODONTIC HAND FILES. a. (JOE ;22;6;JUNE 1996.) 3. HEPATITIS B IN DENTISTRY : THE CURRENT POSITION (BRIT.DENT,1981,150,89-91.) CONCLUSION : As the saying stich oin time….saves nine goes, it is better to follow sterilization procedures and aseptic tecniques rather than to suffer from diseases or cross infection. “CLEANLYNESS IS NEXT TO GODLYNESS”