Sterilization & disinfection

sterilization

1. STERILIZATION & DISINFECTION 1

2. CONTENTS INTRODUCTION DEFINITION HISTORY STERILIZATION PROTOCOL STERILIZATION METHODS PHYSICAL (a) SUNLIGHT (b) DRYING 2

3. (c) HEAT (d) RADIATION (e) FILTRATION CHEMICAL (a)ALCOHOLS (b)ALDEHYDES (c)DYES (d)HALOGENS (e)SURFACE ACTIVE AGENTS 3

4. SPAULDING’s CLASSIFICATION STERILIZATION MONITORING CONCLUSION REFERENCES 4

5. Today is the age of modern technology coupled with medical challenges. Dental professionals are not only at risk themselves but also pose a pathway of transmission of infection. INTRODUCTION 5

6. Sterilization – A process by which surface or medium is freed of all the micro organisms either in vegetative or spore state. Disinfection- Destruction or removal of all pathogenic organisms or organisms capable of giving rise to infection. Definitions 6

7. Disinfectants are chemical solutions used to clean inanimate objects. Germicides are chemicals that can be applied to both animate (living) and inanimate objects for the purpose of eliminating pathogens. Antiseptics are formulated for application to living tissue. 7

8. Infection  is the invasion of a host organism's body tissues by disease-causing agents, their multiplication, and the reaction of host tissues to these organisms and the toxins they produce. Infectious diseases , also known as  transmissible diseases  or communicable diseases , comprise clinically evident illness (i.e., characteristic medical signs and/or symptoms of disease) resulting from the  infection , presence and growth of pathogenic biological agents in an individual host organisms 8

9. Contamination  is the presence of a minor and unwanted constituent, contaminant or impurity in a material, physical body, natural environment, workplace, etc. Asepsis  is the state of being free from disease-causing contaminants (such as bacteria, viruses, fungi, and parasites) or, preventing contact with microorganisms. 9

10. Italian physician Girolamo Fracastorious first recognized tiny living particles that cause “catching ” of disease in 1546 “the golden age of Microbiology”-mid to late 1800 lord J Lister –demonstrated boiling of instruments, washing hands & surgical linen with phenol reduces complication. HISTORY 10

11. Modern infection control recommendations & sterilization guidelines were stated by Centre for Disease Control in 1973 Comprehensive guidelin es for infection control came into effect in Dec.1991 11

12. It encompasses following steps: transport of contaminated instruments. cleaning of instruments. instrument examination & care. packaging. sterilization methods. STERILIZATION PROTOCOL 12

13. There should be a designated area for instrument reprocessing. Single use instruments should be segregated from multi use instruments. Presoaking: Keeps the instruments wet until a thorough cleaning can occur. prevents blood and saliva from drying on the instruments, facilitating actual cleaning. I)Transport of instruments 13

14. 2. Transport : Instruments transported in a tray or cassette to the designated area. Sharp instruments should be handled carefully by: Use of utility gloves. 14

15. Reduces the number of microbes present Two types- hand scrubbing 2. mechanical cleaning - ultrasonic cleaner , instrument washer. II)CLEANING 15

16. HAND CLEANING Advantage: a very effective method of removing debris Disadvantage : it requires maximum direct contact with contaminated instruments 16

17. Mechanisms of action- Ultrasonic energy produces billion of tiny bubbles in a cleaning solution that collapse and create high turbulence at the surface of instruments which dislodges the debris. Ultrasonic cleaning 17

18. safest & most efficient way to clean sharp instruments. PROCEDURE wear protective utility gloves Place the instruments in cassettes. 18

19. Sonication of loose instruments should be carried out for 8-10minutes and the period doubled(15-20 minutes) for instruments in cassettes . 19

20. Clean instruments should be dried thoroughly in order to prevent them from rusting. A rust inhibitor can also be sprayed on the instruments. Instrument to be processed through steam sterilizer should at least be shaken to remove excess water III) INSTRUMENT EXAMINATION & CARE 20

21. IV) PACKAGING Includes : paper pouches plastic pouches sterilization cassettes Packaging should allow penetration of heat , steam, chemical vapour etc 21

22. VARIOUS METHODS EMPLOYED CLASSIFICATION V) STERILIZATION METHODS CHEMICAL AGENTS PHYSICAL AGENTS 22

23. PHYSICAL AGENTS SUNLIGHT DRYING DRY HEAT MOIST HEAT RADIATION FILTRATION CHEMICAL AGENTS ALCOHOLS ALDEHYDES DYES HALOGENS PHENOLS QUARTENARY AMMONIUM COMPOUNDS SURFACE ACTIVE AGENTS GASES 23

24. PHYSICAL AGENTS 24

25. SUNLIGHT Bactericidal activity - spontaneous sterilization under natural conditions . Action - by ultraviolet rays & heat rays Sterilizing power varies 25

26. DRYING Moisture is essential for bacterial growth. 80% of body weight of bacteria is water. Drying - deleterious effect on bacteria. Viruses and spores are unaffected Unreliable method. 26

27. HEAT Heat - most reliable method & method of choice unless contraindicated. The factors influencing sterilization by heat are: Nature of heat- dry heat or moist heat. Temperature & time. Number of microorganisms present. Characteristics of the organisms. Type of material to be sterilized. 27

28. Thermal death time (TDT) is the length of time required to kill all bacteria in a liquid culture at a given temperature. Thermal death point (TDP) is the lowest temperature at which all bacteria in a liquid culture will be killed in 10 minutes. Decimal reduction time (DRT) is the length of time in which 90% of a bacterial population will be killed at a given temperature (especially useful in canning industry). APPLICATION OF HEAT 28

29. DRY HEAT 29

30. FLAMING A simple & effective method. Loops or wires, glass slides, cover slips Instruments held on a Bunsen flame till red-hot . 30

31. INCINERATION In the past, bodies of disease victims were burned to prevent spread of infection. This is an excellent method for safely destroying contaminated materials. 31

32. HOT AIR OVEN This is the most widely used method of sterilization by dry heat . Penetrating power is low, so long periods of exposure to high temperatures needed- 160˚C ( 320 ˚ F ) – 1 hr Arrange instruments to allow proper contact Fan fitted to distribute air evenly. 32

33. HOT AIR OVEN 33

34. Uses- Glasswares,forceps,scissors,scalpels,pharm-aceuticals etc. Disadvantages: Long sterilization cycle. Requires an accurate pyrometer. May damage heat sensitive plastic. 34

35. MOIST HEAT 35

36. MOIST HEAT 36

37. 1. Pasteurization – The material is heated at Holder method - 63 C for 30 minutes Flash process - 72 C for 15-20 sec followed by sudden cooling 13 C or lower. All non- sporing pathogens such as mycobacteria , brucellae & salmonellae are destroyed . 37

38. II.BOILING Boiling is highly unreliable as a sterilization technique; not recommended for sterilizing surgical instruments. Vegetative bacteria killed almost immediately at 90-100 C, but sporing bacteria require prolonged periods of boiling. 38

39. A minimum exposure period of 30min. is recommended to kill vegetative bacteria. Sodium bicarbonate 2% conc. is added to increase the efficiency of process. 39

40. Means intermittent exposure at 100 C Principle : that one exposure kills vegetative organisms, between heatings the spores being in a favorable nutrient medium become vegetative forms which get killed during subsequent heating. Used for gelatin media, media containing sugars. TYNDALLIZATION 40

41. Saturated steam under pressure . Cheap & nontoxic Penetrates fabric Method of choice for all items except those which are moisture or heat sensitive. STEAM UNDER PRESSURE AUTOCLAVES 41

42. 4 parameters of importance Pressure Temperature Time Steam 42

43. PRINCIPLE Water boils when its vapour pressure equals that of surrounding atmosphere . When pressure inside the closed vessel increases, the temp at which water boils also increases. 43

44. When steam comes in contact with a cooler surface it condenses to water and gives up its latent heat to that surface and moisture which together denature microbial proteins. MECHANISM 44

45. AUTOCLAVES A variety of materials such as dressings, instruments, laboratory wear, media & pharmaceutical products can be sterilized . 45

46. AUTOCLAVES 115 C, for 45 min 121 C, for 15-20 min 134 C , for 3 min STERILIZATION TIMES 46

47. USES Culture media Aqueous solutions Empty bottles and impervious containers Surgical instruments Wrapped dry goods and dressings 47

48. Items containing solvents, volatiles or corrosive chemicals Radioactive material What should not be autoclaved? 48

49. Small office sterilizer involves four cycles namely 1. Heat up cycle 2. Sterilizing cycle. 3. Depressurization cycle. 4. Drying cycle. CYCLES 49

50. Add water & load the chamber. Turn on the unit. Air is pushed out by steam. Set temperature is reached. 1. Heat up cycle 50

51. Begins after the desired temp is reached. Sterilizer maintains temperature for the set time. At the end of sterilization cycle, depressurization cycle begins. 2. Sterilizing cycle 51

52. Steam is slowly released. Decrease in temperature & pressure. At the end of this cycle items are wet 3. Depressurization cycle 52

53. To remove the moisture content from the material sterilized. Achieved either by vaccum cycle or automatic open door dying cycle. 4. Drying cycle 53

54. Hospital type of sterilizer consists of large chamber which is connected to a steam line which eliminate the need to generate its own steam These have a vacuum system for air removal such that when the steam enters it has better chance of coming in contact with every thing in the chamber Require the temperature of 250 F 54

55. Advantages- Short efficient cycle Most rapid Disadvantages- Corrosion of carbon steel instrument Possibly destruction of heat sensitive instrument Advantages and disadvantages of steam autoclave 55

56. NON-IONISING I R Rays U V Rays IONISING Gamma Rays High Energy Electrons V)Sterilization by radiation 56

57. MECHANISM OF ACTION-GENERATION OF HEAT IR RAYS for rapid mass sterilization of syringes UV RAYS for storage of sterilized instruments NON-IONISING RADIATION 57

58. X-rays and gamma rays have wave length shorter than UV light. As these rays can pass through microbial molecules, they force electrons out of their shells, thereby causing ionization. Used f or syringe,swab,catheter sterilization. Ionising radiation 58

59. Like CO2,ARGON etc. Time contact is very less upto 35 sec. Not commonly used due to cost factor involved. VI)LASERS 59

60. Cells of all types killed by intense ultrasonic & sonic vibrations Limited practical significance for sterilization Valuable in instrument cleaning VII)ULTRASONIC & SONIC VIBRATIONS 60

61. Forced passage of liquids through a filter of porosity small enough to retain any microorganism contained in them. A positive or negative pressure is necessary to draw the fluid through the filter into a sterile container e.g.. A filtering flask Used for sterilizing sera, solutions of sugars, vaccines, antibiotics used for culture media. VIII)FILTRATION TECHNIQUE 61

62. Earthenware candles Berkefield,Mandler Chamberland Asbestos and asbestos paper discs,e.g.Seitz Sintered glass filters Cellulose membrane filters Gradocol and modern membrane filters TYPES OF FILTERS 62

63. CHEMICAL AGENTS 63

64. Ethyl alcohol and isopropyl alcohol are most frequently used. Act by denaturing bacterial proteins. Concentration required : 60-90% in water. Protein slows its action,1%mineral acid or alkali enhances it. Effective against both gram+ve and – ve bacteria, not sporicidal . 1. ALCOHOLS 64

65. Isopropyl alcohol is preferred as it is better fat solvent, more bactericidal and less volatile Flammable. Methyl alcohol is effective against fungal spores and used for treating cabinets and incubators affected by them. 65

66. FORMALDEHYDE Active against the amino group of protein molecule. Markedly bactericidal, sporicidal and virucidal Commercial formalin is 40 % solution of formaldehyde in water with 10 % methanol to prevent polymerization. 2. ALDEHYDES 66

67. Borax formaldehyde solution with 0.5%sodium tetraborate and 4%formaldehyde in water is used to disinfect clean metal instruments. For gaseous disinfection,eg . For fumigating wards, sick rooms etc the atmosphere should have high relative humidity, over 60% and temp of atleast 18’c. 67

68. GLUTARALDEHYDE Markedly bactericidal,virucidal including HIV and mycobacteria and to a lesser extent spores. Concentration required 2 %. 68

69. Ability to penetrate organic material is poor. Less corrosive. Can be used to disinfect cytoscopes,endoscopes , corrugated rubber tubes, face masks, metal instruments,polythene tubes. 69

70. Obtained by distillation of coal tar between temp 170-270C. active against gram+ve and – ve bacteria,mycobacteria,but little activity against spores and viruses. Act by causing cell membrane damage, releasing cell contents and causing lysis 3. PHENOLS 70

71. Resistant to inactivation by organic matter Phenolic products like Lysol and cresol are good general disinfectants but are toxic to humans. Related products chlorophenols and chloroxyphenols are less toxic, less irritant but inactive against pseudomonas. 71

72. - LYSOL is used to disinfect linen - 3%lysol,0.5% phenol or 0.1% p- chloro -m-cresol is used for preserving sera and vaccines. 72

73. IODINE Aqueous and alcoholic solutions used as skin disinfectants Actively bactericidal, virucidal,and fairly active against spores It inhibits protein synthesis 5. HALOGENS 73

74. Chlorine is used in free, hypochlorite as well as chloramine form Kills vegetative bacteria Kills viruses like HIV,HBV It is very effective against HBV and HIV viruses, therefore its use is recommended at 1:10 dilution for disinfection of blood spills CHLORINE 74

75. ANILINE DYES Brilliant green, malachite green and crystal violet React with acid groups in cell More active against gram+ve than gram- ve bacteria, no activity against tubercle bacilli Non irritant,non toxic Inhibited by organic material. 6. DYES 75

76. ACRIDINE DYES Proflavine,acriflavine,euflavine,aminacrine . Impair DNA complexes of organisms and destroy reproductive capacity of the cell. More active against gram+ve bacteria than gram- ve . 76

77. 7. SURFACE ACTIVE AGENTS Alter energy relationship at interfaces producing a reduction of interfacial tension. 4 groups: cationic, anionic, nonionic and amphoteric . 77

78. 8. QUARTENARY AMMONIUM COMPOUNDS Surface active cationic compounds. Bactericidal, but not sporicidal Effective against Gram + ve bacteria. Examples Cetyl trimethyl ammonium. bromide (cetavlon or cetrimide) 78

79. Only chemical sterilant Cidal action against bacteria,spores & viruses. It is an excellent sterilizer of heat sensitive items. specially used for sterilizing -sutures, dental equipments, clothing, fiber endoscopes, heart-lung machines, respirators. 9. ETHYLENE OXIDE GAS 79

80. It is highly toxic, irritant, mutagenic & potentially carcinogenic It is highly flammable, but when mixed with CO2 this danger is minimized. Advantages can be used at a lower temperature leaves no residue heat sensitive items can be sterilized. 80

81. Disadvantages high cost of equipment. toxicity of the gas. explosive & inflammable. longer period of aeration. 81

82. Classification of instrument sterilization 82

83. SPAULDING’S CLASSIFICATION LEVEL PROCESS MATERIALS Critical Sterilization Autoclave Chemiclave Dry heat Immersion in full strength glutraldehyde Items that are used in surgery which are pierce burs, extraction forceps elevators needles files, Bone rongeurs ,. 83

84. SPAULDING’S CLASSIFICATION LEVEL PROCESS MATERIALS Semi-Critical Sterilization Autoclave Chemiclave Dry heat Immersion in full strength glutraldehyde Items that do not necessarily penetrate soft and hard tissues but which cross the vermilion border into the oral cavity-mouth mirrors hand piece, anesthetic syringes, impression trays. 84

85. SPAULDING’S CLASSIFICATION LEVEL PROCESS MATERIALS Non-Critical Surface Disinfection - Phenolics -Iodophors -Quaternary Ammonia compounds Items used in dentistry which do not cross the vermilion border or penetrate the oral tissues-chair light handles, instrument trays, bracket tables chair controls, Air/water syringes , hoses dental chairs. 85

86. To ensure that the sterilization is complete various monitoring indicators are there: 1.biologic indicators 2. chemical indicators 3.physical indicators STERILIZATION MONITORING 86

87. Most reliable method Bacillus stearothermophilus spores for steam or chemical vapor sterilization Bacillus stearothermophilus,a thermophile that requires to be cultivated 55-60˚C.Its spores are killed at 121˚C in 12min. Culture grown aerobically on nutrient agar for 5days is suspended in sterile water to a concentration of one million spores per ml. Small strips of filter paper soaked in the suspension are dried at room temp and packed in envelopes. BIOLOGICAL MONITORING 87

88. After autoclaving, envelope is cut with a sterile scissors and strip transferred to a recovery medium,eg.thioglycolate broth with strict precautions against contamination. Tube incubated for 7 days at 55˚C and examined for growth. An unautoclaved spore strip is used as positive control and uninoculated tube of medium as negative control. Results in terms of degree of heat resistance of preparation used. 88

89. Chemical monitoring BROWNE’S STERILIZER has red solution which turns green when heated at 115˚C for 25min(type 1),or 15min(type 2), or at 160˚C for 60min(type 3) Stored at 20˚C to avoid pre mature color change Bowie-Dick autoclave tape test for steam penetration 89

90. Involves observing the gauges and displays on the sterilizer and recording the temperature, pressure and exposure time. PHYSICAL MONITORING 90

91. SOME CAUSES OF STERILIZATION FAILURE Improper cleaning of instruments Improper temperature Improper loading of sterilizer Improper Timing Improper Packaging Improper Method of Sterilization 91

92. Sterilization of the instruments Diagnostic instruments such as mouth mirror, explorer and probe: sterilized by dry heat, chemical vapour ethylene oxide or steam autoclave. Rubber dam, stainless steel clamps and frame - compatible with all methods. STERILIZATION OF SPECIFIC MATERIALS 92

93. DENTAL HANDPIECES- Steps :– External disinfection using 100% isopropyl alcohol. Remove the bur. Internal cleaning and lubrication with pressurized spray can. Place hand piece in a bag prior to sterilization. Sterlize in an autoclave. 93

94. Dental burs Dry heat and ethylene oxide and chemical vapor sterilization. Sterilization of endodontic instruments Endodontic instruments should first be clean of debris. 94

95. Absorbent points , broaches , files and other root canal instruments - sterilized immediately before use in hot bead sterilizer. Endodontic instruments - sterilized by exposure for 3 sec. to laser beam. Dappen dish sterilized by swabbing thoroughly with tincture of thimerosal followed by alcohol. 95

96. Long handle instruments - sterilized by dipping the working point on alcohol and flaming twice. Gutta percha cones- sterilized by immersing it in 5.2% sodium hypochloride for 1 min than rinse the cone with hydrogen peroxide and dry it between the two layers of sterile gauge. 96

97. Carry sterilized instruments in proper containers. Used instruments usually sterilized by boiling at camp site. Instruments can also be cold sterilized using chemical solutions such as glutaraldehyde . Maintainence of proper asepsis using universal precautions. Sterilization & disinfection at camp site 97

98. There are numerous microorganisms in our environment which are potential cause of infection. It is therefore essential for us to protect ourselves & the patients from cross infection. Thus, a deeper knowledge of sterilization & disinfection is of paramount importance for us being dentists. CONCLUSION 98

99. Ananthnarayan , Paniker.Textbook of microbiology.6 th edition. Kapoor Vinod,Textbook of oral & maxillofacial surgery.2 nd edition Samaranayak l.p.Essentials of microbiology for dentistry,2 nd edition References 99

100. Bhatia Rajesh,Essentials of medical microbiology,2 nd edition Baweja C.P.Textbook of microbiology,3 rd edition Textbook of Microbiology:by Surinder Kumar 1 st Edition 100