Sterilization and Disinfection in Prosthodontics

Brief explanation of sterilization and disinfection methods. In-detail explanation of procedures for sterilization and disinfection of materials and armamentarium used in Prosthodontics.

1. STERILIZATION AND DISINFECTION IN PROSTHODONTICS Presented by: Dr. Jehan Dordi I year MDS 1

2. Contents Introduction Terminologies Need for Sterilization and Disinfection Difference between Sterilization and Disinfection Sterilization Methods of Sterilization Recent Advances Test for sterilization Disinfectants Methods of disinfection Levels of disinfection Spaulding's Classification Unit Dose Concept 2

3. Sterilization in Prosthodontic practice Disinfectants in Prosthodontic practice Management of Infectious Patient Management of Implant room/Operation Theatres. Review of literature References 3

4. INTRODUCTION 4

5. Terminologies Sterilization: It is defined as a process by which article, surface or medium is freed of all living micro-organisms either in vegetative or spore state. Disinfection: The destruction or removal of all pathogenic organisms, or organisms capable of giving rise to infection. Asepsis: It is the state of complete absence of viable pathogenic microorganisms in any environment . 5

6. Antiseptics: They are agents that can be safely applied on the skin or mucous membrane to prevent infection by inhibiting the growth of bacteria . Bactericidal agent/ germicides: They are substances that can kill bacteria . Bacteriostatic agents: They prevent the multiplication of bacteria which may , however, remain alive. Decontamination : It is the process of rendering an article or area free of contaminants, including microbial, chemical , radioactive and other hazardous materials from an area, object or body surface . 6

7. Need for Sterilization and Disinfection Micro-organisms are ubiquitous. They are found in the surroundings, on inanimate objects and on the surface of the human body. Since they cause contamination, infection and decay, it becomes necessary to remove or destroy them. 7

8. All hospitals need to sterilize their equipment and supplies. Even the smallest private clinic requires sterile surgical instruments for minor procedures, and sterile dressing materials. If a hospital has a full surgical unit, the sterilization of surgical instruments and linen, together with dressing materials for the wards and operating theatre, plays a key role in infection control . Henceforth to prevent cross-contamination between patient to patient or between patient and operator and to run a safe sterile practice sterilization and disinfection of instruments and materials is very necessary 8

9. Disinfection Sterilization This technique minimizes the number of microorganisms but does not eliminate them completely. This technique is the elimination of all the microorganisms. This method does not eliminate bacterial spores This method kills bacteria as well as vegetative spores It is not an absolute condition It is an absolute condition Disinfection method is used for decontamination of surfaces and air. Sterilization process is used for decontamination of food, surgical equipment's, instruments and several medicines Disinfectants are commonly used in daily life Sterilization is used in surgical operations and various labs where sterile conditions are pre-requisite. 9

10. Disinfection Sterilization Disinfection process do not require a strict guidelines to be followed The sterilization process are well laid down and follow a strict protocol to completely kill the pathogens. Disinfected objects have less number of micro-organism No viable organisms present on sterilized items 10

11. STERILIZATION 11

12. Methods of Sterilization Physical agents Sunlight Drying Dry heat: By flaming, incineration or using hot air Moist heat: By boiling, steam at atmospheric pressure , steam above atmospheric pressure Filtration: Using candles, asbestos pads, membranes Radiation Ultrasonic and sonic vibrators Chemical agents Alcohols: ethyl, isopropyl, trichlorobutanol Aldehydes : formaldehyde, glutaraldehyde Orthophthalaldehyde Peracetic acid, Hydrogen peroxide Hypochlorous acid Dyes Halogens Phenols Surface-active agents Metallic salts Gases: ethylene oxide, formaldehyde, beta propiolactone 12

13. PHYSICAL AGENTS Sunlight: Active germicidal effect due to combined effect of Ultraviolet rays and heat rays . Drying: 4/5 th of weight of bacterial cell consist of water and hence drying has a deleterious effect on many bacteria . Heat: The killing effect of heat is due to protein denaturation, damage by oxidising molecules, destroying cell constituents and the toxic effect of elevated levels of electrolyte. There are 2 types of heating method: Dry and moist heat 13

14. Dry Heat Flaming: An inoculating loop or wire, the tip of forceps and searing spatulas can be sterilized by holding them over a Bunsen flame till they become red hot. Inoculation loops carrying infective material may be dipped in a disinfectant before flaming to prevent spattering . Incineration: This is an excellent method for terminal sterilization for destroying biomedical waste . 14

15. Hot air oven: This is the most widely used method of sterilization by dry heat. Sterilization is achieved by conduction. The heat is absorbed by the surface of the item to be sterilized, which then penetrates to the centre, until the entire item reaches the desired temperature. A holding period of 160 degree for 2 hours is necessary to sterilise glassware, forceps, scissors, scalpels, all glass syringe, swabs. Glass-wares should be perfectly dry before placing in oven. 15

16. External and Internal view of Hot air oven 16

17. Sterilisation control for hot air oven: Physical : Temperature monitoring by thermocouples can be carried out. Chemical: A Browne's tube (green spot) is used- A green color is produced after 60 minutes at 160°C or 115 minutes at 150°C, suggesting complete - sterilization. 17

18. Biological: Heat-resistant spores of a non-toxigenic strain of Clostridium tetani or Bacillus subtilis are used to indicate efficiency of dry heat sterilisation. 18

19. Moist heat Temperatures below 100 C Pasteurization of milk: The milk is heated at either 63°C for 30 minutes or 72°C for 15-20 seconds , followed by cooling quickly to 13 °C or lower. By these process, all non sporing patho g ens such as mycobacteria, Brucella and salmonellae are destroyed . Coxiella burnetii is relatively heat-resistant and may survive the holder method . 19

20. Inspissation: Media such as Lowenstein-Jensen and Loeffler's serum are rendered sterile by heating at 80- 85°C for half an hour/on three successive days in an inspissator. 20

21. Temperature at 100°C Boiling: Vegetative bacteria are killed immediately at 90-100°C but bacterial spores can withstand long periods of boiling. In cases where boiling is considered adequate, the material should be immersed in the water and boiled for 10-30 minutes. Boiling is not recommended for sterilization of instruments used for surgical procedures . 21

22. Steam at atmospheric pressure (100 °): An atmosphere of free steam is used to sterilize culture media which may decompose if subjected to higher temperatures . A Koch or Arnold steamer is usually used . 22

23. Tyndallisation or Intermittent S terilisation : It is a method used for media containing sugars or gelatin . An exposure to 100°C for 20 minutes on three successive days is used. The principle is that the first exposure kills all vegetative bacteria, and the spores, since they are in a favorable medium, will germinate and be killed on subsequent exposure to 100 °C for 20 minutes. 23

24. Steam under pressure: The equipment used is an autoclave . Principle: The principle of the autoclave or steam sterilizer is that when water boils , its vapor pressure equals that of the surrounding atmosphere . Hence, when pressure inside a closed vessel increases , the temperature at which water boils also increases, generating steam. 24

25. When steam comes into contact with a cooler surface, it condenses and transmits its latent heat to that surface (1600 ml steam at 100°C and at atmospheric pressure condenses into 1 ml of water at 100°C and releases 518 calories of heat) . The large reduction in volume sucks in more steam and the process continues till the temperature of that surface equalizes with that of steam. Condensed water ensures moist heat for killing the microbes present on the material. 25

26. Types of autoclaves Vacuum autoclaves in which air is evacuated from a metal chamber by vacuum pump are now becoming popular in dentistry. In center sterile supply units in hospitals they are sometimes referred to as porous load autoclaves. These vacuum autoclaves are more desirable for routine dentistry than the gravity displacement type for the sterilization of hollow devices such as dental handpieces. 26

27. Gravity displacement autoclaves are small, automatic bench-top autoclaves. They work on the principle of downward displacement of air as a consequence of steam entering at the top of the chamber. For Gravity displacement autoclaves, a sterilization cycle of 134°C for 3–4 min at 207 kPa is recommended for both wrapped and unwrapped dental instruments. 27

28. Autoclaves used in dentistry Type N : air removal in type N sterilizers is achieved by passive displacement with steam. They are non-vacuum sterilizers designed for non-wrapped solid instruments. Type B (vacuum) : these sterilizers incorporate a vacuum stage and are designed to reprocess load types such as hollow, air-retentive and packaged loads. A number of different cycles may be provided . Each cycle should be fully validated and used in accordance with instructions provided by both the sterilizer manufacturer and the instrument manufacturer(s). 28

29. The sterilization cycle The sterilization cycle can be divided into three periods: the heating-up period , the holding period and the cooling period . For the N-type non-vacuum bench-top autoclave (routinely used in dentistry), this entails: 1. R emoval of air by a vacuum pump or downward displacement of air by incoming steam while the chamber is heated to the selected temperature. 2. Holding the load, which is sterilized, for the appropriate period at the selected temperature and pressure. 29

30. 3. D rying the load to its original condition by a partial vacuum (this is assisted by the heat from the jacket) 4. R estoration of the chamber to atmospheric pressure by rapid exhaustion of steam. Method Temperature (C) Holding time (in minutes) Chamber pressure Autoclave 121 15 15 lbs per square inch 126 10 20 lbs per square inch 133 03 30 lbs per square inch 30

31. Sterilization control: Sterilization control is similar to that of dry heat sterilization as described earlier except for the use of Geobacillus stearothermophilus, which is used as the test organism for checking sterilization by steam under pressure. This is a thermophilic organism with an optimum growth temperature of 55- 60°C and its spores require an exposure of 12 minutes at 121 °C to be killed. Biological indicators are the only process indicators that directly monitor the lethality of a given sterilization process. 31

32. Test for Sterilization A bowie dick tape is used for testing of sterilization . Bowie Dick tape is applied to articles begin autoclaved. If the process has been satisfactory, the strip will change its color completely. 32

33. Filtration Types of filters Candle filters are manufactured in different grades of porosity and have been used widely for the purification of water for industrial and drinking purposes. They are of two types Unglazed ceramic filters (for example, (chamberland and Daulton) and Diatomaceous earth filter ; (for example, berkefeld and mandler). 33

34. Sintered glass filters They are prepared by heat fusing finely powdered glass particles of graded sizes. They have low absorptive property and can be cleaned easily but are brittle and expensive. 34

35. Membrane filters They are made of cellulose esters or other polymers and have largely replaced other types of filters. They are routinely used in water purification and analysis, sterilization and sterility testing, and for the preparation of solutions for parenteral use . They come in a wide range of average pore diameters the size being the 0.22mm most wide used for sterilisation 35

36. Radiation Two types of radiation are used for sterilization. Non ionizing and Ionizing. Infrared and ultraviolet rays are of the non-ionizing , low-energy type, while gamma rays and high-energy electrons are the ionizing , high energy type. 36

37. Non-ionizing radiation: Here , electromagnetic rays with wavelengths longer than those of visible light are used. These are, to a large extent, absorbed as heat. Infrared radiation is used for rapid mass sterilization of prepacked items such as syringes and catheters. Ultraviolet radiation is used for disinfecting enclosed areas such as biosafety cabinets in laboratories, entryways, operation theatres and laboratories. 37

38. Ionizing radiation : X-rays , gamma rays and cosmic rays are highly lethal to DNA and other vital con stituents. They have very high penetrative power. Since there is no appreciable increase in temperature in this method , it is referred to as cold sterilization. Commercial plants use gamma radiation for sterilizing items like plastics, syringes , swabs, catheters, animal feeds, fabric and metal foils 38

39. Ultrasonic Vibrators: Used instruments are soaked into a container containing 70% isopropyl alcohol for removal of organic debris. A fter removing instruments rinse thoroughly in warm water to remove all chemicals. As a final step insert the instruments into the ultrasonic vibrator and operate for 30 minutes, after which sterile instruments are rendered. Ultrasonic vibrators are generally used for non-critical items. 39

40. Recent advances in sterilization Plasma sterilization: Plasma is known as the fourth state of matter and consists of ions, electrons or neutral particles . A radio frequency energy is applied to create an electromagnetic field. Into this, hydrogen peroxide vapors are introduced which generates a state of plasma containing free radicals of hydrogen and oxygen . This state renders the articles sterile by denaturing all microorganisms. Arthroscopes , urethroscopes, etc ., are sterilized by plasma sterilization. 40

41. Flash sterilization: Flash sterilization was originally defined by Underwood and Perkins as sterilization of an unwrapped object at 1320°C for 3 minutes at 27-28 lbs. of pressure in a gravity displacement sterilizer. Flash sterilization is considered acceptable for processing cleaned patient-care items that cannot be packaged, sterilized, and stored before use . It also is used when there is insufficient time to sterilize an item by the preferred package method. Effects of sterilization on periodontal instruments, JOP, vol 53, no:7, 2011. 41

42. DISINFECTANTS 42

43. CHEMICAL AGENTS An ideal antiseptic or disinfectant should : Have a wide spectrum of activity and be effective against all organisms. Be active in the presence of organic matter Be effective in acid as well as alkaline media Have speedy action Have high penetrating power Be stable 43

44. Mode of action of chemical agents: By protein coagulation By disruption of the cell membrane resulting in exposure, damage or loss of contents By removal of free sulfhydryl groups essential for the functioning of the enzymes By substrate competition of enzymes necessary for the metabolism of the cell 44

45. Alcohols E thyl alcohol (ethanol) and isopropyl alcohol are the most frequently used. They are used mainly as skin antiseptics at a concentration of 60- 90% in water. They act by denaturing bacterial proteins. T hey have no action on spores Methyl alcohol is effective against fungal spores and is used for cleaning cabinets and incubators. A pad moistened with methanol and a dish of water (to ensure high humidity) are kept inside the chamber which is left at working temperature for several hours. 45

46. Aldehydes Formaldehyde is active against the amino group in the protein molecule . In aqueous solutions it is markedly bactericidal , sporicidal and virucidal. It is used to preserve anatomical specimens, and for destroying anthrax spores in h air and wool. 10% formalin containing 0.5 % sodium tetraborate is used to sterilize clean metal instruments. Formaldehyde gas is used for sterilizing instruments, heat-sensitive catheters and for fumigating wards, isolation rooms and laboratories. 46

47. Glutaraldehyde Has an action similar to that of formaldehyde. It is especially effective against the tubercle bacilli , fungi and viruses. It has no deleterious effect on cement or lenses of instruments. Hence , it is used to sterilise cystoscopes, bronchoscopes, rubber anaesthetic tubes , plastic endotracheal tubes and polythene tubing . It can also be used for metal instruments. 47

48. Orthophthalaldehyde H as bactericidal activity . It is used to cleanse endoscopes between patients as it is quick, effective and safe. 48

49. Peracetic acid has a good sterilization effect on bacteria, particularly common antibiotic-resistant bacteria such as methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus and Clostridium difficile. Hypochlorous acid is generated from the reverse reaction of sodium hypochlorite and hydrogen peroxide . It has bactericidal activity against common pathogenic organisms. It is active against biofilms and microorganisms within the biofilms . 49

50. Dyes The aniline dyes include brilliant green, malachite green and crystal violet. They do not act against tubercle bacilli. Hence, malachite green is used in the Lowenstein-Jensen medium as a selective agent. The are non-irritant and non-toxic to the tissues. They are inhibited by organic material. Lethal effects on bacteria are believed to be due to their reaction with the acid groups in the cell . 50

51. Acridine dyes They are not as selective as the aniline dyes. They are minimally affected by the presence of organic matter . Important dyes in this group are proflavine, acriflavine, euflavine and aminacrine. They impair the DNA complexes of the organisms and prevent replication. 51

52. Halogens Iodine in an aqueous and alcoholic solution has been widely used as a skin disinfectant. It is bactericidal, with moderate action against spores. It is active against the tubercle bacteria and viruses . Compounds of iodine with non-ionic wetting or surface-active agents known as iodophores have better action than aqueous or alcoholic solutions of iodine . 52

53. Chlorine and its compound hypochlorite have been used as disinfectants over time. They are markedly bactericidal and virucidal. Town water supplies, swimming pools, food and dairy industries use chlorine for disinfection. The organic chloramines are used as antiseptics for dressing wounds. 53

54. Phenols These compounds are obtained by distillation of coal tar between temperatures of 170°C and 270°C. Bactericidal effect of phenols is due their capacity to cause cell membrane damage, inactivation o f membrane-bound oxidases and dehydrogenases leading to lysis and death of the microorganism. Low concentrations of phenol prec pi tate prote ins . 54

55. Phenols is widely used as disinfectants in hospital. Commonly used compounds are Lysol and cresol They are not readily inactivated by the presence of organic matter; hence, they are good general disinfectants Chlorhexidine (Hibitane) is a relatively non-toxic skin antiseptic and wound dressing. They are active against most Gram-positive organisms and fairly effective against Gram-negative bacteria. 55

56. 56 Commonly used disinfectants & their concentrations

57. Gases Ethylene oxide: This is a colorless liquid with a boiling point of 10.7C and highly penetrating at normal temperature and pressure . It has a sweet , ethereal smell and is highly inflammable. It is highly explosive at concentrations greater than 3%. Combination with 10% carbon dioxide or nitrogen makes it less explosive. 57

58. It acts by alkylating the amino, carboxyl, h ydroxyl and sulfhydryl groups in protein molecules within the microbes and spores. It also reacts with DNA and RNA (rendering them virucidal). It is potentially toxic to human beings, causing mutagenicity and carcinogenicity. It diffuses through many types of porous materials and readily penetrates some plastics . It is especially used for sterilizing heat-sensitive equipment like heart-lung machines , respirators, suture materials, dental equipment, books and clothing. It has a wide application within and outside the hospital. It is unsuitable for fumigating rooms because of its explosive property. 58

59. Formaldehyde gas: This is employed for fumigation o f operation theatres and other rooms . The sealed room is left unopened for 48 hours after fumigation;. The gas is neutralized with ammonia(300 ml for every liter of formaldehyde used) . Fumigation of operation theatres is no longer preferred. 59

60. Betapropiolactone : This is a condensation product of ketane and formaldehyde. It is no longer used for fumigation as it is carcinogenic. Hydrogen peroxide fogging: Bactericidal action is by oxidizing the cell wall of the organism. This has replaced fumigation. It has the advantage of short cycle time and is non-toxic . 60

61. Surface-active agents They are substances that alter the energy relationship at interfaces, producing a reduction in surface tension. They are widely used as wetting agents, detergents and emulsifiers . 61

62. Mechanism : These act on the phosphate groups of the cell membrane and also enter the cell. The membrane loses its semi-permeability and the cell proteins are denatured. They act on bacteria, but have no action on spores, tubercle bacilli and most viruses. 62

63. Metallic salts Though all salts have a certain amount of germicidal action , salts of heavy metals have greater action. Silver, copper and mercury salts are used as disinfectants . They are protein coagulants and have the capacity to combine with free sulfhydryl groups of cell enzymes . 63

64. Thimerosal, phenyl mercury nitrate and mercurochrome are less toxic and are used as mild antiseptics and have marked bacteriostatic but weak bactericidal and limited fungicidal action . Copper salts are used as fungicides. 64

65. LEVELS OF DISINFECTION 65

66. High-level disinfectant : This is a chemical that kills all microbial pathogens except large numbers of spores. It may have some activity against a smaller number of spores if the contact time is increased. For example, glutaraldehyde and hydrogen peroxide . Uses: They are active against Gram-positive and Gram-negative bacteria, spores and M. tuberculosis 66

67. Intermediate-level disinfectant : A chemical that kills all microbial pathogens including mycobacteria and non-enveloped viruses except spores . For example, alcohol, phenolic compounds and iodophores. Uses: Destroys M. tuberculosis , vegetative bacteria, most viruses and fungi . 67

68. Low-level disinfectant : A chemical that kills only vegetative bacteria , fungi and lipid-enveloped viruses. For example, quaternary ammonium compound . Uses: K ill most bacteria and most fungi, but not M. tuberculosis or spores 68

69. INSTRUMENT CLASSIFICATION BASED ON POTENTIAL TO SPREAD INFECTION (Spaulding's classification) 69

70. In 1968, Dr. E. H. Spaulding classified medical/surgical instruments as Critical, Semi‑critical and Non‑critical based on their potential to spread infections. The classification helps to decide how to proceed with the instruments. 70

71. Critical items Critical items are those which enter sterile tissue or the vascular system and pose a high risk of infection if the article is contaminated. They must be sterilized by autoclaving if heat-stable or with ethylene oxide or hydrogen peroxide gas plasma if heat-sensitive . For e.g. Surgical instruments, scalers, scissors, dental burs, scalpel blades, forceps, cardiac catheters, implants, etc. 71

72. Semi-critical items Articles which come in contact with mucous membranes or non-intact skin are called semi-critical items. They require high-level disinfection. Glutaraldehyde is the most commonly used high-level disinfectant. Endoscopes and bronchoscopes undergo high-level disinfection prior to and between patients. Some semi-critical items like thermometers and blood pressure cuffs for neonates require only intermediate level disinfection . This is done by disinfecting with alcohol as the articles may not be compatible with glutaraldehyde. For e.g. Mouth mirror, impression trays, hand-pieces, probe, tweezers, amalgam condensers 72

73. Non-critical items These items come in contact with intact skin but not mucous membranes. They can be cleaned or treated with low-level disinfectants as they carry no risk of transmitting microorganisms to the patients directly . For e.g. X-ray tubes, light handles, radiograph head/cone, blood pressure cuff, face bow 73

74. Unit Dose Concept Unit dose concept was introduced with purpose- to minimize cross contamination. Refers to dispensing of amount of materials sufficient to accomplish a particular procedure, prior to patient contact. Dispose of excess material at completion of procedure 74

75. STERILIZATION IN PROSTHODONTIC PRACTICE 75

76. Sterilization of Diagnostic Instruments (Mouth mirror, Probe, Explorer) Dry the diagnostic instrument with help of wipes. Only absolutely dry instruments must be placed in the sterilizer, in order to avoid calciferous deposits and/or water spots . Instruments are autoclaved at 121° C . In order to prevent staining and corrosion, the steam must be free of particles. When several instruments are sterilized, the maximum capacity of the sterilizer must not be exceeded. After sterilization instruments must be stored and transported in the rooms and containers designated by the practice. The instruments should be processed as soon as possible after use. 76

77. Sterilization of Impression Trays After the impression has been removed from the metallic impression trays the trays are washed with running water and are made free from the particles adhering to it. The trays are the properly dried and placed in autoclave for sterilization at 121° C. 77

78. Sterilization of H andpiece Several ways to control the spread of contaminating matter between two patients have been recommended. The most common methods of asepsis control are as follows: Protection from any contact with the fluids present within the oral environment, Chemical disinfection, Thermal sterilization Disinfection using microwaves, Disinfection via irrigation, Single use hand-pieces. Among the above techniques, moist heat using saturated water vapor's (autoclave) offers the best results as regards the sterilization of handpieces in the short time. 78

79. Step 1. After the end of the dental procedure the handpiece must be operated for 5-10 seconds over the wash basin or a similar container while ejecting water and air . Step 2. Then, after being detached from the tubing's and connections with the unit, it must be meticulously washed and brushed under running water. Step 3. Then, it must be dried with an absorbent paper. Step 4. After external cleaning, the handpiece is reconnected to the tubing's and operated for 3-5 seconds only with air so that any water residues are removed from the interior of the tubing. 79

80. Step 5. Then, the handpiece is lubricated with the lubricant recommended by the manufacturer and operated again for 10-20 seconds only with air so that the lubricant is properly distributed throughout the sensitive areas of the head of the handpiece. Step 6. After the end of this procedure, the handpiece along with the bur extractor are enclosed in a special pouch which is made airtight with either a self-adhesive tape or a thermosealer . Step 7. The handpiece and the bur extractors are placed in the autoclave, taking care not to over-pack the pouches and ensuring that the air can pass unhampered. 80

81. Depending on the manufacturer's indications, the autoclave is programmed to operate at 121C for 20 minutes or at 134 C for 13 minutes. After these cycles have finished, the handpieces and the bur extractors are sterilized and are ready to be used. Step 8. Just before re-use, some handpieces must be lubricated again with an appropriate lubricant. 81

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85. Sterilization of Burs Burs should be sterilized independently of their type or the area of the mouth in which they have been used. Step 1. A necessary step prior to sterilizing a bur is meticulous cleaning to remove tooth debris, residues of dental materials, blood clots or a paste-like mixture with saliva of all the above. The most widely accepted cleaning method for burs and other micro instruments are ultrasonic devices (baths) using suitable solutions and with the addition of enzymes with a proteolytic action. 85

86. In these baths using suitable solutions at a temperature of about 60°C, burs vibrate at a frequency of 60-80 kHz for at least 15 minutes. After the end of this procedure, burs are free from foreign matter as well as oxides which are very often deposited on their shank. Step 2. After removal from the ultrasonic bath, burs must be dried using absorbent paper and hot air. Step 3. They must then be placed in an appropriate device for sterilization, depending on the material they are made of. More specifically: Burs made of common carbon steel should not be placed in the autoclave because they will undergo oxidation. Burs made of stainless steel or tungsten carbide are not so affected. 86

87. 3) Dry heat ovens, ovens for chemical vapor sterilization and ethylene oxide ovens are suitable for sterilizing all types of burs. However, dry heat ovens, due to prolonged heating involved, may seriously damage the cutting edge of the burs. 4) Using various aldehydes and phenols for at least 30 minutes offers adequate sterilization while after 10 hours chemical sterilization is achieved. Nevertheless, they may damage the integrity of rotating cutting instruments. 87

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90. Sterilization of Facebows & Bite forks Parts of facebow which are made of metal can be sterilized in autoclave. It is important to note that earpieces of facebow be removed before sterilization. Before facebow and bite fork is kept in autoclave it is necessary to wipe it with dry cloth. Facebow and bite fork can be autoclaved at 121 C. 90

91. Sterilization of Dental Implants. The following products are delivered non sterile: Transfers , Analogs, Drivers, Overdenture, Abutments, Transfer screws, Drill Extension, Parallel Pin , Transfer Screws and plastic handle. It is recommended to sterilize the components and instruments prior to placing in oral cavity. If modification has been made to the components and instruments clean prior to sterilization. Dental implants and components are pre-cleaned prior to sterilization. 91

92. Steps in Pre-cleaning of components: Remove the debris in lukewarm water (<40 C) and immerse devices in cleaning solution Scrub devices with soft bristled nylon brush Flush re-useable devices with channels/ lumina using cleaning solution. Rinse with water. Load devices into washer/disinfector Run cleaning and disinfection cycles Run drying cycle Dry with compressed air or wipes 92

93. Removal of residual tissue or bone debris by immersing the instruments in lukewarm water. Pre-cleaning in an ultrasonic bath is recommended. Immerse the instruments in enzymatic cleaning solution (enzymatic detergent with pH between 7-10) with lukewarm water temperature not more than 40 C. 93

94. Scrub the component with nylon brush until visible soil and all debris are removed. Flush the internal channel/ lumina with 20ml cleaning solution using the irrigation needle connected to a 20ml syringe 94

95. Components are loaded in a instrument tray before placing in washer/ disinfector. Kit boxes are disassembled before cleaning and disinfection 95

96. Sterilization of implant components Inspection: Before sterilization visual inspection for cleanliness should be performed with magnifying glasses. Packaging of instruments: Place instruments in sterilization pouches. Sterilization: Steam sterilize the device in a sterilization pouch for 4 mins at 132 C. Dry the device for 20 mins 96

97. DISINFECTION IN PROSTHODONTIC PRACTICE 97

98. Methods Of Disinfecting Impressions Spraying Immersion 98

99. Different Impressions Disinfection of Alginate Impressions can be done with 0.5% sodium hypochlorite. Iodophores Immersion disinfection for prolonged periods will cause distortion due to imbibition. Beyerle, M.P., Hensley, D.M., Bradley Jr, D.V., Schwartz, R.S. and Hilton, T.J., . Immersion disinfection of irreversible hydrocolloid impressions with sodium hypochlorite. Part I: Microbiology. Int J Prosthodont.2014 , 7(3),234-8 99

100. Agar- Reversible Hydrocolloid: Found to be stable when immersed in 1:10 dilution sodium hypochlorite or 1:2 iodophor. Recommended immersion time is 10 minutes . Giblin, J., Podesta, R. and White, J., Dimensional stability of impression materials immersed in an iodophor disinfectant. Int J Prosthodont. 2010 , 3(1). 72-7 100

101. Zinc Oxide Eugenol Immersion It can be disinfected in 2% glutaraldehyde Iodophores or Chlorine compounds. Adverse effect have been reported on ZOE immersed for 16 hours in diluted hypochlorite . Olsson, S., Bergman, B. and Bergman,M., Zinc oxide-eugenol impression materials. Dimensional stability and surface detail sharpness following treatment with disinfection solutions Swed Dent J.2012 , 6(4),177. 101

102. Impression Compound Immersion in 1:10 dilution sodium hypochlorite or iodophor for specified time period has been found to be useful for disinfecting impression compound impressions. Bhat, V.S., Shetty, M.S. and Shenoy, K.K., Infection control in the prosthodontic laboratory. J Indian Prosthodont Soc 2007, 7(2),62. 102

103. Elastomeric Impression Materials Polysulphide and Addition Silicone : Glutaraldehyde, Iodophor, 0.5% sodium hypochlorite should be used for its disinfection. Thouati, A., Deveaux, E., Iost, A. and Behin, P., Dimensional stability of seven elastomeric impression materials immersed in disinfectants. J Prosthet Dent. 2016 , 76(1),8-14. 103

104. Polyether: Spraying in iodophor, 0.5% Sodium hypochlorite should be used. Prolonged immersion causes distortion . Polyether shows dimensional changes on immersion in 2% glutaraldehyde . Drennon, D.G. and Johnson, G.H., The effect of immersion disinfection of elastomeric impressions on the surface detail reproduction of improved gypsum casts. J Prosthet Dent. 2012, 63(2),233-241. 104

105. Disinfection Of Wax Bites & Wax Rims Wax rims and wax bites should be disinfected by the spray wipe spray method using an iodophor. Rinse & spray may be more appropriate for wax bites. For adequate disinfection these should remain for longer time in tuberculocidal disinfection. After the second spray, they can be enclosed in a sealed plaster bag for the recommended time. These items probably should be rinsed again after disinfection to remove any residual disinfectant. 105

106. Disinfection Of Bite Registrations Bite registrations made of various materials or compound can be handled in the same manner as impressions of the same materials. These registrations also can be disinfected, using the rinse spray rinse technique, with most EPA registered hospital level tuberculocidal disinfectants used as sprays (chlorine compounds should not be applied to ZOE ). After disinfection, the registration should be rinsed again to remove residual disinfectant. 106

107. Disinfection o f Casts ADA recommends that stone casts be disinfected by the spraying until wet or immersing in a 1:10 dilution of sodium hypochlorite or an iodophor. Casts to be disinfected should be fully set (i.e. stored for at least 24 hours). Microwave irradiation of casts for 5 mins at 900W gives high level disinfection of the gypsum casts 107

108. Disinfection Of Custom acrylic resin impression trays Custom acrylic resin impression trays should be disinfected by spraying with surface disinfectants or immersing in either 1:2 iodophor or 1:10 sodium hypochlorite. They should be rinsed thoroughly to remove any residual disinfectant and allowed to dry fully before use. After use in the mouth custom trays should be discarded. 108

109. Dental Prosthesis and Appliances The ADA recommends disinfection by immersion in iodophors or chlorine compounds. Although both of these disinfectants are somewhat corrosive, studies have shown little effect on chrome cobalt alloy with short-term exposure (10 minutes) to iodophors or 1:10 hypochlorite. 109

110. Damage of heat cured denture base resin has been shown to occur after only 10 minutes of immersion in a glutaraldehyde with phenol buffer, although immersion in 2% alkaline glutaraldehyde did not damage the acrylic surfaces. Given the tissue toxicity of glutaraldehyde's and phenolic, however iodophors or chlorine compounds are preferred for disinfection of acrylic appliances. Prostheses never should be stored in a disinfectant before insertion. After disinfection and thorough rinsing, acrylic items can be stored in diluted mouthwash until inserted. 110

111. Cast partial dentures are disinfected using iodophors solution or 2% glutaraldehyde solution for 10 minutes. Damage of heat cured denture base resin has been shown to occur after only 10 minutes of immersion in glutaraldehyde. 111

112. Fixed metal/porcelain prosthesis may be disinfected by immersion in glutaraldehyde's for the time recommended for tuberculocidal inactivation by the disinfectant manufacturer . In addition several clinical services have confirmed that fixed prosthesis can be disinfected by short immersion in diluted hypochlorite without apparent harm to the device. 112

113. The higher the content of noble metal, the less the likelihood of adverse effects on the metal core should be taken to minimize the exposure times of metals to potentially corrosive chemicals. Unglazed porcelain should not be exposed to any disinfectant and (porcelain firing/ glazing will suffice), fixed metal prostheses can be sterilized with ethylene oxide or even by autoclaving if desired . Any device that has been immersed in a disinfectant should be rinsed thoroughly before delivery to the patient. 113

114. Prostheses or appliances that have been worn by patients should be cleaned thoroughly before disinfection by scrubbing with a brush and an antiseptic hand wash or by cleaning in an ultrasonic unit. Dentures or other acrylic appliances that have been worn by patients and require repair should be disinfected, after cleaning and before handling should be handled (i.e. with gloves) as contaminated even after disinfection. The porous nature of acrylic makes such devices difficult to disinfect adequately. 114

115. Robert J. Boylan et al used UV light with a wavelength of 254nm as a mode of sterilizing complete dentures, partial dentures and a rubber base impression contaminated with fine known species of microorganisms. The results showed that killing of microorganisms with greater than 98% within 15 seconds and 99% either 30 seconds and 100% in 2 minutes. They also concluded that UV light cannot be used as a sole means of disinfecting the impressions because of shadowing effect that allows the survival of microorganisms unexposed to UV light. 115

116. Disinfection of Dentures with Soft liners Disinfection of dentures with soft liners can be done by soaking the dentures in 2% alkaline glutaraldehyde solution for 10 minutes or by soaking in 5% sodium hypochlorite solution for 10 minutes. After disinfection is done the dentures are washed with water before re-inserting. 116

117. Protective eye wear: It may be in the form of glasses and / or a facemask. It should prevent trauma to the eye tissue from flying droplets / aerosols. Protective glasses should be washed with soap first, these rinsed with water and wiped with an appropriate surface disinfectant . Plastic safety lenses can also be immersed in alkaline glutaraldehyde solution and should be thoroughly rinsed to avoid possible irritation to skin and eyes. 117

118. Management of instruments after use: They should be cleaned and dried, lubricated if necessary and packaged before loading into the autoclave. Cleaning involves an initial presoaking with detergent solution containing disinfectants to soften organic debris and begin microbial kill. After cleaning the instruments should be dried. S urfaces like unit handles, light handle, light switch, chair controls, head rest knob, trolley handle, trolley and 3-way syringes cannot be disconnected and sterilized and therefore need to be treated with disinfectants covered with a protective barrier . 118

119. However instruments which enter oral cavity and are connected to some of the equipment e.g. air rotor and surgical handpiece, ultrasonic inserts / tips, airwater syringe tips and light cure probes / tips should be disconnected, sterilized and rinsed. Disinfection of surfaces involves the cleaning of surfaces, after every patient and application of a disinfectant chemical. These chemicals include alcohol (spirit), iodophor products, synthetic phenols, glutaraldehyde, chlorines etc. The advantages of barriers include ease and speed of insertion, standard sizes and the protection of equipment from damage by chemicals, blood and fluids. 119

120. Spittoons should be flushed with water, scrubbed and disinfected. Waste buckets should be used with disposable plastic bags as liners to be changed wherever necessary. 120

121. Dental Unit W aterlines : Disinfection and management Q uality of water in dental unit waterlines (DUWLs) attached to handpieces, ultrasonic sealers and air/ water syringes has been debated widely. The source of water to the dental unit is either directly from municipal supply or via water reservoir bottles usually filled with distilled water or normal water. 121

122. After entering the unit, it passes through a multichannel control box that distributes the water to hoses (DUWLs) feeding various attachments such as the high-speed handpiece, the air/water syringe and the ultrasonic scaler. The main risk to dental staff and patient health from DUWL contamination comes from opportunistic and respiratory pathogens such as Legionella , non-tuberculous mycobacteria (NTM) and Pseudomonas . These organisms can be amplified in the biofilm to reach infective concentrations, with the potential for inhalation-associated respiratory infections or direct contamination of surgical wounds. 122

123. All DUWLs should be flushed for 2 min at the beginning of each day, prior to commencing treatment and at the end of the day. The DUWL should be flushed for 20–30 s between patients to reduce temporarily the microbial count, as well as to clean the waterline of materials that may have entered from the patient’s mouth. This includes handpieces, ultrasonic scalers and air/water syringes. All DUWLs should be fitted with non-retractable devices, to prevent suck-back ( backflow/back-siphon age) of material into the municipal water supply. 123

124. Water from DUWL should never be used as an irrigant in procedures involving breaches of the mucosa and bone exposure. During surgical procedures use sterile solutions or coolant/irrigant administered by an appropriate delivery device, for example, sterile bulb syringe, sterile tubing that bypasses DUWLs or sterile single-use devices. 124

125. Laboratory A sepsis Dental practitioners regularly send clinical material to the laboratory: impression material, dentures sent to the technology laboratory or pathological samples such as pus or biopsy specimens referred to pathology laboratories . The dentist is obliged to deliver all such items in a manner that obviates infectious hazards, whether during transport or within the laboratory. Blood and saliva must be carefully cleaned from the impressions and denture work by washing under running water and disinfection, and, if appropriate, placed in plastic bags before transport to the laboratory. Proprietary disinfectant soaking solutions are preferred to sprays for decontaminating the microbes retained on impression surfaces. 125

126. The dental laboratory itself should be regarded as a clean (not contaminated) area, and appropriate protocols for disinfection of surfaces and material, as well as regular and timely renewal of disinfectant solutions, should be established. Smoking and eating should be prohibited. Microbiological specimens sent to the laboratory should be securely bagged to avoid contamination of personnel who handle the items. The request form should be separately enclosed to prevent contamination. Biopsy specimens should be put in a sturdy container with a secure lid to prevent leakage during transport. 126

127. Care should be taken when collecting specimens to avoid contamination of the external surface of the container . 127

128. Maintenance of Wooden handle spatulas, Blow-torches, Rubber bowls & Shade- guides After manipulation chairside wooden handled spatulas should be cleaned and disinfected. Other times such as Blow torches should be disinfected after use, or the area to be touched should be covered with a barrier such as plastic wrap to prevent contamination. Rubber bowls should be cleaned and disinfected after chairside use. 128

129. Items such as shade guides should be cleaned and disinfected to avoid cross contamination . If iodophors are used on shade guides, they should be wiped with water or alcohol after the exposure time to remove any residual. 129

130. Management of Infectious Patients 130

131. Transmission of Infectious Pathogens like HIV, HBV etc. Pathogenic organisms like HIV can be transmitted in dental settings through: Direct contact with blood, oral fluids or patient materials. Indirect contact with contaminated objects. Contact of conjunctiva, nasal or oral mucosa with droplets containing microorganisms generated from an infected person. 131

132. Modes of Occupational E xposure Patient to DHCP (Dental Health Care Personnel), including dentists, hygienists and assistants. From DHCP to patient. From patient to patient. 132

133. Prevention Strategies (Universal Protection Protocol) The different prevention protocol includes the following: Personal Protective Equipment's Cubicle preparation Personal protective equipment's Gloves, masks, protective eye wears Puncture resistant gloves and thimbles Double gloves 133

134. Barriers for Preventing Cross- Contamination of Infection Gloves: After contact with each patient, gloves should be removed, and hands should be washed and then re-gloved before treating another patient. Exposure to disinfectants or other chemicals often cause defect in gloves, thereby diminishing their value Latex heavy rubber gloves, also called utility gloves should be used in management of HIV patients. 134

135. Protective clothing's such as gowns, clinic jackets or similar outer protective garments which are disposable should be used. Masks: Surgical masks or chin length plastic face shields should be worn to protect the face and oral and nasal mucosa when a discharge of body fluids is anticipated 135

136. Handling of sharp instruments and needles: If a patient requires multiple injection over time then the needle should be recapped between each use to avoid needle stick injury. Disposable syringes, needles, scalpel blades, and other sharp items should be discarded in puncture resistant biohazard container that are easily acceptable. 136

137. Cubicle Preparation Surface disinfection Disinfecting counter tops Any item that cannot be autoclaved should be disinfected with a fresh iodophor solution and protective cover should be placed. Surfaces can be covered with plastic wrap, aluminium foil or impervious backed absorbent paper. Counter tops should also be disinfected with appropriate disinfectants. 137

138. Proper Hand Washing Technique The steps included in proper hand washing techniques include: Palm to palm Right palm over left dorsum and left palm over right dorsum Palm to palm finger interlaced Fingers to opposite palms Rotational rubbing of right thumb clasped over left and vice versa Rotational rubbing backwards and forward 138

139. Hand Washing Techniques 139

140. Frequently and less frequently missed areas during hand washing 140

141. 141

142. Bio-medical Waste Segregation 142

143. 143

144. 144

145. 145

146. All waste from HIV seropositive and AIDS patients must be treated as infected waste. Disposable plastic aprons and gloves must be worn when handling infected material. Dispose off infected items as follows: Place into a disposable YELLOW plastic bag and seal. Place this inside a second YELLOW plastic bag and seal. Affix “STANDARD UNIVERSAL PRECAUTION” label to outside of YELLOW plastic bag in a prominent position. Disposal Of Infected Clinical Waste 146

147. Remove protective clothing and dispose of as clinical waste. Wash hands. Make arrangements for collection and disposal of bagged waste. All waste in YELLOW plastic bags should be sent for incineration. 147

148. Disposal of Contaminated Linen All linen from HIV seropositive and AIDS patients must be treated as infected linen. Disposable plastic apron and gloves must be worn when handling infected linen. Grossly contaminated heavily blood soaked linen must be carried to the sluice area to be bagged. It should be placed in the appropriate water-soluble laundry bag at the bedside and sealed. This water-soluble bag is then placed in double yellow bags and incinerated . 148

149. Affix “Standard Universal Precaution” label to the outside of the bag in a prominent position. It should be sent to the laundry immediately. The infected/contaminated linen should not be handled by laundry staff it is kept into the washing machine with very high temperature 71°C for 25 minutes. After placing the linen in the appropriate bags remove the protective clothing and dispose off as clinical waste . 149

150. Disposal, Disinfection & Sterilization Of Contaminated Equipment Use disposable items whenever possible and dispose of as clinical waste. Wear protective clothing when dealing with contaminated equipment. Upon completion of procedure dispose of protective clothing as clinical waste. 150

151. Contaminated Instruments ( Stainless steel & polypropylene instruments, bowels, kidney dishes etc.) Clean the instruments with running water and dry. Place the instruments in surgical plate. Apply some amount of alcohol over the instruments and burn it. Next place them in an autoclavable disposal bag. Secure the neck of the bag for transportation. Arrange transportation of contaminated items for decontamination and sterilization. Incineration of some instruments is also carried out. 151

152. STERILIZATION OF IMPLANT ROOM/ OPERATION THEATRE 152

153. Fumigation of Operation Theatre/ Implant room To sterilize the operation theatre formaldehyde gas (bactericidal & sporicidal , virucidal ) is widely employed as it is cheaper for sterilization of huge areas like operation theatres. Formaldehyde kills the microbes by alkylating the amino acids and sulfhydryl group of proteins and purine bases. In spite of the gas being hazardous continues to be used in several developing countries. 153

154. Fumigation usually involves the following phases : First the area to be fumigated is usually covered to create a sealed environment. Next the fumigant is released into the space to be fumigated; then, the space is held for a set period while the fumigant gas percolates through the space and acts on and kills any infestation in the product. Next the space is ventilated so that the poisonous gases are allowed to escape from the space, and render it safe for humans to enter. 154

155. Procedure of Fumigation Thoroughly clean windows, doors, floor, walls and all washable equipment's with soap and water. Close windows and ventilators tightly. If any openings found seal it with cellophane tape or other material. Switch off all lights, A/C and other electrical & electronic items 155

156. Personal care during fumigation Adequate care must be taken by wearing cap, mask, foot cover, spectacle. Formaldehyde is irritant to eye & nose; and it has been recognized as a potential carcinogen. So the fumigating employee must be provided with the personal protective equipment's. 156

157. REVIEW OF LITERATURE 157

158. Rai R, Anand V, Loushambam P. Disinfection Of Alginate Impression Materials Using Uv Lights Coated With Candida Albicans . Global Journal For Research Analysis. 2018 Oct30;7(10 ). Rai et al conducted a study to evaluate the efficacy of ultra-violet light in decreasing the colony counts of Candida albicans after coating the irreversible hydrocolloid impression material with Candida albicans colonies . A circular master die (dimensions: diameter-30mm, thickness-3mm ) was fabricated. Samples were prepared with alginate impression materials. They were coated with Candida albicans colonies with standardization. 158

159. Three different tubes were used in ultra-violet light unit corresponding to 8watts, 16watts, and 24watts . The times of exposure were 15, 30, 60, 90, 120 and 180 seconds. The results were tabulated and statistically analysed . It was found that ultra-violet light exposure more efficiently decreases the colony counts of Candida albicans on samples. 159

160. Sreekumar S, Varghese K, Abraham JP, Jaysa JJ. An in vitro evaluation of the efficiency of various disinfection and sterilization methods to decontaminate dental handpieces. J Dent Res Rev 2018;5:50-3. Sreekumar et al did a study to evaluate the efficiency of various disinfection and sterilization methods to decontaminate dental handpieces. For the study sixty contaminated handpieces were selected and divided into four groups of 15 handpieces . They were then contaminated using a mixture of Streptococcus salivarius , Escherichia coli, and Candida albicans . Sterilization using autoclave and disinfection procedures using a commercially available disinfectant ( Decident ™) and 70% isopropyl alcohol was done on each group . 160

161. The handpieces were then subjected to manual scrubbing followed by bacteriological culture. The study revealed that moist autoclave is the best way to decontaminate the dental handpieces. Further, it was shown that proper cleaning of the instrument prior to autoclave, as recommended by the American Dental Association’s Centers for Disease Control and Prevention (CDC), is required for 100 % efficiency . Statistically significant presence of S. salivarius and E. coli was found in samples disinfected with Decident ™ and 70% isopropyl alcohol, respectively . The study revealed that moist autoclave, following the procedures recommended by the CDC, still remains as the gold standard of sterilization of dental handpieces. 161

162. Farrugia C, Cassar G, Valdramidis V, Camilleri J. Effect Of Sterilization Techniques Prior To Antimicrobial Testing On Physical Properties Of Dental Restorative Materials. Journal Of Dentistry. 2015 Jun 1;43(6):703-14 . Farrugia et al did a study to evaluate Effect Of Sterilization Techniques Prior To Antimicrobial Testing On Physical Properties Of Dental Restorative Materials. The aim of this study was to investigate any changes to the microstructure and surface properties of selected dental materials after sterilization carried out prior to subjecting them to antimicrobial testing. Initial microbial contamination on the material, as well as other possible sources of contamination were also assessed . The materials investigated included dentine replacement materials ( Chemfil Superior1, Ionoseal1, Dyract Extra1 and SDR1). The materials were characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The test materials were sterilized using alcohol, steam, ultraviolet light (UV) and ethylene oxide and any changes to these materials were then assessed by SEM, microhardness testing and Fourier transform infrared (FT-IR) spectroscopy. 162

163. Material microbial levels before treatments were assessed by plate counting technique and turbidity tests. Possible contamination through dispensers was assessed by analyzing the CFU/sample . Ethylene oxide affected the microstructure of the Chemfil , Ionoseal and Dyract , resulting in flattening of the Si–O stretching vibrations and deposition of chlorine and calcium respectively in Chemfil and Dyract . Varied contamination was demonstrated on all materials when incubated in anaerobic conditions. It was concluded that the different sterilization techniques affected the microstructure of the materials under investigation. Samples of materials produced in sterile conditions could also be contaminated with bacteria, either from the material itself or through the dispensing apparatus. 163

164. Clinical significance: Results of antimicrobial studies cannot be extrapolated clinically as the material sterilization treatment results in changes to material chemistry and microstructure , which could in turn affect the materials’ antimicrobial activity. 164

165. Basso MF, Giampaolo ET, Vergani CE, Pavarina AC, Machado AL, Jorge JH. Occlusal pressure analysis of complete dentures after microwave disinfection: a clinical study. Journal of Prosthodontics. 2017 Oct;26(7):606-10. Basso et al did a study to evaluat the effect of microwave disinfection protocols on the occlusal pressure pattern of dentures after microwave disinfection. Dentures were constructed for 40 patients and evaluated as follows (n=20). Group 1: Patients had the maxillary dentures submitted to microwave disinfection , once a week, for 4 weeks. Group 2: Patients had the maxillary dentures submitted to microwave disinfection, three times a week, for 4 weeks. Occlusal contacts were recorded on five occasions: 30 days after denture insertion and before first disinfection (baseline or control group); 1 week after disinfection; 2 weeks after disinfection ; 3 weeks after disinfection; 4 weeks after disinfection. 165

166. Occlusal contacts were analyzed by T-Scan III. Intergroup analysis was performed using the Mann-Whitney test and intragroup analysis using the Friedman test with significance of 5 %. The results showed no significant difference between groups during the periods . The data on parameters loss of denture adaptation or complaints showed that patients used their dentures regularly for eating and expressed comfort and satisfaction in all experimental periods. The evaluation of functional occlusion revealed that the distribution of the occlusal contacts remained unaltered after disinfection . Microwave disinfection protocols as studied in this report did not influence occlusal contacts of the complete dentures. 166

167. References Ananthanarayan And Panikers . Textbook Of Microbiology. 10 th Edition. India: Universal Press; 2016. Lakshman Samarannayake . Essential Microbiology For Dentistry. 5 th Edition. Poland: Elsevier; 2018. Baveja C.P. Textbook Of Microbiology. 11 th Edition. India; ACP Publishers; 2011. Rai R, Anand V, Loushambam P. Disinfection Of Alginate Impression Materials Using Uv Lights Coated With Candida Albicans . Global Journal For Research Analysis. 2018 Oct 30;7(10). Farrugia C, Cassar G, Valdramidis V, Camilleri J. Effect Of Sterilization Techniques Prior To Antimicrobial Testing On Physical Properties Of Dental Restorative Materials. Journal Of Dentistry. 2015 Jun 1;43(6):703-14. 167

168. Rani L. Sterilization Protocols In Dentistry-a Review. Journal Of Pharmaceutical Sciences And Research. 2016 Jun 1;8(6):558. Brandt R, Coffey J, Baker Ps. Infection Control In A Prosthodontic Residency Program. Journal Of Prosthodontics. 2013 Mar;2(1):51-5. Bhat Vs, Shetty M, Shenoy K. Infection Control In The Prosthodontic Laboratory. The Journal Of Indian Prosthodontic Society. 2017 Apr 1;7(2):62. Sreekumar S, Varghese K, Abraham JP, Jaysa JJ. An in vitro evaluation of the efficiency of various disinfection and sterilization methods to decontaminate dental handpieces. J Dent Res Rev 2018;5:50-3 . Boylan RJ, Goldstein GR, Schulman A. Evaluation of an ultraviolet disinfection unit. Journal of Prosthetic Dentistry. 1987 Nov 1;58(5):650-4. 168

169. Pavan S, Arioli Filho JN, Dos Santos PH, Nogueira SS, Batista AU. Effect of disinfection treatments on the hardness of soft denture liner materials. Journal of prosthodontics. 2007 Mar;16(2):101-6. 169

170. THANK YOU 170