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Disinfection in prosthodontics 08





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  2. 2. INTRODUCTION • Microorganisms are ubiquitous. • Since pathogenic microorganisms cause contamination, infection and decay, it becomes necessary to remove or destroy them from materials and areas. • This is the objective of infection control and sterilization. 3
  3. 3. • Infection control (IC) is an essential part of dentistry. • Potential for disease transmission in the dental clinic and lab is well documented. • Potential pathogens can be transported to lab via orally soiled impressions, dental prostheses/appliances. • Microorganisms can be transferred from contaminated impressions to dental casts. • Oral bacteria can remain viable in set gypsum for up to 7 days.
  4. 4. DEFINITIONS • INFECTION CONTROL – Also called “exposure control plan” by Occupational Safety and Health Administration is a required office program that is designed to protect personnel against risks of exposure to infection. • EXPOSURE – is defined as specific eye, mouth, other mucous membrane, non intact skin, or parenteral contact with blood or other potentially infectious materials. 5
  5. 5. • STERILIZATION - Use of a physical or chemical procedure to destroy all microorganisms including substantial numbers of resistant bacterial spores. • STERILE - Free from all living microorganisms; usually described as a probability (e.g., the probability of a surviving microorganism being 1 in 1 million). 6
  6. 6. • DISINFECTION: Destruction of pathogenic and other kinds of microorganisms by physical or chemical means. Disinfection is less lethal than sterilization, because it destroys the majority of recognized pathogenic microorganisms, but not necessarily all microbial forms (e.g., bacterial spores). • DISINFECTANT: A chemical agent used on inanimate objects to destroy virtually all recognized pathogenic microorganisms, but not necessarily all microbial forms (e.g., bacterial endospores). • Asepsis: Asepsis is the state of being free from disease-causing contaminants (such as bacteria, viruses, fungi, and parasites). The term asepsis also often refers to those practices used to promote or induce asepsis in an operative field in surgery or medicine to prevent infection. 7
  7. 7. CHAIN OF INFECTION • All links must be connected for infection to take place PathogenPathogen SourceSource ModeModeEntryEntry SusceptibleSusceptible HostHost (sufficient virulence & adequate numbers) (allows pathogen to survive & multiply) (of transmission from source to host) (portal that the pathogen can enter the host) (i.e., one that is not immune)
  8. 8. Mechanism for transfer of infectious material 1) Cross contamination 2) Direct contact transmission 3) Indirect contact transmission 4) Droplet infection 5) Air borne infections 6) Vehicle
  9. 9. Cross contamination • Refers to spread of microorganisms from : – One source to another – Person to person – Person to an inanimate object & then to another person
  10. 10. Direct contact transmission • Infection is spread from – one person to another without an intermediate object.
  11. 11. ndirect contact transmission • Infection is spread from one person to another. • By way of an environment surface / droplets / or other vehicle. Droplet infection • Infection acquired by inhalation of droplets or aerosols that contain microorganisms or viruses from another person.
  12. 12. Vehicle • Term refers to : substance / object that carries infectious material from one person to another, directly or indirectly. • The small particle of an aerosol have the potential to penetrate & lodge in the smaller passages of the lungs & are thought to carry the greatest potential for transmitting infections (AEROSOLS & SPLATTER IN DENTISTRY; STEPHEN K. ET AL JADA, 135, 429-437, APRIL 2004) • A study conducted by Harrel et al on aerosol splatter from operative field showed that the airborne material was spread for a distance of atleast 18 inches from the operative site.
  13. 13. Pathway of cross contaminat ion Source of microorga nism Mode of disease spread Site of entry into body Infection control procedure Patient to dental team Patients mouth Direct contact Droplet infection Breaks in skin Inhalation by dental team Through breaks in skin of dental team Gloves/hand washing Immunization Masks Rubber dam Mouth rinsing Gloves; hand washing Protective clothing Face shield Rubber dam Mouth rinsing
  14. 14. Pathways of cross contamin ation Source of microorga nism Mode of disease spread Site of entry into body Infection control procedure Dental team to patient Dental teams hands Dental teams mouth Direct contact Indirect contact Droplet infection Through mucosal surfaces of patients Blood on items used in patients Inhalation by patient Through oral Gloves/ hand washing Immunization Gloves ;hand washing Immunization Instrument sterilization Surface disinfection Mask Face shield
  15. 15. Pathways of cross contamina tion Source of microorga nism Mode of disease spread Site of entry into body Infection control procedure Patient to patient Patients mouth Indirect contact Through oral mucosal surfaces of patients Instrument and hand piece sterilization Sterilization monitoring Surface covers Mask; Eyewear Flush water units Use disposable items Office to community Patient's mouth Indirect contact Cuts in skin Waste disposals Waste management Disinfection of impressions Proper management of laundry Dental teams families Dental teams body fluids Direct or indirect contact Intimate contact immunization
  16. 16. Requirements of infection control • For ideal cross infection control procedures:- – Should be simple, – Easily reproduced, – Economical, – Should not involve a great deal of surgery time, – Should be easily understood by all staff, – Should not involve toxic substances.
  17. 17. Instrument sterilization Surface disinfection Aseptic technique INFECTION CONTROL Personal protection Equipment asepsis Patient screening
  19. 19. PRINCIPLE 1- STAY HEALTHY Sir William Osler tells “soap and water and common sense are the best disinfectant”
  24. 24. OBJECTIVES OF INFECTION CONTROL  To protect the patient and members of the dental team from contracting infections during dental procedures  To reduce the numbers of pathogenic micro-organisms in the dental operatory to the lowest possible level.  To implement a high standard of infection control when treating every patient (universal precautions)  To simplify infection control, thus allowing the dental team to complete treatment with minimal inconvenience. 27
  25. 25. STRATEGY TO ACHIEVE INFECTION CONTROL • All patients must be screened. • Barriers for personal protection. • Careful aseptic techniques. • Sterilization & disinfection. • Disposal of contaminated waste safely. • Laboratory asepsis. 28
  26. 26. PERSONAL BARRIER PROTECTION • Personal protective equipment (PPE), or barrier precautions, are a major component of Standard precautions. • PPE is essential to protect the skin and the mucous membranes of personnel from exposure to infectious • The various 5 barriers PPE are 1. Head cap 2. masks, 3. Gloves, 4. protective eye wear, & 5. over garments 29
  27. 27. Head cap • Hair should be neatly tied back and kept out of treatment field. • should be covered with head cap to avoid hair contacting the patients mouth. • If not covered the hair may act as a source of infection, • Personnel must protect their hair with surgical cap while encountering heavy spatter eg. Ultrasonic scaling device.
  28. 28. Face masks• Protective value -to reduce post operative infection in patients caused by microorganisms in respiratory tracts of surgeons, - to protect the dentist from disease agents that might be present in sprays or aerosol particles. • Aerosols are airborne debris, smaller than 5ųm in diameter, that remain suspended in air. • Splatter are larger blood contaminated droplets which may contain sharp debris. • When airborne infection isolation precautions are necessary (e.g., for TB patients), a National Institute for Occupational Safety and Health (NIOSH)- certified particulate-filter respirator (e.g., N95, N99, or N100) should be used.
  29. 29. Requirements:- • Prevent inward and outward passage of microorganism, • Filter particles produced during dental procedures, • Have minimal marginal leakage. Uses of masks • any time there is risk or spraying or splashing of fluids during patient care activities. • to protect against aerosol spatter. N-95 MASK FOR TB
  30. 30. PROTECTIVE EYEWEAR CAUSES OF EYE DAMAGE:  Aerosols and spatter may transmit infection  Sharp debris projected from mouth while using air turbine handpiece, ultrasonic scaler may cause eye injury.  Injuries to eyes of patients caused by sharp instruments especially in supine position. Therefore both the clinician and patients must use protective eyewear. • Protective eyewear consists of glasses with solid eyeshields. • Eyewear must be put on with clean hands before gloving and must be removed after gloves are removed. • Eyewear and shields must be cleaned and disinfected with water based disinfectant 33
  31. 31. GLOVES All clinical personnel must wear treatment gloves during all procedures. Types: 1. Latex gloves 2. Vinyl gloves 3. Nitile gloves 4. General purpose utility gloves  Latex gloves are the preferred operatory gloves.  Gloves manufactured by DOUBLE DIP process are better than single dip because they have less pinholes & use less irritating catalyzing coagulants. 34
  32. 32. • Gloves powdered using cornstarch or cetylpyridium chloride is better than talcum powder (mineral) which may cause irritation. • Medical gloves are manufactured as single-use disposable items that should be used for only one patient, then discarded. • Gloves should be changed between patients and when torn or punctured. • Gloves must have < than 4% leak detectable by a water test.( FDA regulation) Gloves removal 35
  33. 33. • Utility gloves – Heavy latex gloves – Heavy or thin nitrile gloves – Thin co polymer gloves – Thin plastic gloves • Other gloves – Heat resistant gloves – Dermal gloves polymer gloves nitrile gloves plastic glovesDermal gloves
  34. 34. Limitations of gloves • Offer little protection against injuries with sharp objects such as instruments needle scalpel and blades. • Precautions to be taken -Clinical personnel must wear treatment gloves during all treatment procedures, -If any leak detected, remove gloves wash hands and put on fresh gloves, -Should not be washed with hand soaps, reduces glove integrity. • Storage - store them out of sunlight. -should be tightly closed in heavy plastic bags, to minimize oxidation.
  35. 35. Latex allergy • Hypersensitivity to latex –true latex allergy or a reaction to accelerators & antioxidants used in processing. • Thiuram a chemical used in fabrication- reported to cause allergic response. In march 1988- polyether component- causative agent. • Processing- during processing ammonia is added as a preservative, which degrades the sap proteins to produce allergens.
  36. 36. • The final manufacturing process leaches the allergens from the rubber products by soaking them in hot water. Leaching water should be changed repeatedly to decrease the concentration of latex antigens. • The rubber is hardened by the process of vulcanization i.e addition of sulfur. • Reports of hypersensitivity to latex products have increased in oral health care workers since introduction of universal precaution in early 1980s (JADA Sep 1994, vol.125, P1189)
  37. 37. Clinical features Mild - dermatitis of hands and fingers - swelling Serious - wheezing - anaphylaxis - 6-7%- surgical personnel- allergic Precautions – use vinyl gloves - synthetic polymer gloves.
  38. 38. PROTECTIVE OVERGARMENTS • Worn to protect the skin and the clothing, • Should be changed when ever moist or visibly solid, • Requirements - light weight -should cover arm, chest, up to neck and lap when seated. - made of cotton/ synthetic fiber. - thick enough to protect skin and street clothing • Laundry done with regular detergent. • Hot water up to 70ºc or cool water containing 50- 150ppm chlorine is used as anti microbial. 41
  39. 39. HAND WASHING • Hand hygiene (e.g., hand washing, hand antisepsis, or surgical hand antisepsis) considered the single most critical measure for reducing the risk of transmitting organisms. • The microbial flora of the skin, consist of transient and resident microorganisms . Transient flora, which colonize the superficial layers of the skin, are easier to remove by routine hand washing. 42
  40. 40. • Resident flora attached to deeper layers of the skin are more resistant to removal and less likely to be associated with such infections. • For routine dental examinations procedures, hand washing is achieved by using either a plain or antimicrobial soap and water. • The purpose of surgical hand antisepsis is to eliminate transient flora and reduce resident flora to prevent introduction of organisms in the operative wound, if gloves become punctured or torn. • Skin bacteria can rapidly multiply under surgical gloves if hands are washed with soap that is not antimicrobial . Thus, an antimicrobial soap or alcohol hand rub with persistent activity should be used before surgical procedures. 43
  41. 41. • At the beginning of a routine treatment period, watches and jewelry must be removed and hands must be washed with a suitable cleanser. • Hands must be lathered for at least 10 seconds, rubbing all surfaces and rinsed. • Clean brushes can be used to scrub under and around the nails. • Must be repeated at least once to remove all soil. 44 HANDWASHING TECHNIQUE
  42. 42. HAND CLEANSERS • CHLORHEXIDINE BASED – these contain 2- 4% chlorhexidine gluconate with 4% isopropyl alcohol in a detergent solution with a pH of 5.0 to 6.5. They have broader activity for special cleansing(e.g: for surgery, glove leaks, or when clinician experiences injury). But it can be hazardous to eyes. • POVIDONE IODONE – contain 7.5-10% povidone iodine, used as a surgical hand scrub. • PARACHLOROMETEXYLENOL(PCMX) – they are bactericidal and fungicidal at 2% concentration. Non irritating and recommended for routine use. • ALCOHOL HAND RUBS- ethyl alcohol and isopropyl alcohol are widely used at 70% concentration. They are rapidly germicidal when applied to the skin. 45
  43. 43. • According to the CDC (CENTRE OF DISEASE CONTROL), patient-care items (e.g., dental instruments, devices, and equipment) are categorized as critical, semi critical, or noncritical, based on the potential risk of transmitting infection if the item becomes contaminated during use. 46 Sterilization & Disinfection
  44. 44.  Instruments that contact cut tissues or penetrate tissues are considered to be critical items that require thorough cleaning and sterilization for reuse. Examples are  Forceps, periosteal elevators, cross bars  Scalpels, scissors, suture needles  Bone chisels  Surgical burs  Scaling instruments  Endodontic instruments  Semicritical items that touch mucosa are the air/water syringe tip, suction tips, prophy angle, and hand pieces. Others (air/water syringe handle etc) are handled or touched interchangeably with treatment instruments that become contaminated with blood and saliva. Examples are  Mouth mirrors  Burs  Hand pieces  Tweezers  Restorative instruments  Impression trays 47
  45. 45. • Semi critical items must be removed for cleaning and sterilization unless they are either disposable or can be protected from contamination with disposable plastic covers. • Noncritical items are environmental surfaces such as chairs, benches, floors, walls, and supporting equipment of the dental unit that are not ordinarily touched during treatments. Examples are  Medication bottles  Light cure tips  Glass slab and cement spatula  Instrument trays  Orthodontic pliers  Dapen dish • Contaminated noncritical items require cleaning and disinfection. 48
  46. 46. DISINFECTION • Disinfection is a less effective process than sterilization because it does not kill bacterial endospores. • Disinfectants are antimicrobial agents that are applied to non-living objects to destroy microorganisms, the process of which is known as disinfection • Two functions:- – Must be an effective antimicrobial agent, – Must not adversely affect dimensional accuracy or surface texture of impression materials and resulting gypsum cast. • Want to reduce likelihood of ill fitting, nonfunctional prostheses 49
  47. 47. Criteria for an ideal disinfectant:-  Broad spectrum of activity  Acts rapidly  Non corrosive  Environment friendly  Is free of volatile organic compounds  Nontoxic, hypoallergenic & no staining  Good penetrating and cleaning ability, 50
  48. 48. Levels of disinfection:- • High level- inactivates bacterial spores and all forms of bacteria,fungi,and viruses depending on contact time can be either a disinfectant or a steriliant. • Intermediate level- inactivates all forms of microorganisms except spores,kills mycobacterium tuberculosis var bovis. • Low level – inactivates vegetative bacteria and some lipophilic viruses but is not tuberculocidal or sporocidal. • Hospital level disinfectant kills staphylococcus aureus, pseudomonas aeurginosa and salmonella 51
  49. 49. DISINFECTANTS 52
  50. 50. CHEMICALS ADVANTAGES DISADVANTAGES CHLORINES Rapid action Broad spectrum Economical Prepare solution daily Diminished activity by organic matter Corrosive IODOPHORES Broad spectrum Few reactions Residual biocidal activity Few reactions Unstable at high temperatures Dilution and contact time critical Discoluration Prepare solution daily SYNTHETIC PHENOLS Rapid action Broad spectrum Compatible with most metal Degrades certain type of plastic over time Difficult to rinse Film accumulation Alchol base products are fair to poor cleaning ability
  51. 51. DENTAL LABORATORY • All disinfection procedures are accomplished prior to delivery to lab. • Done in dental operatory or professional work area. • Recommend a sign and monitor system be implemented stating “Only Biologically Clean Items Permitted”
  52. 52. INCOMING ITEMS • Rinse under running tap water to remove blood/saliva, • Disinfect as appropriate, • Rinse thoroughly with tap water to remove residual disinfectant, • No single disinfectant is ideal or compatible with all items & • Annotate the DD Form 2322: “Disinfected with ______ for _____minutes”
  53. 53. OUTGOING ITEMS • Clean and disinfect before delivery to patient, • After disinfection: rinse and place in plastic bag with diluted mouthwash until insertion, • Do not store in disinfectant before insertion & • Label the plastic bag: “This case shipment has been disinfected with ______ for _____ minutes”
  54. 54. IMPRESSIONS • Many studies have been performed to evaluate effects of various disinfectants on different types of impression materials, • Research findings have been contradictory, • No single disinfectant is compatible with all impression materials, • The least distortion is associated with products having the shortest contact times
  55. 55. • Many variables can affect impression materials:- – Composition and concentration of disinfectants, – Exposure time and compatibility of various disinfectants with specific impression materials & – Physical/chemical properties can vary in a given category of material or disinfectant. • Do an in-office “test run” when using new combinations of impression materials and disinfectants. • Consult dental materials’ manufacturers regarding their compatibility with disinfectants • The ADA recommends chemical disinfection of all impressions and dental prostheses An acceptable disinfectant is sodium hypochlorite
  56. 56. METHODS OF DISINFECTION 1.Spraying, Dipping & 2. Immersing. • Exposure time should be that recommended by the manufacturer of disinfectant for tuberculocidal disinfection. • Iodophors, 5.52% sodium hypochlorite (1:10 concentration) with minimum contact time of 10mins , chlorine dioxide, phenols, and other approved products are all acceptable. • Polyether materials cannot be immersed in disinfectants due to potential for absorption and distortion. • Immersion disinfectants can only be used once before discarding (except for glutaraldehydes).
  57. 57. • Most reports indicate dimensional stability is not significantly affected by immersion technique. • Clean and rinse impression in dental operatory – Cleaning efficiency can be improved by gently scrubbing impression with camel’s hair brush and antimicrobial detergent. • Sprinkle dental stone into impression before rinsing to aid in cleaning. • Cleaning and rinsing – Reduces bio-burden present – Lessens overall microbiologic challenge to disinfectant.
  58. 58. • Spray, dip, or immerse impression in appropriate intermediate- or high-level disinfectant and place in sealed bag. • Disinfection can be accomplished in the dental operatory or a professional work area depending on facility policy & • After required contact time, rinse impression and pour-up.
  59. 59. SPRAY TECHNIQUE • Rinse entire impression/tray under running tap water after removal from oral cavity. • Trim excess impression material from noncritical areas – Reduces number of microorganisms and organic debris present. • Place impression in bag and liberally spray the entire impression/tray. • Seal bag to create “charged atmosphere” – Reduces exposure to vapors and liquid
  60. 60. • Remove from bag at end of exposure time; rinse and pour. • Once stone has set, remove cast from impression. • Dispose of impression material and disposable tray (if applicable) in general waste & • Sterilize reusable tray (if applicable).
  61. 61. • Advantages – Uses less disinfectant, – Same disinfectant can often be used to disinfect environmental surfaces. • Disadvantages – Probably not as effective as immersion, – Can be released into air increasing occupational exposure.
  62. 62. DIPPING/IMMERSION TECHNIQUE • Select disinfectant with short exposure time to minimize distortion and deterioration of surface quality of resulting stone cast. • Follow same procedures as above except fully immerse or dip impression in disinfectant for recommended exposure time • Do not use water based glutaraldehyde solutions with a pH of 8 or higher for since this might affect the gypsum surface.
  63. 63. DENTAL CASTS • Very difficult to disinfect • Cast should be fully set (at least 24 hours) before disinfection. • Is preferable to disinfect impression. • If casts must be disinfected: – Place casts on end to facilitate drainage, – Spray with iodophor or chlorine product, then rinse. • Another option – Soak casts for 30 minutes in 0.5% concentration of sodium hypochlorite and saturated calcium dihydrate solution (SDS) – SDS is produced by placing uncontaminated, set gypsum (i.e. stone) in a container of water
  64. 64. ORALLY SOILED PROSTHESES • Scrub with brush and antimicrobial soap to remove debris and contamination. • Place prosthesis in sealable plastic bag or beaker filled with ultrasonic cleaning solution or calculus remover. • Place in ultrasonic cleaner for required time as specified by manufacturer of ultrasonic cleaner . • Place cover on ultrasonic cleaner to reduce spatter potential. • Remove and rinse under running tap water, dry, and accomplish required work.
  65. 65. SUB-SURFACE DISINFECTION • Place prosthesis in sealable plastic bag containing 1:10 dilution of sodium hypochlorite or other intermediate- to high-level disinfectant (not glutaraldeyde or phenols). • Place in ultrasonic cleaner for 10 minutes
  66. 66. DENTAL PROSTHESES • Do not exceed manufacturer’s recommended contact time on metal components to minimize corrosion. • There is little effect on chrome-cobalt alloy with short-term exposures (10 minutes). • Do not store in disinfectant before insertion. • Store in diluted mouthwash until insertion.
  67. 67. STERILIZATION • Heat sterilize all metal and heat-stable instruments that contact oral tissues, contaminated appliances, or potentially contaminated appliances after each use. • Examples: facebow fork, metal impression trays, burs, polishing points, rag wheels, laboratory knives
  68. 68. IMPRESSION TRAYS • Precleaning removes bio-burden and any adherent impression material. • Ultrasonic cleaning can aid in removing residual set gypsum. • Chrome-plated or aluminum trays – Clean, package & heat sterilize. • Single-use trays – Discard after one use. • Custom acrylic trays – Can be disinfected (by spray or immersion), then rinsed (if to be used for second appointment).
  69. 69. WAX BITES/RIMS, BITE REGISTRATIONS • Immersion disinfection may cause distortion to some items – Use spray disinfection. • Heavy-body bite registration materials – Usually not susceptible to distortion and can be disinfected in same manner as an impression of the same material
  70. 70. DISINFECTION • Prosthodontic items contaminated by handling should be disinfected (by spray or immersion technique based on type of item) after each use. • Examples: alcohol torch, facebow, articulator, mixing spatula, mixing bowl, lab knife, shade/mold guide
  72. 72. CLEANING AND DISINFECTION STRATEGIES FOR BLOOD SPILLS • Strategies for decontaminating spills of blood and other body fluids differ by setting and volume of the spill. • The person assigned to clean the spill should wear gloves and other PPE as needed. • Visible organic material should be removed with absorbent material (e.g., disposable paper towels discarded in a leak- proof, appropriately labeled container). 75
  73. 73. • Nonporous surfaces should be cleaned and then decontaminated with either an hospital disinfectant effective against HBV and HIV or an disinfectant with a tuberculocidal claim (i.e., intermediate-level disinfectant). • However, if such products are unavailable, a 1:100 dilution of sodium hypochlorite (e.g., approximately ¼ cup of 5.25% household chlorine bleach to 1 gallon of water) is an inexpensive and effective disinfecting agent. 76
  74. 74. STERILIZATION • There are 4 distinct stages for instrument sterilization: 1) Pre cleaning disinfection, using holding solutions 2) Pre – sterilization cleaning. 3) Sterilization 4) Aseptic storage. 77
  75. 75. The four accepted methods of sterilization are : A. Steam pressure sterilization (autoclave) B. Chemical vapor pressure sterilization- (chemiclave) C. Dry heat sterilization (dryclave) D. Ethylene oxide sterilization • Patient load, turnaround time for instrument reuse, instrument variety and quality must all be balanced against the type of sterilizer selected. 79
  76. 76. STEAM UNDER PRESSURE (AUTOCLAVING) • Principle – it involves heating up of water to generate steam in a closed chamber, producing a moist heat that rapidly kills microorganisms. • As the steam is produced in a closed chamber it completely saturates the sterilization chamber, replacing the cooler air and increasing the pressure. • Saturated steam heats the article rapidly by releasing latent heat. Condensation of steam and contraction leads to negative pressure on articles.  Moist heat kills microorganisms through protein coagulation, RNA and DNA breakdown and release of low molecular weight intracellular constituents.  Instruments made of alloys of carbon steel and tungsten carbide are susceptible to corrosion during repeated autoclaving. The use of 2% sodium nitrite solution coating minimizes such damage.
  77. 77. STEAM HEAT STERILIZATION • Steam heat sterilization /autoclaving: a) standard cycles –20-30min at 250 degree Fahrenheit under pressure 15 pounds b)flash cycles –3-10min at 273 ºF under pressure 30 pounds. • Types of steam sterilizers : – small office sterilizers – hospital type sterilizers
  78. 78. Cycles in small office sterilization • Heat up cycle • Sterilization cycle • De-pressurization cycle • Drying cycle
  79. 79. 1.THE HEAT-UP CYCLE After the water is added the chamber is loaded, the door is closed and the unit is turned on, and the heat up cycle begins to generate steam. Steam pushes out the air in the chamber (called gravity air removal) and when the set up temperature is reached, the sterilization cycle begin 2.THE STERILIZING CYCLE Here the set temperature is maintained for the required period of time. Typical pre- set sterilizing cycles are: a)250 degree f – 30 min b)250 degree f -15 min c)273 degree f -10 min d)273 degree f- 3 min
  80. 80. 3.THE DEPRESURIZATION CYCLE • At the end of sterilization cycle the depressurization cycle starts and the steam is slowly released, with a decrease in temperature and pressure 4.THE DRYING CYCLE • At the end of depressurization cycle all the items inside are wet. • This cycle maintains heat inside the chamber to evaporate the remaining water but the chamber is opened to the air so that the water vapour can escape and the items can be dried. • Some sterilizers have automatic drying cycles. • With others, the door is simply opened about one-half inch for a time to let the moisture escape.
  81. 81. • Advantages of Autoclaves. Autoclaving is the most rapid and effective method for sterilizing cloth surgical packs and towel packs. Is dependable and economical Sterilization is verifiable. 85
  82. 82. • Disadvantages of Autoclaves.  Items sensitive to the elevated temperature cannot be autoclaved.  Autoclaving tends to rust carbon steel instruments and burs.  Instruments must be air dried at completion of cycle. 86
  83. 83. Small office sterilizers • Operates through four cycles : Heat up cycle, the Sterilizing cycle, the Depressurization cycle, the Drying cycle. • Usual chamber diameter is 8-12 inches, may have a small cassette containing the instruments that is inserted into the sterilizer. • Some units also have printout devices that records the time and temperature of each cycle to help maintain sterility assurance.
  84. 84. Hospital - Type Sterilizers • Used in :Hospitals, Dental schools ,Large clinics. • They have – larger chambers ,direct connection to steam line ,or direct connection to water line, – vacuum system for air removal from the chamber – post sterilization vacuum cycle that removes the steam and water after the sterilization cycle. • Loading –the manufactures instructions has to be strictly followed. • Sterilizing temperature-time ranges from 250-273 ºf ; 3-30 min.
  85. 85. Flash sterilization cycles • Operates at 3 min at higher temperatures. • 132 degree c at 30lbs pressure. • 3 min for unwrapped & 7 min for wrapped items. • Used only for emergency situations. • Disadvantages are recontamination weakens sterility assurance.
  86. 86. Advantages • Kills the organisms and spores at lower temperatures in shorter duration. • High penetrating power. • Liquid and water solutions retain structure (sterilizes water based liquids in standard cycles). Disadvantages • It corrodes carbon steel instruments. • Materials must be air dried at completion of the cycle. • Heat sensitive materials can be destroyed.
  87. 87. CHEMICAL VAPOR PRESSURE STERILIZATION (Chemiclaving) • The 1938 patent of Dr. George Hollenback and the work of Hollenback and Harvey in 1940s culminated in the development of an unsaturated chemical vapor system , also called Harvey Chemiclave. • Principle is that although some water is necessary to catalyze the destruction of all microorganisms in a relatively short time, water saturation is not necessary. • Kills microorganisms by destroying vital proteins. 91
  88. 88. • Chemical vapor pressure sterilizers operate at 270° F (131° C) and 20 pounds of pressure. • They must be used with a prescribed chemical and should be properly labeled to satisfy OSHA's Chemical Hazard Communication Standard. • Unsaturated chemical-vapor sterilization involves heating a chemical solution of primarily alcohol with 0.23% formaldehyde in a closed pressurized chamber 92
  89. 89. Advantages of Chemiclaves  Carbon steel and other corrosion-sensitive instruments are said to be sterilized without rust.  Relatively quick turnaround time for instruments.  Load comes out dry.  Sterilization is verifiable. Disadvantages of Chemiclaves  Items sensitive to the elevated temperature will be damaged Vapor odor is offensive, requires aeration.  Heavy cloth wrappings of surgical instruments may not be penetrated to provide sterilization. 93
  90. 90. DRY HEAT STERILIZATIONConventional Dry Heat Ovens Dry heat sterilization is readily achieved at temperatures above 320° F (160° C) for 30 mins. Instrument loads may take 30- 90 mins to reach that temperature, so to provide a margin of safety, instruments must be sterilized at 160ºC for 2 hours. They have heated chambers that allow air to circulate by gravity flow (gravity convection). Packs of instruments must be placed at least 1 cm apart to allow heated air to circulate. 94
  91. 91.  Kills microoragnisms primarily by an oxidation process. Protein coagulation also occurs depending on the water content of protein.  High concentrations of mercury vapor can develop in a dry heat oven that has been used to sterilize amalgam instruments. Thus great care must be taken to scrap amalgam of any instrument. 95
  92. 92. • Short-Cycle, High-Temperature Dry Heat Ovens  It is a high-temperature process that uses a forced-draft oven (a mechanical convection oven that circulates air with a fan or blower)  It reduces total sterilization time to 6 minutes for unwrapped and 12 minutes for wrapped instruments.  These short-cycle high-temperature dry heat ovens operate at approximately 370° to 375° F . 96
  93. 93. • Advantages of Dry Heat Sterilization  Carbon steel instruments and burs do not rust, corrode, if they are well dried before processing.  Industrial forced-draft hot air ovens usually provide a larger capacity at a reasonable price.  Rapid cycles are possible at high temperatures.  Low initial cost and sterilization is verifiable. • Disadvantages of Dry Heat Sterilization  High temperatures may damage more heat-sensitive items, such as- rubber or plastic goods.  Sterilization cycles are prolonged at the lower temperatures.  Must be calibrated and monitored 97
  94. 94. Glass bead sterlizer • Working temperature- 218°c(424.4ºf) • Working time –15s • Pre heating time ranged from –15min to 3.5 hrs • Disadvantages: Transfer of glass beads to the root canal, resulting in blockage.
  95. 95. HOT SALT STERILIZER • W.T- 218ºC. • W.Time –10s. • More safer than glass bead sterilizer. • Pre heating required. • Larger instruments should be immersed in for 20s
  96. 96. ULTRASONIC CLEANERS AND SOLUTIONS • Ultrasonic cleaning is the safest and most efficient way to clean sharp instruments. • An ultrasonic cleaning device should provide fast and thorough cleaning without damage to instruments; have a lid, well-designed basket, and audible timer; and be engineered to prevent electronic interference with other electronic equipment • ultrasound (usually from 20–400 kHz) 100
  97. 97. • Operate the tank at one-half to three-fourths full of cleaning solution at all times- Use only cleaning solutions recommended by ultrasonic device manufacturers. Aqueous cleaning solutions contain detergents, wetting agents and other components, • Operate the ultrasonic cleaner for 5 minutes or longer as directed by the manufacturer to give optimal cleaning. • Devices, that-have less than two transducers do not pass the foil test and are not suitable for instrument cleaning. 101
  98. 98. ETHYLENE OXIDE STERILIZATION (ETO) o Was first used in 1940’s by US army. o Ethylene oxide sterilization is the best method for sterilizing complex instruments and delicate materials because of extreme penetrability of the ETO molecule and low temperature(70ºF- 140ºF). o Kills microorganisms by reacting chemically with nucleic acids. The basic reaction is alkylation of hydroxyl groups. o It is a gas at room temperature (B.P 10.8ºC). o Alkalizing agent, exerts lethal affect on proteins of bacteria. o Uses- nearly all material whether metal , plastic, rubber or cloth. o Highly inflammable (mixed with carbon dioxide) o Well ventilated room necessary. o Time 2- 12 hrs ( depending on temp and concentration) 102
  99. 99. Advantages: Operates effectively at low temperatures Gas is extremely penetrative Can be used for sensitive equipment like handpieces. Sterilization is verifiable Disadvantages: Potentially mutagenic and carcinogenic. Requires aeration chamber ,cycle time lasts hours Usually only hospital based. 103
  100. 100. OTHER STERILIZATION METHODS • Heat-sensitive critical and semicritical instruments and devices can be sterilized by immersing them in liquid chemical germicides registered by FDA as sterilants. • Items need to be – 1) rinsed with sterile water to remove toxic or irritating residues; – 2) handled using sterile gloves and dried with sterile towels; and – 3) delivered to the point of use in an aseptic manner. 104
  101. 101. • They can kill bacterial spores in 6 to 10 hours. • Sterilants used for high-level disinfection of items for reuse are glutaraldehydes at 2% to 3% concentrations which kills by altering essential protein components. • Glutraldehyde molecules has two active carbonyl groups which react with proteins through cross linking reactions. • High-level disinfection is used mainly for plastic items that enter the mouth and that cannot withstand heat sterilization like plastic cheek retractors and photographic mirrors. • Disadvantages include prolonged time taken, irritating to skin & cannot be monitored with biological indicators. 105
  102. 102. NEW METHODS OF STERILIZATION  Various new methods of sterilization are under investigation and development. 1. Peroxide vapor sterilization - an aqueous hydrogen peroxide solution boils in a heated vaporizer and then flows as a vapor into a sterilization chamber containing a load of instruments at low pressure and low temperature 2. Ultraviolet light - exposes the contaminants with a lethal dose of energy in the form of light. The UV light will alter the DNA of the pathogens. Not effective against RNA viruses like HIV. The optimum wavelength for UV sterilization is 260 nm 106
  103. 103. STORAGE OF STERILIZED ITEMS • The storage area should contain enclosed storage for sterile items and disposable (single-use) items. • Storage practices for wrapped sterilized instruments can be either date- or event-related • Dental supplies and instruments should not be stored under sinks or in other locations where they might become wet. 107
  104. 104. Principles And Procedures For Handling And Cleaning Instruments After Treatment • The safest and most efficient instrument cleaning procedures involve ultrasonic cleaning of used instruments kept in a perforated basket or cassette throughout the cleaning procedure. • Wear protective utility gloves at all times to handle contaminated instruments. • Organic debris on instruments is likely to reduce activity of the disinfectant. • Used instruments are commonly placed in an anti microbial solution as this softens and loosens debris. 108
  105. 105. • Next, move the or basket of instruments into an ultrasonic cleaning device, rinse them, and then carefully inspect the instruments for debris. • Dip instruments likely to rust into a rust inhibitor solution. Drain & dry instruments with absorbent towel. • Still wearing protective gloves, properly package the instruments together with internal and external sterilization indicators suited to the sterilization process use. • Cloth packs, wraps, or commercial paper/plastic bags are suitable for instrument containment if they are compatible with the method of sterilization. 109
  106. 106. PRECAUTIONS TO AVOID INJURY EXPOSURE • Engineering controls are the primary method to reduce exposures to blood from sharp instruments and needles. • Work-practice controls establish practices to protect personnel whose responsibilities include handling, using, or processing sharp devices. 110
  107. 107. • Work-practice controls for needles and other sharps include placing them in appropriate puncture-resistant containers located as close as feasible to where the items were used. • Sharp end of instruments must be pointed away from the hand • Work-practice controls include removing burs before disassembling the handpiece from the dental unit, restricting use of fingers in tissue retraction during suturing and administration of anesthesia, and minimizing uncontrolled movements of sharp instruments. 111
  108. 108. • Used needles should never be recapped or otherwise manipulated by using both hands, or any other technique that involves directing the point of a needle toward any part of the body. • A one-handed scoop technique, a mechanical device designed for holding the needle cap to facilitate one-handed recapping, or an engineered sharps injury protection device (e.g., needles with resheathing mechanisms) should be employed for recapping needles. 112
  109. 109. • Personnel should never bend or break needles before disposal because this practice requires unnecessary manipulation. 113
  110. 110. POST EXPOSURE PROPHYLAXIS Management of exposure includes: A. General wound care and cleaning. B. Counseling of the exposed worker regarding blood borne pathogens. C. Source patient testing for HBV,HCV and HIV (consent required). D. Documentation of the incident and review. E. Post exposure assessment and prophylaxis for the health care worker. 114
  111. 111. HBV POSTEXPOSURE MANAGEMENT 115 IF AND THEN Source pt is +ve for HBsAG Exposed worker not vaccinated Worker should receive vaccine series  should receive single dose of HB immunoglobulin within 7 days. Exposed worker has been vaccinated Should be tested for anti- HBs & given 1 dose of vaccine & 1 dose of HBIG if < 10 IU
  112. 112. 116 IF AND THEN Source pt is –ve for HBsAg Exposed worker not vaccinated Worker should be encouraged to receive hepatitis B vaccine. Exposed worker has been vaccinated No further action is needed. Source pt refuses testing or not identified Exposed worker not vaccinated Should receive HB series HBIG should be considered Exposed worker has been vaccinated Management should be individualized.
  113. 113. HIV POSTEXPOSURE MANAGEMNT 117 IF THEN AND Source pt has AIDS OR Source pt is HIV+ve OR Source Pt refuses to be tested Exposed worker should be counseled about risk of infection. Should be tested for HIV infection immediately Should be asked to seek medical advice for any febrile illness within12 weeks Refrain from blood donation & take appropriate precautions Exposed worker testing –ve initially should be retested 6 weeks, 12 weeks & 6 months after exposure.
  114. 114. 118 IF THEN AND Source pt is tested & found -ve Baseline testing of the exposed worker with follow up testing 12 weeks later Nil Serological testing must be done & decisions must be individualized Nil
  115. 115. CLINICAL WASTE DISPOSAL Regulated medical waste is only a limited subset of waste: 9%-15% of total waste in hospitals and 1%-2% of total waste in dental offices. Examples of regulated waste found in dental-practice settings are solid waste soaked or saturated with blood or saliva (e.g., gauze saturated with blood after surgery), extracted teeth, surgically removed hard and soft tissues, and contaminated sharp items (e.g., needles, scalpel blades, and wires. 119
  116. 116. • Regulated medical waste requires careful containment for treatment or disposal. • A single leak-resistant biohazard bag used for containment of non sharp regulated medical waste. • Puncture-resistant containers with a biohazard label- used as containment for scalpel blades, needles, syringes, and unused sterile sharps. • All containers with blood or saliva (e.g., suctioned fluids) can be carefully poured down a utility sink or drain. • Adding 5% hypochlorite in water to suctioned fluids is recommended before disposing into the drain. • Multiple bloodborne pathogens, are not stable in the environment for long periods, and the discharge of limited quantities of blood into the sanitary sewer is considered a safe method for disposing of these waste materials. 120
  120. 120. • Properly labeled containment to prevent injuries and leakage. • Medical wastes are “treated” in accordance with state and local EPA (Environmental Protection Agency) regulations. • Processes for regulated waste include autoclaving and incineration. 124
  121. 121. Tips for protecting dental instruments. • Clean as soon as possible to remove corrosive materials such as blood. • Keep instruments from knocking against each other as much as possible during the cleaning process. • Do not store for longer period of time in water or chloride solutions. • Only use cleaning solutions that are recommended for dental or medical instruments.
  122. 122. • Rinse well after cleaning. • Use distilled or deionised water in steam sterilizers to avoid water spotting of instruments and damage to sterilizer. • Use rust inhibiters for carbon steel items. • Dry items prior to processing through dry heat or chemical vapour temperature.
  123. 123. CONCLUSION • As we have discussed lots of infections & preventive methods , which will make sure the safety for both the doctors & patients. • So, it is the duty & responsibility for each & every doctor and a technician to follow the infection control protocol such as sterilization & disinfection methods in order to protect the patients from contagious disease & microorganisms 127
  124. 124. REFERENCES 1. The art & science of operative dentistry- Sturdevant. 2. Textbook of microbiology – Davis & panikar 3. Textbook of hospital dentistry-Harold.a.Black 4. Davidsons principles and practice of medicine 5. Practical Infection Control in Dentistry -James A. Cottone 6. CDC. Guidelines for infection control in dental health-care settings – 2003. MMWR 2003; 52(No. RR-17):1–66. Available at 7. Infection Control Cover Story JADA VOL.134, MAY 2003. 8. Textbook of medical microbiology – Gupte. 9. Google 128
  125. 125. 129 THANK YOU
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