Sterilization of dental instruments in dentistry

It is needed for dental practice

1. Sterilization Dr. Nilima Roy BDS, DDS Assistant Professor & Head Dept. of Dental Pharmacology Update Dental College

2. Objectives Definition, Aims & objectives of sterilization Classify different methods of sterilization. Advantages, disadvantages, differences among the different methods of sterilization. The procedure of sterilization of dental instrument . The ideal method of sterilization. Procedure of sterilizing dental hand pieces. Methods of infection control in dental clinic.

3. Definition Sterilization is the process by which all the viable microorganisms ( Bacteria, virus, fungus & parasite) including their spores are killed or inhibi ted.

4. Aims or objectives of sterilization To reduce the numbers of pathogenic microorganisms . To break the cycle of infection & eliminate cross contamination. To treat every patient & instrument as they are capable of transmitting infectious disease. To protect patient and health care workers from infection and its consequence.

5. Classification of Sterilization A. Physical- 1. Sunlight 2. Heat 3. Radiation 4. Filtration. 1. Heat- Dry heat Red heat Flaming Hot air oven Incineration

6. Moist heat Below 100 C Pasteurization Water bath Vaccine bath Inspissation At 100 C Boiling Steaming Tyndallization Koch’s steamer Above 100 C Autoclave

7. 2. Radiation X ray Gamma ray Beta ray UV ray Infrared ray. 3. Filtration Berkefeld Chamberland Seitz Sintered glass Membrane filter

8. B. Chemical Alcohol Phenol Ethylene oxide Halogens Heavy metal Aldehyde Dyes Gaseous : Halogen Ethylene oxide Glutaraldehyde

9. Methods of sterilization There are several way of achieving sterilization. Most commonly used method are follows: By steam or moist heat at a raised atmospheric pressure, in an autoclave. By dry heat/hot air, at normal atmospheric pressure, in a dry oven. By use of ethylene oxide. By low-temperature steam and formaldehyde. By irradiation.

10. Principles of sterilization All used instruments should be thoroughly cleaned, all deposits of blood and debris should be removed before sterilization. It is essential for the sterilization agent (heat, steam, gas) to be in contact with every surface of each item to be sterilized for the specific period of time at the specific temperature. All sterilizing equipment must be regularly serviced and maintained by suitably qualified engineers. The manufacturer’s instructions should be strictly adhered to its operation and maintenance.

11. Sterilization can be achieved Sterilization can be achieved by following mechanism: By denaturation protein( dry heat) By disruption of cell membranes & denaturating their enzymes & coagulation of protein .( moist Heat) By oxidization.( Dry heat) By interruption of DNA synthesis. ( Radiation )

12. Moist heat method of sterilization Below 100 c: Pasteurization: According to WHO it may be defined as heating of milk to such temperature and for such period of time as are required to destroy pathogen.( Mycobacterium bovis , Brucella, Salmonella, Listeria, Streptococcus) Types: Holding method: 63-66 c for 30 mins Flash method: 72 c for 15 sec ( Milk, Fruit juice) followed by rapid cooling. Use: Milk and other liquid food stuffs.

13. Inspissation means stiffening of protein without coagulation by heating. It is done between 75-80 degree c 30 min daily on three consecutive days. Uses: Media containing serum( Loeffler’s serum), eggs(Lowenstein- jensen ) etc. INSPISSATION

14. Vaccine Bath /water Bath Serum or body fluids containing coagulable protein can be sterilized by heating in a water bath at 56 degree C for 1 hour for several successive day. Vaccine are sterilized in a vaccine water bath at 60 degree C for 1 hour.

15. At 100 c: Boiling: Boiling at 100 c for 30 min is sufficient to kill all vegetative organisms but not the spores .( it leads to disinfection) Material sterilized : Metallic syringe, needle, rubber goods, blunt metallic forcep & tray . Advantages: Kills most vegetative microorganism. Glass wares can be disinfected by placing them in boiling water. Disadvantages: 1.Some bacterial spore are resistant to boiling & can survive.

16. Steaming: Single exposure: Koch’s or Arnold’s steam sterilizer are useful for those media which are decomposed at higher temperature. steaming at 100 c for 90 mins.( leads to disinfection) Tyndallization : steaming at 100 C for 20 to 45 min for 3 successive days with overnight resting period .

17. Tyndallization / intermittent sterilization steam exposure at 100 degree c in a steam sterilizer for 20 mins, followed by overnight incubation at 37 degree & this cycle is repeated next 2 days. Kills all organisms except spore on first day. Spores, if present, germinate into vegetative bacteria during the incubation period & get destroyed during steaming on the 2 nd day. Third day – kills the remaining cell.

18. Tyndallization / intermittent sterilization Its main use is for destroying the endospore from the food or nutrient media. Heat labile ingredients such as sugar, egg, serum, gelatine. Suitable for sterilizing items which does not sustain high pressure & temperature of autoclave.

19. Above 100 c: Moist heat in the form of pressurized steam-most dependable method. Incorporated in to a device called Autoclave. Autoclave: it is a high pressure device used to allow the application of moist heat above the normal atmosphere boiling point of water. Autoclaving is one of the most common methods of sterilization. Structure: The autoclave machine consist of vertical or horizontal cylinder contain H2O and is heated by electric heater just below the cylinder. The object is placed on a perforated tray above the water level.

20. Principle of Autoclave: At atmospheric pressure water boil at 100c Boiling point of water increased if it is heated under pressure. Steam under pressure unmixed with air has more temperature than mixed with air. When the steam come in contact with cool surface, it condenses to water liberating latent heat. This heat increase the penetration power of moist heat. So, microbes & spores are effectively killed .

21. Pressure, Temperature, Holding time chart: Pressure Pounds/sq inch Temperature Celsius Holding time minute 3 134 3 15 121 15 10 115 30

22. Instrument Sterilization in Autoclave: Linen substance OT gown, Cap, Mask, draping sheet, bed cover. Surgical instrument: retractor, forceps. All types of metallic instrument except sharp instruments. Suturing materials: Silk, nylon, cotton, surgical gauze. Agar based culture media.

23. Advantage of Autoclave Disadvantage of Autoclave The results consistently good ,reliable and increases the efficacy of sterilization. Blunting & corrosion of sharp instruments High temperature can be obtained & the temperature can be raised /fallen according to need. not acceptable for heat sensitive substance(Damage to certain rubber goods, plastic) Time efficient Expensive Provides excellent penetration Rust may occur 100% spore are killed Efficacy may loss to air trap Wide range of instrument can be sterilized It is difficult to perform No toxic residue remain Failed to sterilized due to faulty packing of load.

24. Dry heat method of sterilization : Higher temperature in the range of (160-180).Exposure time up to 2 hours . By Denaturation of bacterial protein, Oxidative damage . Red heat: It is a process where materials are hold in the flame of a Bunsen burner until it becomes red. Temperature is above 100c. Material used in red heat: Wire loop, needle, tip of forceps etc Flaming: Not allowed to get red heat. Article passed through the flame. Sterilized substance: mouth of culture bottle & test tube, mouth of the catheter tip, glass slide , cover slip, scalpel etc.

25. Hot air oven : A hot air oven is a type of dry heat sterilization. It is used on equipment that can not be wet & which do not get damage by high temperature such as laboratory glass wares, glass syringes & instruments. Hot air is a poor conductor of heat & has poor penetrating capacity. High temperature damage fabrics & melts rubber/plastic, hence should not be sterilize by this method.

26. Hot air oven

27. Sterilizing by dry heat is accomplished by conduction. The heat is absorbed by the outer surface of item, then passes towards the centre of the item. The entire item will reach the temperature required for sterilization to take place.

28. Temperature and time Temperature Celsius Time Min 160 60 170 40 180 20

29. Materials sterilized by this method Metallic instruments. All sharp instruments- Scissors, Forceps, scalpel, Knife. All dry glass ware- petridish , Glass syringes, glass slab, pipettes, flasks, test tubes Steel burs, bone cutting burs. Powder, oils, fats, greases.

30. Hot air oven Advantage Disadvantage Glass item can’t be damage by high temperature. Time consuming because of Poor penetration. No rust formation. Non corrosive. Cooling time is longer. Sharpness is preserved. Temperature is lost (brittle). It can destroy spore. Protein containing media can not be sterilized because heat denatures protein.

31. Glass beads sterilizer : It is a dry heat method of sterilization. This method employs a heat transfer device. The media used are glass beads, molten metal or salt kept in a cup or crucible. Temperature achieved is of 220 c. The method employs submersion of small instruments such as endodontic files and burs, rotary instruments into the beads and are sterilized in 10 seconds provided they are clean.

32. Glass beads sterilizer

33. incineration Disposal of contaminated materials by direct burning. Soiled dressings, contaminated cloths, bedding of patient, pathological materials(sputum, stool).

34. Radiation Ionizing radiation Gamma ray( kill spore) X-ray ( only vegetative) Cathod ray (only vegetative) As there is no increase in temperature its also referred as cold sterilization. Short wave length. High degree of penetration Destroy vegetative & spores. High sterilizing efficiency. Disadvantages: the time required for sterilization is long. Uses: Disposable syringes, Needle, IV sets, Cannulas, gloves, dressing pack, plastic syringe, plastic tube. In pharmaceuticals, food industry .

35. Ionizing radiation Non ionizing r adiation: No n-ionizing radiation 1. UV light 2.Infrared radiation: purify air Longer wave length. Low sterilizing efficiency. Don’t kill spores Uses: In hospital particularly ward, OT. School. Laboratories.

36. filtration It is one kind of sterilization which is used to separate pathogenic microorganism rather than to kill them. This method is used for liquid & air quality control, disinfection, sterilization. These filters contain pores of very small diameter. When liquid or gas pass through the pores, contaminants larger than pores are filtered out. The smaller the pores, the more particles it can screen out, but it also takes more energy to force the liquid & gas through it.

37. Types-1. Depth filters : In this slurry penetrate to a point where the diameter of solid particles is greater than that of the tortuous voids or canal. Berkefeld filter. Chamberland filter. Asbestos filters: Seitz filter. Sintered glass filter. 2. Membrane filter : These circular disc shaped filters are made of polymeric materials. e.g. cellulose , Polyester etc.

38. filtration Sterilized substance: Filtration of fluid containing anti-serum. Filtration of fluid containing toxic. Heat labile drugs. I/V solution. Separation of soluble products from micro-organism. To separate virus from bacteria. Purification of drinking water.

39. Factor responsible for filtration Size of pores. Size of particles. Electrostatic attraction between pores & particles. Ph of the materials to be filtrated. Amount of protein. Filtration pressure Type of filter use.

40. Chemical sterilization Chemical commonly used are- Iso-propyl alcohol (70%) /ethanol/ alcohol : disruption of cell membrane. Phenol & phenol derivatives : lysol , 5%cresol for sharp instrument. Denature protein & altering membrane permeability. Halogen( 100 to 1000ppm of free chlorine, iodine): chlorine as water disinfectant, povidone iodine 10% as a skin antiseptic. Aldehyde:: Formaldehyde : sterilization of room, bedding, clothing. Glutaraldehyde 2%: surgical equipment, endoscopes.

41. Advantages of chemical sterilization Carbon steel & other corrosion sensitive burs, instruments & pliers are said to be sterilized without rust or corrosion. Instruments sensitive to high temperature can be sterilized. High penetration power. Phenol, glut a raldehyde & formaldehyde solutions persist for long time after applied & remain active in the presence of organic compound.

42. Disadvantages of chemical sterilization Towels & heavy cloth wrapping of surgical instrument may not be penetrated to provide sterilization. Takes long times to sterile. These solution cause skin irritation, therefore all equipment must be thoroughly rinsed with sterile water after soaking. Vapors from these solution irritating to the skin, eyes & respiratory tract. So wear a gloves & goggles, limit exposure time, used in well ventilated areas. Some of these solutions are expensive.

43. Gaseous sterilization Ethylene oxide : colorless & highly penetrating gas. used to sterilized plastic , rubber goods, heart-lung machines & others materials which are spoiled by heat. 2. Formaldehyde 3% to 8%: widely employed for fumigation of OT & others room.

44. Gaseous sterilization Fumigation is a process of gaseous sterilization which is used for killing organism & prevention of microbial growth in air, surface of wall or floor. Fumigation usually involves the following phases: First the area to be fumigate 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.

45. Creating the formaldehyde gas: Electric Boiling fumigation Method: For each 1000 cu.ft of the volume of the operation theatre 500 ml of formaldehyde (40% solution) added in 1000ml of water in an electric boiler. Switch on the boiler, leave the room and seal the door. After 45 minutes (variable depending to volume present in the boils apparatus) switch off the boiler without entering in to the room.

46. Formaldehyde gas sterilizer

47. Fumigation to be neutralized Neutralize residual formalin gas with Ammonia by exposing 250 ml of Ammonia per liter of Formaldehyde use Place the ammonia solution in the centre of the room and leave it for 3 hours to neutralize the formalin vapor.

48. Ethylene oxide Advantages: Very effective to kill microorganism. Penetration power is more. Compatible with materials not withstanding heat. Disadvantages: Highly flammable. Maintain for a period of 10 hours. Residual ethylene oxide must be ventilated.

49. Ethylene oxide sterilizer

50. Difference between sterilization and disinfection Disinfection Sterilization This technique minimizes the number of microorganisms but not eliminate them completely. This technique is elimination of all the microorganisms. This method does not eliminate bacterial spore. This method kills bacteria as well as vegetative and spores. It is not an absolute condition. It is an absolute condition . It is used for decontamination of surfaces and air. It is used for decontamination of surgical equipments ,food, instruments. Commonly used in daily life. Sterilization is used in surgical operations and various labs where sterile condition are pre-requisite.

51. How will you sterilize dental instruments Dental instruments are classified into three categories- Critical: Needles, surgical instrument, catheter. Semi critical: Endoscopes, endotracheal tube. Non critical : Sphygmomanometers. depending on their risk of transmitting infection & they need to sterilize among their uses.

52. Classifications of materials Item Comes in contact with Type recommended Critical Tissue, vascular space Sterilization Semi-critical Mucous membrane Non intact skin High level disinfectant Non-critical Intact skin only Not mucous membrane Intermediate or low level disinfectant

53. Classifications of materials

54. To achieve sterilization of any Dental instrument three definite stages are to be completed- Pre sterilization cleaning Sterilization process. Aseptic storage

55. Pre- sterilization process Objective: Removal of the organic matters, blood & saliva which provide protective barrier for micro organisms. There are three method of cleaning: Manual: simplest & cheapest method but time consuming. Soaps & detergents are commonly used in this method. Ultrasonic: Conversion of electrical energy into vibratory sound waves which pass through a soap solution containing the instruments. It used mainly for burs, bone files, bone cutter, artery forceps etc. Mechanical washing : High pressure jets of water with or without a detergents which remove debris of instruments. Small instruments like burs, blade are not suitable for this type of cleaning.

56. sterilization process All metallic blunt dental instrument should be sterilized by autoclave. It is the best method of sterilization. Dental sharp instrument should be sterilized by hot air oven. Chemical sterilization also can be used. Endodontic instrument should be sterilized be glass beads sterilizer

57. Aseptic storage The maintenance of sterility during transportation and storage is very importance. Instruments are kept wrapped until ready for use. To reduce the risk of contamination sterile packs must be handled as little as possible. Sterilized packs should be allowed to cool before storage, otherwise condensation will occur inside the packs. To prevent communication from rodents, ants & cockroaches, the store must be subjected to adequate pest control. Materials should be stored at least 8° of the floor and 18° from the ceiling. Sterile packs must be stored & issued in correct date order, the packs preferably are stored in drums that can locked.

58. Sterilization of hand piece While using hand piece in patients mouth blood, saliva, tooth cutting debris & restorative materials maybe drawn into its working portion. Hence it should be properly sterilized between patient exposure to prevent cross infection. Protocol: Clean the hand piece by wiping visible debris using suitable disinfectant such as alcohol. Run it for minimum of 30 seconds to discharge residual water & air. Clean it thoroughly with soap & detergent solution. Reattach hand piece to the unit & run dry. Lubrication of hand piece should be done before sterilization with lubricant. Finally place the instruments in paper pack & seal it. Now hand piece can be sterilized by autoclaving.

59. Hand pieces

60. High risk group for Hbv infection People from endemic region. Pregnant mother with chronic HBV carrier. Intravenous drugs abusers. People with multiple sex partners. Hemophilic & other patient requiring blood & blood product. Health care providers who have contact with blood. Person at occupational risk of HBV infection.

61. Do you think boiling is an ideal sterilizing method? Justify your answer . Boiling is not an ideal sterilizing method because, at atmospheric pressure the normal boiling point is around 100°c at this temperature can kill only vegetative forming organisms. It does not kill the spore forming organisms. So need to boil the items for a very long period of time or intermittent boiling may be used. It does not generate much higher temperature where microbes that are boiling resistant can survive. Truly boiling is not highly efficient, making it one of the most reliable forms of sterilization.

62. Difference between autoclave & boiling Autoclave Boiling Temperature range of autoclave is around 121°c to 135°c. The temperature is around 100°c Autoclaving carries much more heat is able to kill more effectively the harmful microbes. It carries less heat than autoclaving which is not able to kill more effectively the microbes. Autoclaving kill spores forming organisms. It does not kill the spore forming microbes. Autoclave have the option of setting the desire time & temperature. Does not have the option of setting desire temperature. It is highly efficient making it one of the most reliable form of sterilization. Not like autoclave.

63. Difference between autoclave & chemical sterilization Autoclave Chemical sterilization Autoclave is useful & carrying out industrial & laboratory process that require high temperature & pressure conditions. In chemical sterilization instruments are sensitive to high temperature can be sterilized. Carbon steel can get damaged due to moisture exposure. Carbon steal & other corrosion sensitive instrument are said to be sterilized without any rust or corrosion. Mode of action by steam. By different chemicals like phenol, gluteraldehyde , formaldehyde etc. Takes desire times to sterile. Take long time to sterile. It does not cause any skin, eye irritation. It may causes irritation to skin, eyes & respiratory tract

64. Difference between autoclave & hot air oven Autoclave Hot air oven Autoclave is a deviceof instrument sterilization that uses time, temp & pressure to kill all form of microbes. Basically sterilizing use time & temp to kill all form of microbes. Requires minimum of 121 °c with steam pressure of 15 p/sq inch. Usually takes about an hour at 160° c. Steam autoclave can process various materials simultaneously in less time possible. It is relatively slower than autoclaving. B lunting & Corrosion of sharp instrument. Sharpness is preserve & no rust form. Are relatively more expensive. Are relatively less expensive.

65. Infection control in dental chamber /dentistry Vaccination Precise medical history: History of any exposures, diagnostic tests or treatment of disease specially high risk disease. Barrier technique: Use of gloves. Use of gowns. Masks & head caps. Protective eye wear. Face shields.

66. 4. Care of operator’s hand: Washing of hands before, between & after patients which means a thorough initial scrubbing of all surface of nail, hands & lower arms first with soap followed by an antimicrobial solution. 5. Sterilization: 1. Critical 2. Semi-critical 3. Non-critical 6. Dental equipment sterilization 7. Disinfection: Glutaraldehyde, sodium hypochlorite, iodophores etc..

67. Other methods of infection control Use of disposable materials. Prevention of biofilms . Prevention of needle stick injury. Disposal of waste.

68. Spore killing methods of sterilization Autoclave. Hot air oven. 2%Glutaraldehyde. Ethylene oxide.