sterilization

1. STERILIZATION &
DISINFECTION
1

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

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

4. • SPAULDING’s CLASSIFICATION
• STERILIZATION MONITORING
• CONCLUSION
• REFERENCES
4

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

24. PHYSICAL AGENTS
24

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

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

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

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

29. DRY HEAT
29

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

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

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

33. 33

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

35. MOIST HEAT
35

36. MOIST HEAT
Sterilization
By
Moist heat
Moist heat at
Below 100˚C
e.g..
pasteurization
Moist heat
At 100˚C
•Boiling
•Tyndallization
Moist heat
At above 100˚C
Autoclave
36

37. 1.Pasteurization –
 The material is heated at
 Holder method - 630C for 30 minutes
 Flash process - 720C for 15-20 sec
followed by sudden cooling 130C or
lower.
 All non-sporing pathogens such as
mycobacteria, brucellae & salmonellae
are destroyed.
37

38. II.BOILING
 Boiling is highly unreliable as a
sterilization technique; not recommended
for sterilizing surgical instruments.
 Vegetative bacteria killed almost
immediately at 90-1000C, but sporing
bacteria require prolonged periods of
boiling.
38

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

40. • Means intermittent exposure at 1000C
• Principle : that one exposure kills
vegetative organisms, between heatings
the spores being in a favorable nutrient
medium become vegetative forms which
get killed during subsequent heating.
• Used for gelatin media, media containing
sugars.
TYNDALLIZATION
40

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

42. • 4 parameters of importance
• Pressure
• Temperature
• Time
• Steam
42

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

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

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

46. • AUTOCLAVES
– 1150C, for 45 min
– 1210C, for 15-20 min
– 1340C, for 3 min
STERILIZATION TIMES
46

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

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

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

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

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

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

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

54. • Hospital type of sterilizer consists of large
chamber which is connected to a steam line
which eliminate the need to generate its own
steam
• These have a vacuum system for air removal
such that when the steam enters it has better
chance of coming in contact with every thing in
the chamber
• Require the temperature of 2500 F 54

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

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

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

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

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

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

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

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

63. CHEMICAL AGENTS
63

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

82. Classification of
instrument sterilization
82

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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