The document discusses sterilization and disinfection in dentistry. It begins with introducing the importance of sterilization due to the risk of transmission of infections from dental professionals to patients. It then defines key terms like sterilization, disinfection, antisepsis, and classifications. The document goes on to describe various sterilization methods including physical methods like heat and radiation, and chemical methods. It provides details on sterilization of dental instruments and monitoring sterilization effectiveness.

1. 1

2. 2
• INTRODUCTION
• DEFINITION
• HISTORY
• SPAULDING’s CLASSIFICATION
• STERILIZATION PROTOCOL
• STERILIZATION METHODS
(a) PHYSICAL
(b) CHEMICAL

3. 3
• STERILIZATION OF OPERATIVE AND
ENDODOTIC INSTRUMENTS
• STERILIZATION MONITORING
• RECENT ADVANCES IN STERILIZATION
• CONCLUSION
• REFERENCES

4. • 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.
• 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 sterilization and disinfection.
4

6. • 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.
6

7. • 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
7

8. • 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.
8

9. • 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.
9

10.  Hippocrates of Cos (460-377 BC), was the first to
separate medicine from philosophy and disproved the
idea that disease was punishment for sin. He also
advocated irrigation of wounds with wine or boiled water,
foreshadowing asepsis.
 Ignaz Semmelweis, an Hungarian obstetrician, advocated
in 1847 the value of handwashing and fingernail
scrubbing. 10

11. Joseph Lister, an English physician,
reduced the mortality rate of his patients
in 1867 by using a carbolic solution
spray as he operated, he then used it in
the wound.
Charles Chamberland, Louis Pasteur’s
pupil and collaborator, developed the
first pressure steam sterilizer, or
autoclave in 1876. 11

12. 12
 Aesculap created the first rigid instrument container,
originally made of stainless steel, in Germany. In the early
1900’s, responding to the needs of the military hospitals
and aid stations, Aesculap manufactured chrome-plated
containers for safe transport of sterileinstruments.

13. • 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
13

14. LEVEL PROCESS
Critical Sterilization
Autoclave
Chemiclave
Dry heat
Immersion in
full strength
glutraldehyde
MATERIALS
Items that are used in surgery
which pierce soft and hard
tissues.
burs, extraction forceps,
elevators, needles, files, Bone
rongeurs.
14
SPAULDING’S CLASSIFICATION

15. LEVEL
Semi-
Critical
PROCESS
Sterilization
Autoclave
Chemiclave
Dry heat
Immersion in
full
strength
glutraldehyde
MATERIALS
Items that do not necessarily
penetrate soft and hard
tissues but which cross the
vermilion border into the
oral cavity- mouth mirrors,
Handpiece,
anesthetic
syringes,impression
trays.
15

16. LEVEL PROCESS
Non-
Critical
Surface
Disinfection
-Phenolics
-Iodophors
-Quaternary
Ammonia
compounds
MATERIALS
Items used in dentistry
which do not cross the
vermilion border or
penetrate the oral
tissues- chair light
handles, instrument
trays, bracket, chair
controls, Air/water
syringes, hoses, dental
chairs
16

17. It encompasses following steps:
 Transport of contaminated instruments.
 Cleaning of instruments.
 Instrument examination & care.
 Packaging
 Sterilization methods.
17

18. • 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.
18

19. 2. Transport:
• Instruments transported in a tray or cassette to
the designated area.
• Sharp instruments should be handled
carefully by : Use of utility gloves.
19

20. Reduces the number of microbes present
Two types-
1. Hand scrubbing
2. Mechanical cleaning - ultrasonic cleaner,
instrument washer.
20

21. HAND CLEANING
21
Disadvantage :
It requires maximum direct contact with
contaminated instruments.

22.  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.
22

23.  safest & most efficient way to
clean sharp instruments.
PROCEDURE
• wear protective utility gloves
• Place the instruments in
cassettes.
 Sonication of loose instruments
should be carried out for 8-
10minutes and the period
doubled(15-20 minutes) for
instruments in cassettes. 23

24. • 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
24

25. 25
•Includes : paper pouches, plastic
pouches, sterilization cassettes
•Packaging should allow
penetration of heat , steam,
chemical vapour etc.

26. CLASSIFICATION
26
CHEMICAL AGENTSPHYSICAL AGENTS

27. 27
 SUNLIGHT
 DRYING
 DRY HEAT
 MOIST HEAT
 RADIATION
 FILTRATION
CHEMICAL
AGENTS
 ALCOHOLS
 ALDEHYDES
 DYES
 HALOGENS
 PHENOLS
 QUARTENARY AMMONIUM
COMPOUNDS
 SURFACE
ACTIVE AGENTS
 GASES

28. 28

29. 29

30. •Moisture is essential for growth of
bacteria
•80% of bacterial cell weight is water
•Drying hence has a deleterious effect
•Unreliable & of theoretical interest
only
•Spores are not affected
30

31. •Refrigeration: 5o C
•Freezing: -20o C
•Ordinary refrigeration has a bacteriostatic
effect but does not kill. Metabolic rate of
some microbes is so reduced that they
cannot reproduce or synthesize toxins
•Growth of pathogenic bacteria slows down
at refrigerator temperature & can be used
to preserve. 31

32. • Most reliable
• Universally applicable
• Method of choice – whenever applicable
• 2 types – Dry & Moist
• Materials damaged by heat – Sterilized at low
temperature or longer periods or repeated
cycles
32

33. •DRT also called D-value refers to the time required
at a certain temperature to kill 90% of the
organisms being studied
•Thus after a colony is reduced by 1 D, only 10% of
the original organisms remain.
•E.g. if a organism is reduced by 90% after exposure
to temperatures of 300° F for 20 minutes, the D-
value would be written as D300F = 20 minutes
• Sterilization-resistant organism are given a unique
D-value.
33

34. •Used in thermal death time calculations
•The z-value of an organism is the
temperature, in degrees (Fahrenheit or
Celsius), that is required for the thermal
destruction curve to move one log cycle.
•Simply, temperature required for one log
reduction in the D-value.
34

35. 35

36. •Nature of heat
 Dry or Moist
•Temperature & Time
Time required is inversely proportional
to temperature
Thermal death time (TDT) – Minimum time
required to kill a suspension of organisms at a
predetermined temperature in a specified
environment 36

37. •Number of microbes
More number of microbes there are to begin with,
longer it takes to eliminate the entire population
•Characteristics of organisms
Vegetative bacteria & virus are more susceptible &
spores are more resistant.
• Nature of contaminated material
Presence of organic substances, proteins, nucleic
acid, starch, fats & oils, increase the TDT
High acid/ alkaline pH increases bacterial
killing 37

38. •Dry heat
 Protein denaturation
 Oxidative damage
 High electrolyte level toxicity
• Moist heat
Coagulation & Denaturation of
enzymes/ structural proteins
38

39. •Red heat - Item to sterilized are held almost
vertically in a Bunsen flame until red hot along
their whole length, almost up to the tip of their
metal holder.
•Items sterilized by red heat –
 Inoculating wire loops
 Points of forceps
•Flaming – Only exposed to the flame for a few
seconds & not heating to red hot. E.g Scalpel
blades, glass slides, mouth of culture tubes. 39

40. 40

41. 41

42. 42
•Excellent & safe method
•Material destroyed completely –reduced to ashes
•Very high temperatures reached
•Used for – Pathological wastes, surgical dressing,
animal carcasses, plastics like PVC/ polythene
•Avoid – Materials made of polystyrene as they emit
black dense smoke

43. 43
DR R
SATHYAJITH

44. •Most widely used method by dry heat
•Used - When can withstand high temperatures &
when affected by contact with steam
•Parts – Electric heater, Fan to provide forced air
circulation, Temperature indicator, Control
thermostat & timer, Open mesh shelving, Heating
coils on wall/floor & adequate wall insulation –
Inner layer poor conductor & outer metallic
44

45. P
M

46. •Preparation of load
 No overloading – to allow free circulation of
air
 Articles should be thoroughly clean &
perfectly dry
 Test tubes & flasks – Should be wrapped in
paper
 Avoid – Rubber except silicon, Cotton plugs,
Plastics
46

47. • Sterilizing cycle
Sterilization hold time – It is set to 160o C for
2hours or 170o C for 1hour or 180o C for 30min
Cutting instruments like used in ophthalmic
surgery should be sterilized at 150o C for 2hours
Oils, glycerols & dusting powder holding
time recommended is 150o C for 1hour.
47

48. 48
•Cooling takes several hours –Open the door
after chamber & load have cooled below 80o C
or else glassware will crack.
Glassware such as tubes, flasks, all glass syringes,
petri dishes, pipettes.
Metal instruments like forceps, scissors &
scalpels
Nonaqueous materials & powders, oils & greases
in sealed containers, swab sticks placed in test
tubes.

49. •Safe – No water used & no pressure build up
inside
•Smaller –But as effective as autoclave
•Cheaper –Suitable for small laboratory
• Rapid –also higher temperatures reached
• Dry heat penetrates more slowly
• Heating effect if not uniform
• Not reliable method for sterilization 49

50. 50
Sterilization
By
Moist heat
Moist heat at
Below 100˚C
Moist heat
At 100˚C
Boiling
Tyndallization
Moist heat
at above 100˚C
AutoclavePasteurization,
water bath,
Inspissations

51. 51
 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.

52. •Literally means the process of thickening by
dehydration
•Also called fractional sterilization
•Used when heating high-protein (Egg) containing
culture media like Lowenstein-Jenson & Loeffler’s
serum slope.
•Heated at 80o C for 30min (2hrs*) on 3 successive
days
52

54. •Washing or rinsing laundry or eating utensils
at 70- 80o C for few minutes will kill most
non sporing microorganisms.
54

55. 55
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.

56. A minimum exposure period of 30min. is
recommended to kill vegetative bacteria.
 Sodium bicarbonate 2% conc. is added to
increase the efficiency of process.
56

57. • 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.
57

58. •Process of sterilization using saturated steam
under high pressure above 100o C
•Principle – water boils when its vapor pressure
equals that of surrounding atmosphere.
•When pressure inside a closed vessel increases,
the temperature at which water boils also
increases
•Steam condenses to water & gives up its latent heat
to the cooler surface it comes in contact with.
Energy available from this latent heat is
considerable
58

59. 59

60. 1.Steam jacketed autoclave:
Double walled chamber in which steam at 121
degree is introduced from an external source.
Steam enters the jacket from which it enters the
chamber migrating downwards replacing the air
which is expelled through a discharge tap at the
bottom.
2. Flash autoclaves:
It sterilizes at 134 degree for 3 –5minutes.
Used in operation rooms in emergency situations
60

61. 1. Sufficient water is put in the cylinder.
2. Articles are kept above the perforated shelf
3. Lid is screwed tight
4. Autoclave is heated
5. Discharge tap is kept open
6. Safety valve is adjusted to required pressure
7. Steam-air mixture is allowed to escape freely till
all air is displaced
61

62. 8.Discharge tap closed
9.Steam pressure rises inside
10. Safety valve opens when it reaches the desired set
level (15psi)
11. Excess steam escapes
12. Holding period calculated from now (15min)
13. Heater turned off when holding period over.
14. Cool the autoclave till pressure inside equals
atmospheric pressure
15. Discharge tap is open & later lid is opened.
62

63. 63
DR R
SATHYAJITH

64. •Air must be allowed to escape from the chamber
because the temperature of air-steam mixture is
lower than that of pure steam
•If the discharge tap is opened when pressure inside
is high, liquid media will boil violently & spill
from the container & can also explode
•If discharge tap is opened after pressure inside
has fallen below atmospheric pressure, excessive
water would have evaporated & lost from the
media
•Materials be arranged to ensure free circulation of
steam inside the chamber
64

65. •MOA – Bacterial proteins coagulates & condensed
water ensures moist condition for killing
•Sterilizing culture media, aqueous solutions, rubber
materials, dressing materials, gowns, dressing, linen,
gloves, instruments & pharmaceutical products
•For all materials that are water containing,
permeable or wettable
•Useful for materials unable to withstand higher
temperature of hot air.
65

66. •Filter paper strip impregnated in 104 spores of
Geobacillus stearothermophilus (ATCC7953) used
•Placed in least accessible & coolest part
•Inoculated in TSB& incubated at 56o C for 5days
•It withstands 121o C for upto 12min
66

67. 9:09
PM
97
After
autoclaving,
flexible
Endospore strip vial is squeezed to
break ampule and
release medium
onto spore strip.
Yellow
medium
means
spores are
viable;
autoclaved
objects are
not sterile.
Red
medium
means
spores
were
killed;
autoclaved
objects are
sterile.
Cap that
allows
steam to
penetrate
Flexible
plastic
vial
Crushable
glass
ampule
Nutrient
medium
containing pH
color indicator

68. •More lethal –action of moist heat
•Quicker in heating up articles
•Greater penetration of porous material like
cotton plugs, paper & cloth wrappers,
surgical linen, hollow apparatus.
68
 What should not be autoclaved?
• Items containing solvents, volatiles or
corrosive chemicals
• Radioactive material

69. NON-IONISING
 I R Rays
 U V Rays
IONISING
 Gamma Rays
 High Energy Electrons
69

70.  Mechanism of action- Generation of heat
 IR RAYS
 for rapid mass sterilization of
syringes
 UV RAYS
 for storage of sterilized instruments
70

71. X-rays and gamma rays have wave length shorter
than UV light.
•Cold sterilization
No appreciable increase in temperature
Commercial plants use gamma rays emitted from
radioactive elements like Cobalt 60
•Uses – Sterilizing in pharmacy & medicine (Abx,
hormones, sutures, vaccines) / packaged disposable
articles ( IV lines, catheter, syringes, Gloves).
71

72. • Like CO2,ARGON etc.
• Time contact is very less upto 35 sec.
• Not commonly used due to cost factor involved.
72

73. • Cells of all types killed by intense ultrasonic & sonic
vibrations
• Limited practical significance for sterilization
• Valuable in instrument cleaning
73

74. •Filtration is commonly the mechanical
operation which is used for the separation of
microbes from fluids (liquids or gases) by
interposing a medium through which only the
fluid can pass.
74

75. •Heat sensitive solutions – For sterilization of
pharmaceuticals, ophthalmic solutions, culture
media, oils, antibiotics etc.
•Separation of bacteriophages & bacterial toxins
from bacteria
•Isolating organisms which are scanty in fluids
•Concentration of bacteria from liquids
•Isolation of viruses – pore size of 0.22mcm
75

76. •Earthware filters
•Asbestos filters
•Sintered glass filters
•Membrane filters
•Syringe filters
•Vacuum & ‘In-line’ filters
• Pressure filters
• Air filters
76

77. 77
 “Flash” steam sterilization was originally defined by
Underwood and Perkins as sterilization of an
unwrapped object at 1320C for 3 minutes at 27-28 lbs.
of pressure in a gravity displacement sterilizer.
Depends on the type of sterilizer and the type of item
(i.e., porous vs non-porous items).

79. 79

80. • 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.
80

81. • 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.
81

82. 2.ALDEHYDES
• 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.
82

83. – 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 180c.
83

84. • GLUTARALDEHYDE
– Markedly bactericidal,virucidal including HIV
and mycobacteria and to a lesser extent spores.
– Concentration required 2%.
84

85. – 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.
85

86. • 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
86

87. • 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.
87

88. 88

89. 5. HALOGENS
• IODINE
– Aqueous and alcoholic solutions used as
skin disinfectants
– Actively bactericidal, virucidal,and fairly
active against spores
– It inhibits protein synthesis
89

90. CHLORINE
• 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
90

91. 6. DYES
• 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.
91

92. • 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.
92

93. 93
– Alter energy relationship at interfaces
producing a reduction of interfacial tension.
– 4 groups: cationic, anionic, nonionic and
amphoteric.

94.  Surface active cationic
compounds.
 Bactericidal, but not sporicidal
 Effective against Gram +ve
bacteria.
 Examples
 Cetyl trimethyl ammonium.
bromide (cetavlon or cetrimide)
94

95. 95

96. 96

97. 97

98. 98

99. 99

100. 100

101. 101

102. 102

103. 103

104. 104

105. 105

106. 106

107. 107

108. 108

109. 109

110. 110

111. 111

112. 112

113. • Toensure that the sterilization is complete
various monitoring indicators are there:
1.biologic indicators
2. chemical indicators
3.physical indicators
113

114.  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.
114

115. • 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.
115

116. 116
• 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

117. • Involves observing the gauges and displays
on the sterilizer and recording the
temperature, pressure and exposure time.
117

118. 118
• Improper cleaning of instruments
• Improper temperature
• Improper loading of sterilizer
• Improper Timing
• Improper Packaging
• Improper Method of Sterilization

119.  Various new methods of sterilization are under investigation and
development.
 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
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. 119

120. 120
 Plasma is basically ionized gas. When you apply
an electric field to a gas, it gets ionized into
electrons and ions.
Plasma is usually comprised of UV photons,
ions, electrons and neutrals.
A plasma is a quasi-neutral collection
capable of collective behavior
Their combined photolytic, chemical and
electric action efficiently kills most micro-
organisms.

121. Ozone sterilization is the newest low-temperature
sterilization method recently introduced in the US and
is suitable for many heat sensitive and moisture
sensitive or moisture stable medical devices
Ozone sterilization is compatible with stainless steel
instruments.
Ozone Parameters - The cycle time is approximately 4.5
hours, at a temperature of 850F – 940F.
121

122. • 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.
122

123. • Ananthnarayan ,Paniker.Textbook of microbiology.6th
edition.
• Baweja C.P.Textbookof microbiology,3rd edition
• Sturdevant’s art and science of Operative
Dentistry,5th edition, Theodore M. Roberson, Harald
O.Heymann, Edward J. Swift
• Grossman’s endodontic practice, 12th
edition, B. Suresh Chandra, V. Gopi Krishna
• http://www.cdc.gov/oralhealth/infectioncontrol/gui
deline/index.htm
• Recent advances in sterilization by William, A.Rutala
and David Weber (Emerging Inectious Diseases)
123