Basic seminar 3 sterilization and disinfection

STERILIZATION AND
DISINFECTION

CONTENTS
STERILIZATION :
 INTRODUCTION
 HISTORY
 DEFINITIONS AND TERMINOLOGIES
 PRINCIPLES AND GOALS OF STERILIZATION
6/5/2018 Basic Seminar 3 - Dr. Barkha. S. Tiwari 3

 AGENTS USED IN STERILIZATION
 STERILIZATION MONITORING
 METHODS USED FOR STERILIZATION
 NEWER METHODS IN STERILIZATION

DISINFECTION :
 AGENTS USED FOR DISINFECTION
 IDEAL REQUIREMENTS
 LEVELS OF DISINFECTION
 GENERAL RULES FOR SURFACE DISINFECTION
 NEWER PARADIGMS IN DISINFECTION

STERILIZATION

INTRODUCTION
• Microorganisms are ubiquitous since they cause
contamination, infection and decay, it becomes necessary to
remove or destroy them from materials or from areas. This is
the object of sterilization.
• The method employed depends on the purpose for which it is
carried out, the material which has to be sterilized and the
nature of microorganisms that are to be removed or destroyed.

HISTORY
Giroloma Fracastorius (1546) proposed a contagium
vivum as a possible cause of infectious disease.
Antony Van Leewenhock (1667) first observed
bacteria and called them as ‘little animacules’, he also
discovered microscope.
Louis Pasteur (1822-95)- Father of Microbiology
introduced steam sterilizer, hot-air oven and autoclave.
He also coined the term ‘vaccine’

• Joseph Lister (1867) introduced antiseptic techniques in surgery.
• He demonstrated that boiling instruments, washing hands and
spraying phenol in air around the patient before surgery, reduces
the incidence of post-operative infections.

Robert Koch (1843-1910) introduced staining techniques,
culture and his criteria of identifying a microorganism
known as Koch’s postulates.
Semmelweiss and Holemeus – first recognized
importance of hand washing in reducing infection.
John Tyndall introduced pasteurisation and
tyndallization.

DEFINITIONS AND TERMINOLOGIES
STERILIZATION – The process by which an article, surface, or
medium is freed of all living microorganisms either in vegetative
or spore state . (Ananthanarayan)
DISINFECTION – The destruction or removal of all pathogenic
organisms, or organisms capable of giving rise to infection.
(Ananthanarayan)

DISINFECTANT – An agent that kills most pathogens but not
necessarily endospores on inanimate objects. Eg: Alcohols,
Aldehydes, etc.
Efficacy can be classified as – High, Intermediate or Low.
STERILANT - Some disinfectant will kill spores when
prolonged exposure time (3-12 hrs) and called chemical sterilant.
SEPSIS - Presence of infection , infectious agent or infectious
material

ASEPSIS - Methods which prevent contamination of wounds
and other sites by ensuring that only sterile objects and fluids
come in contact with them and that the risk of air borne
contamination is minimized.
ANTISEPTICS - Chemical agents applied to living tissues to
reduce the number of micro-organisms present by inhibiting their
activity or by destruction.
Thus all antiseptics could be used as disinfectants but all
disinfectants cannot be used as antiseptics because of toxicity.

BIOCIDE: A substance that kills all living organisms including
spores, both pathogenic and non pathogenic.
BIOSTAT: An agent that prevents the growth of microorganisms
but does not necessarily kill them. The removal or neutralization
of biostat may allow for the regrowth of microorganisms.
BACTERICIDAL AGENT : or germicides are those which are
able to kill bacteria.
BACTERIOSTATIC AGENT : are those which only prevent
the multiplication of bacteria ; which however, may remain alive.
Eg- soaps, detergents.

DECONTAMINATION – It refers to process of rendering an
article or area free of danger from contaminants, including
microbial, chemical, radioactive and other hazards.
CLEANING – The process which removes visible
contamination, but does not necessarily destroy microorganisms.
SANITIZATION - This term is sometimes used as a synonym
for disinfection, particularly used with reference to food
processing & catering.

GOALS AND PRINCIPLES OF
STERILIZATION
GOALS
Removal of microorganisms or destroy them from materials or
from areas since they cause contamination, infection and decay.
MICROBIOLOGY - To prevent contamination
SURGERY - To maintain asepsis
DRUG & FOOD - For ensuring the safety

PRINCIPLES
1. All used instruments must be thoroughly cleaned.
2. Agent must be in contact with every surface of each
instrument to be sterilised.
3. All sterilising equipments must be regularly serviced.
4. Manufacturer’s instructions should be strictly followed.

Sterilizaton can be divided into four stages:
a) Pre-sterilization cleaning
b) Packaging
c) The Sterilization Process
d) Aseptic storage

INSTRUMENT PROCESSING

Presterilization cleaning: It is achieved by either by
 Cleaning using a washer disinfector (most preferred method)
 Manual combined with ultrasonic cleaning
 Manual cleaning (the least preferred)

• Disinfector cycle includes 5 steps:
1. Flush
2. Wash
3. Rinse
4. Thermal disinfection
5. Drying

STERILIZATION MONITORING
Sterilization procedures should be monitored through a
combination of
1. Mechanical,
2. Chemical and
3. Biological techniques

It should be designed to evaluate the sterilizing conditions and
the procedure's effectiveness.
Because spores used in BIs (biological indicators) are more
resistant and present in greater numbers than are the common
microbial contaminants found on patient care equipment, an
inactivated BI indicates that other potential pathogens in the load
have also been killed.
A biological indicator is the only type of monitor that provides
direct evidence that sterilization process conditions are sufficient
to kill spores. It uses microbes that are highly resistant to the
type of sterilization process you are monitoring

COLOUR CHANGE STERILIZATION
INDICATORS
• Color indicators are also included on the outside and inside of
equipment sterilized in paper packages.
The white stripes on the tape change to black when the appropriate
conditions (temperature) have been met.
Expiration dates should be printed on all equipment packs.

• Bacillus stearothermophillus spores : Steam or chemical vapor
sterilization monitoring.
• Bacillus subtilis spores : For dry heat or ethylene oxide gas
sterilization monitoring.
• These spore strips are filter paper strips impregnated with
spores and sealed in an envelope through which the sterilizing
agent penetrates.
• There are no B.I. available to test chemical sterilants and
disinfectants.

CLASSIFICATION OF AGENTS
A. PHYSICAL AGENTS
B. CHEMICAL AGENTS

PHYSICALAGENTS
1. Sunlight
2. Drying
3. Heat
a. Dry heat
-Flaming
-Hot air oven

b. Moist heat
-Temperature below 1000C (Pasteurization)
- Temperature at 1000C (Boiling)
-Steam at atmospheric pressure i.e. at 1000C.

4. Filtration
-Candle filters
-Asbestos filters
-Sintered glass filters
-Membrane filters
5. Radiation
-Nonionizing radiation
-Ionizing radiation
6. Ultrasonic and sonic vibration

SUNLIGHT
Sunlight possesses appreciable bactericidal activity and plays an
important role in the spontaneous sterilization that occurs under
natural conditions.
The action is primarily due to its content of Ultraviolet Rays.
Semple and Grieg showed that, in India, typhoid bacilli exposed
to the sun on pieces of white drill cloth were killed in 2 hours,
whereas controls kept in the dark were still alive after 6 days.

This is one of the natural methods of sterilization in cases of
tanks, rivers and lakes.
• ADVANTAGES: Direct sunlight as in tropical countryside
where it is not filtered by ozone layer and impurities in the
atmosphere, has an active germicidal effect due to the
combined effect of ultraviolet and heat rays.
• DISADVANTAGES: Many microorganisms still remain
viable as active sunlight is not efficient in destroying them.

DRYING
• Moisture is essential for bacterial growth.
• Drying therefore has a deleterious effect on most bacteria.
• Although, viruses and spores are unaffected by drying.
Therefore, it is a very unreliable method.

HEAT
Nature of heat
Temperature
& time
Type of
material
No of
micro-organisms
Characteristics
of organism

DRY HEAT
Time : Temperature of exposure.
FO value FO value at a particular temperature other than 121oC
is the time in minutes required to provide the lethality equivalent
to that provided at 121oC .
THERMAL DEATH TIME (TDT) is a concept used to
determine how long it takes to kill a specific bacteria at a
specific temperature.

THERMAL DEATH POINT (TDP)
The temperature at which all organisms of a culture will be killed
by heat either instantaneously or within an arbitrary brief finite
period.
FLAMING
INCINERATION
HOT AIR OVEN
INFRARED

• It is used to sterilize :
1. Bacterial inoculating loops
2. Dental broaches
3. Burs
4. Scalpels, needles and cover slips

FLAMING
A simple & effective method
• Tip of the instruments are held in a Bunsen
flame till they become red-hot.
• These materials may be dipped in a
disinfectant before flaming.

INCINERATION
This is an excellent method for safely destroying materials such
as contaminated cloth, animal carcasses and pathologic materials.
• Its a high temperature dry oxidation process, that reduces
organic and combustible waste to inorganic incombustible
matter and results in a very significant reduction of waste-
volume and weight.
• The process is usually selected to treat wastes that cannot be
recycled, reused or disposed off in a land fill site.

• Waste types not to be incinerated are :
a. Pressurized gas containers
b. Large amounts of reactive chemical wastes
c. Silver salts and photographic or radiographic wastes
d. Halogenated plastics such as PVC
e. Waste with high mercury or cadmium content such as broken
thermometers, used batteries and lead-lined wooden panels
f. Sealed ampules or ampules containing heavy metals.

TYPES OF INCINERATORS
A. Double-chamber pyrolytic incinerators which may be
especially designed to burn infectious health-care waste.
B. Single-chamber furnaces with static grate, which should
be used only if pyrolytic incinerators are not affordable.
C. Rotary kilns operating at high temperatures, capable of
causing decomposition of genotoxic substances and heat-
resistant chemicals.

HOT AIR OVEN
•This is the most widely used method of
sterilization by dry heat.
•Heat does not penetrate materials easily
and thus, long periods of exposure to
high temperatures are necessary.
•Conventional dry heat ovens have heated
chambers that allow air to circulate by
gentle flow (gravity convention).

MECHANISM OF ACTION
• Coagulation and oxidation of proteins.
• The oven is usually heated by electricity, with
heating elements in the wall of the chamber.
• Since hot air is a bad conductor of heat its
penetrating power is low.
• It must be fitted with a fan to ensure even
distribution of air and elimination of air
pockets.
• The material should be arranged so as to
allow free circulation of air in between the
objects6/5/2018 Basic Seminar 3 - Dr. Barkha. S. Tiwari 45

• PARAMATERES: Standard exposure
for 1 hour at 170o C.
• TYPES :
1. DRY HEAT OVEN TYPE OF
STERILISER ( STATIC)
(60-120 minutes at 3200 F)
The heating coils in the bottom or sides of the unit cause
hot air to rise inside the chamber through natural
convection

RAPID HEAT TRANSFER
(FORCED AIR) / SHORT CYCLE
HIGH TEMEPRATURE DRY
HEAT OVEN
6 minutes for unwrapped
instruments
12 minutes for wrapped instruments.
8 minutes for handpiece and
medical kits
180 -190o C
Heated air is circulated throughout
the chamber at a high velocity,
permitting more rapid transfer of
energy from the air to the
instruments, thereby reducing the
time needed for sterilization.

Time and temperature – recommended by Medical Research Council
TEMPERATURE (o C) HOLDING TIME (minutes)
160-169 45-50
170-179 18-20
180-189 7.5-10
190-199 1.5-3

INDICATIONS
 Glass wares (petri dishes, pipettes, flasks)
 Forceps
 Scissors
 Scalpels
 Glass syringes
 Swabs
 Pharmaceutical products e.g. Liquid (paraffin)
 Test tubes and flasks should be wrapped in a
paper
 Oils, greases, petroleum jelly

ADVANTAGES
• Effective and safe sterilization of metal instruments and
mirrors
• It does not affect many moisture sensitive compounds.
• No corrosion of carbon steel instruments and burs
• Cost-effective
DISADVANTAGES
• Long cycles
• Poor penetration
• Uneven heating
• Damage to heat sensitive items (Plastics, Rubber)
• Heavy loads of instruments , crowding of packs and heavy
wrapping easily defeat sterilization.6/5/2018 Basic Seminar 3 - Dr. Barkha. S. Tiwari 50

GLASS BEAD STERILIZER
• This method involves heat transfer
device.
• The media used are glass beads of 1mm
in diameter and a metal cup.
• The method employs submersion of
endodontic instruments and burs into
the beads.

• The beads heat up and transfer it to
the metal surface in contact.
• Working temperature - 210º -
230ºC for 10-30 seconds
• Working time –15 seconds.
• Pre heating time ranged from – 15
– 20 minutes.

• Disadvantage: Only working end of the file is immersed,
leaving the handles still contaminated.
• Not suitable for hollow instruments.
• Larger beads – Not effective in transferring heat to endodontic
instruments as large air spaces between the beads reduce
efficiency of the sterilizer

HOT SALT STERILIZATION
• Similar to glass bead sterilizer
• More safer than glass bead sterilizer.
• Pre heating required .
• Higher temperature than glass bead sterilizer as granules are
smaller so air space between granules is reduced and
conductivity of heat by salt is higher.

• Larger instruments should be immersed in for 20 seconds.
• To sterilize instrument- immerse at least ¼ the inch below the
salt’s surface and in the peripheral area of sterilizer
• Commercial table salt-
1% Sodium silicoaluminate , Magnesium carbonate / Sodium
carbonate used.
It pours more readily and will not become fused under heat.
**Pure sodium chloride- not used as high heat may cause
fusion of granules.

• Salt containing dextrose not to be used as it may coalesce the
granules of salt at high heat.
• Salt carried to the root canal – easily irrigated.
• Salt to be changed weekly or more often- depending on the
degree of humidity.
 Temperature : 425 o F (218 o C) and 475o F (246o C).
 Thermometer inserted in the salt to monitor temperature.
 Broaches, files and reamers - 5 seconds.
 Absorbent points and cotton pellets - 10 seconds.

MOIST HEAT STERILIZATION
MOIST HEAT
Temp. below
100 o C
Pasteurisation
Vaccine Bath
Inspissation
Temp. at 100 o C
Boiling
Steam at atm.
Pressure (100 o C)
Tyndallization
Steam under
pressure Autoclave

STEAM IS A VERY EFFECTIVE STERILIZING
AGENT SINCE IT:
1. Liberates latent heat when it condenses to form water,
potential microbial (cidal) activity.
2. Contracts in volume during condensation, thus reinforcing
penetration.

• Temp below 100 
• PASTEURISATION : 63ºC, 30 minutes (Holder method)
: 72 ºC, 15 seconds (Flash method)
• VACCINE BATHS : 60 ºC, 1 hour
• Temp at 100 
BOILING STEAM AT ATMOSPHERIC PRESSURE
10-30 min Koch & Arnold’s steamer
2% NaHCO3 Tyndallisation
(100 o C for 20 minutes)

PASTEURIZATION
• Developed by Louis Pasteur to prevent the spoilage of
beverages. Used to reduce microbes responsible for spoilage
of beer, milk, wine, juices, etc.
• Classic Method of Pasteurization: Milk was exposed to 65oC
for 30 minutes.

THERE ARE 3 METHODS
HOLDER METHOD
• It involves heating up to 62.90C for 30 min.
Although thermophilic bacteria thrive at this
temperature; they are of little consequence because
they cannot grow at body temperature.
FLASH PASTEURIZATION
• This method uses a temperature of 71.60 C for 15
seconds followed by cooling to 130C.
High Temperature Short Time (Flash Modification
Pasteurization (HTST): Used today. Milk is
exposed to 72oC for 15 seconds.

Ultra High Temperature Pasteurization (UHT): Milk is treated
at 140oC for 3 seconds and then cooled very quickly in a
vacuum chamber.
Advantage: Milk can be stored at room temperature for several
months.
ULTRA- PASTEURIZATION
• This method uses a temperature of 820 C for 3 seconds.

INSPISSATION
 Vaccines of nonsporing bacteria are heat inactivated in special
vaccine baths at 600 for 1 hour.
 Serum or body fluids containing coaguable proteins can be
sterilised by heating at 560 for 1 hour for several successive
days.

BOILING
• Heat at 100oC or more at sea level kills vegetative forms of
bacterial pathogens, almost all viruses, and fungi and their
spores within 10 minutes or less.
• Denaturation of proteins.
• Endospores and some viruses are not destroyed this quickly.
However brief boiling will kill most pathogens.

• Material should be immersed in water and boiled for 10-30
minutes but the lid of the sterilizer should not be opened.
• Hepatitis virus: can survive up to 30 minutes of boiling.
• Endospores: can survive up to 20 hours or more of boiling.
• Reliable sterilization with moist heat requires temperatures
above that of boiling water.

TYNDALLIZATION
• Also known as compressed or saturated
steam.
• This is an inexpensive method using a
Koch or Arnold steamer.
• Principle
– steam under pressure is hotter.
– higher the pressure the higher the
temperature

• Liquids were sterilized by this method at 1000C for 30 minutes
on each of 3 successive days.
• Also called Fractional sterilization, because a fraction was
accomplished on each day.
• Also called Tyndallization after its developer John Tyndall, and
• Intermittent sterilization because it has a stop and start operation.

MECHNISM OF ACTION
• During the first day’s exposure, steam
kills virtually all organisms except
bacterial spores and it stimulates spores
to germinate vegetative cells.
• During overnight incubation the cells
multiply and are killed on second day.
• Again the material is cooled and a few
remaining spores germinate only to be
killed on the 3rd day.
***This method also fails
because certain spores ( eg; some
anaerobes ) fail to germinate. A
suitable medium for germination
such as broth is required”.

AUTOCLAVE
• Moist heat in the form of pressurized
steam is regarded as the most
dependable method for destruction of all
forms of bacterial life including spores.
• This method is incorporated into a device
called the Autoclave.
• Autoclave means ‘self locking’.
• Over a hundred years ago, French &
German microbiologists developed the
autoclave.6/5/2018 Basic Seminar 3 - Dr. Barkha. S. Tiwari 69

TYPES OF AUTOCLAVES
• Type N: Sterilization is achieved by passive displacement with
steam.
• They are non-vaccum and used for non-wrapped solid
instruments.
• Type B: They are vaccum sterilizers designed to reprocess
load types such as hollow, air-retentive and packaged loads.
• Type S: They are specially designed to reprocess specific load
types.

PRINCIPLE
• Water boils when its vapour pressure equals
that of the surrounding atmosphere.
• Hence pressure inside a closed vessel
increases , thus the temperature at which
water boils also increases.
• Saturated steam has a high penetration
power.
• When steam comes in contact with a cooler
surface, it condenses to water and gives up
its latent heat to that surface.6/5/2018 Basic Seminar 3 - Dr. Barkha. S. Tiwari 71

• The large reduction in volume
sucks in more steam to the area
and the process continues till the
temperature of the surface is
raised to that of the steam.
• Condensed water ensure moist
conditions for killing the
microbes present.
• “LATENT HEAT EFFECT”

MECHANISM OF ACTION
• Moist heat denatures & coagulates the protein of a microbe.
• Higher efficiency of penetration & faster microbicidal action than dry
heat.
• (Moist heat penetrates material much more rapidly than dry heat
because water molecules conduct heat better than air).

2 Basic Types
Horizontal / Downward
displacement steriliser
Vertical / Vacuum steam
steriliser
Small bench top
autoclave at 136C
at 32 pounds for 5
minutes
Porous load
autoclave at 121C,
at 20 pounds
pressure for 30
minutes.

PARAMETER
• Standard conditions are 1210 C at 15 psi of pressure for at least
15 minutes.
Or
• 1320 C for 3 - 7 minutes at 30 psi for unwrapped instruments,
add 5 mins for moderately packed.
• Instruments should be packaged in muslin cloth, paper, nylon,
aluminium foil, steam permeable plastic.

STERILISATION MONITORING
 Biologic indicators; spores of Bacillus Stearothermophillus
(thermophilic organism) with a growth of 550- 600 C.
 Its spores require exposure of 12 minutes at 1210C to be
sterilised.

Recommended Cycles
Settings for general wrapped items:
Temp. - 121 degree C, Pressure - 20
PSI
Time -- 30 min Setting
Settings for bottled solutions:
Always vent bottles to avoid bursting!
Temp. - 121 degree C, Pressure - 20
PSI
Time -- 30 min Setting
Temperature Holding time
1210C 15min
126 0C 10 min
134 0C 3min

• Setting for "Flashing" an unwrapped instrument:
Temp. – 132 degree C, Pressure - 30 PSI
Time -- 4-7 Min Setting
• Flash sterilization :-
Sterilization cycles – operate at high temp – shorter time
3-10 min at 131 0 C

WRAPPING OF INSTRUMENTS

AUTOCLAVED INSTRUMENTS
USES
Dressings
Instruments
Laboratory ware
Media
Pharmaceutical products
Rubber items

DISADVANTAGES
• Causes rust & corrosion of non-
stainless steel instruments , carbide
burs.
• Damage to plastic & rubber.
• Dulls unprotected cutting edges.
• Items may be wet after cycle.
• Deposits with use of hard water.
ADVANTAGES
• Time efficient.
• Good penetration of fabric and paper
wrapping.
• Effective against spores.
• Sterilizes water based liquids
(irrigating solution) in standard cycles.

PRE-VACCUM AUTOCLAVE
• A new form of autoclave called the Prevacuum autoclave has
been developed, which draws air out of the chamber at the
beginning of the cycle. The major advantage of this is minimal
exposure.
• Temperature – 132 0C to
134 0C
• Pressure – 28 to 30 lb/in2
• Time – 4 minutes

GRAVITY DISPLACEMENT
AUTOCLAVES
• Small, automatic bench-top autoclaves.
• They work on the principle of downward displacement of air
as a consequence of steam entering at the top of the chamber.
• They are not recommended now

FILTRATION
• Removal of microbes by passage of a liquid or gas through a
screen like material with small pores.
• Used to sterilize heat sensitive materials like vaccines,
enzymes, antibiotics, and some culture media.

Types:
• Candle filters: Purification of water for
industrial & drinking purposes
a) Unglazed porcelain ( Chamberland &
Doulton filters)
b) Diatomaceous earth ( Berkefeld &
Mandler filters. )

• Membrane filter (0.22 µm pore diameter) - widely used in
water purification and analysis, sterilisation and sterility
testing
a)Cellulose acetate/cellulose nitrate/polycarbonate.
• HEPA filters: - High Efficiency Particulate Air filters.
a) Remove 99.97% of 0.3µm particles
• Used in operating rooms and burn units
• To remove bacteria from air.

6/5/2018
Basic Seminar 3 - Dr.
Barkha. S. Tiwari
88
RADIATION
Radiation
Non-
ionising
Infrared Ultraviolet
Ionising
X-rays Gamma
rays
Cosmic
rays

Non – Ionising Radiation
INFRA RED ULTRAVIOLET
Wavelength > Light Disinfecting enclosed
Absorbed as heat areas like entryways ,
Rapid mass sterilization OT , labs
of prepacked items
(syringes , catheter)
89

Ionising radiation
• X rays
• Gamma rays
• Beta rays
short wavelength  high penetrating power
electrons from atoms stripped
highly reactive radicals (-OH&H+) formed
DNA breakage of the organisms
D E A T H

• But ionizing radiation is not
harmful in a particular case.
• The case is related to how
long you are exposed.
USES
• Plastics
• Syringes
• Swabs
• Catheters
• Surgical catgut
• Bone tissue graft.

ULTRASONIC VIBRATIONS
• Microorganisms in the fluid are disintegrated by the external
pressures.
•The current trend is to use ultrasonic as a cleaning agent to
follow the process by sterilization in an autoclave.

• When propagated in fluids ultrasonic vibrations cause
formation of microscopic bubbles or cavities and the water
appears to boil.
• Some observers call this COLD BOILING.
• The cavities rapidly collapse & send out shock waves. The
formation and implosion of the cavities is known as
CAVITATION.

FREEZING
• Freezing can both kill and preserve depending on various
factors.
• Repeated freezing and thawing are much more destructive to
bacteria than prolonged storage at freezing temperature.
• If bacteria are rapidly subjected to temperature below –350C,
ice crystals that form within the cell produce a lethal effect
during defreezing.
• Two freezing cycles have been proved to be more lethal.

– Ice crystal disruption:
(i)Freezing kills by ice crystal
disruption of cells and molecules.
(ii)Freezing slowly is generally more
harmful than rapid (or flash) freezing.
LYPOPHILIZATION (FREEZE-DRYING)
A process used for preserving biological material, by removing
water from the sample, that involves first freezing the sample and
then drying it under vacuum, at a very low temperature.

NEWER METHODS IN STERILIZATION
1. CHEMICLAVE
• This system depends on heat, water
and chemical combination for it’s
efficacy.
• The temperature and pressure
required is greater than that for
autoclave.
• It is known as a Chemiclave /
Harvey Sterilizer.

• Instead of distilled water a solution of 78.28% alcohol,
0.23%formaldehyde, ketone, acetone and water is used to
produce the sterilizing vapor.
• Temperature : 1310C at 20 pounds pressure for 20 to 40 minutes.

Advantages
Short cycle.
No rusting or corrosion.
Dry instruments at the end of the cycle.
Automatic preset cycle timing.
Disadvantages
Heat sensitive instruments.
Chemical odors (fumes).
Liquids cant be sterilized.
Special solution required.

2. Sterilization by Cold Atmospheric Plasma
 Plasma is the fourth state of matter, discovered by the British
physicist Sir William Crookes in the year 1879.
 It is a collection of stripped particles. Once the electrons are
stripped from atoms and molecules, those particles change
state and become plasma.
 Plasmas are naturally energetic because stripping electrons
uses constant energy.
 Other well-known plasmas include lightning, neon signs, and
fluorescent lights.

 Cold Atmospheric Plasma (CAP) is known as non-thermal
because it has electrons at a hotter temperature than the heavy
particles that are at room temperature.
 Gases that can be used to produce CAP are Helium, Argon,
Nitrogen, Heliox (a mix of helium and oxygen), and air.
 The mechanism of plasma sterilization is related to the
abundance of plasma components, like reactive oxygen
species, ions and electrons, and UV and electromagnetic fields.
 Also, plasma can affect not only the contacted point but also
the area around it.

 Yang Hong Li et al. stated that plasma sterilization, with the
advantage of low temperature, fastness, thoroughness, safety,
overcomes the deficiency of the traditional sterilization
technology, and may become a novel method for killing
microbe.
 To develop a dental sterilizer which can sterilize most
materials, such as metals, rubbers, and plastics, the
sterilization effect of an atmospheric pressure non-thermal air
plasma device was evaluated by Su-Jin Sung et al. It was
proved that the atmospheric pressure nonthermal air plasma
device was effective in killing both Escherichia coli and
Bacillus subtilis.6/5/2018 Basic Seminar 3 - Dr. Barkha. S. Tiwari 101

STERILIZATION
• Liquid sterilization process (Endoclens)
• New plasma sterilizer (Sterrad 50)
• Rapid readout ethylene oxide biological indicator
• ETOX (Attest)
• LASER

TO BE
CONTINUED..

• A Fomite is any nonliving object or substance capable of
carrying infectious organisms such as germs or parasites and
hence transferring them from one individual to another.
• For eg. Skin cells, hair, bedding, clothing, stethoscopes,
neckties, IV drip tubes, catheters etc.

Bunsen Burner
• Types of Flames
1. Roaring blue flame (700oC)
2. Blue flame (500oC)
3. Safety flame (3000C)
• The flame has an
1. Outer oxidizing zone
2. Middle reducing zone
3. Inner unburned gases

DISINFECTION

CHEMICALAGENTS
-Alcohols
a. Ethyl alcohol
b. Isopropyl alcohol
c. Methyl alcohol
d. Trichlorobutanol
-Aldehydes
a. Formaldehyde
b. Gluteraldehyde

Dyes
a. Aniline dyes
b. Acridine dyes
Halogens
-Phenols
-Surface active agents
-Metallic salts
Gases
a. Ethylene oxide
b. Formaldehyde
c. Beta propionolactone6/5/2018 Basic Seminar 3 - Dr. Barkha. S. Tiwari 109

IDEAL REQUIREMENTS
1. Broad and wide spectrum of activity
2. Fast acting (even in presence of organic matter)
3. Non toxic
4. Surface compatibility
5. Easy to use
6. Odourless
7. Economical

8. Be stable
9. High penetrating power
10. Should not cause local irritation and sensitivity
11. High solubility
12. Effective : acid and alkali

• Factors that determine potency of disinfectants:
1) Concentration of substance
2) Time of action
3) pH of medium
4) Temperature
5) Nature of organisms
6) Presence of extraneous material

MECHANISM OF ACTION
• Act in various ways –
• Protein coagulation
• Disruption of cell membrane
• Removal of sulphydryl groups
• Substrate competition
A compound resembling the
essential substrate of the
enzyme diverts or misleads the
enzymes necessary for the
metabolism of the cell and
causes cell death

TYPES OF DISINFECTION USED IN DENTISTRY
(Recommended by ADA & CDC )
Surface disinfection : Used for treatment of surfaces like
cabinets, tables , chairs , lights etc.
Immersion disinfection : Immersion of plastics and instruments
in liquid disinfectant
Time required : 5-30 minutes.
Immersion sterilization : Prolonged contact with disinfectant
Time required (6-10 hours).
Disinfectant has the capacity to kill all micro organisms and
infective agents.

1.High level disinfectants –
• These disinfectants inactivate resistant bacterial spores,
Gram-positive and Gram-negative bacteria, M.tuberculosis.
E.g. Ethylene Oxide Gas, Immersion Gluteraldehyde Solutions
2. Intermediate level disinfectants–
• These disinfectants do not inactivate spores during routine use
but they destroy other forms of microbes, vegetative bacteria,
most viruses, fungi, M.tuberculosis.
E.g.Formaldehyde, Chlorine Compounds, Iodophors, Alcohols,
Phenolic Compounds.
LEVELS OF DISINFECTION

3. Low level disinfectants –
• Provide the narrowest antimicrobial range, most bacteria and
fungi but not M. tuberculosis.
E.g. Quaternary Ammonium Compounds, simple phenols and
detergents.
• Such compounds are suitable for cleaning environmental
surfaces.

SPAULDING (1872) classified dental
instruments as:
• CRITICAL : They penetrate the skin or
mucosa including bone.
E.g- Needles, scalers, burs, scalpels, surgical
instruments, dental explorers, endodontic
files.
• SEMI-CRITICAL : These items contact, but
do not penetrate intact skin or mucous
membrane.
E.g- Amalgam condensers, hand pieces,
mirrors, cheek retractors, impression trays

• NON-CRITICAL : These items (also known as clinical
contact surfaces) come in contact with intact skin but not
mucous membranes.
E.g- Chair surfaces, radiographic equipment, blood pressure
cuffs, facebows, pulse oximeters, examination and curing
lights, computers
A. Critical: Sterilize
B. Semi-critical: Sterilize, High
level disinfection
C. Non-critical: Intermediate level
disinfectant.

ALCOHOLS
1. ETHYLALCOHOL / PROPYLALCOHOL (70%) :
• Mixed with water and used for skin antisepsis prior to
cannulation, injection and hand-scrubbing.
• "Some water must be present for alcohols to disinfect
because they act by coagulating (permanently denaturing)
proteins, and water is needed for the coagulation
reactions.
• Also the mixture penetrates more deeply than pure alcohol
into most materials to be disinfected"

2. ISOPROPYLALCOHOL
• It is preferred to ethyl alcohol as it is a better fat solvent, more
bactericidal and less volatile.
• It denatures proteins & lipids, and leads to cell membrane
disintegration.
• It is used to disinfect the skin prior to cutaneous injections.
• It is active against gram positive, gram negative, & acid fast
organisms at a concentration of 50-70%
• ‘Isopropyl alcohol’ or ‘rubbing alcohol’ has high
bactericidal activity in concentration as high as 99%.6/5/2018 Basic Seminar 3 - Dr. Barkha. S. Tiwari 120

DISADVANTAGES :
• Relatively inefficient in the presence of blood and saliva.
• Lacks sporicidal activity.
• Causes corrosion of metals

• Effective against fungal spores and is used for treating cabinets
and incubators.
• Chambers are wiped with liberal amounts of methanol.
• However methyl alcohol is toxic and inflammable.
3.METHYLALCOHOL

Sterillium:
• Effective, Rub-in hand disinfectant
• Composition: 2-propanol- 45gms
1-propanol-30gms
ethyl-hexadecyl-dimethylammonium-
ethylsulphate-0.2gms
Directions for use:
1. Hygienic Hand Disinfection: Rub sterillium well over
clean, dry hands and nail grooves for 30 secs.
2. Surgical Hand Disinfection: Rub sterillium well over clean,
dry hands, grooves and upto elbows for 3 mins.6/5/2018 Basic Seminar 3 - Dr. Barkha. S. Tiwari 123

ALDEHYDES
1. GLUTERALDEHYDE
• 2% CIDEX solution is effective. It destroys vegetative
cells within 10 to 30 minutes and spores in 10 hours.
• It is recommended for use on surgical instruments where
residual blood may be present.
• It does not damage delicate objects, and therefore it can be
used to sterilize optical equipment such as the optic fiber
endoscopes.

• It is an agent of choice for disinfecting metal containing dental
instruments & used as a sterilizing agent.
• Kills by denaturation of proteins.
• Gluteraldehyde will disinfect in 10 minutes and will
sterilize after 6- 10 hours immersion at room temperature.

ADVANTAGES
1. High biocidal activity.
2. Tuberculocidal, sporicidal.
3. Used only as immersion sterilization/disinfectant.
4. Active in organic debris.
5. Doesn’t degrade rubber & plastic items.

DISADVANTAGES
1. It can damage many metal items.
2. E.g. nickel coated impression trays & carbon steel burs
will often discolor and corrode, respectively when
immersed in gluteraldehyde solution for prolonged periods.
3. It can cause hypersensitivity on repeated exposure so
instruments immersed in gluteraldehyde should be
thoroughly rinsed in sterile water prior to use.

USES OF GLUTERALDEHYDE
1. Surgical instruments where residual blood may be present.
2. Scopes (optic fibre endoscopes, cytoscopes,
bronchoscopes, etc.)
3. Treat corrugated rubber tubes, anaesthetic tubes, face
masks, plastic endotracheal tubes, metal instruments,
polythene tubing.

FORMALDEHYDE
(a Component of Chemiclave)

• It is gas at high temperature & solid at room temperature.
• In aqueous solutions, it is bactericidal, sporicidal and virucidal.
• To make a solution of 10% Formalin, 9parts of water are added
to 1part of 40% (aqueous) Formaldehyde.
• Formalin is utilized for inactivating virus in vaccines &
producing toxoids from toxins. In the gaseous form,
formaldehyde is expelled into a closed chamber where it is
used as a sterilant for surgical equipment, hospital gowns and
medical instruments.

• However penetration is poor and the surface must be exposed
to the gas for up to 12hours for effective sterilization.
(Fumigation)
• Formaldehyde leaves a residue and instruments must be rinsed
before use.
• Can cause hypersensitivity reactions.
• Formalin residues can be neutralized by using ammonia. (250
ml ammonia per litre of formalin)

USES OF FORMALDEHYDE
1. Against bacteria, viruses, spores
2. Anatomic specimen preservation
3. 10% Formalin + 0.5% sodium
tetraborate – sterilised clean
instruments.
4. Heat sensitive catheters
5. Fumigating sick rooms, laboratories.
6. Disinfecting- clothing, bedding,
furniture (under controlled
conditions) in hospitals.

Korsolex disinfectant:
• Composition – Gluteraldehyde: 15.2g
Formaldehyde: 19.7g
Direction for use:
Using gloves, dilute 5parts of Korsolex Rapid to 95 parts of
clean tap water to get 5% solution.
Dip pre-rinsed instruments in prepared Korsolex Rapid
solution

ANILINE DYES
• Brilliant green, malachite green & crystal
violet.
• They are more active against gram positive
organisms.
• Gentian violet is used for the T/t of trench
mouth and Candida Albicans infection.
• Interference with cell wall appears to be the
mode of activity (BACTERIOSTATIC in
high dilution).

ACRIDINE DYES
• Acriflavine , Proflavine, Euflavine, Aminacrine.
• These dyes are used as antiseptics for staphylococcal
infections in wounds.
• They act by combining directly with DNA, thereby stopping
RNA synthesis.

• These dyes are more active against gram positive organisms
than against gram negative but are not as selective as the
aniline dyes.
• Acridine dyes are often referred to as “flavines” because of
their yellow colour.
• They are active even in the presence of serum or pus unlike
aniline dyes.

OXIDANTS
An oxidizing agent is a substance that has the ability to oxidize
other substances (cause them to lose electrons)
1. Halogens
2. Hydrogen peroxide
3. Potassium permanganate

HALOGENS
• Highly reactive elements.
• Two halogens Chlorine & Iodine are commonly used
for disinfection.

1. CHLORINE
• Available as
-- gas
-- organic compound (organochloride, chlorocarbon)
-- inorganic compounds (hydrogen chloride)
• Most commonly used as HYPOCHLORITES
• The disinfectant action results from it’s ability to liberate free
chlorine.
• In aqueous solutions the liberated Cl ions reacts with water
to form hypochlorous acid.
• Concentration – 0.05 - 0.5% , contact time - 10 minutes.6/5/2018 Basic Seminar 3 - Dr. Barkha. S. Tiwari 139

Used in water supplies and
swimming baths.
Chlorox & Purex bleach used
for household sanitation & in the
disinfection of food utensils.
Chlorinated lime is used as
bleaching agent in textile
industry.
CHLORAMINES: such as
chloramines - T are organic
compounds that contain chlorine and
amino groups.
These compounds release free
chlorine more slowly than
hypochlorite solutions and are more
stable. They are used for general
wound antisepsis and root canal
therapy.

2. SODIUM HYPOCHLORITE
• Active component of household bleach.
• Household bleach (5% hypochlorite) diluted 1: 10 to 1:100 in
water used as antimicrobial and also to disinfect plastics.
• Kills vegetative bacteria, viruses and few bacterial spores.

• In dentistry- it is used as an intracanal medicament. (first
suggested by Grossman in 1941)
 Mechanism of action
1. Chlorine in aqueous solution exists in two forms-
hypochlorite (OCl-) and hypochlorous acid (HOCl)
2. It is responsible for breakdown of proteins into amino
groups.
3. Hypochlorite dissolves necrotic tissue because of its high
alkaline nature
4. To increase the efficacy, 1% sodium bicarbonate is added.

5.25% Hypochlorite - irrigation of root canal.

Precautions to be taken while using Sodium Hypochlorite
Solution.
1. If NaOCl gets extruded to periapical tissues, it causes
excruciating pain, periapical bleeding and swelling.
2. Medications like antibiotics and analgesics should be
prescribed accordingly.
3. Also during irrigation, the needle with very small diameter to
be used and never locked in the canal.

• DAKIN’s solution
• 0.5% sodium hypochlorite solution was used by H. D. Dakin
extensively for wounds during the I & II World War In
Europe.

Advantages
• It causes tissue dissolution
• It has antibacterial and bleaching action
• It causes lubrication of canals
• Economical
• Easily available

Disadvantages
• Because of its high surface tension, its ability to wet dentin is
less.
• Irritant to tissue periapically
• If comes in contact, it may cause gingival inflammation
• Bleach the clothes if split
• Bad odour and taste
• Vapours can irritate the eyes

IODINE
• Iodine is more reactive and more germicidal.
• Iodine acts on the tyrosine portions of protein molecules.
• Tincture of iodine
2% iodine solution in ethyl alcohol used as an antiseptic for
application over skin and mucous membrane.

IODOPHORS
• When iodine is complexed with certain organic material the
compound is called IODOPHOR - retains germicidal action
of iodine & reduces caustic & staining effects.
Povidine-iodine 5% & 0.9% NaCl is
used for irrigation (Betadine).

HYDROGEN PEROXIDE
• It is used to rinse wounds, scrapes and abrasions.
• The area foams & effervescence as catalase in the tissue
breaks down hydrogen peroxide to oxygen & water.
• The furious bubbling removes microorganisms mechanically.
• Anaerobic bacteria are sensitive to H2O2 because sudden
release of oxygen gas inhibits their growth.

• New forms of H2O2 are more stable than traditional forms and
do not decompose spontaneously.
• Inanimate material such as soft contact lenses, utensils, and
heat sensitive plastics can be disinfected within 30 minutes.

In dentistry:
• 3% of hydrogen peroxide is used as an irrigant
• The rapid release of nascent oxygen [O] in contact with
organic tissue effervescence dislodges the necrotic tissue
and dentinal debris.

PHENOLS

CARBOLIC ACID AND
OTHERS
• Following its introduction as a surgical antiseptic by Lister in
1865, phenol was widely used as a disinfectant.
• Since most phenolic disinfectants have a low solubility in
water, they are formulated with emulsifying agents, such as
soaps, which also increase their antimicrobial action.

ACTION:
• They act as cytoplasmic poisons by penetrating and disrupting
cell wall, thereby leading to denaturation of intracellular
proteins.
• Phenol is active against gram positive bacteria.
• Bactericidal at 1% and fungicidal at 1.3%.

HEXACHLOROPHENE:
Uses: Skin disinfectant
Presurgical disinfection for patients/surgeons.
CHLOROXYLENOL
• Non corrosive, non irritant
• Used as antiseptic, poor activity against many
bacteria
• DETTOL - 4.8 % chlorxylenol + 9 % terpinol +
13% alcohol

CRESOL
• 3-10 times more active than carbolic acid
• 50% soapy emulsion, LYSOL
CLEARSOL & STERLICOL
Widely used in hospitals and labs

SURFACE ACTIVE AGENTS
• Classified as cationic, anionic, nonionic and amphoteric
compounds.
ANIONIC SURFACE ACTIVE AGENTS
• These are active at acid ph.
• These agents cause gross disruption of the lipoprotein
framework of the cell membrane and also have mechanical
cleansing action. , e.g. Soaps and fatty acids

DISADVANTAGES
• Inability to penetrate organic debris .
• Incompatible with Ca, Mg, and iron of hard
water.
E.g. Benzalkonium Chloride.

NON-IONIC SURFACE ACTIVE
AGENTS
These agents are relatively nontoxic and few
promote bacterial growth.
E.g. Tween 80 (Polysorbate) facilitates the
diffused growth of mycobacterium
tuberculosis and provides a source of Oleic
acid which is stimulatory to the organism.

CATIONIC SURFACE ACTIVE AGENTS
• Quarternary ammonium compounds –
• Acetyl trimethyl ammonium bromide.
CETAVLON
SAVLON – 3.0% cetrimide + 0.3% CHX
AMPHOTERIC SURFACE ACTIVE AGENTS
• Also known as surfactants (eg. Dodecylbenzenesulfonate)
• ‘Tego’ compounds – no longer used now.

METALLIC SALTS- BISGUINIDES
(CHLORHEXIDINE, HIBITANE)
• Non toxic skin antiseptic.
• Most effective against gram positive organisms
• Fairly effective against gram negative organisms.
• Aqueous solution used in treatment of wounds.
• 4% SOLUTION– SURGICAL SCRUB
• 0.4%- solution in detergent.
• 0.2 % - anti-plaque agent.

• 2% - denture disinfectant.
• 0.12% - root canal irrigant.
• Available as dihydrochloride, diacetate, gluconate.
• Wide range of activity against gram positive or gram negative
organisms.
• Low activity against spores/viruses.

CHLORHEXIDINE GLUCONATE
• It exhibits both antiplaque & antibacterial properties.
• Bacteriostatic at low concentration & bactericidal at high
concentration

Mechanism of action:-
• The Dicationic CHX molecule, attaches to the pellicle by one
cation, and to the bacteria attempting to colonize the tooth surface
with the other. This is called the ‘Pin-Cushion Effect’.
• At low concentration this results in increased permeability with
leakage of intracellular components including potassium.
• At high concentration chlorhexidine causes precipitation on
bacterial cytoplasam & cell death.
• Once adsorbed; shows a persistant bacteriostatic action lasting in
excess of 12 hours – ‘Substantivity’

GASES
1.Formaldehyde gas
2.Betapropionolactone BPL
3.Ethylene oxide

 Formaldehyde gas
• 150 grams of KMnO4 + 280 ml Formalin
• Fumigation of operation rooms.
• When formaldehyde gas is used, doors must be sealed and left
unexposed for 48 hours.

 Betapropionolactone (BPL)
• Condensation product of ketone and formaldehyde.
• More efficient for fumigation than formaldehyde.
• Rapid biocidal action but carcinogenic potential.
• 0.2% BPL is used for sterilisation of biological products.

 Ethylene oxide
• Colorless liquid
• Boiling point of 10.70 C
• Highly penetrating gas with a sweet ethereal smell
• Highly inflammable, highly explosive
• When mixed with 10% CO2 or nitrogen , explosion is limited.

MECHANISM OFACTION
• Alkylating the hydroxyl, carboxyl, amino and sufhydryl
groups in protein molecules.
• Reacts with RNA & DNA.
• Requires a special chamber and proper ventilating facilities
because it is toxic and carcinogenic.
• Humidification of the load is necessary before sterilization
because the biocidal activity increases in the presence of
moisture.

• The chamber then must be flushed with inert gas for 8-12
hours to ensure that all traces of ethylene oxide are removed
otherwise, the chemical will cause “cold burns” on contact
with skin.

Testing the disinfectant
Determination of phenol coefficient: The disinfectant to be tested
is compared with phenol on a standard microbe.
1. Rideal walker test-
• Phenol is considered as standard, and corresponding rating
system is called “phenol coefficient”
• This is a figure expressing the disinfecting power of any
disinfectant.
• It is the ratio of the dilution of the disinfectant that kills a
microorganism to the dilution of phenol that kills the organism
in the same time under identical conditions.

• Disinfectants that are more effective have coefficient >1 and
less effective have coefficient <1.
2. Chick martin test-
• Method of testing the invitro efficiency of the bactericidal
agent by a standard culture of Salmonella Typhi.
• Disinfectant acts in presence of organic matter (yeast
suspension) and is tested for a fixed period of time against
various concentration of phenol solution.

INSTRUMENT DIVISION

BRACKETS, BAND MATERIALS
Standard steam
Autoclave
Chemical vapor
Ethylene oxide
Dry heat sterilizing cycles.

DISINFECTION OF ELASTOMERIC LIGATURES
2% gluteraldehyde
ORTHODONTIC MARKING PENCILS
-Wiping with a sterile gauze
-Soaking pencil tips in disinfectant

DENTAL HAND-PIECES
1. Surface contamination control
2. Sterilisation

• Most common is autoclaving.
• Chemical vapor pressure sterilization can also be used.
• Etox gas- most gentle method
• Etox processing takes several hours /overnight.
• Dry heat sterilization – generally not recommended.
NSK High Speed Handpiece
Sterilization recommended – autoclave

• Remove the bur and dismantle the handpiece if possible, to
allow for more effective treatment. Treat all parts together.
• Remove organic matter with a small brush.
• For lubrication-Spray ‘PANA – SPRAY’ for 1-2 seconds into
the drive tube before autoclaving.
• For Average use- lubrication at the end of each day’s work
• Above average use - lubricate twice a day(one at lunch time,
and one at the end of the day’s work)

• The following disinfectants are effective against AIDS-related
virus:
70 % ethanol for one hour.
2 % freshly prepared glutaraldehyde, or
1 % available iodine solution for 30 minutes.

IMPRESSIONS
• The ADA recommends that all impressions must be rinsed to
remove saliva; blood and debris followed by disinfection
before cast and die stone are sent to a dental laboratory.
The laboratory disinfects
appliance and then
transports
it in a heat-sealed bag to the
dentist

Item Recommended method Alternative method
Impressions
Alginate Rinse, get rid of excess water, spray with
0.1% sodium hypochlorite, put in closed
container for 10 seconds.
Iodophors can also be
used.
Zinc oxide
eugenol paste
Rinse, get rid of excess water, spray with
0.1% sodium hypochlorite, put in closed
container for 10 secs.
Iodophors can also be
used.
Polysulphide
rubber base
Rinse, immerse in 2% gluteraldehyde for
10 minutes, rinse
Iodophors, sodium hypo
chlorite can also be used
Polyether Chlorine compounds
Silicon rubber Gluteraldehyde, iodophors, chlorine
compounds.
Impression
compound
Rinse under running tap water and
immerse in Iodophors or chlorine
compounds

• Recommendations For Disinfecting Impression Materials
Impression
Materials
Disinfectants
Gluteraldehyde Iodophors Sodium
hypochlorite
Alginate No Yes Yes
Polysulfide Yes Yes Yes
Silicones Yes Yes Yes
Polyethers No Yes Yes
Reversible
hydrocolloid
No Yes Yes
ZnOE PASTE Yes Yes

• Sterilization of conservative instruments
Instruments 1st choice 2nd choice 3rd choice
Metal instr. Moist heat Dry heat chemical
Surgical burs Moist heat Dry heat chemical
Handpieces Moist heat chemical -
Airotor Moist heat chemical -
Cautery tip Gas chemical -
M.mirror Moist heat chemical Dry heat
3-way syr. Moist heat chemical Dry heat

RUBBER DAM
• Once the rubber dam is applied, the teeth and the dam should
be thoroughly swabbed with a large pellet of cotton soaked in
a quick evaporating, non staining antiseptic i.e. 2%
Glutaraldehyde.
• Ray : Has recommended 2% Benzalkonium chloride in 5% of
isopropyl alcohol.
• Moller : Prefer swabbing with hydrogen peroxide followed by
tincture of iodine.

Rubber Dam Part Sterilization method
Rubber dam clamps Autoclaving or dry heat
sterilization
Plastic Frame
Metal Frame
Gluteraldehyde
Autoclaving
Rubber dam punch Autoclaving or dry heat
Rubber dam sheet Disposable

Instruments Sterilizer used Method of sterilization
Dapen Dish Merthiolate
70% alcohol
Swabbed with merthiolate followed
by alcohol
Reamers, files
broaches,
spreaders
Hot salt sterilizer Immersing it in hot salt sterilizer
for 5 sec
Gutta Percha cones 5.2% sodium hypochlorite Kept sterile in screw capped vials
containing alcohol until
sterilization. Immersing it in
sodium hypochlorite for 1 min then
rinse the cone with hydrogen
peroxide and dry it between 2
layers of sterile gauze
Silver cones Glass bead sterilizer Immersing it in 55 sec
Paper points Hot salt sterilizer Immersing for 10 sec by placing its
butt head first
Glass slabs
Cement spatula
Iodine and alcohol Swabbing the surface with iodine
and double swabbing with alcohol.
Tips of cotton pliers 90% alcohol, flaming Tips of cotton pliers are dipped in
alcohol and then subjected to

COMPOSITE FILLING INSTRUMENTS
• All composite instrument can be heat sterilized by the
acceptable methods, not exceeding 350 o C/177oF.
1. Steam autoclave
2. Chemical vapor
3. Dry heat
4. Ethylene oxide

DENTAL BURS
• IN AUTOCLAVE
• By submerging burs in 2% Sodium nitrite solution.
• Burs kept in small metal/glass beaker with perforated lid
(eg. Metal Salt Shaker)

ENDODONTIC FILES
• For surface disinfection during canal debridement- Banker’s
Sponge soaked in 70% Isopropyl alcohol/proprietary
quaternary ammonium solutions.

• The protocol comprises 10 vigorous strokes in a scouring
sponge soaked in 0.2 % Chlorhexidine solution.
• They can also be sterilized in autoclave and with sodium
hypochlorite.
Ni-Ti ENDODONTIC INSTRUMENTS

CONCLUSION
• It is our most important duty to preserve and maintain the
health of our patients and ourselves due to alarmingly high risk
of getting infected by dangerous diseases like hepatitis-B, TB,
herpes, HIV etc.
• As it is always said that PREVENTION IS BETTER THAN
CURE, sterilization and disinfection should be practiced
regularly to prevent others and ourselves from getting infected.

REFERENCES
 Ananthanarayan R, and C. K. Jayaram Paniker. Textbook Of
Microbiology. Bombay: Orient Longman, 1981.
 Samaranayake LP. Essential Microbiology For Dentistry.
Edinburgh: Churchill Livingstone/Elsevier, 2006.
 Peter Soben. Essentials Of Preventive And Community
Dentistry. New Delhi: Arya (Medi) Publishing House, 2003.

 A textbook of Preventive and Social Medicine. Park 23rd
edition.
 Chandra, Gopi Krishna V, Grossman LI. Grossman's
Endodontic Practice. New Delhi: Wolters Kluwer
Health/Lippincott Williams & Wilkins, 2010.
 A textbook of Endodontics, Nisha Garg, 2nd Edition
 Practical Infection Control in Dentistry, James A.Cottone, 2nd
Edition.

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