The document discusses various methods of sterilization, including physical and chemical agents, with historical context provided around Louis Pasteur's contributions. It details four chemical methods: steam pressure, chemical vapor pressure, dry heat, and ethylene oxide sterilization, each with specific applications and procedures. Additionally, it highlights the significance of sterilization in dentistry to ensure the safety of both patients and practitioners by preventing infection from non-sterile instruments.

1. Presented by
- Vikrant singh

2. CONTENTS
• Definition
• Introduction
• Agents used in sterilization
- Physical
- Chemical
• Four chemical methods of sterilization
- Steam pressure sterilization
- Chemical vapor pressure sterilization
- Dry heat sterilization
- Ethylene oxide (ETOX) sterilization
• Uses

3. INTRODUCTION
DEFINITION
• Sterilization is a process by which an article, surface or medium is
made free of all microorganisms either in vegetative or spore form.
OR
• Sterilization is defined as killing all forms of life, including the most
heat resistant forms ,i.e., bacterial spores ,etc.
HISTORY
• For first time sterilization was introduced and developed by
renowned scientist Louis Pasteur(1822-1895). He is responsible for
development of Steam heat sterilization , hot air oven, autoclave,
Pasteurization, etc.

4. AGENTS USED INAGENTS USED IN
STERILIZATIONSTERILIZATION
PHYSICAL METHODSPHYSICAL METHODS
1.1. Sun lightSun light
2.2. HeatHeat
a) Dry heata) Dry heat
b) Moist heatb) Moist heat
3. Ozone3. Ozone
• FiltrationFiltration
• RadiationRadiation

5. CHEMICAL METHODS
1. Alcohols
2. Aldehydes
3. Phenols
4. Oxidizing agents
5. Salts
6. Surface active agents
7. Halogens
8. Dyes
9. Gases

6. PHYSICAL METHODS
1. Sunlight
Sunlight has an active germicidal effect due to its content of
ultraviolet rays. It is a natural method of sterilization in cases
of water in tanks, rivers and lakes.
2. HEAT
Heat is most reliable and commonly employed method of
sterilization. Two types of heat are used, dry heat and moist
heat.
The following procedures are used for sterilization by
Dry heat :-
• RED HEAT
• FLAMING
• INCINERATION
• HOT AIR OVEN

7. MOIST HEAT STERILIZATION
This method of sterilization may be used at different
temperatures as follows.
- At temperature100˚C
• Boiling
Boiling for 10 to 30 minutes may kill most of the vegetative forms
but many spores withstand boiling for a considerable time.
• Tyndallisation
steam at 100 ˚C for 20 minutes on three successive days is used
• Steam sterilizer
Koch’s or Arnold’s sterilizer at 100 ˚C for 90 minutes is
usually used for material which may decompose at high
temperature of autoclave.
- At temperature above 100 ˚C
• Autoclave

8. 3. Ozone
- It is a technique of low temperature sterilization ,i.e., 25˚C to 35˚C
- Ozone sterilizer uses oxygen, water and electricity to produce ozone within
the sterilizer and provide sterilization without producing toxic chemicals.
4. Filtration
- This process is done mainly for antibiotic solutions, sugars, etc.
5. Radiation
- two types of radiation techniques may be used for sterilization
• Ionizing radiations
In this, X rays, gamma rays are used which are lethal to all cells including
bacteria. They damage the DNA through various mechanisms.
• NON ionizing radiations
These include UV and infrared radiations which acts by denaturizing
bacterial protein and DNA.

9. Chemical Method of sterilization
1. Alcohol
- Ethyl alcohol and isopropyl alcohol are most frequently used. They
act by denaturing bacterial proteins. But they are significantly
active only when there concentration is more that 60 to 70 % in
water.
- They have no virucidal or sporicidal activity
2. Aldehydes
different concentration of different Aldehydes are used against
different kind of microbes.
3. Phenols
The lethal effect of phenol is due to cell membrane damage, thus
releasing cell contents and causing lysis.
4. Halogens
Chlorine and iodine are two commonly used.

10. 5. Oxidizing agents
hydrogen peroxide, per acetic acid, etc. are used by releasing free radicals
which are the active ingredients in these methods.
6. Salts
salts of heavy metals such as copper, mercury, silver, etc. gives toxic
effects on bacteria.
7. Surface Active Agents
• substances which alters energy relationships at interfaces,
producing a reduction of surface tension, are known as surface active
agents or surfactants.
• They are bactericidal for almost all gram positive bacteria.
8. Dyes
They have very low bactericidal activity.
9. Gases
Formaldehyde gas, Ethylene Oxide, Betapropiolactone(BPL)

11. STEAM PRESSURE
STERILIZATION
(AUTOCLAVE)
• Sterilization with steam pressure is performed in a steam Autoclave.
•
than dry heat. Bacteria are more susceptible to moist heat as
bacteria protein coagulates rapidly.
PRINCLIPLE
• When steam comes in contact with a cooler surface, it condenses to
water and liberates its latent heat to that surface. E.g. 1600ml of
reduction in volume sucks in more steam to the same site and the
process continues till the temperature of the article is raised to that
of steam. The condensed water produces moist conditions for killing
the microbes present.

12. Components of Autoclave
• Autoclave is a modified pressure cooker or boiler.
• It consist of a vertical or horizontal cylinder of gun metal or stainless steel in a
supporting iron case
• The lid is fastened by screw clamps and rendered air tight by asbestos washers.
• The lid bears a discharge tap for air and steam, a pressure gauge and a safety
valve
Procedure
• tank is filled with sufficient water and the material to be sterilized is placed on a tray.
• The lid is closed with the discharge tap open.
• The heater is put on
• Safety valve is adjusted to required pressure.
• After boiling of water, the steam and air mixture is allowed to escape till the air has
been displaced.
• The discharge tap is now closed
• The steam pressure now rises inside and when it reaches the desired level, safety
valve open releases excess steam. From this point, the holding period counts.
• After the holding period, heating is stopped and autoclave is allowed to cool till the
pressure gauge indicates normal pressure.
• The lid is now opened and material is allowed to remove.

13. TYPICAL AUTOCLAVES
• Vertical cylinder type
Autoclave
• Horizontal cylinder
type Autoclave

14. Advantages of autoclaving:-
• autoclaving is the most rapid and effective method for sterilizing cloth
surgical packs and towel packs (other methods are not suitable for cloth
packs)
• Automated models are available, although they may be evaluated with a
biological spore test monitoring system.
Disadvantages of Autoclaving
• Items sensitive to the elevated temperature cannot be autoclaved.
• Autoclaving tends to rust carbon steel instruments.
• Steam seems to corrode the steel neck and shank portions of some
diamond instruments and carbide burs.

15. CHEMICAL VAPOR PRESSURE
STERILIZATION
(chemiclaving)
• They are similar to steam sterilizers but sterilization is carried out by
chemiclave through chemical vapors under pressure.
• Chemical vapor pressure sterilizers operate at 270˚F (131 ˚C) and
20 lb of pressure and have a cycle of time approximately 30
minutes.
• They must be used with a prescribed chemical.
• Newer models seem to handle Aldehydes vapors well.

16. A TYPICAL CHEMICLAVE

17. ADVANTAGES OF CHEMICLAVING :-
• Carbon steel and other corrosion-sensitive burs, instruments, and pilers are
said to be sterilized without rust or corrosion.
• Have a wide spectrum of activity and effective against all microorganism
including bacteria (both vegetative as well as spore forms), viruses,
protozoa and fungi.
• Have high penetration power so performs a quick action.
DISADANTAGES OF CHEMICLAVING :-
• Items sensitive to the elevated temperature are damaged.
• Towels and heavy cloth wrappings of surgical instruments may not be
penetrated to provide sterilization.
• Biologic spore test monitoring strips need to be routinely used to confirm the
heat penetration of heavy packs before using them
• Only fluid purchased from the sterilizer manufacturer can be used.
• Only dry instruments should be loaded, and the door gasket should be
checked for leaks to avoid frequent sterilization monitoring failures.

18. DRY HEAT STERILIZATION
To perform this technique of sterilization, Hot air oven is used
HOT AIR OVEN
• The oven Is electrically heated and is fitted with a fan to ensure adequate
and even distribution of hot air in the chamber.
• Oven is also fitted with a thermostat that maintains the chamber air at a
chosen temperature.
• Individual instruments must be heated at 320 ˚F or 160 ˚C for 30 minutes
(holding time)
Note:- increasing the total time by 50% as a safety factor is recommended.
• Total time required also based on efficiency of the oven based on its size,
the size of load and how instruments are packaged.
• Without careful calibration, more sterilization failures are obtained with
gravity convection dry heat ovens than any other type of sterilizer.
• Packs instruments must be placed at least 1cm apart to allow heated air to
circulate.

19. Two typical hot air ovens
• Cox rapid heat transfer
dry heat sterilizer
• Typical hot air oven

20. Advantages of dry heat sterilization
• Carbon steel instruments and burs do not rust, corrode, or lose their temper
or cutting edges if they are well dried before processing.
• Industrial forced-draft hot air ovens usually provide a larger capacity at a
reasonable price.
• Rapid cycles are possible at high temperature.
Disadvantages of dry heat sterilization
• High temperature may damage more heat sensitive items such as rubber or
plastic goods
• Sterilization cycles are prolonged at lower temperatures.
• Heavy loads of instruments, crowding of packs and wrapping easily prevent
sterilization
• Cycles are not automatically timed on some models
• Inaccurate calibration, lack of attention to proper settings and adding
instruments without restarting the timings are other common sources of
error.

21. ETHYLENE OXIDE (ETOX)
STERILIZATION
• ETOX sterilization is the best method for sterilizing complex
instruments and delicate materials.
Ethylene oxide
• It is a colorless liquid with boiling point of 10.7 ˚C
• It is effective against all types of microorganisms including viruses
and spores.
• It has a potential toxicity towards humans including mutagenicity,
carinogenicity.
• It is highly flammable.
• It is specially used for sterilizing plastic and rubber articles,
respirators, heart lung machine, sutures, Dental equipments,
cloths,etc.

22. ROOM TEMPERATURE
ETHYLENE OXIDE STERILIZER

23. Clinical Notes :-
• ETOX gas is the best way to sterilize rotary handpieces.
• Automatic devices sterilize items in several hours and operate at elevated
temperature below 100˚C.
• Less expensive devices operate overnight to produce sterilization at room
temperature.
• Porous and plastic materials absorb gas and require aeration for 24 hours or
more before it is safe for them to contact skin or tissues.
• Units with large chambers sizes hold more instruments or packs per cycle;
however they are expensive.

24. SIGNIFICANCE OF
STERILIZATION IN DENTISTRY
• Many instruments used in dentistry are reusable, and to ensure
safety of patient and even practitioner, it is mandatory to maintain
sterility of instruments which has to be used.
• A non sterile instrument may contain both vegetative forms as well
as spores of microorganism which may infect person when comes in
contacts with tissues.
• Sometimes during moving, packaging of disposable instruments
such as syringes, etc. may rupture resulting in lose of their sterility