Sterilization

SEMINAR-5
Presented by
Akhil C A
First Year PG
Dept. Of Public Health Dentistry
SCB Dental College, Cuttack 2

• INTRODUCTION
• TERMINOLOGIES
• HISTORICAL BACKGROUND
• METHODS OF STERILIZATION
• STERILIZATION IN DENTAL SETTING
• CONCLUSION
• REFERENCES
3

• Microorganisms are ubiquitous.
• They are found in the surroundings, on inanimate objects and
on the surface of the human body.
• Since they cause contamination, infection and decay, it
becomes necessary to remove or destroy them.
• Methods to remove or kill microorganisms are known as
sterilization.
• The methods of sterilization used depend on the purpose for
which it is carried out, the material to be sterilised and the
nature of the microorganisms to be removed or destroyed.
Ananthanarayan R. Textbook of microbiology. 10th ed. Hyderabad: University Press ; 2016.
4

• Disinfectant : Usually a chemical agent (but sometimes a physical agent)
that destroys disease causing pathogens or other harmful microorganisms,
but might not kill bacterial spores. It refers to substances applied to
inanimate objects.
• Disinfection : Thermal or chemical destruction of pathogen and other
types of microorganisms. Disinfection is less lethal than sterilization
because it destroys most recognized pathogenic microorganisms but not
necessarily all microbial forms (e.g., bacterial spores).
• Sterilization : Validated process used to render a product free of all forms
of viable microorganisms including bacterial spores. Sterilizer is the
apparatus used to sterilize medical devices, equipment
or supplies by direct exposure to the sterilizing agent.
Park K. Park's textbook of Preventive and social medicine. 25th ed. India: Bhanot Publishers; 2017.
5

• Antiseptic : Substance that prevents or arrests the growth or
action of micro-organisms by inhibiting their activity or by
destroying them. The term is used especially for preparations
applied topically to living tissue.
• Asepsis : Prevention of contact with micro-organism.
• Sanitizer : Agent that reduces the number of bacterial
contaminants to safe levels as judged by public health
requirements. Commonly used with substances applied to
inanimate objects.
6

• Sterile : State of being free from all living microorganisms.
• Germicide : Agent that destroys micro-organisms, especially
pathogenic organisms
• Detergent : Surface cleaning agent that makes no
antimicrobial claims on the label. They comprise a hydrophilic
component and a lipophilic component. It acts by lowering
surface tension e.g. soap which removes bacteria along with
dirt.
7

• Ignaz Semmelweis in Vienna, Austria (1818-1865) in 1847
demonstrated the value of handwashing with antiseptic
solutions, when he obtained considerable reduction in the
death rate from puerperal fever.
• He is also called the
• “Father of infection control” and
• “Saviour of mothers.”
8

• Joseph Lister (1827-1912) was also successful in reducing the
number of wound infections by prophylactic application of an
antiseptic (carbolic acid) to wounds.
• In 1865, after some doubtful beginnings, he managed for the
first time to heal without infection the open leg fracture of a
child hit by a car.
9

• From then on, Lister laid out a protocol to sterilize the surgical
instruments, the hands of the surgeon, the dressings and the
wounds with solutions of carbolic acid, and even designed a
sprayer to diffuse the substance in the air of the operating
room.
10

• When he died at the age of 84 on February 10, 1912, he left
behind a drastic reduction in the mortality of surgical patients
due to infections.
• According to statistics collected by himself, the decrease went
from almost 50% of those operated on to only 15%.
11

A. Physical
methods
B. Chemical
methods
12

A.Physical methods
1. Sunlight
2. Heat
(a ) Dry heat
(b) Moist heat
3. Ozone
4. Filtration
5. Radiation to a level that is no longer harmful to health.
13

B.Chemical Methods
1. Phenol and related compounds
2. Quaternary ammonia compounds
3. Halogens and their compounds
4. Alcohols
5. Formaldehyde
6. Oxidizing agents
7. Metals
8. Lime
9. Ethylene oxide
14

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.
15

2. Heat
• Heat is the most reliable and commonly employed method of
sterilization. It should be the method of choice unless
contraindicated.
• Two types of heat are used-
1. Dry heat
2. Moist heat
16

Principle
• (i) Dry heat kills the organisms by denaturation of bacterial
protein, oxidative damage and by the toxic effect of elevated
levels of electrolytes.
• The possibility of DNA damage is also incriminated as one of
the mechanisms of inactivations of microbes.
• (ii) Moist heat kills the microorganisms by denaturation and
coagulation of proteins.
17

Factors influencing
(i) Nature of heat: Dry heat or moist heat
(ii) Temperature and duration: The time required for sterilization
is inversely proportional to temperature to which organisms are
exposed.
(iii) Characteristic of microorganisms and spores present:
Bacterial spores are killed by moist heat at 121 °C for 15 minutes.
Most vegetative bacteria, fungi and viruses are killed in 30
minutes at 65°C by moist heat.
18

(iv) Type of material: A high content of organic substances tend
to protect the vegetative form and spores against the lethal
action of heat. Materials containing organic substances require
more time for sterilisation. Proteins, sugars, fats and starch are
some of the organic substances.
19

•Red heat
•Flaming
•Incineration
•Hot air oven
DRY HEAT
STERILISATION
20

1. Red heat
• Inoculating wires or loops,tips of forceps and needles are held
in the flame of a bunsen burner till they become red hot.
21

2.flaming
• Glass slides,scalpels and mouths of culture tubes are passed
through bunsen flame without allowing them to become red
hot.
22

3.Incineration
• By this method, infective material is
reduced to ashes by burning.
• Instrument named incinerator may
be used for this purpose.
• soiled dressings animal carcasses, bedding
and pathological materials are dealt with
this method.
23

4.Hot air oven
• Most commonly used method of sterilization by dry heat.
• The oven is electrically heated and is fitted with a fan to
ensure adequate and even distribution of hot air in the
chamber.
• It is also fitted with a thermostat that maintains the chamber a
chosen temperature
24

25

Temperature and time
• 160° for 2 hrs (holding time) is required for sterilization
(previously it was 160°C for one hour).
• However, alternative temperatures and holding time include
170°C for one hour and 180°C for 30 minutes.
26

Uses
• It is used for sterilization of
1. Glasswares like glass syringes, petridishes, flasks, pipettes
and test tubes.
2. Surgical instruments like scalpels,scissors,forceps etc.
3. Chemicals such as liquid paraffin, fats,
sulphonamides,powders etc.
27

Precautions
1. It should not be over loaded .
2. The material should he arranged in a manner which allows free
circulation of air.
3. Material to be sterilized should be perfectly dry.
4. Test tubes, flasks etc. should be fitted with cotton
5. Petridishes and pipettes should be wrapped in paper.
6. Rubber materials(except silicone) or any inflammable material
should not be kept inside the oven.
7. The oven must be allowed to cool
28

Sterilization control
1. The spores of Bacillus subtilis subsp. niger are kept inside the
oven.These spores should be destroyed if the sterilization is
proper.
2. Thermocouples may also be used.
3. Browne‘s tube with red spot is available. After proper
sterilisation a green color is produced (after two hours at
160°c.)
29

• At a temperature below 100°C
• At a temperature of 100°C
• At a temperature above 100°C
MOIST HEAT
STERILISATION
This method of sterilization may be used at different temperatures as follows.
30

1) At a Temperature below 100°C
• Pasteurisation Of Milk
• Inspissation
• Vaccine Bath
• Low Temperature Steam Formaldehyde ( LTSF)
Sterilization
31

a)Pasteurisation of milk
• Two types of method
• Holder method (63°C for 30 minutes)
• Flash method (72°C for 20 seconds followed by cooling quickly
to 13°C or lower) are used.
• All non-sporing pathogens such as mycobacteria , brucellae
and salmonellae are killed except Coxiella burnetii which being
relatively heat resistant may survive in holder method.
32

(b) Inspissation
• Some serum or egg media , such as Lowenstein-Jensen's and
Loeffier's serum, are rendered sterile by heating at 80-85°C
temperature for half an hour daily on three consecutive days.
This process of sterilization is called inspissation.
• The instrument used is called inspissator.
33

(c)Vaccine bath
• Bacterial vaccines are sterilized in special vaccine baths at
60°C for one hour.
• Serum or body fluids can be sterilized by heating for one hour
at 56°C in a water bath on several successive days.
34

(d)Low temperature steam formaldehyde ( LTSF) sterilisation
• In this method steam at sub-atmospheric pressure at the
temperature of 75°C with formaldehyde vapour is used.
• Bacillus stearothermophilus has been used as biological
control to test the efficacy of LTSF sterilisers.
35

2) At a Temperature of 100°C
• Boiling
• Tyndallisation
• Steam steriliser
36

(a) Boiling
• Boiling for 10 to 30 minutes may kill most of the vegetative
forms but many spores withstand boiling for a considerable
time.
• When better methods are not available, boiling may be used
for glass syringes and rubber stopper.
• It is not recommended for the sterilization of instruments for
surgical procedures.
37

(b)Tyndallisation (fractional sterilization)
• Steam on three successive days is known as tyndallisation or
intermittent sterlization.
• The principle is that the first exposure kills all the vegetative forms,
and in the intervals between the heatings the remaining spores
germinate into vegetative forms which are killed on subsequent
heating.
• It is used for sterilization of egg, serum or sugar containing media
which are damaged at higher temperature of autoclave.The
instrument commonly used is Koch's or Arnold's steam steriliser.
38

(c) Steam steriliser at 100°C for 90 minutes
• Koch's or Arnold's steam steriliser.
• Usually used for media which are
decomposed at high temperature of autoclave.
• The articles are kept on a perforated tray through which steam can
pass.
• They are exposed to steam at atmospheric pressure for 90 minutes.
• Most of the vegetative forms are killed by this method except
thermophiles.
39

AUTOCLAVE
Principles:
1. Steam above100°C or saturated steam has a better killing power than dry
heat.
2. Bacteria are more susceptible to moist heat as bacterial protein coagulates
rapidly.
3. Saturated steam can penetrate porous material easily.
4. When steam comes into contact with a cooler surface it condenses to water
and liberates its latent heat to that surface.
5. The large 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.
6. The condensed water produces moist conditions for killing the microbes
present.
40

Components of autoclave
• Autoclave is a modified pressure cooker or boiler. It consists of a
vertical or horizontal cylinder of gunmetal or stainless steel in a
supporting iron case.
• The lid is fastened by screw clamps and rendered air tight by an
asbestos washer.
• The lid bears a discharge tap for air and steam, a pressure gauge and
a safety valve .
• Heating is generally done by electricity.
• The steam circulates within the jacket and is supplied under high
pressure to the inner chamber where materials are kept for
sterilisation
41

42

Sterilization conditions
• Temperature - 121 °C Chamber pressure - 15 lbs per square
inch -Holding time - 15 minutes
• These conditions are generally used, however, sterilization can
also be done at higher temperatures, at
• 126°C - 20 lbs -10 minutes or
• 133°C- 30 lbs - 3 minutes.
43

Uses
1. To sterilize culture media ,rubber material, gowns, dressing,
gloves etc.
2. It is particularly useful for materials which cannot withstand
the higher temperature of hot air oven .
3. For all glass syringes, hot air oven is a better sterilizing
method.
44

Precautions
1. The air must be allowed to escape from the chamber as
temperature of air-steam mixture is lower than that of pure
steam.
2. Materials should be arranged in such a manner as to ensure
free circulation of steam inside the chamber.
45

Sterilization control
(i) Thermocouple-It is to record the temperature directly by a
potentiometer .
(ii) Bacterial spores- Spores of bacillus stearo thermophilus are used as
the test organism.
• This organism has an optimum growth temperature of 55- 60 °C and
its spores are killed in 12 minutes at 121 °C.
(iii) Chemical indicators - Browne's tube contains red solution which
turn green, when exposed to temperature of 121 °C for 15 minutes in
autoclave.
(iv) Autoclave tapes
46

3. Ozone
• Low Temperature sterilization by ozone-Ozone sterilizer uses
oxygen, water and electricity to produce ozone within the
sterilizer and provide sterilization without producing toxic
chemicals.
• It runs at lower temperature ie. 25°C-35° In this device, oxygen
molecules (02) are separated into atomic oxygen (0) in the
presence of intense electrical field. This atomic oxygen (0)
combines with other oxygen molecules (02) to form ozone (03).
48

4. Filtration
• This method of sterilization is useful for substances which get
damaged by heat process e.g. sera, sugars, antibiotic solutions etc.
Uses of filtration
1. To sterilize sera, sugars and antibiotic solutions.
2. Separation of toxins and bacteriophages from bacteria.
3. To obtain bacteria free filtrates of clinical samples for virus
isolation.
4. Sterilization of hydatid fluid.
5. Filter discs retain the organism which can then be cultured e.g.
testing of water samples for Cholera vibrios or typhhoid bacilli.
49

Types of filters
• 1)Candle filters are manufactured in different grades of porosity and
have been used widely for the purification of water for industrial
and drinking purposes.
• They are of two types- unglazed ceramic filters (for example,
Chamberland and Doulton) and Diatomaceous earth filters(for
example, Berkefeld and Mandler).
• 2)Sintered glass filters are prepared by heat-fusing finely powdered
glass particles of graded sizes.
• They have low absorptive property and can be cleaned easily, but
are brittle and expensive.
50

• 3)Membrane filters made; of cellulose esters or other
polymers have largely replaced other types of filters.
• They are routinely used in water purification and analysis,
sterilization and sterility testing, and for the preparation of
solutions for parenteral use.
• They come in a wide range of average pore diameters (APD) ,
the 0.22µm size being the most widely used for sterilization .
51

• 4)Air filters- These filters are used to deliver clean bacteria-
free air to a cubicle or a room.
• High efficiency particulate air HEPA filters are used in air
filtration in laminar air flow system in microbiology
laboratories. HEPA filters can remove particles of 0.3 μm or
larger.
• 5)syringe filters- Syringes fitted with membrane of different
diameters are available. For sterilisation, the fluid is forced
through the disc (membrane) by pressing the piston of the
syringe.
53

5. Radiations
• Two types of radiations
-ionising and non-ionising radiations.
Ionising radiations include gamma rays, X-rays and cosmic rays.
• They have very high penetrating power.
• They are highly lethal to all cells including bacteria. They damage
DNA by various mechanisms.
• Gamma radiations from a Cobalt 60 source are commercially used in
sterilisation of disposable items such as plastic syringes,swabs,
culture plates, cannulas,catheters.
55

• This method is also known a cold sterilization because there is
no appreciable increase in temperature.
• The advantages of this method include speed , high
penetrating power (it can sterilize materials, through outer
packages and wrappings), and the absence of heat.
• Bacillus pumilis has been used for testing the efficacy of
ionising radiations.
56

Non - ionising radiations
• These include infrared and ultraviolet (UV) radiations. Infrared is
used for sterilization of syringes and catheters.
• Uv radiation with wavelength of 240 to 280 nm has marked
bactericidal activity.
• It acts by denaturation of bacterial protein and interference with
DNA replication.
• UV radiation is used for disinfecting enclosed areas such as
bacteriological laboratory, inoculation hoods, and operation
theatres.
57

B Chemical Methods
• Desired qualities of an ideal disinfectant
1. Have wide spectrum of activity and effective against all
microorganisms including bacteria (both vegetative and spore
forms), viruses, protozoa and fungi.
2. Act in the presence of organic matters.
3. Have high penetration power and quick action.
4. Stable and effective in acidic as well as in alkaline conditions.
5. Should not corrode metals.
58

6. Be compatible with other disinfectants.
7. Should not cause local irritation.
8. Should not be toxic if absorbed into circulation.
9. Should be safe and easy to use.
10. Should be easily available and cheap.
• Articles which cannot be sterilized by boiling or autoclaving
may be immersed in chemical disinfectants
59

Chemical Methods
4. Alcohols
5. Formaldehyde
6. Oxidizing agents
7. Metals
8. Lime
9. Ethylene oxide
60

• (1) Phenol : Pure phenol or carbolic acid is the best known member
of this group. Pure phenol is not an effective disinfectant. It is used
as a standard to compare the germicidal activity of disinfectants.
• (2) Crude phenol :Mixture of phenol and cresol. It is a dark oily
liquid. It is effective against gram positive and gram negative
bacteria, but only slowly effective against spores and acid-fast
bacteria. It is also effective against certain viruses. Not readily
inactivated by organic matter. In 5 % strength, it may be used for
mopping floors and cleaning drains.Aqueous solutions of 0 .2 - 1 %
are bacteriostatic.
61

• (3) Cresol : Cresol is an excellent coal-tar disinfectant. It is 3 to
10 times as powerful as phenol, yet no more toxic.Cresol is
best used in 5 to 10 % strength for disinfection of faeces and
urine.Cresol is an all purpose general disinfectant.
• (4) Cresol emulsions : Cresol emulsified with soap is known as
"saponified cresol". Lysol,izal and cyllin are cresol emulsions.
Lysol contains 50- 60 % cresol. They are very powerful
disinfectants.
62

• (5) Chlorhexidine (hibitane) :
• This is one of the most useful skin antiseptics.
• Highly active against vegetative grampositive organisms, and
moderately active against grampositive microbes.
• It is soluble in water and alcohol. It is inactivated by soaps and
detergents. 0.5 % alcoholic or aqueous solutions can be used
as effective hand lotions.
• Creams and lotions containing 1 % chlorhexidine are
recommended for burns and hand disinfection
63

• 6) Hexachlorophane : This antiseptic is highly active against gram-positive
organisms, but less active against gram negative organisms. It is slow in
action , but shows a cumulative effect on the skin and is compatible with
soaps. Thus it may be incorporated in soap preparations without loss of
activity.
• (7) Dettol : Dettol (chloroxylenol) is a relatively non-toxic antiseptic and
can be used safely in high concentrations.
• It is more easily inactivated by organic matter than many other phenolic
disinfectants. It is active against streptococci, but worthless against some
gram negative bacteria.
• Dettol (5%) is suitable for disinfection of instruments and plastic
equipment; a contact of at least 15 minutes will be required for
disinfection.
64

• (1) Cetrimide : It is manufactured under the trade name "cetavlon".
It is actively bactericidal against vegetative gram-positive organisms,
but much less so against gramnegative organisms.
• Cetavlon is soluble in water; it has a soapy feel. It may be used in 1-
2 % strength.
• (2) Savlon : Savlon is a combination of cetavlon and hibitane. Plastic
appliances may be disinfected by keeping them in normal strength
savlon for 20 minutes. Savlon 1 in 6 in spirit is more effective than
savlon 1 in 20 aqueous solution.
• Clinical thermometers may be best disinfected in savlon 1 in 6 in
spirit in just under 3 minutes.
65

• a. Chlorine and chlorine compounds : They are potent
bactericidal, fungicidal , sporicidal, tuberculocidal and
virucidal. Since long time chlorine has been used as
disinfectant in water treatment.
66

• (1) Bleaching powder: Bleaching powder or chlorinated lime
(CaOCl2) is a white amorphous powder with a pungent smell of
chlorine.
• A good sample of bleaching powder
contains about 33 % of "available chlorine" .
• It kills most of the organisms when used in the strength of 1 to 3 %.
• Bleaching powder is widely used in public health practice in India for
disinfection of water, faeces and urine; and as a deodorant.
• A 5% solution is suitable for disinfection of faeces and urine allowing
a period of one hour for disinfection.
67

• (2) Hypochlorites : Hypochlorites are the most widely used
chlorine disinfectant, available as liquid (e.g. sodium
hypochlorite) or solid (e.g. calcium hypochlorite).
• The most prevalent chlorine products are aqueous solutions of
5.25- 6.15 % of sodium hypochlorite, usually called household
bleach.
• They have a broad spectrum of antimicrobial activity, do not
leave toxic residues, are unaffected by water hardness, are
inexpensive and fast acting, remove dried or fixed organisms
and biofilms from surfaces .
68

• (3) Chlorine tablets : Under various trade names (viz. ,
halazone tablets) they are available in the market.
• They are quite good in disinfecting small quantities of water.
• (4) Alternative compounds that release chlorine and are used
in the health-care setting include demand release chlorine
dioxide, sodium dichloro isocyanurate, and chloramine-T.
• The advantage of these compounds over hypochlorites is that
they retain chlorine longer and so exert a more prolonged
bactericidal effect.
69

• b. Iodine
• (1) Iodine solutions or tinctures have been used as antiseptic
on skin or tissue since long time. Iodine is bactericidal,
fungicidal, virucidal and lethal to spore-bearing organisms.
Iodine is cheap, readily available and quick in action.
• (2) Iodophores : An iodophore is a combination of iodine and a
solubilizing agent or carrier; the resulting complex provides a
sustained-release reservoir of iodine and releases small
amounts of free iodine in aqueous solution.
70

• The best known and most widely used iodophore is povidone-
iodine (Betadine). They are non-irritant and do not stain the
skin.
• Besides their use as an antiseptic, iodophores have been used
for disinfecting blood culture bottles and medical equipment.
71

• 4. Alcohols
• Ethyl and isopropyl alcohols are commonly used as antiseptics and
disinfectants. Ethyl alcohol in the form of industrial methylated spirit
is the alcohol most commonly used for skin disinfection and hand
washing.
• Pure alcohol has no powers of disinfection but when diluted with
water to 60- 90 % vol/vol, it is potent bactericidal,
fungicidal,virucidal and tuberculocidal , but does not destroy
bacterial spore.
• Its activity decreases rapidly below 50 per cent concentration. 70
per cent alcohol is lethal in a period of seconds to all types of non-
sporing bacteria.
72

5. Formaldehyde
• More commonly known in solution as formalin ,formaldehyde
is a highly toxic and irritant gas which precipitates and destroys
protein.
• It is effective against vegetative bacteria, fungi and many
viruses but only slowly effective against bacterial spores (e.g. ,
tetanus spores) and acid-fast bacteria.
• It does not injure fabrics and metals. It may be used as a 2-3 %
solution (20- 30 ml of 40 percent formalin in one litre of water)
for spraying rooms, walls and furniture.
73

• Formaldehyde gas is most commonly used for disinfection of
rooms.
• The gas is most effective at a high temperature and a relative
humidity of 80-90 %.
• The gas may also be used for disinfection of blankets, beds,
books and other valuable articles which cannot be boiled.
74

• Glutaraldehyde: When buffered with sodium bicarbonate to
pH 7.5–8.5, this has potent bactericidal, mycobactericidal,
sporicidal, fungicidal, and virucidal action. The buffered
solutions should be used within 2 weeks of preparation.
• It is available under the brand name Cidex.
• A 2 % solution provides a high level of disinfection, which
approximates sterilization.
• It is the only disinfectant that can be reused. It is less toxic
than formaldehyde
75

• 6. Oxidizing agents
• a. Potassium permanganate : It is a purplish black crystalline
powder that colours everything it touches through strong
oxidizing action, which limits its use.
• It is used to disinfect aquariums and is also widely used in
community swimming pools to disinfect ones feet before
entering the pool.
• It is also used to disinfect fruits and vegetables.
76

(b)Hydrogen peroxide
• Hydrogen peroxide is bactericidal, virucidal, sporicidal and
fungicidal. It is used in hospital setting to disinfect surfaces. It
is used as solution alone or in combination with other
chemicals as a high level disinfectant.
• A 0.5 % accelerated hydrogen peroxide demonstrated
bactericidal and virucidal activity in 1 minute and
mycobactericidal and fungicidal activity in 5 minutes.
• A 3 % solution is also used as an antiseptic and for cleaning
wounds and discharging ulcers.
77

(c)Peracetic acid
• It is a disinfectant produced by reacting hydrogen peroxide
with acetic acid. It is broadly effective against microorganisms
and is not deactivated by catalase and peroxidase, the
enzymes that break down hydrogen peroxide.
• It inactivates gram-positive and gram-negative bacteria, fungi
and yeast in less than 5 minutes at less than 100 ppm.
• In the presence of organic matter, 200- 250 ppm is required.
For viruses, the dose range is wide ( 12- 2250 ppm).
78

• 7. Metals as microbicides
• Anti-infective activity of some heavy metals has been known
since antiquity.
• Heavy metals such as silver have been used for prophylaxis of
conjunctivitis of the new-born, topical therapy for burn
wounds, and bonding to indwelling catheters.
• Metals such as silver, iron, and copper could be used for
environmental control, disinfection of water or reusable
medical devices, or incorporated in to medical devices.
79

• 8. Lime
• Lime is the cheapest of all disinfectants. It is used in the form
of fresh quick lime or 10-20 % aqueous suspension known as
"milk of lime".
• As lime wash, it is used for treating walls. As a deodorant, lime
is sprinkled in cattle sheds and stables and in public places
where urinals and latrines are located.
80

• 9. Ethylene oxide
• Heat-sensitive articles may be sterilized at 55-60 0C by
ethylene oxide which kills bacteria, spores (e.g. , tetanus
spores) and also viruses. Ethylene oxide is explosive, therefore,
it is mixed with carbon dioxide (12 %).
• Water vapour is also often added to the mixture (relative
humidity 33 %) since it increases the efficiency of the gas.
• Ethylene oxide has been effectively used to sterilize fabrics ,
plastic equipment, cardiac catheters, books, etc; but the
process is difficult to control.
81

Factors affecting the efficacy of sterilization
1. Cleaning
• Failure to adequately clean instruments results in higher
bioburden, protein load, and salt concentration. These will
decrease sterilization efficacy.
2. Pathogen type
• Spore-forming organisms are most resistant to sterilization.
However, the contaminating microflora on surgical
instruments consists mainly of vegetative bacteria.
82

3. Biofilm accumulation
• Biofilm accumulation reduces efficacy of sterilization by
impairing exposure of the sterilant to the microbial cell.
4. Lumen length and lumen diameter
• Increasing lumen length and decreasing lumen diameter
impairs sterilant penetration. May require forced flow through
lumen to achieve sterilization.
83

5. Restricted flow
• Sterilant must come into contact with microorganisms. Device
designs that prevent or inhibit this contact (e.g. sharp bends,
blind lumens) will decrease sterilization efficacy.
6. Device design and construction
• Materials used in construction may affect compatibility with
different sterilization processes.
84

Categories of Patient-Care Items
• Critical.
• Semicritical.
• Noncritical.
• Based on intended use and the potential risk of disease
transmission
Morbidity and Mortality Weekly Report (MMWR) [Internet]. Guidelines for Infection Control in Dental Health-Care Settings .2003. MMWR 2003[cited 2021Apr22].
Available from: https://www.cdc.gov/mmwr/index.html 86

Critical Items
• Penetrate soft tissue or contact bone, enter into or contact the
vascular system or other normally sterile tissue.
• Greatest risk of transmitting infection.
• Must be heat sterilized between use, or sterile single-use,
disposable devices must be used.
• Examples: surgical instruments and periodontal scalers.

Semicritical Items
• Contact mucous membranes or non-intact skin (e.g., exposed
skin that is chapped, abraded, or has dermatitis).
• Lower risk of transmission.
• Should be heat sterilized or high-level disinfected.
• Examples: mouth mirrors, amalgam condensers, and reusable
impression trays.

Dental Handpieces
• Follow manufacturer’s instructions to safely reprocess dental
handpieces and accessories (e.g., low-speed motor, reusable
prophylaxis angles).
• Clean and heat sterilize between patient uses.
• Do not subject the handpiece to high-level disinfection and do
not simply wipe the surface with a low-level disinfectant.

Digital Sensors
• Follow manufacturer’s instructions to safely reprocess digital
radiography equipment.
• Ideally, barrier protection should be used, followed by cleaning and
heat sterilization or high-level disinfection between patients.
• If the item cannot tolerate these procedures, then at minimum,
barrier protection should be used, followed by cleaning and
disinfection with an intermediate-level disinfectant between
patients.

Noncritical Items
• Contact intact skin.
• Barrier protect or clean and disinfect (if visibly soiled) using a
low to intermediate-level (i.e., tuberculocidal) disinfectant.
• Examples: x-ray head or cone, facebows, blood pressure cuff.

Single-Use (Disposable) Devices
• Intended for use on one patient during a single procedure.
• Usually not heat-tolerant.
• Cannot be reliably cleaned.
• Do NOT reprocess.
• Examples: syringe needles, prophylaxis cups, and plastic
orthodontic brackets.

The preferred methods of sterilisation in a dental office
• Steam pressure sterilization (autoclave)
• Unsaturated chemical vapor pressure sterilization(chemiclave)
• Dry heat sterilization(dryclave)
• Other Methods of Sterilization
- Liquid chemical germicides:
- Ethylene oxide gas (ETG)
- Bead sterilizers

• Heat sterilization methods are for several reasons:
1. Effective.
2. Relatively easy to use.
3. Comparatively inexpensive.
4. Readily monitored for effectiveness.
• Liquid chemical disinfectants/sterilants should be used only
when heat will damage an item.

Unsaturated chemical vapour sterilization
• Unsaturated chemical vapour sterilization involves heating a
chemical solution of primarily alcohol with formaldehyde in a
pressurized chamber.
• This method of sterilization is ideally suited to carbon steel
instruments (e.g. dental burs) because the low level of water
present during the cycle results in less corrosion than might be
expected with steam sterilization.
• Instruments must be dry before sterilization

Advantages of chemical vapour sterilization
• Is relatively quick.
• Does not rust or corrode metal items. Is very reliable.
• Can be used with packaged items (paper packaging only).
• Can be monitored for effectiveness.
Disadvantages of chemical vapour sterilization
• Requires good ventilation owing to fumes. Won't penetrate fabric-
wrapped packs. Damages some plastics.
• Requires replacement of special solution, increasing cost.
• Requires hazardous waste disposal of the sterilizing solution.

Bead sterilizers:
• Historically, bead sterilizers have been used in dentistry to
sterilize small metallic instruments (e.g. endodontic files). This
method employs a heat transfer device.
• The media used are glass beads or salt and the temperature
achieved is 220°C.
• The method employs submersion of small instruments such as
endodontic files and burs into the beads; they are sterilized in
10 seconds provided they are clean.

Accomplished by the following steps
• Presoaking : A presoaking solution (phenolic compounds) prevents drying of
debris, helps to dissolve or soften organic debris and sometimes helps in
microbial killing.
• Cleaning : Cleaning can be done either by hand, scrubbing or with the use of
ultrasonic devices.
• Corrosion control and lubrication : Instruments must be dried prior to
sterilization to decrease chances of corrosion.The non-stainless steel
instruments should be coated with a rust inhibitor.
• Packaging : The instruments can be packed individually or in small groups and
distributed on sterile or disposable disinfected trays for use at chair side.. See-
through polyfilm bags or pouches facilitate instrument identification.

• Sterilization : Autoclaving is the most accepted method of
sterilization of surgical instruments as it eliminates bacteria,
viruses, fungi and spores. Dry heat ovens or the unsaturated
chemical vapour sterilizers are the other means of sterilization.
• Handling sterile instruments : Post sterilization procedures
involve drying, cooling, storage and distribution. As far as
possible the sterile packages or trays should not be handled,
till required for use, to reduce recontamination.

• Storage : Sterile packs and trays should be kept in dry, low
dust, low traffic areas away from sinks and sewer of water
pipes, at least a few inches above the floor.
• Distribution : Sterilized packs can be placed on sterile,
disposable trays for use at chair side. Placing unwrapped or
wrapped instruments in drawers for direct use at chair side is
not recommended.

Sterilization Monitoring: Types of Indicators
• Mechanical:Measures time, temperature, and pressure.
• Chemical:Change in color when physical parameter is
reached.
• Biological (spore tests):Uses biological spores to asses the
sterilization process directly.
Indicators are specific to the type of sterilization used.

Mechanical Monitoring
• Monitor each load with mechanical (physical) indicators:
• Time.
• Temperature.
• Pressure.

Chemical Monitoring
• Use an internal chemical indicator in every package. If the
internal indicator is not visible from the outside, then also use
an external indicator.
• Chemical indicators may be integrated into the package
design.
• Inspect indicator(s) after sterilization and at time of use.
• If the appropriate color change did not occur, do not use the
instruments.

Biological Monitoring
• Assess sterilization process directly by killing known highly
resistant microorganisms.
• Use biological indicators (spore tests) at least weekly.
Available from: https://www.cdc.gov/mmwr/index.html
107

• To conclude, sterilization, disinfection, and cleaning are the mainstay of
hospital infection control activities.
• When properly used, disinfection and sterilization can ensure the safe use
of invasive and noninvasive medical devices.
• The method of disinfection and sterilization depends on the intended use
of the medical device: critical items (those that contact sterile tissue) must
be sterilized prior to use; semicritical items (those that contact mucous
membranes or nonintact skin) must undergo high-level disinfection; and
noncritical items (those that contact intact skin) should undergo low-level
disinfection.
• Cleaning should always precede high-level disinfection and sterilization.
Current disinfection and sterilization guidelines must be strictly followed.
Rutala WA, Weber DJ. Disinfection and Sterilization in Health Care Facilities: What Clinicians Need to Know. Clinical Infectious Diseases.
2004;39(5):702–9.
108

1. Park K. Park's textbook of Preventive and social medicine.
25th ed. India: Bhanot Publishers; 2017.
2. Ananthanarayan R. Textbook of microbiology. 10th ed.
Hyderabad: University Press ; 2016.
3. Baveja CP. Textbook of microbiology. 5th ed. New Delhi: Arya
Publications; 2005.
4. Morbidity and Mortality Weekly Report (MMWR) [Internet].
Guidelines for Infection Control in Dental Health-Care
Settings — 2003. MMWR 2003[cited 2021Apr22]. Available
from: https://www.cdc.gov/mmwr/index.html
109

5. Rutala WA, Weber DJ. Disinfection and Sterilization in Health Care
Facilities: What Clinicians Need to Know. Clinical Infectious
Diseases. 2004;39(5):702–9.
6. Appendix C: Methods for Sterilizing and Disinfecting Patient-Care
Items and Environmental Surfaces [Internet]. Centers for Disease
Control and Prevention.[cited 2021Apr22]. Available
from:https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5217a4.
htm
7. WHO Guidelines on Hand Hygiene in Health Care: First Global
Patient Safety Challenge Clean Care Is Safer Care [Internet].
National Center for Biotechnology Information. U.S. National
Library of Medicine; [cited 2021Apr22]. Available from:
https://pubmed.ncbi.nlm.nih.gov/23805438/
110

• 3 main classes of autoclaves you can choose from:
• Class N (the most compact small autoclaves)
• Class B (nicknamed “big small”, or “medium” autoclaves)
• Class S (all other types of autoclaves, including the largest steam sterilizers)
• Class N steam sterilizers are essentially small dental autoclaves, that are perfect
if you’re looking for the most space saving solution, and you only need to
sterilize certain materials. The “N” stands for “naked solid product”, so be wary,
as these dental steam sterilizers cannot be used to treat fabrics such as textiles.
These machines also don’t always make use of the vacuum described above.
• Class S covers a much less defined category of autoclaves, where the details are
mostly found in the technical descriptions provided by the manufacturer.
• The letter “B” stands for “big small”, meaning that despite their smaller size
(which is also perfect if you don’t work at a huge dental clinic),they can provide
an excellent performance.
113

• Flush devices connected to dental unit air and water system for 20- 30
seconds between patients.
• Flush dental waterlines at the beginning and at the end of the day.
• Insert only sterile needles and syringes into multi-dose vials.
• Clean and disinfect blood spills immediately.
• Dispose of all single-use devices after use on patient.
• Use sterilized instruments for every patient.
• Decontaminate or properly contain and label extracted teeth.
• Properly dispose of extracted teeth containing amalgam.
• Heat sterilize extracted teeth before using them in educational settings.
• Disinfect dental prostesis and impressions before sending to the laboratory.
114

• DENTAL RADIOGRAPHY CDC(MMWR),dec19,2003vol.52 •
Contamination of working area occurs from saliva. • X-ray tube
head, exposure selector and timer button are likely to get
contaminated by saliva. • Precaution to be taken up : 1. Put on
gloves. 2. Place the film packets and film holders in special tray. 3.
Contaminated films(exposed films) to be placed in separate tray. 54
• 55. 4. Film holding device to be rinsed in running water to remove
saliva. 5. Metallic part to be autoclaved. 6. Plastic attachments to be
kept in chlorhexidine solution. 7. Wipe the x-ray tube head,
exposure selector, timer button and film packets with detergents. 8.
Tube can be wrapped in disposable plastics. 9. Film packets to be
discarded in yellow bags.
115

• ROTARY INSTRUMENTS - BURS Diamond and carbide burs: After use they
are placed in 0.2% gluteraldehyde and sodium phenate (Eg. Sporicidin) for
at least 10 minutes, cleaned with a bur brush or in an ultrasonic bath.
Sterilize in an autoclave or dry heat Steel burs: May get damaged by
autoclaving. Can be sterilized by using a chemical vapor sterilizer or glass
bead sterilizer at 2300C for 20-30 seconds. 62
• 63. ENDODONTIC INSTRUMENTS CDC(MMWR),dec19,2003vol.52 • Glass
Bead or salt sterilizer is the best option, but they do not sterilize the
handle. • Sterilization achieved in 10 seconds • Dry heat is used, with
instruments in closed metal or perforated metal boxes. • Sterilization
achieved at 218oC for 15 seconds • Gutta percha points are pre-sterilized.
• Contaminated points are sterilized by 5.25% sodium hypochlorite.(1 min
immersion). • Then rinse with hydrogen peroxide & dry it. 6
116

• In the mid-1800s, studies by Ignaz Semmelweis in Vienna, Austria, and Oliver Wendell
Holmes in Boston, USA, established that hospital-acquired diseases were transmitted via
the hands of HCWs.
• He also noted that doctors and medical students often went directly to the delivery suite
after performing autopsies and had a disagreeable odour on their hands despite
handwashing with soap and water before entering the clinic. He hypothesized therefore
that “cadaverous particles” were transmitted via the hands of doctors and students from
the autopsy room to the delivery theatre and
• caused the puerperal fever.
• As a consequence, Semmelweis recommended that hands be scrubbed in a chlorinated
lime solution before every patient contact and particularly after leaving the autopsy
room.
• Following the implementation of this measure, the mortality rate fell dramatically to 3%
in the clinic most affected and remained low thereafter.
120

• Clinical hand washing, since then, has prevented millions of
deaths of humankind. In the present times too, his idea of
hand hygiene plays a central role in COVID-19 pandemic
management. Authors present a brief account of life and work
of this maverick genius, who was born “too early in the
darkness.” He is also called the “Father of infection control”
and “Savior of mothers.”
122

• When surgeon Joseph Lister died at the age of 84 on February
10, 1912, he left behind a drastic reduction in the mortality of
surgical patients due to infections. According to statistics
collected by himself, the decrease went from almost 50% of
those operated on to only 15%.
123

• In 1864, while practicing as a professor of surgery at the
University of Glasgow, Lister discovered the work of a French
chemist named Louis Pasteur. When he read in Recherches sur
la putrefaction that fermentation was due to germs, microbes
invisible to the eye, he sensed that the same cause could
explain the infection of wounds.
125

• Following the ideas of Pasteur, Lister looked for a chemical
substance with which to annihilate the germs. After several
tests he arrived at carbolic acid (now called phenol), a
compound extracted from creosote that was then used to
prevent the rotting of railway sleepers and the wood of ships,
and which was also applied to the wastewater of cities. In
1865, after some doubtful beginnings, he managed for the
first time to heal without infection the open leg fracture of a
child hit by a car.
126

• From then on, Lister laid out a protocol to sterilize the surgical
instruments, the hands of the surgeon, the dressings and the
wounds with solutions of carbolic acid, and even designed a
sprayer to diffuse the substance in the air of the operating
room, which was definitely not pleasant. But the results made
up for the inconvenience, and in 1867 Lister was able to
publish his findings and his antiseptic method in a series
of articles in the magazine The Lancet.
127

• From our current perspective, we might be surprised by the
generous use of the corrosive and toxic phenol, which
nowadays is handled in laboratories with special care. But
from Lister, today we have his revolutionary idea that drew the
line between old-fashioned surgery and its modern
incarnation. And we have Listerine.
128

10. Miscellaneous inactivating agents
a. Pasteuri.zation
b. MicrowC1ve : Microwaves are used in medicine for
disinfection of soft contact lenses, dental instruments,
dentures, milk, and urinary catheters for intermittent
selfcatheterization.
• However, microwaves must only be used with products; that
are compatible (e.g., do not melt).
129

• Microwaves are radio-frequency waves, which are usually used
at a frequency of 2450 MHz. The microwaves produce friction
of water molecules in an alternating electrical field.
• The intermol12cular friction derived from the vibrations
generates hea1t.
• The microwaves produced by a "hometype“ microwave oven
(2.45 GHz) completely inactivate bacterial cultures,
mycobacteria viruses, and G.
• stearothermophilus spores within 60 seconds to 5 minutes
depending on the challenge organism.
130

• Flushing and Washer Disinfectors : Flushing and washer-
disinfoctors are automated and closed equipment that clean
and disinfect objects from bedpans, urinals and washbowls to
surgical instruments and anesthesia tubes.
• They have a short cycle of a few minutes. They clean by
flushing with warm water, possibly with a detergent, and then
disinfect by flushing the items with hot water or with steam.
• Because this machine empties, cleans, and disinfects, manual
cleaning is eliminated, fewer disposable items are needed, and
fiewer chemical gemicides are used.
131

• Ultraviolet radiation :
• The wavelength of UV radiation ranges from 328 nm to 210
nm. Its maximum bactericidal effect occurs at 240-280 nm.
• Mercury vapour lamps emit more than 90 per cent of their
radiation at 253. 7 nm, which is near the maximum
microbicidal activity (155). UV radiation has been employed in
the disinfection of drinking water, air, titanium implants and
contact lenses.
• Bacteria and viruses are more easily killed by UV light than the
bacterial spores.
132

• Ozone : Ozone has been used for years as a drinking water
disinfectant. Ozone is produced when 0 2 is energized and split
inito two monatomic (01) molecules. The monatomic m,ygen
molecules then collide with 0 2 molecules to form ozone·,
which is 0 3
• • Ozone is a powerful oxidant that destroys microorganisms
but it is highly unstable (i.e. halflife of 22 minutes of room
temperature).
133

• Steam Sterilization
• Among sterilization methods, steam sterilization is the most widely used for wrapped and unwrapped critical and
semicritical items that are not sensitive to heat and moisture. When using an autoclave, the load must be placed so
that steam can circulate freely around each item, because steam must be able to reach all instrument surfaces at a
required temperature and pressure for a specified time in order to kill all microorganisms and achieve sterilization.
Be sure to follow the autoclave manufacturer's operating instructions
• The majority of tabletop sterilizers used in dental practice are gravity displacement sterilizers, although prevacuum
sterilizers are becoming widely available. Prevacuum sterilizers are fitted with a pump to create a vacuum in the
chamber and to ensure air removal from the sterilizing chamber before the chamber is pressurized with steam.
Relative to gravity displacement, this procedure allows faster and more positive steam penetration throughout the
entire load.
• Autoclave
• An autoclave is a self locking machine that sterilizes with steam under pressure, achieved by the high temperature.
Autoclaves are the universally accepted means for sterilization.
• It is generally accepted that an autoclave chamber must reach at least 121°C at 15 Psi for a minimum of 30 minutes
to ensure adequate sterilization. Sterilization time may vary depending on the quantity and density of items in the
autoclave chamber. Overloading must be avoided.
• Instruments and materials for sterilizing in the autoclave are usually enclosed in the muslin wrappers as surgical
packs. These packs should be porous to allow steam to penetrate and reach the instruments.
• The autoclave is employed for the sterilization of the instruments, extraction forceps, surgical instruments,
explorers etc. The sterilized instruments should remain wrapped until next used.
134

• Testing of efficacy
• Autoclave indicator tape and autoclave indicator bags change colour when the proper temperature
has been reached. While the indicator tape quick-check should be conducted with every load, it
must be supplemented periodically by use of a biological indicator (such as Bacillus spores) buried in
the center of a load to confirm the sterilization.
• Advantages of steam sterilization
• Is quick and easy to use.
• Allows loads to be packaged, making it easier to maintain items in a sterile state.
• Penetrates fabric and paper wrappings.
• Can be readily monitored for effectiveness.
• Is economical and very reliable.
• Disadvantages of steam heat sterilization
• May cause rust and corrosion (corrosion inhibitors such as sodium nitrite are available that may
reduce this problem).
• May damage plastics.
• May blunt certain sharp items.
135

• Dry Heat Sterilization
• Dry heat is used to sterilize materials that might be damaged by moist heat (e.g. burs and certain orthodontic
instruments). Although dry heat has the advantages of low operating costs and being non-corrosive, it is a
prolonged process and the high temperatures required are not suitable for certain patient care items and devices
with temperatures ranging from 300 degrees F (149 degrees C) and upward can be used for sterilization.
• Dry heat sterilizers used in dentistry include static-air and forced-air types. The static-air type is commonly called an
oven-type sterilizer. The forced-air type is also known as a rapid heat transfer sterilizer. Heated air is circulated
through 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 compared to the oven-type sterilizer.
• Advantages of dry heat sterilization
• Is very reliable.
• Rust and corrosion are not a problem, provided that items are dry prior to sterilization. Is easy to use and requires
little maintenance.
• Can be readily monitored for effectiveness.
• Disadvantages of dry heat sterilization
• Usually requires longer processing times than do steam sterilization or unsaturated chemical vapour.
• Damages some plastics.
• Requires careful loading.
• May char fabric.
• High temperatures may prohibit use with some materials and may melt or destroy some metal or solder joints.
136

Other Methods of Sterilization
• Liquid chemical germicides: Heat-sensitive critical and semicritical instruments and devices can be sterilized by
immersing them in liquid chemical germicides. However, items sterilized in this manner can require approximately
12 hours of complete immersion.
• Additionally items sterilized in this manner must be rinsed with sterile water to remove any toxic or irritating
residues, handled using sterile gloves and dried with sterile towels, delivered to the point of use in an aseptic
manner and then used immediately.
• Because of these limitations, they are almost never used to sterilize instruments. Rather, these chemicals are more
often used for high-level disinfection of heat-sensitive semicritical instruments and devices. Shorter immersion
times (12-90 minutes) make high-level disinfection more practical than sterilization; however, instruments and
devices disinfected in this manner must still be handled as if sterile (e.g. rinsed with sterile water, dried with sterile
towels, etc.) and used immediately.
• Chemical sterilants (e.g. glutaraldehyde, peracetic acid, hydrogen peroxide) are powerful, sporicidal chemicals and
are highly toxic. Instruments can be sterilized by placing them in a 2% solution of glutaraldehyde for 6-10 hours.
The chemical sterilants must only be used according to manufacturer's instructions and for those applications
indicated on their label. Misapplications include use as an environmental surface disinfectant or instrument holding
solution.
• Alcohols are effective as skin antiseptics.Usually a 50% to 80% ethyl alcohol solution is recommended.
• In general, use of heat-sensitive semicritical items that must be processed with liquid chemical germicides is
discouraged; heat-tolerant or disposable alternatives are available for the majority of such items.
137

• Dental prosthesis, impressions, orthodontic appliances and other
prosthodontic materials (e.g. occlusal rims, temporary prosthesis,
bite registrations) should be thoroughly rinsed under gentle running
water to remove blood, saliva or debris.
• The disinfection can be done by a short-term immersion in 0.5% or
1% sodium hypochlorite. In addition, immersion in glutaraldehydes,
povidone-iodine diluted in water or halogenated phenol has no
apparent effect on the dimensional stability of rubber materials.
• The best time to clean and disinfect the impressions, prosthesis or
appliances is as soon as possible after removal from the patients
mouth, before drying of blood and saliva.
138

• (5) The microbicidal activity of a new disinfectant,
"superoxidized water" has been examined. The concept of
electrolyzing saline to create a disinfectant or antiseptic is
appealing because the basic materials of saline and electricity
are inexpensive and the end product (i.e. , water) does not
damage the environment.
• The main products of this water are hypochlorous acid (e.g., at
a concentration of about 144 mg/L) and chlorine.
139

• Multiple semicritical dental devices that touch mucous membranes are attached to the air or waterlines of the dental unit. Among these
devices are high and low-speed handpieces, prophylaxis angles, ultrasonic and sonic scaling tips, air abrasion devices and air and water
syringe tips. These devices have the potential for retracting oral fluids into their internal compartments. Restricted physical access limits
their cleaning. This indicates that retained patient material can be expelled intraorally during subsequent uses.
• Any dental device connected to the dental air/water system that enters the patient's mouth should be run to discharge water, air or a
combination for a minimum of 20- 30 seconds after each patient.
• This procedure physically flushes out patient material that might have entered the turbine, air and waterlines.
• Heat methods can sterilize dental handpieces and other intraoral devices attached to air or waterlines.
• Proper scrubbing with detergent, water and drying followed by wiping with a suitable chemical disinfectant is essential for those
ultrasonic scalers, handpieces and air syringes that cannot be sterilized.
• For processing any dental device that can be removed from the dental unit air or waterlines, neither surface disinfection nor immersion
in chemical germicides is an acceptable method.
• Manufacturer's instructions for cleaning, lubrication and sterilization should be followed to ensure both the effectiveness of the process
and the longevity of handpieces.
• Some components of dental instruments are permanently attached to dental unit waterlines and although they do not enter the
patient's oral cavity, they are likely to become contaminated with oral fluids during treatment procedures.
• Components (e.g. handles or dental unit attachments of saliva ejectors, high- speed air evacuators and air/water syringes) should be
covered with impervious barriers that can be changed after each use.
• If the item becomes visibly contaminated during use, dental practitioner should clean and disinfect with a disinfectant (intermediate-
level) before use on the next patient.
140

• First, formaldehyde-alcohol has been deleted as a recommended chemical sterilant or high-level
disinfectant because it is irritating and toxic and not commonly used. Second, several new chemical
sterilants have been added, including hydrogen peroxide, peracetic acid 58, 69, 70, and peracetic
acid and hydrogen peroxide in combination. Third, 3% phenolics and iodophors have been deleted
as high-level disinfectants because of their unproven efficacy against bacterial spores, M.
tuberculosis, and/or some fungi. 55, 71 Fourth, isopropyl alcohol and ethyl alcohol have been
excluded as high-level disinfectants 15 because of their inability to inactivate bacterial spores and
because of the inability of isopropyl alcohol to inactivate hydrophilic viruses (i.e., poliovirus,
coxsackie virus).72 Fifth, a 1:16 dilution of 2.0% glutaraldehyde-7.05% phenol-1.20% sodium
phenate (which contained 0.125% glutaraldehyde, 0.440% phenol, and 0.075% sodium phenate
when diluted) has been deleted as a high-level disinfectant because this product was removed from
the marketplace in December 1991 because of a lack of bactericidal activity in the presence of
organic matter; a lack of fungicidal, tuberculocidal and sporicidal activity; and reduced virucidal
activity.49, 55, 56, 71, 73-79 Sixth, the exposure time required to achieve high-level disinfection has
been changed from 10-30 minutes to 12 minutes or more depending on the FDA-cleared label claim
and the scientific literature. 27, 55, 69, 76, 80-84 A glutaraldehyde and an ortho-phthalaldehyde
have an FDA-cleared label claim of 5 minutes when used at 35°C and 25°C, respectively, in an
automated endoscope reprocessor with FDA-cleared capability to maintain the solution at the
appropriate temperature. 85
141

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