Sterilization and disinfection in dental clinics /certified fixed orthodontic courses by Indian dental academy

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Leader in continuing dental education
www.indiandentalacademy.com

CONTENTS
TERMINOLOGIES
HISTORY
RATIONALE
CLASSIFICATION
CONCLUSION
REFERENCES

TERMINOLOGIES
Sterilization
- Process of destruction or removal of all viable
microorganisms from an object or from a particular
environment .
- Total inactivation of all forms of microbial life in
terms of the organism’s ability to reproduce .


Disinfection

- Refers to the use of physical process or
chemical agent (disinfectants) that promotes
killing, inhibition, or removal of pathogenic
microorganisms (usually on inanimate objects)
but not bacterial endospore.


Sepsis – growth

of microorganisms or the presence
of microbial toxins in the blood and other tissues.
Asepsis -

refers to any practice that prevents the
entry of infectious agents into sterile tissues and
thus prevents infection.


Antisepsis – aseptic technique practiced in

health care, ranges from sterile methods that
uses chemical agents (antiseptics) which are
applied directly to exposed body surfaces,
wounds, and surgical incision to destroy or inhibit
vegetative pathogens.


- is an agent used to reduce the viability of
a microbial population below a threshold level that
causes infection.
- Disinfectants are used on inanimate objects.
Disinfectant

Antiseptic - chemical

agents that opposes sepsis or
putrefaction either by killing microorganisms or by
preventing their growth.
- Term commonly used for agents that are
applied topically to living tissues.

HISTORY
Zaccharias Jansen in 1590 and Robert Hooke iin
1660 opened the world of microbes to mankind by
their inventions of microscopes.
AntonVan Leeuwenhoek-.””’”animolecules;”1667
through his handcrafted microscope-observed
tooth scrapings.
in 1667 through www.indiandentalacademy.com microscope
his handcrafted

“ The Golden Age of MICROBIOLOGY”
Louis Pasteur (France)
Robert Koch (Germany)
Igniz Semmelweiss (Vienna),
Oliver Wendell Holmes (USA),
Lord Joseph Lister (England)
Louis Pasteur (France).

Willoby Miller (USA) who came to be known as the
“Father of oral Microbiology”” in mid-concept of prevention of disease through
“Infection Control Procedures”

INFECTION
“Defined as an invasion and multiplication of

micro organisms in body tissues.
Transmission:
Source

Mode of Transmission


Susceptible Host

CROSS INFECTION
Defined as the transmission of infectious agents

between patient and the staff within a “clinical
environment”.

Causes
P Patients suffering from the infectious illness. ing finf

Patients in prodromal phase of infection .
Carriers of infectious organism.

INFECTION VERSUS CROSSINFECTION
Pathways


Patient to dental team



Patient to patient



Dental team to patient



Dental office to community

CHAIN OF INFECTION
All links must be connected for infection
to take place
Pathogen
Susceptible Host
Source

Entry www.indiandentalacademy.com

Mode

Goal of Infection control

“Eliminate or reduce the number of microbes
shared between people”


Infection Control In Dental Office
Dental office designing and maintenance.
 Patient screening
 Personal protection

Immunization
ii. Hand hygiene, washing and care
iii. pre procedural mouth wash
 Personal protective equipment
i. Gloves
ii. face mask
i.


Dental Office Designing And Maintenance.
1. Cabinetry
2. Floor covering
3. Work surfaces
4. Ventilation

Patient screening
Patient medical history.
Identify patients at high risk
to harbor potentially
infectious organisms and
those who may have
increased susceptibility to
infections.

Personal protection
Immunization
 Hand washing .
Antiseptic mouth rinses

for the patient


1

5

9

2

4

3

6

10

7

11

8

12

Personal protective equipment (PPE)
PPE is designed to protect the skin and the

mucous membranes of the eyes, nose, and
mouth of dental health-care personnel (DHCP)
from exposure to infectious or potentially
infectious materials.


Gloves
Types of gloves;
i.

Sterile surgical gloves

ii.

Over gloves
( Avoids cross-contamination)

iii. Examination gloves
Powder-free (preferable)
 Latex – inexpensive but could be
allergic
 Polyurethane – strong and nonallergic
 Nitrile – strong and non-allergic
 Vinyl – non-allergic

iv. Utility gloves.




Nitrile gloves
Puncture and cut resistant to handle
contaminated sharps
Neoprene gloves
Handle hot objects and to avoid
burns/scalds (while removing sterile
instrument packs from sterilizer)

Recommendations for Gloving

Remove gloves that
are torn, cut or punctured

Do not wash, disinfect
or sterilize gloves for reuse



Face Mask




Protective eye wear


Proper clinical attire

Wear gowns, lab coats, or uniforms that
cover skin and personal clothing likely to
become soiled with blood,
saliva, or infectious material.


DYNAMICS OF STERILIZATION &
DISINFECTION
Microorganisms are not killed instantly when

exposed to a lethal agent .

The kinetics of death of a microbial population

is exponential.

The rate of disinfection varies with the

concentration of the disinfectant.

Factors affecting disinfectant potency
1.

Number of microorganisms

2. Nature of microorganism
3. Temperature ,pH
4. Time

5. Mode of action of the agents

6.Concentration of the agent
7. Presence of exogenous materials


CLASSIFICATION OF INSTRUMENT

STERILIZATION

Proposed by SPAULDING in 1972 according to
the use and degree of contamination patient
care items and equipments are classified as:


Critical



Semi Critical



Non Critical

METHODS OF
MICROBIAL
CONTROL
Physical Agents
Chemical Agents
Chemotherapeutic
Agents

• Heat
• Freezing
• Radiation
• Filtration
• Ultrasonic and
SonicVibration

HEAT

- Most reliable and universally applied method of
sterilization
- 2 kinds of heat :

1. Dry
2. Moist


Thermal Death Time
- Refers to minimum time required to kill all

microbes at a specified temperature in a
specified environment .

Thermal Death Point
- Lowest temperature required to kill all
microbes when time is held constant.

DRY HEAT
Sterilization that requires higher temperature

and longer period of heating .
Denotes air with a low moisture content that
has been heated by flame or electric heating
coil.
Temperature ranges from 160°C – several
thousand degrees.

Mechanism of action :
Denaturation of proteins
Oxidative damage

Its use is limited primarily to sterilization of

glass wares and materials as oils, jellies, and
powders that are impervious to steam.


Forms:

1. Direct

flaming

Loops or wires, glass slides ,cover slips, the tips of
the instruments are held in a Bunsen flame till they
become red-hot.
These materials may be
dipped in a disinfectant
before flaming.

2. Incineration / cremation

This is an excellent method for safely destroying

materials such as contaminated cloth, animal
carcasses and pathologic material, Plastics such as
PVC.
Globally used for the disposal of hospital waste.

3.

Hot air oven

This is the most widely used method of

sterilization by dry heat.

A holding period of 160oC ( 320oF) for 1 hr is used
to sterilize glassware, swabs, liquid paraffin,
dusting powder, fats and grease. It is suitable
for dry powders and water free oily substances.

Glassware should be perfectly dry before being
placed in the oven.
The British pharmacopoeia
 recommends a holding period
of 1hr at 1500C for oils, glycerol,
and dusting powder.



ADVANTAGES
Effective and safe sterilization of metal

instruments and mirrors.
No corrosion of Carbon steel instruments and

burs.
Does not rust or corrode.

DISADVANTAGES
Long cycles
Poor penetration
Uneven heating
Cannot sterilize liquids
Is generally unsuitable for handpieces

4.Glass Bead And Hot Salt Steriliser
 The glass bead sterilizer uses

a metal cup with glass beads
of 1 mm diameter in it.
The hot salt container uses

ordinary table salt.

The temperature range for both varies from 425o F

to 475o F .
Both are used to

sterilise endodontic
instruments.

MOIST HEAT

kills bacteria faster than dry heat.
Temperature ranges from 60-135°C.
Mechanism of actionDenaturation and coagulation of proteins
Loss of functional integrity of

membranemolecules

microorganism

Time required for
sterilization

Most mesophilic nonsporeformers

60°C for 30min

S. Aureus & S. faecalis

60°C for 60min

Vegetative form of all bacteria, fungi & yeast

80°C for 5-10min

Heat resistant sporeformers

120°C for 4min
100°C
www.indiandentalacademy.com for 5.5min is required

Can be performed by 3 methods 1.Temperature below 1000c
2.Temperature at 1000c
3.Temperature above 1000c


Temperatures below 1000C
PASTEURIZATION
Its purpose is to reduce the bacterial population of

a liquid such as milk and destroy organisms that
may cause spoilage.
Spores are not affected by this method .
 Destroys Mycobacterium tuberculosis.

There are 3 methods
Holder method

Heats up to 62.90C for 30 min….. although
thermophilic bacteria thrive at this temperature; they
are of little significance because they cannot grow at
body temperature.


Flash pasteurization

This method uses a temperature of 71.60 C

for

15 sec. followed by cooling to 130C.
Ultra pasteurization

This method uses a temperature of 820 C for
3 sec.


ADVANTAGES
Rapid, economic , no elaborate equipment,

good penetration and harmless to wide range
of dental materials.


DISADVANTAGES
 Dulls the cutting edges.
 Causes corrosion.
 Possible deposits from use of hard water


Steam at atmospheric pressure
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 higher the temperature.

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

Steam Under Pressure
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.

The basic principle is that

when the pressure of a gas
increases, the
temperature
increases .

It is important to note that sterilizing agent is moist
heat but not the pressure.

Pressure

15 lbs/sq. inch

Temperature

121.50C


Recommended Cycles
Settings for general wrapped items:
 Temp. - 121 degree C

Pressure - 20 PSI

 Time -- 30 min Setting

Settings for bottled solutions:
 Temp. - 121 degree C , Pressure - 20 PSI

Setting for "Flashing" an unwrapped instrument:
 Temp. – 132 degree C
Pressure - 30 PSI
 Time - 4-7 Min Setting
This method can be used for a broad variety of

items such as instruments, clothing, glassware,

DISADVANTAGES
Plastic ware melts in high heat.
Sharp instruments become dull and corrode.
Use of heavy water may leave deposits.


GAS STERILIZATION
Ethylene oxide: The use of ETO is recognized by

the American Dental association (ADA) and Centers
for Disease control and prevention (CDC)
as an acceptable method of sterilization.

 i) Those that can be damaged by heat

and/ or moisture.
 ii) Those that can be cleaned and
dried thoroughly.

This chemical is effective

as a virucidal
agent, is sporicidal,
does not damage materials,
and can evaporate without
residues.


CHARACTERISTICS
Temperature : room temperature (250C/750F)
Cycle time : 10-16 hours (depending on material)
Acceptable materials : paper, plastic bags

Advantages :
-High capacity for penetration.
-Does not damage heat-labile material.
-Evaporates without leaving a toxic residue.

Disadvantages:
-Slow,

requires long cycle time.
-Uses toxic/hazardous chemical.
-Items must be cleaned and dried thoroughly
before exposure.
-Causes tissue irritation if not well aerated..

FREEZING
Primarily used in the preservation of bacterial

cultures.
In freezing, the formation of ice crystals outside the
cell causes the withdrawal of water from the cell
interior, resulting in an increased intracellular
electrolyte concentration and denaturation of
proteins.
The cell membrane is damaged, and a leakage of
intracellular organic compounds ensues.

Lyophilization (

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 very low
temperature.


RADIATION

- Defined as energy emitted from atomic activities
and dispensed at high velocity through matter or
space.
-2 types
Ionizing radiation: Radiation that have sufficient
energy to remove an electron completely from an
atom and produce an electrical charge (ionization).
Nonionizing radiation: Energy absorbed by the
molecule cannot remove an electron completely, the
excitation produced often leads to photochemical

Ionizing radiation
- Electromagnetic rays: X-ray, alpha, beta & gamma
rays

- Can penetrate a solid barrier, bombard a cell, enter it,

and dislodge electrons from molecules.

- Breaks DNA, creates massive mutations.
- Sterilizes catgut , nylon sutures, plastic, syringe,

Non-ionizing radiation
- Ex. Ultraviolet light
- Effectiveness of UV light as a lethal and mutagenic
agent is closely related to its wavelength (240280nm); optimum at about 260nm which
corresponds with the absorption maximum of DNA.


Lethal effect on bacteria is attributed to absorption.
kills the organism.
Primarily used to control airborne infections, where

it is used for the disinfection of enclosed areas such
as nurseries, hospital wards.

FILTRATION

-An effective method to remove microbes from air
and liquids.
- Separates microorganism from
contaminated
solution.
- Used to prepare liquids that cannot withstand
heat (heat-labile), including serum and other blood
products, vaccines, drugs, IV fluids, enzymes and
culture media.

- TYPES
1.

Seitz – asbestos – cellulose
2. Sintered glass – glass filaments
3. Chamberland – unglazed porcelain
4. Berkefeld – diatomaceous earth
5. Membrane filter – cellulose ester
-High efficiency particulate air (HEPA) filters

provide a flow of sterile air to hospitals.

ULTRASONIC VIBRATIONS
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. Microorganisms in the fluid
are quickly 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.


 Destroys structural integrity of cell membrane

(protein & lipids).

Net effect is the release of small metabolites
from the cell that interferes with the active
transport and energy metabolism.


 Agents:
 Surface active agents

Cationic – most effective
• Anionic
• Non-ionic – not effective
• Amphoteric
 Phenolic compound
 Alcohol
•


I. Surface active agents
-

Substances that alter the energy relationship at
interfaces producing a reduction of surface or
interfacial tension.

-

They disrupt the integrity of cell membrane
that results in the loss of molecules from the
cytoplasm and affects the proton motive force
which provides energy for solute transport.

Cationic Agents

Quarternary ammonium compound

- Bactericidal for a wide range of organisms, gram (+)

species are more susceptible
- Ex. Benzalkonium chloride ( Zephiran )
Used primarily in hand or face washes
 Acts on phospholipids,changes cell
permeability.
Benzalkonium application many include
disinfecting instruments and preserving drugs in
low concentration form.

Anionic Agents
- Soaps and fatty acid dissociate to yield negatively

charged ions (active at acid Ph).

- Causes gross disruption of the lipoprotein

framework of the cell wall.

- Displays rapid bactericidal action (within 30secs) .
- Effective against gram (+) organisms.


 Diguanides
- Acts at a concentration of (1 – 4) %.
- Antimicrobial activity against vegetative bacteria,
yeasts, and enveloped viruses .
- Disrupts cytoplasmic membrane.
- It may be used together with surface active agents.


Chlorhexidine which is more effective at
pH 7 – 8
Used as a safe antiseptic to prevent body
infection , in oral rinses for treating sore gums,
mouth ulcers and preventing plaque on teeth.
Chlorhexidine digluconate (GynePro feminine
wash)




II Phenolic compound
- At low concentration, causes leakage of cell
contents and irreversible inactivation of membranebound oxidases and dehydrogenases.
- Parent compound : Carbolic acid ( phenol )
Excellent for disinfecting faeces, blood, pus,
sputum & other proteinaceous material.


- Primarily used for testing new bactericidal

agent
- Cresols
- Xylenols

 Phenolics are effective against bacteria, fungi

and viruses.


Phenol derivatives:
• Cresols
- Simplest

of the alkyl phenols
- Ortho-, meta-, paracresols – are applicably more
active than phenol
- Cresols are used to dissolve other chemicals, as
disinfectants
and deodorizers, and to make
specific chemicals that kill Insect pests
- Sold under the trade names: Lysol and Creolin
•

• Xylenols
- Dimethylphenols
- Important class of phenolics with great industrial

importance.

- Used as pesticides and in the manufacture of

antioxidants.


Kills
99.9%
of
germ
s in
30 sec
onds

Hospital disinfectant
deodorant is highly effective
against TB, MRSA, and HIV-1
• Tuberculocidal, virucidal,
fungicidal, bactericidal
•


•

Diphenyl compound

Exhibits unique antibacterial property.
- Hexachlorophene
Topical anti-infective, anti-bacterial agent, often
used in soaps, toothpaste and antiperspirant .
-

• Used as a preservative in cosmetic products.
• PHisoHex, widely used as a very effective
antibacterial skin cleanser in the treatment of
acne.

III. Alcohol
- Disorganizes

lipid structure by penetrating intothe
hydrocarbon region, denatures proteins.

-Concentration between 50%-90% .
-Optimal activity at 70% - 75% .

- Effective against vegetative bacteria, fungi and

viruses .

- Sporicidal activity
- Disinfects work surfaces and, as antiseptics on

skin.


Ethanol / Ethyl alcohol
- Used as skin disinfectant.
- Uses: Sterilizes skin before cutaneous injections.
Disinfects thermometers.
- Most effective at 50-70%
-Effective against gram (+) ,
gram (-) bacteria.

Isopropyl alcohol
- Most

effective at 50-70%

- Recommended as replacement for the sterilization
of thermometers
-Necrosis may result from absorption of vapours
through the lungs during alcohol sponge bath.


1.Acid & alkalies –
Benzoic acid
Lactic acid
Acetic acid
Propionic acid
2. Alcohol
3. Acetone

Agents:
1. Heavy metals
2. Oxidizing agents
3. Dyes
4. Alkylating agents


Heavy Metals
•

Mercurials
• Mercuric chloride – very toxic disinfectant, not
used today.
• Metaphen, Merthiolate, Mercuchrome .

• Silver compounds
• Soluble silver salts or as colloidal preparations.
• Silver nitrate – highly bactericdal for gonococci.
• Silver sulfadiazine – topical cream for burn
patients.

Oxidizing agent
• Halogens
(1)

Iodine

- As I2 at pH value below 6 where maximal
bactericidal action takes place.
- Destroys many microorganisms and viruses
within 3-5 minutes.
- Strong smell and can stain skin and clothings.
- Skin irritant .


Betadine Solution

-

-

-

Iodophores
Enhances stability
Povidone –iodine

-Available in "Swab Aid" pads, Swab Sticks and as a
Surgical Scrub.
- It is a fast-acting, broad-spectrum antiseptic .
- Indicated for degerming skin, wounds and mucous
membranes.
- widely use in hospitals, sanitation and water
purification.

(2)

chlorine

- Hypochlorite, inorganic ,inorganic chloramines.
- The active moiety of hypochlorites and
chlorine is hypochlorous acid.
- Water disinfectant
- Hypochlorites - most useful of the chlorine
compound




Widely used for sanitizing dairy products
and food processing .

 Employed as sanitizers in most households,

hospitals, and public buildings

 Marketed as: Chlorox, Zonrox, Purex

• Hydrogen peroxide
- It

is a weak acid.
- Used in the cleansing of wounds.
- It has strong oxidizing properties and is
therefore a powerful bleaching agent that
is mostly used for bleaching paper.


Dyes
• Triphenyl methane dyes

• Crystal violet, Malachite green, Brilliant
green
• Highly selective for gram (+) organisms
• Used in the laboratory in the formulation of
selective culture media
• Acidine dyes
• Often referred as Flavines .
• Exerts a bactericidal and bacteriostatic effect.
proflavine, acriflavine
• used in wound antisepsis

Alkylating agent
- Glutaraldehydes and formaldehydes .
- Active against bacteria and their spores, viruses,
fungi and protozoa.
-These effects are mediated predominantly via
amine, sulfurhydryl and carboxyl groups on
microbial surface proteins.

Formaldehyde:-

• Aqueous solution containing 37%
formaldehyde (Formalin)
• Paraformaldehyde a poymer (contain 9199% formaldehde)

- Formalin - used for preserving fresh tissues
- when used in high concentration, it
destroys all organisms, including spores.


- Used to inactivate virus in the preparation

of vaccines.
- As a gas – used to decontaminate rooms,
buildings, fabrics, and instruments..


Glutaraldehyde
- used

as “cold sterilant” for surgical instruments
- 10x more effective than formaldehyde as a
bactericidal and sporocidal agent and less toxic.
Ethylene oxide
- Employed in gaseous sterilization, especially on
materials that would be damaged by heat
(polyethylene tubings, drugs).
- Active against all types of bacteria, including
spores & TB bacilli.

Sterilization monitoring
– Biological
– Chemical
– Physical /mechanical


Drying, cooling, storage and recycling of
sterilized instruments


Causes of sterilization failure
Improper loading of sterilization chamber
Improper packing
Improper timing
improper temperature
Improper cleaning of items to be sterilized.


DISINFECTING IMPRESSIONS
Methods:1.Spraying
2.Dipping
3.Immersing

Iodophors, sodium hypochlorite (1:10
concentration), chlorine dioxide, phenols, and
other approved products are all acceptable.

IN ORTHODONTICS
Orthodontic wires:
Disinfected with Iodophor (10 minutes)
Wiped with alcohol gauge ,dried
Placed into paper storage envelopes

Wires can be sterilized by: AUTOCLAVE: 274 degrees-10 minutes.
COLD STERILIZATION: Sporocidin solution,6.75

hrs
DRY HEAT: 375 degrees-1o minutes

Wires used are Nitinol,TMA,0.016 ss wire.

Pliers:
Alcohol
Cold sterilization
Autoclave:250 degrees F, 1 atm-30 mins.
Chemiclave:276 degrees F,1.36 atm,30
mins
 Dryclave: 340 degrees F-I hour

Handpieces:
Alcohol
 Cold sterilization
 Autoclave
 Dryclave



Molar bands:
Cleaned by enzyme disinfectant(15 mins)
Rinsed in running water(1 min)
Sterilized by Autoclave(3 mins)

Orthodontic cutters:
 Wrapped in polyethylene paper
pouches
 Autoclave
 Chemiclave

Elastomeric ligatures:
Banicide (0.5 % Glutaraldehyde)-10 mins
Lysol
Autoclave
Dry heat


CONCLUSION
As the saying goes-"Cleanliness is next to

godliness." All general practitioners and
specialists alike should be educated about
aseptic techniques and their benefits so that
the dental environment is less hazardous one
to work in.


“PREVENTION

IS BETTER THAN CURE”- a

proverb well suited to sterilisation.
DEADLY WORLD OF MICROBIAL PATHOGENS
 Utilisation of proper sterilization,

disinfectants and aseptic procedures helps us
achieve the safety our profession demands .

REFERENCES
Text Book Of Microbiology

Ananthanarayan,6th edition
Art And Science Of Operative Dentistry
Sturdevant
CDC. Guidelines for infection control in dental
health-care settings – 2003. MMWR 2003;
52(No. RR-17):1–66. Available at
www.cdc.gov/oralhealth/infectioncontrol.

Centers for Disease Control and Prevention.

Recommended infection control practices for
dentistry 1993, MMWR 42 (RR-8):1-13.
GlenA.Smith,Glenn R.Carey.Effect of clinical use and
sterilization on selected arch wires.Am J Orthod
Dentofac Orthop 102:153-159,1992.
Robert G.Cash.Trends in Sterilization and
Disinfection procedures.Am J Orthod Dentofac
Orthop 98:292-299,1990.

Gilliam M.Antonios H. Mamandras.Infection

control in Orthodontic office in Canada
112:275-281,1997.
M.R.Fulford.Decontamination of tried in
Orthodontic molar bands.Eur J Orthod25:621622,2003.


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YOU


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