Sterilization final/ dental crown & bridge courses

STERILIZATION AND
DISINFECTION
INDIAN DENTAL ACADEMYINDIAN DENTAL ACADEMY
Leader in continuing Dental EducationLeader in continuing Dental Education
www.indiandentalacademy.com

• DEFINITIONSDEFINITIONS
• HISTORYHISTORY
• RATIONALERATIONALE
• CLASSIFICATION– physicalCLASSIFICATION– physical
-- chemical-- chemical
• INSTRUMENT PROCESSINGINSTRUMENT PROCESSING
• CONCLUSIONCONCLUSION
• REFRENCESREFRENCES

STERILIZATION
• DEFINATIONDEFINATION
The process by which an article, surface or medium isThe process by which an article, surface or medium is
freed of all living microorganisms either in the vegetativefreed of all living microorganisms either in the vegetative
or spore state.or spore state.
OROR
It is defined as freeing the object or substance from allIt is defined as freeing the object or substance from all
life of any kindlife of any kind

DISINFECTION
• The destruction or removal of all pathogenic organisms,The destruction or removal of all pathogenic organisms,
or organisms capable of giving rise to infectionor organisms capable of giving rise to infection
• Disinfection is applicable to all inanimate objectsDisinfection is applicable to all inanimate objects
• DisinfectantDisinfectant is an agent accomplishing disinfectionis an agent accomplishing disinfection

Antiseptic
• It is an ill defined term, used in close relation toIt is an ill defined term, used in close relation to
disinfectantsdisinfectants
• They are generally considered to be substances that killThey are generally considered to be substances that kill
or inhibit microorganisms, especially in contact withor inhibit microorganisms, especially in contact with
body, without causing extensive damage to the fleshbody, without causing extensive damage to the flesh

• SANITISERSSANITISERS are agents including detergents used toare agents including detergents used to
maintain microbial levels at safe acceptable levelsmaintain microbial levels at safe acceptable levels
• ASEPSISASEPSIS is the absence of infectious organisms inis the absence of infectious organisms in
living tissueliving tissue
It is the term applied to any technique designed to keepIt is the term applied to any technique designed to keep
all unwanted microorganisms out of any field of work orall unwanted microorganisms out of any field of work or
observationsobservations

HISTORY
• Zaccharias JansenZaccharias Jansen in 1590 andin 1590 and Robert HookeRobert Hooke in 1660in 1660
opened the world of microbes to mankind by theiropened the world of microbes to mankind by their
inventions of microscopesinventions of microscopes
• It wasIt was Anthony Van LevenhookAnthony Van Levenhook who first describedwho first described
microorganismsmicroorganisms
• Joseph ListerJoseph Lister between 1865 to 1891delineated thebetween 1865 to 1891delineated the
principles of wound infection and asepsisprinciples of wound infection and asepsis
• Further pioneering efforts ofFurther pioneering efforts of Louis PastuerLouis Pastuer added newadded new
dimensions to the field of sterilisationdimensions to the field of sterilisation

• Input by various researchers likeInput by various researchers like John TyndallJohn Tyndall,, RobertRobert
KochKoch etc further accelerated the progress, when finallyetc further accelerated the progress, when finally
in 1890’s the advent of steam sterilisers, sterile gowns,in 1890’s the advent of steam sterilisers, sterile gowns,
drapes and gloves emergeddrapes and gloves emerged
• The modern infection control prevention and sterilisationThe modern infection control prevention and sterilisation
guidelines were stated by the CDC (Centre for Diseaseguidelines were stated by the CDC (Centre for Disease
Control) in 1973 and specific dental infection controlControl) in 1973 and specific dental infection control
guidelines by the ADA and OSHA and EPA in 1978guidelines by the ADA and OSHA and EPA in 1978
revised in 1985 and 1988revised in 1985 and 1988

RATIONALE
• The answer lies in the fact that we sterilize to minimiseThe answer lies in the fact that we sterilize to minimise
and eliminate the spread of infection and diseaseand eliminate the spread of infection and disease
• Infectious agents can spread by direct contact, indirectInfectious agents can spread by direct contact, indirect
contact via a contaminated surface or materialcontact via a contaminated surface or material

• Thus infection control involves-Thus infection control involves-
1.1. Reduction of pathogen concentration to allow normalReduction of pathogen concentration to allow normal
host resistant mechanisms to prevent infectionhost resistant mechanisms to prevent infection
2.2. Break the cycle of infection and eliminate crossBreak the cycle of infection and eliminate cross
infectioninfection
3.3. Treat every patient and instrument as potentiallyTreat every patient and instrument as potentially
infectious and therefore employ universal safetyinfectious and therefore employ universal safety
precautionsprecautions
4.4. Protect patients and personnel from occupationalProtect patients and personnel from occupational
infectioninfection

CLASSSIFICATION
A.A. Mechanical or PhysicalMechanical or Physical
B.B. ChemicalChemical

• Mechanical is further classified intoMechanical is further classified into
1.1. SunlightSunlight
2.2. DryingDrying
3.3. Dry heatDry heat
4.4. Moist heatMoist heat
5.5. FiltrationFiltration
6.6. RadiationRadiation
7.7. Ultrasonic and sonic vibrationsUltrasonic and sonic vibrations

• Chemicals used includeChemicals used include
1.1. AlcoholAlcohol
2.2. AldehydeAldehyde
3.3. DyesDyes
4.4. HalogensHalogens
5.5. PhenolsPhenols
6.6. Surface active agentsSurface active agents
7.7. Metallic saltsMetallic salts
8.8. GasesGases

SUNLIGHT
• It has bactericidal activity and plays an important role inIt has bactericidal activity and plays an important role in
spontaneous sterilization that occurs under naturalspontaneous sterilization that occurs under natural
conditions.conditions.
• Action is due to its content of ultraviolet rays, most ofAction is due to its content of ultraviolet rays, most of
which, however are screened out by glass and thewhich, however are screened out by glass and the
presence of ozone layer.presence of ozone layer.
• Its sterilizing power varies.Its sterilizing power varies.
• Direct sunlight as in tropical countryside where it is notDirect sunlight as in tropical countryside where it is not
filtered by impurities in the atmosphere, has an activefiltered by impurities in the atmosphere, has an active
germicidal effect due to the combined effect of ultravioletgermicidal effect due to the combined effect of ultraviolet
and heat rays.and heat rays.

DRYING
• Moisture is essential for bacteriaMoisture is essential for bacteria
• Drying therefore has a deleterious effect on mostDrying therefore has a deleterious effect on most
bacteriabacteria
• Viruses and spores are unaffected by dryingViruses and spores are unaffected by drying
• So drying is a very unreliable method.So drying is a very unreliable method.

HEAT
• It is the most popular, reliable and widely used method ofIt is the most popular, reliable and widely used method of
sterilizationsterilization
• Two methods —Two methods —
Dry heatDry heat
Moist heatMoist heat

Factors determining the time & temperature
for sterilization
1. Nature of the heat1. Nature of the heat
Heat could be used as sterilizing agent inHeat could be used as sterilizing agent in
either of two forms, which are dry heat and moist heat.either of two forms, which are dry heat and moist heat.
• The killing effect of dry heat is due to proteinThe killing effect of dry heat is due to protein
degeneration, oxidative damage and the toxic effect ofdegeneration, oxidative damage and the toxic effect of
elevated levels of electrolytes.elevated levels of electrolytes.
• The lethal effect of moist heat is due to the denaturationThe lethal effect of moist heat is due to the denaturation
and coagulation of protein. In case of the most resistantand coagulation of protein. In case of the most resistant
forms like bacterial spores the oxidation of cell requiresforms like bacterial spores the oxidation of cell requires
much higher temperatures than vegetative cells.much higher temperatures than vegetative cells.

2.2. Type and number of the organismsType and number of the organisms
Characteristics of the organisms such as species,Characteristics of the organisms such as species,
strain, sporing capacity and also the number willstrain, sporing capacity and also the number will
influence the time and temperature required forinfluence the time and temperature required for
sterilization.sterilization.

3.3. Presence of organic matterPresence of organic matter
The presence of organic substances likeThe presence of organic substances like
proteins, starch, sugar, fats and oils may prevent theproteins, starch, sugar, fats and oils may prevent the
heat from reaching microorganisms thereby increasesheat from reaching microorganisms thereby increases
the time and temperature.the time and temperature.
• The presence of disinfectants and high acid and alkalineThe presence of disinfectants and high acid and alkaline
pH increases bacterial killing and reduces the time andpH increases bacterial killing and reduces the time and
temperature.temperature.

4.4. Type of the material from which the microorganismsType of the material from which the microorganisms
have to be eradicatedhave to be eradicated
• E.g. powder is subjected to dry heat rather than moistE.g. powder is subjected to dry heat rather than moist
heat, because moist heat leaves it soggy whereas salineheat, because moist heat leaves it soggy whereas saline
solutions can be safely sterilized with moist heat.solutions can be safely sterilized with moist heat.

FLAMING
• A simple & effectiveA simple & effective
methodmethod
• Loops or wires ,glassLoops or wires ,glass
slides ,cover slips theslides ,cover slips the
tips of the instruments aretips of the instruments are
held in a Bunsen flame tillheld in a Bunsen flame till
they become red-hot.they become red-hot.
These materials may beThese materials may be
dipped in a disinfectantdipped in a disinfectant
before flamingbefore flaming

INCENERATION
• This is an excellent method for safely destroyingThis is an excellent method for safely destroying
materials such as contaminated cloth, animal carcassesmaterials such as contaminated cloth, animal carcasses
and pathologic materials.and pathologic materials.
• In the past, bodies of disease victims were burned toIn the past, bodies of disease victims were burned to
prevent spread of infection. It is still a common practiceprevent spread of infection. It is still a common practice
to incinerate the carcasses of cattle that have died ofto incinerate the carcasses of cattle that have died of
anthrax because these spores are highly resistant andanthrax because these spores are highly resistant and
cannot be destroyed by other means.cannot be destroyed by other means.
• Plastics such as PVC and polythene can be dealt withPlastics such as PVC and polythene can be dealt with
similarlysimilarly
• Polystyrene materials emit clouds of dense black smokePolystyrene materials emit clouds of dense black smoke
and hence should be autoclaved in appropriateand hence should be autoclaved in appropriate
containers.containers.

Newspaper photograph showing
Spanish-American war performing
incineration

HOT AIR OVEN
• This is the most widely used method of sterilization byThis is the most widely used method of sterilization by
dry heat.dry heat.
• This type of energy does not penetrate materials easilyThis type of energy does not penetrate materials easily
and thus, long periods of exposure to high temperaturesand thus, long periods of exposure to high temperatures
are necessary.are necessary.
• A holding period of 160A holding period of 160oo
C( 320C( 320oo
F) for 1 hr is used toF) for 1 hr is used to
sterilize glassware, swabs, liquid paraffin, dustingsterilize glassware, swabs, liquid paraffin, dusting
powder, fats and grease. It is suitable for dry powderspowder, fats and grease. It is suitable for dry powders
and water free oily substances.and water free oily substances.

• Since hot air is a bad conductor of heat its penetratingSince hot air is a bad conductor of heat its penetrating
power is low.power is low.
• The oven is usually heated by electricity, with heatingThe oven is usually heated by electricity, with heating
elements in the wall of the chamber.elements in the wall of the chamber.
• It must be fitted with a fan to ensure even distribution ofIt must be fitted with a fan to ensure even distribution of
air and elimination of air pockets.air and elimination of air pockets.
• The material should be arranged so as to allow freeThe material should be arranged so as to allow free
circulation of air in between the objects.circulation of air in between the objects.

•
Glassware should be perfectly dry before being placedGlassware should be perfectly dry before being placed
in the oven.in the oven.
• The British pharmacopoeia recommends a holdingThe British pharmacopoeia recommends a holding
period of 1hr at 150period of 1hr at 15000
C for oils, glycerol, and dustingC for oils, glycerol, and dusting
powder.powder.
• The oven must be allowed to cool slowly for about 2hrsThe oven must be allowed to cool slowly for about 2hrs
before the door is opened, since the glassware maybefore the door is opened, since the glassware may
crack due to sudden or uneven cooling.crack due to sudden or uneven cooling.

Hot air oven

• ADVANTAGESADVANTAGES
• Effective and safe sterilization of metal instruments andEffective and safe sterilization of metal instruments and
mirrorsmirrors
• No corrosion of Carbon steel instruments and bursNo corrosion of Carbon steel instruments and burs
• DISADVANTAGESDISADVANTAGES
• Long cyclesLong cycles
• Poor penetrationPoor penetration
• Uneven heatingUneven heating
• Damage to heat sensitive itemsDamage to heat sensitive items

GLASS BEAD AND HOT SALT
STERILISER
• The glass bead steriliser uses a metal cup with glassThe glass bead steriliser uses a metal cup with glass
beads of 1 mm diameter in itbeads of 1 mm diameter in it
• The hot salt container uses ordinary table saltThe hot salt container uses ordinary table salt
• The temperature range for both varies from 425The temperature range for both varies from 425oo
F TOF TO
475475oo
FF
• Both are used to sterilise endodontic instrumentsBoth are used to sterilise endodontic instruments
• The hot salt steriliser is better than the glass beadThe hot salt steriliser is better than the glass bead
steriliser because the glass beads stick to thesteriliser because the glass beads stick to the
instruments and clog the root canal.instruments and clog the root canal.
• Also the material used in the hot salt steriliser is ordinaryAlso the material used in the hot salt steriliser is ordinary
table salt which is readily availabletable salt which is readily available

Electric glass bead or hot salt
steriliser

Moist heat
• Moist heat kills microorganisms by denaturing proteins.Moist heat kills microorganisms by denaturing proteins.
• Denaturation involves changes in the chemical orDenaturation involves changes in the chemical or
physical properties of proteins. It includes structuralphysical properties of proteins. It includes structural
alterations due to destruction of the chemical bondsalterations due to destruction of the chemical bonds
holding proteins in a three dimensional form. As proteinsholding proteins in a three dimensional form. As proteins
revert to a two dimensional form they coagulate &revert to a two dimensional form they coagulate &
become nonfunctional.become nonfunctional.
• Moist heat penetrates material much more rapidly thanMoist heat penetrates material much more rapidly than
dry heat because water molecules conduct heat betterdry heat because water molecules conduct heat better
than air.than air.

Temperatures below 1000
C
• PASTEURIZATIONPASTEURIZATION
• Its purpose is to reduce the bacterial population of aIts purpose is to reduce the bacterial population of a
liquid such as milk and destroy organisms that mayliquid such as milk and destroy organisms that may
cause spoilagecause spoilage
• .Spores are not affected by this method ..Spores are not affected by this method .
• For decades pasteurization has aimed at destroyingFor decades pasteurization has aimed at destroying
mycobacterium tuberculosis, the most heat resistantmycobacterium tuberculosis, the most heat resistant
bacteriabacteria

• There are 3 methodsThere are 3 methods
• Holder methodHolder method
–– It involves heating up to 62.9It involves heating up to 62.900
C for 30 min.C for 30 min.
although thermophilic bacteria thrive at this temperature;although thermophilic bacteria thrive at this temperature;
they are of little consequence because they cannot growthey are of little consequence because they cannot grow
at body temperature.at body temperature.
• Flash pasteurizationFlash pasteurization
-This method uses a temperature of 71.6-This method uses a temperature of 71.600
C forC for
15 sec.followed by cooling to 1315 sec.followed by cooling to 1300
CC
• Ultra pasteurizatUltra pasteurizatii
onon
- This method uses a temperature of 82- This method uses a temperature of 8200
C for 3C for 3
sec.sec.

Temperatures at 1000
C (boiling)
• Vegetative bacteria are killed almost immediately at 90-Vegetative bacteria are killed almost immediately at 90-
10010000
C, but sporing bacteria require prolonged periods ofC, but sporing bacteria require prolonged periods of
boiling.boiling.
• Boiling water is not considered as a sterilizing agentBoiling water is not considered as a sterilizing agent
because destruction of bacterial spores and inactivationbecause destruction of bacterial spores and inactivation
of viruses cannot always be assured. It is considered asof viruses cannot always be assured. It is considered as
a method for disinfectiona method for disinfection
• A minimum exposure period of 30min. is recommendedA minimum exposure period of 30min. is recommended
to kill vegetative bacteria.to kill vegetative bacteria.
• Sodium bicarbonate 2% conc. is added to increase theSodium bicarbonate 2% conc. is added to increase the
efficiency of process.efficiency of process.

• AdvantagesAdvantages
• Rapidity, economic , no elaborate equipment, goodRapidity, economic , no elaborate equipment, good
penetration and harmless to wide range of dentalpenetration and harmless to wide range of dental
materials.materials.
• DiasadvantagesDiasadvantages
• dulls the cutting edgesdulls the cutting edges
• can also cause corrosioncan also cause corrosion

Steam at atmospheric pressure
• Also known asAlso known as compressedcompressed oror saturated steamsaturated steam
• This is an inexpensive method using aThis is an inexpensive method using a Koch or ArnoldKoch or Arnold
steamer.steamer.
• Principle used is steam under pressure is hottePrinciple used is steam under pressure is hotterr andand
higher the pressure the higher the temperaturehigher the pressure the higher the temperature
• Liquids were sterilized by this method at 100Liquids were sterilized by this method at 10000
C for 30minC for 30min
on each of 3 successive days.on each of 3 successive days.
• Also calledAlso called fractional sterilizationfractional sterilization, because a, because a
fraction was accomplished on each day.fraction was accomplished on each day.
• Also calledAlso called TyndallizationTyndallization after its developer Johnafter its developer John
Tyndall, and intermittent sterilization because it was aTyndall, and intermittent sterilization because it was a
stop and start operation.stop and start operation.

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

Tyndall’s cabinet

Steam under pressure
• Moist heat in the form of pressurized steam is regardedMoist heat in the form of pressurized steam is regarded
as the most dependable method for destruction of allas the most dependable method for destruction of all
forms of bacterial life including spores.forms of bacterial life including spores.
• This method is incorporated into a device called theThis method is incorporated into a device called the
autoclaveautoclave..
• Over a hundred years ago, French & GermanOver a hundred years ago, French & German
microbiologists developed the autoclave.microbiologists developed the autoclave.
• The basic principle is that when the pressure of a gasThe basic principle is that when the pressure of a gas
increases the temperature increasesincreases the temperature increases

• As the water molecules in steam become moreAs the water molecules in steam become more
energized, their penetration also increasesenergized, their penetration also increases
• Same principle is used in home pressure cooker.Same principle is used in home pressure cooker.
• It is important to note that sterilizing agent is moist heatIt is important to note that sterilizing agent is moist heat
but not the pressure.but not the pressure.
• Pressure in autoclave –15lbs/sq. inchPressure in autoclave –15lbs/sq. inch
• Temperature - 121.5Temperature - 121.500
CC
• Time - 3 to 30 minTime - 3 to 30 min

Autoclave

• This method can be used for a broad variety of itemsThis method can be used for a broad variety of items
such as instruments, clothing, glassware andsuch as instruments, clothing, glassware and
intravenous solutions etc.intravenous solutions etc.
• Limitations ;Limitations ;
• Plastic ware melts in high heatPlastic ware melts in high heat
• Sharp instruments become dull ( corrosion )Sharp instruments become dull ( corrosion )
• Many chemicals breakdown during the sterilizationMany chemicals breakdown during the sterilization
process, and oily substances cannot be treated sinceprocess, and oily substances cannot be treated since
they do not mix with water.they do not mix with water.
• A new form of autoclave called theA new form of autoclave called the PrevacuumPrevacuum
autoclaveautoclave has been developed, which draws air out ofhas been developed, which draws air out of
the chamber at the beginning of the cycle. The majorthe chamber at the beginning of the cycle. The major
advantage of this is minimal exposureadvantage of this is minimal exposure

Unsaturated Chemical Vapor
Sterilization
• This system depends on heat, water and chemicalThis system depends on heat, water and chemical
combination for it’s efficacycombination for it’s efficacy
• The temperature pressure required is greater than thatThe temperature pressure required is greater than that
for autoclavefor autoclave
• It is known as aIt is known as a chemiclavechemiclave
• Instead of distilled water a solution of alcohol,Instead of distilled water a solution of alcohol,
formaldehyde, ketone, acetone and water is used toformaldehyde, ketone, acetone and water is used to
produce the sterilizing vaporproduce the sterilizing vapor

• Temperature 270Temperature 27000
F(131F(13100
C )at 20 pounds pressure for 20C )at 20 pounds pressure for 20
to 40 minutesto 40 minutes
• AdvantagesAdvantages
short cycle, no rusting or corrosion, dry instruments atshort cycle, no rusting or corrosion, dry instruments at
the end of the cycle, automatic preset cycle timingthe end of the cycle, automatic preset cycle timing
• DisadvantagesDisadvantages
heat sensitivity of instruments, loading dry instruments,heat sensitivity of instruments, loading dry instruments,
chemical odors and constant monitoringchemical odors and constant monitoring

OIL BATHS
• Can be used to sterilise metal instrumentsCan be used to sterilise metal instruments
• It can be heated for a period of 175It can be heated for a period of 17500
C for 15 minutesC for 15 minutes
• Disadvantages include poor sporicidal activity, fireDisadvantages include poor sporicidal activity, fire
hazard, difficult to remove and constant monitoringhazard, difficult to remove and constant monitoring

FILTRATION
• Filters have been used since time immemorialFilters have been used since time immemorial
• It is the method of choice for heat labile liquids andIt is the method of choice for heat labile liquids and
solutionssolutions
• Early pioneer wasEarly pioneer was Charles ChamberlandCharles Chamberland
• Filters are used to purify iv solutions, culture media,Filters are used to purify iv solutions, culture media,
toxoids, beverages etctoxoids, beverages etc

Types of Filters
• CANDLE FILTERSCANDLE FILTERS
• They are manufactured in different grades of porosity &They are manufactured in different grades of porosity &
have been widely used to purify water for industrial andhave been widely used to purify water for industrial and
drinking purposes. They are of 2 typesdrinking purposes. They are of 2 types
• Unglazed ceramic filterUnglazed ceramic filter
• Ex; Chamberland & Doulton filtersEx; Chamberland & Doulton filters
• Diatomaceous earth filterDiatomaceous earth filter
• Ex; Berkefeld & Mandler filtersEx; Berkefeld & Mandler filters

• ASBESTOS FILTERSASBESTOS FILTERS
• They are in the form of disposable, single use discs.They are in the form of disposable, single use discs.
They have high absorbing capacity and tend to alkalinizeThey have high absorbing capacity and tend to alkalinize
filtered liquids They are carcinogenicfiltered liquids They are carcinogenic
• Ex; Seitz filterEx; Seitz filter
• SINTERED GLASS FILTERSSINTERED GLASS FILTERS
• They contain heat fusing finely powdered glass particlesThey contain heat fusing finely powdered glass particles
of graded sizes. They have low absorbing capacity andof graded sizes. They have low absorbing capacity and
can be easily cleaned.can be easily cleaned.

• MEMBRANE FILTERSMEMBRANE FILTERS
They are made up of cellulose estersThey are made up of cellulose esters
(acetate & polycarbonate) or other polymers(acetate & polycarbonate) or other polymers
• They have largely replaced the others.They have largely replaced the others.
• They are routinely used in water purificationThey are routinely used in water purification
• This is particularly valuable because bacteria multiplyThis is particularly valuable because bacteria multiply
and form colonies on a plate of culture medium.and form colonies on a plate of culture medium.
• Pore size 10 to 0.22Pore size 10 to 0.22μμ

• NUCLEOPORE FILTERNUCLEOPORE FILTER
• It is a very thin polycarbonate film with etched holes andIt is a very thin polycarbonate film with etched holes and
pore space of 0.1 to 0.08pore space of 0.1 to 0.08μμ

Radiation
• Visible light is a type of radiant energy detected by theVisible light is a type of radiant energy detected by the
sensitive cells of eye. Wavelength is 400-800 nm.sensitive cells of eye. Wavelength is 400-800 nm.
• Other types of radiations have wavelength longer orOther types of radiations have wavelength longer or
shorter than that of visible light, therefore cannot beshorter than that of visible light, therefore cannot be
detected by human eye.detected by human eye.
• UV light has a wavelength between 100-400nm. mostUV light has a wavelength between 100-400nm. most
destructive to bacteria.destructive to bacteria.

• Radiation may have sufficient energy to remove anRadiation may have sufficient energy to remove an
electron completely from an atom and produce anelectron completely from an atom and produce an
electrical change (electrical change (ionizationionization), or to raise electron to high), or to raise electron to high
energy state (energy state (excitationexcitation).).
• Energy equivalent 10 el .volts is required to pull theEnergy equivalent 10 el .volts is required to pull the
electron completely out of an atom.electron completely out of an atom.

NON IONISING RADIATION
• This include infrared rays and ultraviolet raysThis include infrared rays and ultraviolet rays
• Infra red rays is used for mass sterilization of syringesInfra red rays is used for mass sterilization of syringes

ULTRAVIOLET LIGHT
• When microorganisms are subjected to UV light, cellular DNAWhen microorganisms are subjected to UV light, cellular DNA
absorbs energy & adjacent thymine molecules link together.absorbs energy & adjacent thymine molecules link together.
• Linked thymine molecules are unable to position adenine on mLinked thymine molecules are unable to position adenine on m
RNA molecules during the process protein synthesis therebyRNA molecules during the process protein synthesis thereby
replication of chromosome will be impaired.replication of chromosome will be impaired.
• The damaged organism can no longer produce critical proteins orThe damaged organism can no longer produce critical proteins or
reproduce.reproduce.
• UV light is used to limit airborne or surface contamination in aUV light is used to limit airborne or surface contamination in a
hospital room, pharmacy food service operation.hospital room, pharmacy food service operation.
• UV light does not penetrate liquids or solids and it may causeUV light does not penetrate liquids or solids and it may cause
damage to the human skin.damage to the human skin.

IONIZING RADIATION
• X-rays and gamma rays have wave length shorter thanX-rays and gamma rays have wave length shorter than
UV lightUV light
• As these rays can pass through microbial molecules,As these rays can pass through microbial molecules,
they force electrons out of their shells, thereby causingthey force electrons out of their shells, thereby causing
ionisation.ionisation.
• The ions quickly combine with & destroy proteins andThe ions quickly combine with & destroy proteins and
nucleic acid such as DNA, causing death. Gram +ve arenucleic acid such as DNA, causing death. Gram +ve are
sensitive than gram –ve bacteria.sensitive than gram –ve bacteria.
• Can be used for syringe sterilizationCan be used for syringe sterilization

MICROWAVE
• Microwaves have a wavelength longer than UV light.Microwaves have a wavelength longer than UV light.
• In a microwave oven waves are absorbed by waterIn a microwave oven waves are absorbed by water
molecules.molecules.
• The molecules are set into a high speed motion, and theThe molecules are set into a high speed motion, and the
heat of friction is transmitted to food, which become hotheat of friction is transmitted to food, which become hot
rapidly.rapidly.

LASER
• LASERLASER – Light Amplification by Stimulated Emission of– Light Amplification by Stimulated Emission of
RadiationRadiation
• Resent experiments indicate that laser beams can beResent experiments indicate that laser beams can be
used to sterilize instruments & the air in operating rooms,used to sterilize instruments & the air in operating rooms,
as well as for a wound surface.as well as for a wound surface.
• Various types include COVarious types include CO22 , Argon ,NdYAG etc, Argon ,NdYAG etc

Ultrasonic vibrations
• They are high frequency sound waves beyond the rangeThey are high frequency sound waves beyond the range
of human ear.of human ear.
• When propagated in fluids ultrasonic vibrations causeWhen propagated in fluids ultrasonic vibrations cause
formation of microscopic bubbles or cavities and theformation of microscopic bubbles or cavities and the
water appears to boil.water appears to boil.
• Some observers call thisSome observers call this cold boilingcold boiling..
• The cavities rapidly collapse & send out shock waves.The cavities rapidly collapse & send out shock waves.
The formation and implosion of the cavities is known asThe formation and implosion of the cavities is known as
cavitationcavitation. Microorganisms in the fluid are quickly. Microorganisms in the fluid are quickly
disintegrated by the external pressures.disintegrated by the external pressures.
• The current trend is to use ultrasonic as a cleaning agentThe current trend is to use ultrasonic as a cleaning agent
to follow the process by sterilization in an autoclave.to follow the process by sterilization in an autoclave.

FREEZING
• Freezing can both kill and preserve depending onFreezing can both kill and preserve depending on
various factorsvarious factors
• It’s primary use has been in the preservation of bacterialIt’s primary use has been in the preservation of bacterial
cultures.cultures.
• Repeated freezing and thawing are much moreRepeated freezing and thawing are much more
destructive to bacteria than prolonged storage atdestructive to bacteria than prolonged storage at
freezing temperature.freezing temperature.
• If bacteria are rapidly subjected to temperature belowIf bacteria are rapidly subjected to temperature below
–35–3500
C, ice crystals that form within the cell produce aC, ice crystals that form within the cell produce a
lethal effect during defreezing.lethal effect during defreezing.

CHEMICAL METHODS OFCHEMICAL METHODS OF
STERILIZATIONSTERILIZATION

Infection control with chemicals
IDEAL REQUIREMENTS of a chemical disinfectantIDEAL REQUIREMENTS of a chemical disinfectant
1. Broad spectrum1. Broad spectrum
2. Fast acting2. Fast acting
3. Non toxic3. Non toxic
4. Surface compatibility4. Surface compatibility
Should not corrode instruments and other metallicShould not corrode instruments and other metallic
surfaces and cause disintegration of cloth, rubber orsurfaces and cause disintegration of cloth, rubber or
other materialsother materials

5. Easy to use5. Easy to use
6. Odourless6. Odourless
7. Economical7. Economical
8. Be stable8. Be stable
9. High penetrating power9. High penetrating power
10. Should not cause local irritation and sensitivity10. Should not cause local irritation and sensitivity
11. High solubility11. High solubility
Should be soluble in water and have a substantialShould be soluble in water and have a substantial
shelf lifeshelf life

• Infection control in dentistry requires the use ofInfection control in dentistry requires the use of
disinfectants in several formsdisinfectants in several forms
1.1. Surface disinfectantsSurface disinfectants
2.2. Immersion sterilantsImmersion sterilants
3.3. Immersion disinfectantsImmersion disinfectants
4.4. Hand antimicrobialsHand antimicrobials

• Surface disinfectionSurface disinfection is the treatment ofis the treatment of
envioronmental surfaces such as cabinets, chairs, lights,envioronmental surfaces such as cabinets, chairs, lights,
x-rays and similar surfaces where the items are too largex-rays and similar surfaces where the items are too large
or sensitive to be immersed in disinfecting chemicals. Itor sensitive to be immersed in disinfecting chemicals. It
is accomplished by spraying or wiping the solution on theis accomplished by spraying or wiping the solution on the
surfacesurface
• Immersion disinfectionImmersion disinfection also called cold sterilisationalso called cold sterilisation
is the immersion of instruments, plastics, in a liquidis the immersion of instruments, plastics, in a liquid
disinfectant. Time is usually 5 to 30 minutesdisinfectant. Time is usually 5 to 30 minutes

• Immersion sterilizationImmersion sterilization is the use of an agent thatis the use of an agent that
has the capability of killing all living microorganisms andhas the capability of killing all living microorganisms and
infective agents in 6 to 10 hours. The items should beinfective agents in 6 to 10 hours. The items should be
completely immersed in the solutioncompletely immersed in the solution
• Hand antimicrobial treatmentHand antimicrobial treatment it is the specific art ofit is the specific art of
washing or otherwise treating hands with a chemicalwashing or otherwise treating hands with a chemical
soap or lotion with resulting reduction in the number ofsoap or lotion with resulting reduction in the number of
hand microbeshand microbes

• A classification of chemical disinfectants was proposedA classification of chemical disinfectants was proposed
byby SpauldingSpaulding in 1972in 1972
• It was originally developed for classifying hospitalIt was originally developed for classifying hospital
instruments but now has been modified for dentalinstruments but now has been modified for dental
instrumentsinstruments
• Patient care items are classified -- criticalPatient care items are classified -- critical
semicriticalsemicritical
non criticalnon critical
• Three levels of disinfection are -- highThree levels of disinfection are -- high
intermediateintermediate
lowlow

PATIENT CARE ITEMS
• CRITICAL:-CRITICAL:-
• Penetrate or touch broken skin or mucous membranes.Penetrate or touch broken skin or mucous membranes.
• Needles, Scalpels, surgical instruments, mirrors, dentalNeedles, Scalpels, surgical instruments, mirrors, dental
explorers.explorers.
• SEMICRITICAL:-SEMICRITICAL:-
• Touch intact mucous membranes.Touch intact mucous membranes.
• Amalgam condensers, handpieces ultrasonic cleaners.Amalgam condensers, handpieces ultrasonic cleaners.
• NON CRITICAL:-NON CRITICAL:-
• That do not touch mucous membranes.That do not touch mucous membranes.
• Counter tops, light handles, chair surfaces.Counter tops, light handles, chair surfaces.

LEVELS OF DISINFECTION
1.1. High level disinfection – these disinfectants mustHigh level disinfection – these disinfectants must
inactivate resistant bacterial spores and all otherinactivate resistant bacterial spores and all other
microbial formsmicrobial forms
E.g. ethylene oxide gas, immersion gluteraldehydeE.g. ethylene oxide gas, immersion gluteraldehyde
solutionssolutions
2. Intermediate level disinfection– these disinfectants do2. Intermediate level disinfection– these disinfectants do
not inactivate spores during routine use but theynot inactivate spores during routine use but they
destroy other forms of microbesdestroy other forms of microbes
E.g. formaldehyde, chlorine compounds, iodophors,E.g. formaldehyde, chlorine compounds, iodophors,
alcohols, phenolic compoundsalcohols, phenolic compounds

3. Low level disinfectants provide the narrowest3. Low level disinfectants provide the narrowest
antimicrobial rangeantimicrobial range
E.g. quaternary ammonium compounds, simpleE.g. quaternary ammonium compounds, simple
phenols and detergentsphenols and detergents
Such compounds are suitable for cleaningSuch compounds are suitable for cleaning
environmental surfacesenvironmental surfaces

Ethylene oxide
• Ethylene oxide is a gas at temperature above 10.8Ethylene oxide is a gas at temperature above 10.800
CC
• It has excellent penetration capacity and is sporicidal asIt has excellent penetration capacity and is sporicidal as
well as virucidal .well as virucidal .
• However, it is both toxic and highly explosive.However, it is both toxic and highly explosive.
• Its explosiveness is reduced by mixture withIts explosiveness is reduced by mixture with Freon gasFreon gas
• The gas is released into tightly sealed chamber where itThe gas is released into tightly sealed chamber where it
circulates for up to 4hrs. with carefully controlledcirculates for up to 4hrs. with carefully controlled
humidity.humidity.
• The chamber then must be flushed with inert gas for 8-The chamber then must be flushed with inert gas for 8-
12hrs. To ensure that all traces of ethylene oxide are12hrs. To ensure that all traces of ethylene oxide are
removed otherwise, the chemical will cause “removed otherwise, the chemical will cause “coldcold
burns”burns” on contact with skin.on contact with skin.

• It is used to sterilize paper, leather, wood, metal andIt is used to sterilize paper, leather, wood, metal and
rubber as well as plastics.rubber as well as plastics.
• In hospitals it is used to sterilize catheters, artificial heartIn hospitals it is used to sterilize catheters, artificial heart
valves, heart-lung machine components and opticalvalves, heart-lung machine components and optical
equipment.equipment.
• Used in chemiclavesUsed in chemiclaves

ALDEHYDES
• GLUTERALDEHYDEGLUTERALDEHYDE
• 2% solution is effective. It destroys vegetative cells2% solution is effective. It destroys vegetative cells
within 10 min to 30min and spores in 10 hrswithin 10 min to 30min and spores in 10 hrs
• It is recommended for use on surgical instrumentsIt is recommended for use on surgical instruments
where residual blood may be present.where residual blood may be present.
• It does notIt does not damage delicate objects, and therefore it candamage delicate objects, and therefore it can
be used to sterilize optical equipment such as the opticbe used to sterilize optical equipment such as the optic
fiber endoscopes.fiber endoscopes.

• DISADVANTAGEDISADVANTAGE
• It can damage many metal items.It can damage many metal items.
• E.g. nickel coated impression trays & carbon steel bursE.g. nickel coated impression trays & carbon steel burs
will often discolour and corrode, respectively whenwill often discolour and corrode, respectively when
immersed in gluteraldehyde solution for prolongedimmersed in gluteraldehyde solution for prolonged
periodsperiods
• It can cause hypersensitivity on repeated exposure soIt can cause hypersensitivity on repeated exposure so
instruments immersed in gluteraldehyde should beinstruments immersed in gluteraldehyde should be
thoroughly rinsed in sterile water prior to usethoroughly rinsed in sterile water prior to use

• FORMALDEHYDEFORMALDEHYDE
It is gas at high temperatures & solid at roomIt is gas at high temperatures & solid at room
temperature.temperature.
• In aqueous solutions, it is bactericidal, sporicidal andIn aqueous solutions, it is bactericidal, sporicidal and
virucidal.virucidal.
• When 37 gms. of the solid are suspended in 100ml ofWhen 37 gms. of the solid are suspended in 100ml of
water a solution calledwater a solution called formalinformalin results.results.
• Formalin is utilized for inactivating virus in vaccines &Formalin is utilized for inactivating virus in vaccines &
producing toxoids from toxins.producing toxoids from toxins.
• 10% Formalin containing 0.5% sodium tetraborate is10% Formalin containing 0.5% sodium tetraborate is
used to sterilize clean metal instruments.used to sterilize clean metal instruments.

• In the gaseous form, formaldehyde is expelled into a closedIn the gaseous form, formaldehyde is expelled into a closed
chamber where it is used as a sterilant for surgical equipment,chamber where it is used as a sterilant for surgical equipment,
hospital gowns and medical instruments.hospital gowns and medical instruments.
• However penetration is poor and the surface must be exposed toHowever penetration is poor and the surface must be exposed to
the gas for up to 12hrs. for effective sterilization. ( Fumigation)the gas for up to 12hrs. for effective sterilization. ( Fumigation)
• Formaldehyde leaves a residue and instruments must be rinsedFormaldehyde leaves a residue and instruments must be rinsed
before use.before use.
• Can cause hypersensitivity reactionsCan cause hypersensitivity reactions

Beta Propiolactone (BPL)
• It is a condensation product of ketone and formaldehydeIt is a condensation product of ketone and formaldehyde
• Is less explosive than ethylene oxide, but its penetratingIs less explosive than ethylene oxide, but its penetrating
power is more limited.power is more limited.
• As a liquid it is used to sterilize vaccines, sera andAs a liquid it is used to sterilize vaccines, sera and
surgical ligatures.surgical ligatures.
• However, it is carcinogenic & is therefore used onlyHowever, it is carcinogenic & is therefore used only
under restricted conditions.under restricted conditions.

ALCOHOL
• Effective skin antiseptics and valuable disinfectants forEffective skin antiseptics and valuable disinfectants for
medical instruments.medical instruments.
• Ethyl and isopropyl alcoholEthyl and isopropyl alcohol are most frequently usedare most frequently used
• Isoprpyl alcohol is prefered to ethyl alcohol as it is aIsoprpyl alcohol is prefered to ethyl alcohol as it is a
better fat solvent ,more bactericidal and less volatilebetter fat solvent ,more bactericidal and less volatile
• It is active against vegetative bacterial cells, including theIt is active against vegetative bacterial cells, including the
tubercle bacillus,tubercle bacillus,
• It denatures proteins & lipids, and leads to cellIt denatures proteins & lipids, and leads to cell
membrane disintegrationmembrane disintegration
• It is also a strong dehydrating agent.It is also a strong dehydrating agent.
• It is used to sterilize the skin prior to cutaneousIt is used to sterilize the skin prior to cutaneous
injections .injections .

• It is active against gram +ve, -ve, & acid fast organismsIt is active against gram +ve, -ve, & acid fast organisms
at a concentration of 50-70%at a concentration of 50-70%
• ‘‘Isopropyl alcohol’ or ‘rubbing alcohol’ has highIsopropyl alcohol’ or ‘rubbing alcohol’ has high
bactericidal activity in concentration as high as 99%.bactericidal activity in concentration as high as 99%.
• Relatively inefficient in the presence of blood and salivaRelatively inefficient in the presence of blood and saliva
• Lacks sporicidal activityLacks sporicidal activity
• Causes corrosion of metalsCauses corrosion of metals

SURFACE ACTIVE AGENTS
• Substances that alter the energy relationships atSubstances that alter the energy relationships at
interfaces producing a reduction of surface tension areinterfaces producing a reduction of surface tension are
referred to as surface-active agents.referred to as surface-active agents.
• They are widely used in industry as wetting agents,They are widely used in industry as wetting agents,
detergents.detergents.
• Surface active agents are compounds that possessesSurface active agents are compounds that possesses
both water attracting (hydrophilic), and water repellingboth water attracting (hydrophilic), and water repelling
(hydrophobic) groups.(hydrophobic) groups.
• There are 4 types of surface active agents.There are 4 types of surface active agents.
• Cationic surface active agentsCationic surface active agents
• Anionic surface active agentsAnionic surface active agents
• Nonionic surface active agentsNonionic surface active agents
• Amphoteric surface active agentsAmphoteric surface active agents

Cationic Surface Active Agents
(quaternary ammonium compounds )
• They act on the phospholipid present in the cellThey act on the phospholipid present in the cell
membrane, then the non polar portion of the detergentsmembrane, then the non polar portion of the detergents
penetrate into the hydrophobic interior of the membrane.penetrate into the hydrophobic interior of the membrane.
• This changes the permeability of the cellThis changes the permeability of the cell
• It then enters the cell and causes denaturation of theIt then enters the cell and causes denaturation of the
proteinprotein
• More active at an alkaline pH.More active at an alkaline pH.
• They are bactericidal for a wide range of organisms,They are bactericidal for a wide range of organisms,
although gram +ve species are more susceptible.although gram +ve species are more susceptible.

• DisadvantagesDisadvantages
• Inability to penetrate organic debrisInability to penetrate organic debris
• Incompatible with anionic detergents, Ca, Mg, and ironIncompatible with anionic detergents, Ca, Mg, and iron
of hard waterof hard water
• E.g. cetyl trimethyl ammonium bromide (cetavlon orE.g. cetyl trimethyl ammonium bromide (cetavlon or
ctrimide) & benzalkonium chloridectrimide) & benzalkonium chloride

Anionic surface active agents
• These are active at acid pHThese are active at acid pH
• These agents cause gross disruption of the lipoproteinThese agents cause gross disruption of the lipoprotein
framework of the cell membrane and also haveframework of the cell membrane and also have
mechanical cleansing action.mechanical cleansing action.
• e.g. Soaps and fatty acidse.g. Soaps and fatty acids

Nonionic surface-active agents
• These agents are relatively nontoxic and few promoteThese agents are relatively nontoxic and few promote
bacterial growth.bacterial growth.
• E.g. Tween 80 facilitates the diffused growth ofE.g. Tween 80 facilitates the diffused growth of
mycobacterium tuberculosis and provides a source ofmycobacterium tuberculosis and provides a source of
oleic acid which is stimulatory to the organism.oleic acid which is stimulatory to the organism.

Amphoteric surface active agents
• These compounds are also called as TEGO’These compounds are also called as TEGO’
compounds.compounds.
• They are active against a wide range of gram +ve, -veThey are active against a wide range of gram +ve, -ve
organisms and some viruses.organisms and some viruses.

DYES
• Dyes are used as staining agents in laboratory mediaDyes are used as staining agents in laboratory media
where they help to select out certain organisms from awhere they help to select out certain organisms from a
mixture.mixture.
• TYPES –AnilineTYPES –Aniline
AcridineAcridine
• They are Bacteriostatic at high dilutions.They are Bacteriostatic at high dilutions.
• Aniline dyesAniline dyes, in use are brilliant green & crystal violet, in use are brilliant green & crystal violet
have been used for many purposes.have been used for many purposes.
• They are more active against Gram+ve organisms.They are more active against Gram+ve organisms.
• Gentian violet is used for trench mouth and for CandidaGentian violet is used for trench mouth and for Candida
Albicans infection such as oral thrush.Albicans infection such as oral thrush.
• Interference with cell wall construction appears to be theInterference with cell wall construction appears to be the
mode of activitymode of activity

• Acridine dyesAcridine dyes, includes Acriflavine and Proflavine., includes Acriflavine and Proflavine.
• Both dyes are used as antiseptics for staphylococcalBoth dyes are used as antiseptics for staphylococcal
infections in wounds.infections in wounds.
• They act by combining directly with DNA, there byThey act by combining directly with DNA, there by
stopping RNA synthesis.stopping RNA synthesis.
• These dyes are more active against gram +ve organismsThese dyes are more active against gram +ve organisms
than against gram-ve but are not as selective as thethan against gram-ve but are not as selective as the
aniline dyes.aniline dyes.
• These acridine dyes are often referred to asThese acridine dyes are often referred to as “flavines”“flavines”
because of their yellow colourbecause of their yellow colour
• They are active even in the presence of serum or pusThey are active even in the presence of serum or pus
unlike aniline dyes.unlike aniline dyes.

OXIDANTS
• Included in this group are halogens, hydrogen peroxide,Included in this group are halogens, hydrogen peroxide,
and potassium permanganate.and potassium permanganate.
• The oxidizing agents inactivate enzymes by convertingThe oxidizing agents inactivate enzymes by converting
functional –SH groups to the oxidized form.functional –SH groups to the oxidized form.

HALOGEN
• These are a group of highly reactive elements whoseThese are a group of highly reactive elements whose
atoms have 7 electrons in the outer shell.atoms have 7 electrons in the outer shell.
• Two halogens chlorine & iodine are commonly used forTwo halogens chlorine & iodine are commonly used for
disinfection.disinfection.

CHLORINE
• Available as -- gasAvailable as -- gas
-- organic compound-- organic compound
-- inorganic compounds-- inorganic compounds
• Most commonly used as hypochloritesMost commonly used as hypochlorites
• The disinfectant action results from it’s ability to liberateThe disinfectant action results from it’s ability to liberate
free chlorine.free chlorine.
• In aqueous solutions the liberated Cl ions reacts withIn aqueous solutions the liberated Cl ions reacts with
water to form hypochlorous acid,water to form hypochlorous acid,

• Used in water supplies and swimming bathsUsed in water supplies and swimming baths
• Chlorax & purex bleachChlorax & purex bleach used for household sanitationused for household sanitation
& the disinfection of food utensils.& the disinfection of food utensils.
• Chlorinated limeChlorinated lime [NaOCl or Ca (OCl)2] is used as[NaOCl or Ca (OCl)2] is used as
bleaching agent in textile industry.bleaching agent in textile industry.

• DAKIN’s solutionDAKIN’s solution
0.5% sodium hypochlorite solution was0.5% sodium hypochlorite solution was
used by H. D.Dakin extensively for woundsused by H. D.Dakin extensively for wounds
during the I & II World War In Europe, it is usedduring the I & II World War In Europe, it is used
to treat athlete’s footto treat athlete’s foot
• Chloramines such asChloramines such as chloramines-Tchloramines-T areare
organic compounds that contain chlorine andorganic compounds that contain chlorine and
amino groups. These compounds release freeamino groups. These compounds release free
chlorine more slowly than hypochlorite solutionschlorine more slowly than hypochlorite solutions
and are more stable. They are used for generaland are more stable. They are used for general
wound antisepsis and root canal therapywound antisepsis and root canal therapy

• Corrosive to metalsCorrosive to metals
• Irritating to the skinIrritating to the skin
• Destroys fabricsDestroys fabrics
• Solution has to be prepared dailySolution has to be prepared daily

Iodine
• Iodine is more reactive and more germicidal.Iodine is more reactive and more germicidal.
• Iodine acts on the tyrosine portions of proteinIodine acts on the tyrosine portions of protein
molecules.molecules.
• Tincture of iodineTincture of iodine
2% iodine solution in ethyl alcohol used as an2% iodine solution in ethyl alcohol used as an
antiseptic for application over skin and mucousantiseptic for application over skin and mucous
membranemembrane
• IrritatingIrritating
• AllergicAllergic
• Corrodes metalCorrodes metal
• Stains skin and clothesStains skin and clothes

• IodophorsIodophors
They are compounds of iodine with non ionic surfaceThey are compounds of iodine with non ionic surface
active agents that release iodine over a long period ofactive agents that release iodine over a long period of
timetime
• The detergent portion of the complex loosens theThe detergent portion of the complex loosens the
organisms from the surface & halogen kills them.organisms from the surface & halogen kills them.
• ADVANTAGESADVANTAGES
• Less allergicLess allergic
• Less irritating to tissuesLess irritating to tissues
• Do not stain clothesDo not stain clothes
• Prolonged activityProlonged activity

Hydrogen Peroxide (H2O2)
• It is used to rinse wounds, scrapes and abrasions. TheIt is used to rinse wounds, scrapes and abrasions. The
area foams & effervescence as catalase in the tissuearea foams & effervescence as catalase in the tissue
breaks down hydrogen peroxide to oxygen & water.breaks down hydrogen peroxide to oxygen & water.
• The furious bubbling removes microorganismsThe furious bubbling removes microorganisms
mechanically.mechanically.
• Anaerobic bacteria are sensitive to HAnaerobic bacteria are sensitive to H22OO22 because suddenbecause sudden
release of oxygen gas inhibits their growthrelease of oxygen gas inhibits their growth
• New forms of HNew forms of H22OO22 are more stable than traditional formsare more stable than traditional forms
and do not decompose spontaneously.and do not decompose spontaneously.
• Inanimate material such as soft contact lenses, utensils,Inanimate material such as soft contact lenses, utensils,
and heat sensitive plastics can be disinfected within 30and heat sensitive plastics can be disinfected within 30
min.min. www.indiandentalacademy.com

PHENOLS AND THEIR
DERIVATIVES (Carbolic Acid)
• Phenols are obtained by distillation of coal tar betweenPhenols are obtained by distillation of coal tar between
temperatures of 170temperatures of 17000
C and 270C and 27000
C.C.
• Following its introduction as a surgical antiseptic byFollowing its introduction as a surgical antiseptic by
ListeLister in 1865, phenol was widely used as a disinfectant.r in 1865, phenol was widely used as a disinfectant.
• Since most phenolic disinfectants have a low solubility inSince most phenolic disinfectants have a low solubility in
water, they are formulated with emulsifying agents, suchwater, they are formulated with emulsifying agents, such
as soaps, which also increase their antimicrobial action.as soaps, which also increase their antimicrobial action.
• ACTIONACTION
• They act as cytoplasmic poisons by penetrating andThey act as cytoplasmic poisons by penetrating and
disrupting cell wall, thereby leading to denaturation ofdisrupting cell wall, thereby leading to denaturation of
intracellular proteinsintracellular proteins

• Phenol is active against gram +ve bacteriaPhenol is active against gram +ve bacteria
• Bactericidal at 1% and fungicidal at 1.3 %Bactericidal at 1% and fungicidal at 1.3 %
• DrawbacksDrawbacks
• Its activity is reduced in the presence of organic matterIts activity is reduced in the presence of organic matter
• ExpensiveExpensive
• Caustic to the skinCaustic to the skin

CRESOL
• Phenol derivatives containing methyl groups havePhenol derivatives containing methyl groups have
greater germicidal activity and lower toxicity than thegreater germicidal activity and lower toxicity than the
parent compound.parent compound.
• Ortho, meta, paraOrtho, meta, para cresols are appreciably more activecresols are appreciably more active
than phenol and are employed as a mixture namedthan phenol and are employed as a mixture named
“Tricresol”“Tricresol”
• They are not readily inactivated in the presence ofThey are not readily inactivated in the presence of
organic matter and so are good disinfectantsorganic matter and so are good disinfectants

Bisphenols
• It is a combination of 2 phenol moleculesIt is a combination of 2 phenol molecules
• E.G.Hexachlorophene, ChlorhexidineE.G.Hexachlorophene, Chlorhexidine
• HexachloropheneHexachlorophene
• It was used extensively in the 1950s in products such as toothIt was used extensively in the 1950s in products such as tooth
pastes, deodorant and bath soaps.pastes, deodorant and bath soaps.
• It is highly effective against gram –ve organisms esp. staphylococciIt is highly effective against gram –ve organisms esp. staphylococci
& streptococci.& streptococci.
• In 1961 routine daily hexachlorophene bathing of newborn infantsIn 1961 routine daily hexachlorophene bathing of newborn infants
became an accepted procedure in many nurseries in order tobecame an accepted procedure in many nurseries in order to
reduce colonization of umbilical stump & infection of scalp withreduce colonization of umbilical stump & infection of scalp with
streptococcus aureus.streptococcus aureus.
• In 1971, FDA placed strict controls on the use of hexachloropheneIn 1971, FDA placed strict controls on the use of hexachlorophene
and curtailed its use in newborn nursery because numerous studiesand curtailed its use in newborn nursery because numerous studies
indicate that excessive amounts could be absorbed through the skinindicate that excessive amounts could be absorbed through the skin
and cause neurological damage in newborn.and cause neurological damage in newborn.

CHLORHEXIDINE
• This compound was approved in 1976 by FDA asThis compound was approved in 1976 by FDA as
surgical scrub, hand wash, and superficial skin woundsurgical scrub, hand wash, and superficial skin wound
cleanser.cleanser.
• Chlorhexidine in a conc. of 0.2% is also most effectiveChlorhexidine in a conc. of 0.2% is also most effective
antiplaque & antigingivitis agentantiplaque & antigingivitis agent

HEAVY METALS
• Heavy metals are very reactive with proteins, particularlyHeavy metals are very reactive with proteins, particularly
at the sulfydryl groups, and they are believed to bindat the sulfydryl groups, and they are believed to bind
protein molecules together by forming bridges betweenprotein molecules together by forming bridges between
the groups. Because many of the proteins involved arethe groups. Because many of the proteins involved are
enzymes the metabolism is disrupted.enzymes the metabolism is disrupted.
• Heavy metals are not sporicidalHeavy metals are not sporicidal
• E.G. mercury, silver and copperE.G. mercury, silver and copper

INSTRUMENT PROCESSSING
• The steps involved areThe steps involved are
1.1. PresoakingPresoaking
2.2. CleaningCleaning
3.3. Corrosion control and lubricationCorrosion control and lubrication
4.4. PackagingPackaging
5.5. SterilizationSterilization
6.6. Sterilization monitoringSterilization monitoring
7.7. Drying or coolingDrying or cooling
8.8. StorageStorage
9.9. DistributionDistribution
10.10. SharpeningSharpening

Presoaking
• Most disinfectants do not act in the presence of debris,Most disinfectants do not act in the presence of debris,
so they should be removedso they should be removed
• It is easier to remove the debris before it driesIt is easier to remove the debris before it dries
• Placing the instrument in a presoak solution until time isPlacing the instrument in a presoak solution until time is
available for full cleaning prevents drying and begins toavailable for full cleaning prevents drying and begins to
dissolve or soften the debrisdissolve or soften the debris
• Presoak solutions used are detergents, enzymes,Presoak solutions used are detergents, enzymes,
phenols, quaternary ammonium compoundsphenols, quaternary ammonium compounds

Cleaning
• All items to be sterilised must be properly cleaned first-All items to be sterilised must be properly cleaned first-
• It reduces the bioburdenIt reduces the bioburden
• A good cleanig agent shouldA good cleanig agent should
1.1. Provide a pH near neutrality]Provide a pH near neutrality]
2.2. Be blood solventBe blood solvent
3.3. Be effective against protein soilBe effective against protein soil
4.4. Offer low surface tension for soil penetrationOffer low surface tension for soil penetration
5.5. Be easy to rinseBe easy to rinse
6.6. Not damage items being cleanedNot damage items being cleaned
7.7. Be tested in hard and soft waterBe tested in hard and soft water

• Two cleaning methods are-- ManualTwo cleaning methods are-- Manual
UltrasonicUltrasonic
• Manual cleaningManual cleaning– it is an effective method if done– it is an effective method if done
properlyproperly
It is time consuming and increases the chance ofIt is time consuming and increases the chance of
accidental punctureaccidental puncture
• Ultrasonic cleaning– it is more effective ,less timeUltrasonic cleaning– it is more effective ,less time
consuming and safer than hand cleaning. A basketconsuming and safer than hand cleaning. A basket
should be used to hold loose instruments. After cleaningshould be used to hold loose instruments. After cleaning
instruments should be thoroughly washed to remove theinstruments should be thoroughly washed to remove the
debris presentdebris present

Corrosion control and lubrication
• Corrosion controlCorrosion control– if the instruments are to be– if the instruments are to be
sterilized in dry heat, or ethylene oxide gas thesterilized in dry heat, or ethylene oxide gas the
instruments must be dried firstinstruments must be dried first
• If non stainless steel instruments are to be sterilized thenIf non stainless steel instruments are to be sterilized then
a rust inhibitor should be useda rust inhibitor should be used
• LubricationLubrication– lubrication of instruments with moving– lubrication of instruments with moving
parts especially with a water based lubricant is ideal.parts especially with a water based lubricant is ideal.
Silicon or oil based lubricants leave a film that steamSilicon or oil based lubricants leave a film that steam
cannot penetratecannot penetrate

Packaging
• Instruments should preferably be packaged duringInstruments should preferably be packaged during
sterilisationsterilisation
• It reduces the risk of contaminationIt reduces the risk of contamination
• Different types of sterilisers require different wrappingDifferent types of sterilisers require different wrapping
materialsmaterials

Sterilisation
• Three commonly used methods of sterilisation inThree commonly used methods of sterilisation in
dentistry aredentistry are
1.1. Steam autoclaveSteam autoclave
2.2. Unsaturated chemical vaporUnsaturated chemical vapor
3.3. Dry heat ovenDry heat oven

Monitoring of sterilization and
disinfection
• An integral part of the sterilization system is it’sAn integral part of the sterilization system is it’s
efficient monitoringefficient monitoring
• A periodic verification at least weekly should beA periodic verification at least weekly should be
integrated into the systemintegrated into the system
• The different typeThe different type
1.1. Biologic monitoringBiologic monitoring
2.2. Chemical monitoringChemical monitoring
3.3. Physical monitoringPhysical monitoring

Biological monitoring
• Biological monitoring involves the use of spore testsBiological monitoring involves the use of spore tests
called biologic indicators (BI)called biologic indicators (BI)
• These contain bacterial spores more resistant to heatThese contain bacterial spores more resistant to heat
than viruses and vegetative bacteriathan viruses and vegetative bacteria
• These provide the most reliable sterilization indicatorsThese provide the most reliable sterilization indicators
• BI’s contain – Bacillus stearothermophillus spores forBI’s contain – Bacillus stearothermophillus spores for
steam or chemical vapor sterilizationsteam or chemical vapor sterilization
• And Bacillus subtilis for dry or ethylene oxide gasAnd Bacillus subtilis for dry or ethylene oxide gas
sterilisationsterilisation
• These spore strips are filter paper strips impregnatedThese spore strips are filter paper strips impregnated
with spores and sealed in an envelope through which thewith spores and sealed in an envelope through which the
sterilising agent penetratessterilising agent penetrates
• There are no BI available to test chemical sterilants andThere are no BI available to test chemical sterilants and
disinfectantsdisinfectants

Chemical monitoring
• Chemical monitoring involves the use of color changeChemical monitoring involves the use of color change
and other indicatorsand other indicators
• Their purpose is simply to identify items that have beenTheir purpose is simply to identify items that have been
processed through a sterilizerprocessed through a sterilizer
• However they are not perfectly reliable as they changeHowever they are not perfectly reliable as they change
color either early or latecolor either early or late

Physical monitoring
• It is directed towards conditions in the sterilizer thanIt is directed towards conditions in the sterilizer than
conditions within the packs being processedconditions within the packs being processed
• It involves the routine observation of dials, or gaugesIt involves the routine observation of dials, or gauges
indicating time ,temperature and pressureindicating time ,temperature and pressure

Handling sterile instruments
• DRYINGDRYING
• Wet packages after steam sterilizer indicates problemsWet packages after steam sterilizer indicates problems
with package composition, overloading, improperwith package composition, overloading, improper
arrangement, removal of packs too soon or sterilizerarrangement, removal of packs too soon or sterilizer
malfunctionmalfunction
• Packages that remain or become wet may drawPackages that remain or become wet may draw
microorganisms and compromise the integrity of themicroorganisms and compromise the integrity of the
material itselfmaterial itself

• COOLINGCOOLING
• Items being cooled after being removed from the heatItems being cooled after being removed from the heat
sterilizer must remain untouched and protected from thesterilizer must remain untouched and protected from the
environmentenvironment
• Blowing of air over unwrapped instruments willBlowing of air over unwrapped instruments will
recontaminate themrecontaminate them
• Warm items should not be transferred to cold surfacesWarm items should not be transferred to cold surfaces
as it will enhance condensationas it will enhance condensation

• STORAGESTORAGE
• Proper infection control will prevent recontamination ofProper infection control will prevent recontamination of
sterilized instruments regardless of the time betweensterilized instruments regardless of the time between
sterilization and reusesterilization and reuse
• Sterile packs and trays should be kept away in dry, lowSterile packs and trays should be kept away in dry, low
dust, away from water pipes and from heat sourcesdust, away from water pipes and from heat sources

• DISTRIBUTIONDISTRIBUTION
• Sterilized packs containing functional sets or individualSterilized packs containing functional sets or individual
items can be placed on sterile, disposable or at leastitems can be placed on sterile, disposable or at least
cleaned and disinfected trays for use at the chair sidecleaned and disinfected trays for use at the chair side

• ADA RECOMMENDATIONS FORADA RECOMMENDATIONS FOR
STERILIZATION AND DISINFECTION OFSTERILIZATION AND DISINFECTION OF
DENTAL INSTRUMETNS, MATERIALSDENTAL INSTRUMETNS, MATERIALS
COMMONLY USEDCOMMONLY USED

instrumentsinstruments SteamSteam
autoclaveautoclave
Dry heat ovenDry heat oven ChemicalChemical
vaporvapor
EthyleneoxideEthyleneoxide
gasgas
AngleAngle
attachmentsattachments ++ ++ ++ ++++
Burs –carbonBurs –carbon
steelsteel -- ++++ ++++ ++++ discarddiscard
steelsteel
++ ++++ ++++ ++++ discarddiscard
TungstenTungsten
carbidecarbide ++ ++++ ++ ++++ discarddiscard
Stone diamondStone diamond
++ ++++ ++++ ++++
PolishingPolishing
++++ ++ ++++ ++++
SharpeningSharpening
++++ ++++ ++++ --
Flouridee gelFlouridee gel
trays heattrays heat
resistantresistant
++++ == -- ++++www.indiandentalacademy.com

Non reistantNon reistant
traystrays
== == -- ++++discarddiscard
Hand instHand inst
carbon steelcarbon steel
-- ++++ ++++ ++++
StainlessStainless
steelsteel
++++ ++++ ++++ ++++
Hand piecesHand pieces
(++)(++) -- (+)(+) ==
Contra angleContra angle
++++ -- ++++ ==
ProphylaxisProphylaxis
angleangle
++ ++ ++ ==discarddiscard
Imp trays AlImp trays Al
++++ ++ ++++ ++++
ChromeChrome
platedplated
++++ ++++ ++++ ++++
CustomCustom
== == == ++++discarddiscard

plasticplastic
== == == ++++discarddiscard
mirrorsmirrors
-- ++++ ++++ ++++
PolishingPolishing
garnetgarnet
== -- -- ==
RubberRubber
++ -- -- ==
ProphylaxisProphylaxis
cupcup
-- -- -- ==discarddiscard
SalivaSaliva
ejectorsejectors
-- -- -- --discarddiscard
Air HAir H22OO
syringe tsyringe t
++++ ++++ ++++ = discard= discard
X ray filmX ray film
holdersholders
(++)(++) == (+)(+) ++++
CollimatingCollimating
devicedevice
-- == == ++++www.indiandentalacademy.com

DISINFECTANTS IN THE DENTAL
LAB
• IMPRESSIONS:-IMPRESSIONS:-
• Alginate:-Alginate:-
Sodium hypo chlorite spraysSodium hypo chlorite sprays
IodophorsIodophors
glutaraldehydeglutaraldehyde
• Polysulphide:-Polysulphide:-
Sodium hypoSodium hypo chloritechlorite ImmersedImmersed
Chlorine dioxideChlorine dioxide
PhenolsPhenols
• Reversible hydrocolloidReversible hydrocolloid
iodophoriodophor
bleachbleach
glutaraldehydeglutaraldehyde

• Gypsum casts:-Gypsum casts:-
IodophorIodophor Sprayed or soakedSprayed or soaked
10 mi10 mi nsns
• Resin dentures:-Resin dentures:-
Sodium hypo chloriteSodium hypo chlorite ImmersedImmersed
• Wax records:-Wax records:-
IodophorIodophor
Sodium hypo chloriteSodium hypo chlorite Immersed.Immersed.

impresimpres
sionsion
glutaraldeglutaralde
hydehyde
IodophorsIodophors Cl compdCl compd PhenolPhenol PhenolicPhenolic
gluteraldegluteralde
hydehyde
AlginateAlginate -- -- ++ -- --
PolysulphiPolysulphi
dede
++ ++ ++ ++ ++
SiliconSilicon
rubberrubber
++ ++ ++ ++ ++
ZOEZOE ++ ++ -- ?? ++
AgarAgar -- ++ ++ ?? ++
CompounCompoun
dd
-- ++ ++ -- ++

prosthesprosthes
isis
glutaraldglutarald
ehydeehyde
IodophoIodopho
rsrs
ClCl
compoucompou
ndnd
phenolsphenols PhenolicPhenolic
glutaraldglutarald
ehydeehyde
Fixed(metFixed(met
al/porecelal/porecel
ain)ain)
++ +/-+/- -- ?? ++
RemovablRemovabl
ee
(acrylic/po(acrylic/po
recelain)recelain)
-- ++ ++ -- --
RemovablRemovabl
ee
(metal/acr(metal/acr
ylic)ylic)
-- +/-+/- +/-+/- -- --

CONCLUSION
• ““PREVENTION IS BETTER THAN CURE”-PREVENTION IS BETTER THAN CURE”- aa
proverb well suited to sterilisationproverb well suited to sterilisation
• A thorough understanding of the application ofA thorough understanding of the application of
sterilisation will help ensure safety from the invisible butsterilisation will help ensure safety from the invisible but
deadly world of microbial paythogensdeadly world of microbial paythogens
• Hence utilisation of proper sterilization, disinfectants andHence utilisation of proper sterilization, disinfectants and
aseptic procedures helps us achieve the safety ouraseptic procedures helps us achieve the safety our
profession demandsprofession demands

REFRENCES
• Textbook of microbiology- R.Anantnarayan 5Textbook of microbiology- R.Anantnarayan 5thth
EditionEdition
Orient LongmanOrient Longman
• Fundamentals of microbiology- Frobisher 9Fundamentals of microbiology- Frobisher 9thth
EditionEdition
SaundersSaunders
• Infection control and office safety- DCNA April 1991Infection control and office safety- DCNA April 1991
• Local anaesthesia and pain control- Monheim 7Local anaesthesia and pain control- Monheim 7thth
EdtionEdtion
CBS PublishingCBS Publishing
• Practical infection control in dentistry- James CottonPractical infection control in dentistry- James Cotton
• Endodontic practice- Loius Grossman 11Endodontic practice- Loius Grossman 11thth
EditionEdition
Varghese publishing HouseVarghese publishing House

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