Sterlisation and disinfection

1. STERILISATIONSTERILISATION
ANDAND
DISINFECTIONDISINFECTION
DR.ASIF IQBALDR.ASIF IQBAL Date : 14-08-2014Date : 14-08-2014

2. Objective of sterilizationObjective of sterilization
––Removal of microorganisms or destroy themRemoval of microorganisms or destroy them
from materials or from areas since they causefrom materials or from areas since they cause
contamination, infection and decay.contamination, infection and decay.
In microbiology - to prevent contaminationIn microbiology - to prevent contamination
Surgery - to maintain asepsisSurgery - to maintain asepsis
Drug & food -for ensuring the safetyDrug & food -for ensuring the safety

3. DefinitionsDefinitions
 SterilizationSterilization – T– The process by which anhe process by which an
article, surface, or medium is freed of all livingarticle, surface, or medium is freed of all living
microorganisms either in the vegetative ormicroorganisms either in the vegetative or
spore statespore state
 DisinfectionDisinfection – The destruction or removal of– The destruction or removal of
all pathogenic organisms, or organismsall pathogenic organisms, or organisms
capable of giving rise to infectioncapable of giving rise to infection
 SanitizationSanitization - This term is sometimes used- This term is sometimes used
as a synonym for disinfection, particularlyas a synonym for disinfection, particularly
used with reference to food processing &used with reference to food processing &
cateringcatering

4. DefinitionsDefinitions
 AntisepsisAntisepsis – used to indicate the prevention of– used to indicate the prevention of
infection, usually by inhibiting the growth ofinfection, usually by inhibiting the growth of
bacteria in wounds or tissuesbacteria in wounds or tissues
 Bactericidal agentsBactericidal agents
 Bacteriostatic agentsBacteriostatic agents
 CleaningCleaning
 DegermingDegerming

5. HISTORYHISTORY
 The science of microbiology has shed much light on the nature ofThe science of microbiology has shed much light on the nature of
disease. In the nineteenth century the work of Pasteur ,Lister anddisease. In the nineteenth century the work of Pasteur ,Lister and
Koch did much to explain the role of bacteria in disease and toKoch did much to explain the role of bacteria in disease and to
indicate possible methods of practicing safer medicine.indicate possible methods of practicing safer medicine.
 LOUIS PASTEUR (1822-95) was the first scientist to show clearlyLOUIS PASTEUR (1822-95) was the first scientist to show clearly
that bacteria never generate spontaneously and that no growth ofthat bacteria never generate spontaneously and that no growth of
any kind occurs in the sterilized media.any kind occurs in the sterilized media.
 One of his many achievements was the development of theOne of his many achievements was the development of the
technique of controlled heating known as ‘PASTEURISATION’ fortechnique of controlled heating known as ‘PASTEURISATION’ for
the preservation of beverages and food stuffs.the preservation of beverages and food stuffs.

6. Dr. Joseph Lister (Dr. Joseph Lister (1827-1912)1827-1912)
• Discovered the effectiveness of 'carbolic acid,‘Discovered the effectiveness of 'carbolic acid,‘
which was used in controlling typhoid.which was used in controlling typhoid.
Using carbolic acid, Lister was able to keep
his hospital ward in Glasgow free of
infection for nine months.

7. Carbolic acid spray being used at the time of aCarbolic acid spray being used at the time of a
surgerysurgery

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

9. WHY STERILIZATION ISWHY STERILIZATION IS
IMPORTANT IN DENTISTRYIMPORTANT IN DENTISTRY

10. DiseasesDiseases PathogenPathogen
Herpes infectionsHerpes infections Herpesvirus hominis (herpesHerpesvirus hominis (herpes
simplex virus)simplex virus)
SyphilisSyphilis Treponema pallidumTreponema pallidum
Hand-foot-mouthHand-foot-mouth
diseasedisease
CoxsackievirusCoxsackievirus
HerpanginaHerpangina CoxsackievirusCoxsackievirus
GonococcalGonococcal
pharyngitispharyngitis
Neisseria gonorrhoeaeNeisseria gonorrhoeae
CandidiasisCandidiasis Candida albicansCandida albicans
ORAL DISEASES

11. I) HERPES INFECTIONS :
- In this disease, vesicle-type lesions can occur in the
mouth.
-Vesicles during active herpes simplex infections at any
site of the body contain the virus which may be spread
to others by direct contact with these lesions.
-Also, the herpes simplex virus may be present in saliva in
those with oral or lip lesions and possibly in a small
percent of those who are infected but have no active
lesions.
-In such instances, sprays or aeorosols of the saliva may
result in spread of the virus to unprotected eyes of the
dental team.

12. II) HERPANGINA AND HAND-FOOT-MOUTH
DISEASE :
Herpangina appears as vesicles on the
soft palate or elsewhere in the posterior part of
the mouth that break down to ulcers that last for
about a week.
-Fever, sore throat and headache frequently
accompany the vesicular stage.
-The lesions are caused by specific types of
coxackie virus.

13. III) ORAL SYPHILIS .
Treponema pallidum is a spirochete
bacterium and is the causative agent of syphilis.
-About 5-10% of the cases of syphilis first occur in
the mouth in the form of a lesion called a primary
chancre, an open ulcer frequently on the tongue or
lips.
-These lesions do contain the live spirochetes and
may be spread by direct contact.
- The possibility of the spirochete entering small
cuts or breaks in the skin of unprotected hands and
can cause syphilis of the finger.

14. IV) ORAL CANDIDIASIS :
Candida albicans is a yeast that occurs in the
mouth asymptomatically in about one third of adults.
-Such circumstances that may result in oral disease
called thrush or oral candidiasis might include
conditions that disturb our body defense mechanisms
such as the systemic diseases of HIV infection, and
leukemia;
-Spread of C. albicans from a patient’s mouth to the
dental team is theoretically possible through direct
contact with lesions or sprays or aerosols of infected
saliva.

15. PREREQUISITESPREREQUISITES FOR ANFOR AN
IDEAL DISINFECTANTIDEAL DISINFECTANT
AND ROLE PLAYINGAND ROLE PLAYING
FACTORSFACTORS

16. Selection of antiseptics &Selection of antiseptics &
disinfectantsdisinfectants
PrerequisitesPrerequisites
 It should have a wide spectrum of activityIt should have a wide spectrum of activity
 Fast actingFast acting
 Active in the presence of organic matterActive in the presence of organic matter
 Nontoxic to animals or humans ( antiseptic )Nontoxic to animals or humans ( antiseptic )
 Soluble in waterSoluble in water
 It should not separate on standingIt should not separate on standing
 Should have high penetrating powerShould have high penetrating power
 Surface compatibilitySurface compatibility
 Relatively inexpensiveRelatively inexpensive

17. METHODS OFMETHODS OF
MICROBIALMICROBIAL
CONTROLCONTROL
Physical AgentsPhysical Agents
Chemical AgentsChemical Agents
ChemotherapeuticChemotherapeutic
AgentsAgents

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

19. PHYSICAL CONTROL WITH HEATPHYSICAL CONTROL WITH HEAT
 SUNLIGHTSUNLIGHT – Ultraviolet rays– Ultraviolet rays
Typhoid bacilli exposed to sun on pieces ofTyphoid bacilli exposed to sun on pieces of
cloth were killed in 2 hours, where the controlscloth were killed in 2 hours, where the controls
kept in dark were alive after 6 dayskept in dark were alive after 6 days
 DRYINGDRYING - 4/5- 4/5thth
of the bacterial cell is made-upof the bacterial cell is made-up
of waterof water

20. Dry heatDry heat
DIRECT FLAMEDIRECT FLAME
Bunsen burnerBunsen burner

21. IncinerationIncineration

22. HOT AIR OVENHOT AIR OVEN
Radiating dry heatRadiating dry heat
16016000
C ( 320C ( 32000
F) & 2 HoursF) & 2 Hours
useful for sterilizing dry powders, wateruseful for sterilizing dry powders, water
free oily substances, many types of glassfree oily substances, many types of glass
ware such as pipettes, flasks, andware such as pipettes, flasks, and
syringes.syringes.
Advantage – non corrosive methodAdvantage – non corrosive method

23. Hot air ovenHot air oven

24. Moist heatMoist heat
 Temperatures below 100Temperatures below 10000
C/ pasteurizationC/ pasteurization
 Temperatures at 100Temperatures at 10000
C/ boilingC/ boiling
 Steam at atmospheric pressureSteam at atmospheric pressure

25. Pasteurization ( below 100Pasteurization ( below 10000
C )C )
Purpose – To reduce the bacterial population of aPurpose – To reduce the bacterial population of a
liquid such as milkliquid such as milk
Spores are not affected by pasteurizationSpores are not affected by pasteurization
 Holding methodHolding method
62.962.900
C for 30 minutesC for 30 minutes
 Flash pasteurizationFlash pasteurization – 71.6– 71.600
C for 15secC for 15sec
 Ultra pasteurizationUltra pasteurization – 82– 8200
C for 3secC for 3sec

26. BOILING WATERBOILING WATER (100(10000
C)C)
 Less time of exposure are requiredLess time of exposure are required
DenaturationDenaturation of proteins .of proteins .
 Minimum exposure time – 30 minutesMinimum exposure time – 30 minutes
Less reliableLess reliable
Washing soda ( 2% conc.) may be addedWashing soda ( 2% conc.) may be added

27. Fractional sterilization ( steam at atmosphericFractional sterilization ( steam at atmospheric
pressure )pressure )
 TyndallizationTyndallization
( John Tyndall )( John Tyndall )
 IntermittentIntermittent
sterilizationsterilization

28. Free flowing steam at 100Free flowing steam at 10000
C for 30 minutes onC for 30 minutes on
each of 3 successive days.each of 3 successive days.
First dayFirst day - steam kills all organisms except- steam kills all organisms except
spores, and it stimulates spores to germinatespores, and it stimulates spores to germinate
vegetative cellsvegetative cells
Second daySecond day –vegetative cells are killed–vegetative cells are killed
Third dayThird day – kills the remaining cells– kills the remaining cells

29. AUTOCLAVEAUTOCLAVE
Moist heat In the form of pressurized steamMoist heat In the form of pressurized steam
increase in the pressure of the gasincrease in the pressure of the gas
increase in the temperatureincrease in the temperature
As the water molecules in steam becomes moreAs the water molecules in steam becomes more
energized, their penetration increasesenergized, their penetration increases

30. Used for glassware, metal ware, blankets,Used for glassware, metal ware, blankets,
intravenous solutions and a broad variety ofintravenous solutions and a broad variety of
other objectsother objects
Pressure in autoclavePressure in autoclave
- 15pds/sq. inch- 15pds/sq. inch
TemperatureTemperature
–– 121.5121.500
CC
TimeTime
–– 3 to 30 min3 to 30 min

31. AUTOCLAVEAUTOCLAVE

32. LimitationsLimitations
 Plastic ware melts in high heatPlastic ware melts in high heat
 sharp instruments become dullsharp instruments become dull
 Oily substances cannot be treatedOily substances cannot be treated
Prevacuum autoclavePrevacuum autoclave
Temperature - 132Temperature - 13200
C to 134C to 13400
CC
Pressure – 28 to 30 lb/1nPressure – 28 to 30 lb/1n22
Time – 4minutesTime – 4minutes
Advantage – minimal exposure time forAdvantage – minimal exposure time for
sterilizationsterilization

33.  HOT OILHOT OIL
16016000
C for 1 hourC for 1 hour
Advantages – no rusting of instrumentsAdvantages – no rusting of instruments
minimal corrosionminimal corrosion
 SILICONSILICON

34. Physical control by otherPhysical control by other
methodsmethods

35. FILTRATION ( 1980s )FILTRATION ( 1980s )
filter technology – Charles Chamberlandfilter technology – Charles Chamberland
Julius petriJulius petri
Filter – a mechanical device used to removeFilter – a mechanical device used to remove
microorganisms from a solutionmicroorganisms from a solution
Ex; IV solutions,bacteriological media, toxoids,Ex; IV solutions,bacteriological media, toxoids,
pharmaceuticals etc.pharmaceuticals etc.

36. Types of filtersTypes of filters
 Candle filtersCandle filters 1.Unglazed ceramic filters1.Unglazed ceramic filters
Ex; Chamberland filterEx; Chamberland filter
2.Diatomaceous earth filters2.Diatomaceous earth filters
Ex; Berkefeld filterEx; Berkefeld filter
 Asbestos filtersAsbestos filters
 Sintered glass filtersSintered glass filters
 Membrane filtersMembrane filters

37. Membrane filter techniqueMembrane filter technique

38. ULTRASONIC LIGHTULTRASONIC LIGHT
Wave lengthWave length
Visible light is between 400 & 800nmVisible light is between 400 & 800nm
Ultraviolet light is between 100 & 400 nmUltraviolet light is between 100 & 400 nm

39. Mechanism of action
When microorganisms are subjected to UV light
linking of thymine molecules occurs
Demerits;
 It is not effective against bacterial spores
 Does not penetrate liquids or solids
 It may cause damage to human cells

40. Other types of radiationOther types of radiation
 Ionizing radiationIonizing radiation
X-rays & gamma raysX-rays & gamma rays
Both have wavelengths shorter than the UV lightBoth have wavelengths shorter than the UV light
They force electrons out of their shells, therebyThey force electrons out of their shells, thereby
creating ionscreating ions

41.  MicrowaveMicrowave
- Wave length is longer than that of UV light- Wave length is longer than that of UV light
- Molecules are set into a high speed motion- Molecules are set into a high speed motion
 Laser beamLaser beam
LLightight AAmplification bymplification by SStimulatedtimulated EEmission ofmission of
RRadiationadiation

42. ULTRASONIC VIBRATIONSULTRASONIC VIBRATIONS
High frequency sound waves beyond the range of theHigh frequency sound waves beyond the range of the
human earhuman ear
‘‘Cold boiling’Cold boiling’
They cause the formation of bubbles or cavities and theThey cause the formation of bubbles or cavities and the
water appears to boil -water appears to boil - cavitationcavitation
DemeritsDemerits
 Not very effectiveNot very effective
 Liquid is requiredLiquid is required

44. Chemical control ofChemical control of
microorganismsmicroorganisms

45. • Agents that damage cell membraneAgents that damage cell membrane
• Agents that denatures protein
• Agents that modify the functional
group of protein & nucleic acid

46.  Destroys structural integrity of cellDestroys structural integrity of cell
membrane (protein & lipids).membrane (protein & lipids).
Net effect is the release of smallNet effect is the release of small
metabolites from the cell that interferes withmetabolites from the cell that interferes with
the active transport and energy metabolism.the active transport and energy metabolism.

47.  Agents:Agents:

Surface active agentsSurface active agents
• Cationic – most effectiveCationic – most effective
• AnionicAnionic
• Non-ionic – not effectiveNon-ionic – not effective
• AmphotericAmphoteric

Phenolic compoundPhenolic compound

AlcoholAlcohol

48.  Cationic AgentsCationic Agents
Quarternary ammonium compoundQuarternary ammonium compound
- Bactericidal for a wide range of organisms,Bactericidal for a wide range of organisms,
gram (+) species are more susceptiblegram (+) species are more susceptible
• Used primarily in hand or face washesUsed primarily in hand or face washes
• Acts on phospholipids, changes cellActs on phospholipids, changes cell
permeability.permeability.
• Include in disinfecting instruments andInclude in disinfecting instruments and
preserving drugs in low concentration form.preserving drugs in low concentration form.

49.  Anionic AgentsAnionic Agents
- Soaps and fatty acid dissociate to yieldSoaps and fatty acid dissociate to yield
negatively charged ions (active at acid Ph).negatively charged ions (active at acid Ph).
- Causes gross disruption of the lipoproteinCauses gross disruption of the lipoprotein
framework of the cell wall.framework of the cell wall.
- Displays rapid bactericidal action (withinDisplays rapid bactericidal action (within
30secs) .30secs) .
- Effective against gram (+) organisms.Effective against gram (+) organisms.

50.  BiguanidesBiguanides
- Antimicrobial activity against vegetative- Antimicrobial activity against vegetative
bacteria, yeasts, and enveloped viruses .bacteria, yeasts, and enveloped viruses .
- Disrupts cytoplasmic membrane.- Disrupts cytoplasmic membrane.
- It may be used together with surface active- It may be used together with surface active
agents.agents.

51. ChlorhexidineChlorhexidine which is more effective atwhich is more effective at
pH 7 – 8pH 7 – 8

Used as a safe antiseptic to preventUsed as a safe antiseptic to prevent
body infection , in oral rinses for treatingbody infection , in oral rinses for treating
sore gums, mouth ulcers and preventingsore gums, mouth ulcers and preventing
plaque on teeth.plaque on teeth.

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

53.  Primarily used for testing new bactericidalPrimarily used for testing new bactericidal
agentagent
- CresolsCresols
- XylenolsXylenols
 Phenolics are effective against bacteria,Phenolics are effective against bacteria,
fungi and viruses.fungi and viruses.

54. Kills 99.9% ofgerms in30 seconds
• Hospital disinfectant deodorant
is highly effective against TB,
and HIV-1
•It is tuberculocidal, virucidal,
fungicidal, bactericidal

55. • 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.

56. III. Alcohol
- Disorganizes lipid structure by penetrating into
the hydrocarbon region, denatures proteins.
-Optimal activity best at 70% - 75% .

57. - Effective against vegetative bacteria, fungiEffective against vegetative bacteria, fungi
and viruses .and viruses .
- Sporicidal activitySporicidal activity
- Disinfects work surfaces and, asDisinfects work surfaces and, as
antiseptics on skin.antiseptics on skin.

58. 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.

59. 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.

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

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

62. 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 bactericidal for gonococci.
• Silver sulfadiazine – topical cream for burn patients.

63. 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 clothing.
- Skin irritant .

64. 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.
-

65. (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

66. • 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.

67. 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(proflavine, acriflavine) .
• Exerts a bactericidal and bacteriostatic effect.
• Used in wound antisepsis.

68. 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.

69. Formaldehyde:-
• Aqueous solution containing 37%
formaldehyde (Formalin)
• Paraformaldehyde a poymer (contain
91-99% formaldehde)
- Formalin - used for preserving fresh tissues
- when used in high concentration,
it destroys all organisms, including
spores.

70. -
Used to inactivate virus in theUsed to inactivate virus in the
preparation of vaccines.preparation of vaccines.
-
As a gas – used to decontaminateAs a gas – used to decontaminate
rooms, buildings, fabrics, androoms, buildings, fabrics, and
instruments..instruments..

71. 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. f

72. Causes of sterilization failureCauses of sterilization failure
 Improper loading of sterilization chamberImproper loading of sterilization chamber
 Improper packingImproper packing
 Improper timingImproper timing
 improper temperatureimproper temperature
 Improper cleaning of items to be sterilized.Improper cleaning of items to be sterilized.

73. CONCLUSIONCONCLUSION
• IT IS OUR MOST IMPORTANT DUTY TO PRESERVE AND
MAINTAIN THE HEALTH OF OUR PATIENTS AND
OURSELVES.
• WE AND OUR PATIENTS ARE AT ALARMINGLY HIGH
RISK OF GETTING INFECTED BY DANGEROUS DISEASES
LIKE Hepatitis-B, TB, Herpes, HIV ETC.
• TO PREVENT ALL THESE DEADLY DISEASES AND TO
PROTECT OURSELF WE SHOULD TAKE ATMOST
PRECAUTION BY FOLLOWING STRICT STERILISATION
AND DISINFECTION PROCEDURES.

74. ReferencesReferences
 Text book of microbiologyText book of microbiology
-R.Ananthnarayan & C.K.J.Paniker-R.Ananthnarayan & C.K.J.Paniker
 Infection control & office safetyInfection control & office safety
- DCNA ( 1991 April )- DCNA ( 1991 April )
 Infection controlInfection control
- C.H.Miller- C.H.Miller
 Fundamentals of microbiologyFundamentals of microbiology
- Edward Alcamo- Edward Alcamo
 MicrobiologyMicrobiology
- W.K.Joklik & H.P.Willett- W.K.Joklik & H.P.Willett

75. ReferencesReferences
 Robert.G.cash.-Robert.G.cash.- Trends in sterilization procedures andTrends in sterilization procedures and
disinfection procedures in orthodontic officesdisinfection procedures in orthodontic offices
–– AJODO ;1990.Vol.98AJODO ;1990.Vol.98
 Gerald.E.SmithGerald.E.Smith -Glass bead sterilization of orthodontic-Glass bead sterilization of orthodontic
bands –AJODO; Sept 1986bands –AJODO; Sept 1986
 W.F.Hohlt, C.H. MillerW.F.Hohlt, C.H. Miller- Sterilization of orthodontic- Sterilization of orthodontic
instruments in cassettes - AJODO; Nov 1990instruments in cassettes - AJODO; Nov 1990
 G.M.Mccarthy A.H.MamandrasG.M.Mccarthy A.H.Mamandras - Infection control in the- Infection control in the
orthodontic office in Canada - AJODO Sept.1997orthodontic office in Canada - AJODO Sept.1997

76. Thank youThank you