This document discusses sterilization, asepsis, and disinfection. It begins by defining key terms like sterilization, disinfection, and antisepsis. It then discusses the history of asepsis, highlighting pioneers like Semmelweis, Lister, Pasteur, and Bergmann. The document categorizes sterilization methods into physical agents (e.g. heat, radiation) and chemical agents (e.g. phenols, aldehydes, halogens). It describes various sterilization techniques in detail, like autoclaving, dry heat, filtration, and chemical disinfection. Finally, it discusses factors that determine disinfectant potency and ideal properties

1. STERILIZATION AND ASEPSIS

2. Specific Learning Objectives
• To differentiate between various terminologies such as
asepsis, sterilization and disinfection
• To understand the evolution of antisepsis and
disinfection
• To classify and describe the various methods of
setrilization and disinfection
• To understand gloving, gowning and fumigation of
operation theatres
• To explain the universal precautions and protol for
needle stick injury in HIV and Hepatitis B infections

3. INTRODUCTION:
Sterilization : the process by which an article, surface
or medium is freed of all living micro-organisms
either in the vegetative or spore state.
Disinfection : destruction or removal of all
pathogenic organisms or organisms capable of
giving rise to infection
Anti-sepsis : prevention of infection usually by
inhibiting the growth of bacteria in wounds or
tissues

4. HISTORY OF ASEPSIS
Zaccharias Jansen in 1590 and Robert Hooke in 1660 opened the world of
microbes to mankind by their inventions of microscopes
Anton Van Leeuwenhoek :a tradesman and scientist from Netherlands
“Animolecules” in 1667 through his handcrafted microscope. Microbes became
visible when he observed tooth scrapings and gutter water under a simple
microscope.
• Semmelweis (1847) – washing hands prior to delivery reduced puerperal fever
• Lister (1865) –suggested carbolic acid as an antiseptic
•Pasteur and John Tyndall used boiling water to kill bacteria and the process
was known as Pasteurization
• Ernst von Bergmann (1880) – introduced autoclave
•Further acceleration in the field of sterilization, disinfection and infection
control progressed when finally in 1890’s the advent of Steam sterilizers, Sterile
gowns, drapes and Gloves emerged.

5. CLASSIFICATION
PHYSICAL AGENTS:
1) SUNLIGHT
2) DRYING
3) DRY HEAT
a) Flaming
b) Incineration
c) Hot Air
4) MOIST HEAT:
Pasteurisation,
Boiling, Steam Under
Normal Pressure,
Steam Under Pressure.
5) FILTRATION:
Candles, Asbestos
Membranes.
6) RADIATION
7) ULTRASONIC AND
SONIC VIBRATIONS
CHEMICAL AGENTS:
1) ALCOHOLS
2) ALDEHYDES
3) DYES
4)HALOGENS
5) PHENOLS
6) SURFACE ACTIVE
AGENTS
7) METALIC SALTS
8) GASES

6. IDEAL PROPERTIES
An ideal antiseptic or disinfectant should:
1) Have a wide spectrum of activity and be effective against all micro
organisms
2) Be active in the presence of organic matter
3) Be effective in acid as well as alkaline media
4) Have speedy action
5) High penetrating power
6) Be stable
7) Be compatible with other antiseptics and disinfectants
8) Not corrode metals, not cause local irritation or sensitization
9) Not interfere with healing
10) Non toxic if absorbed into circulation
11) To be cheap and easily available
12) Be safe and easy to use

7. FACTORS THAT DETERMINE THE
POTENCY OF DISINFECTANTS
• Concentration of the substance
• Time of action
• pH of the medium
• Temperature
• Nature of the organism
• Presence of extraneous material

8. MODES OF ACTION
• Protein coagulation
• Disruption of cell membrane
• Removal of the free sulphydryl groups
• Substrate competition

9. Physical Agents
SUNLIGHT
 Bactericidal activity
 Under natural conditions
Action: primarily- UV rays
DRYING
 4/5th by wt bacterial cell-water
 Drying-deleterious effect on bacteria
 Unreliable &theoretical interest
 spores are not effected

10. HEAT
 Most reliable method
 Factors influencing:
a. Nature of heat
b. Temperature & time
c. Number of microorganisms present
d. Characteristic of organisms
e. Type of material

11. I. Dry heat
(principle:denaturation of
protein)
1) Flaming:
tips of the instrument held in the
bunsen flame till red hot.
• Indications:
loops/ innoculating wires/forcep
points/ scalpels/needles.
• Disadvantage:
• Not completely sporicidal.
• Restricts the number and size of
instruments.

12. 2. Incineration:
Destruction of materials –
 Soiled dressings
 Animal carcasses
 Bedding
 Pathological materials
 Plastics-PVC, polythene
 Except polystyrene.

13. 3. Hot Air Oven:
 Pastuer-1876
 Holding period-160c-1hr
 Sterilizes-glassware, forceps,
scissors, scalpels, all-glass syringes, swabs, liquid
paraffin,
• Disadv: .dry heat- bad conductor
• poor penetration
• spore resistance
 Control: Clostridium tetani

14. MOIST HEAT
 Temperature <100c
 Pasteurization of milk:
holder method -63c-1/2hr
flash method -72c-15-20 sec
Cooling quickly -13c or lower

15. Temperature at 100c:
Boiling:
 vegetative bacteria-90-100c
 hard water-not to be used
 2%NaHCO3-increases boiling point
of water.

16. Steam at atmospheric pressure 100c
• Also known as compressed or saturated steam
• This is an inexpensive method using a Koch or Arnold steamer.
• Principle
• steam under pressure is hotter
• higher the pressure the higher the temperature
• Liquids were sterilized by this method at 1000C for 30min on each of 3
successive days.
• Also called Fractional sterilization, because a fraction was accomplished on
each day.
• Also called Tyndallization after its developer John Tyndall, and
Intermittent sterilization because it has a stop and start operation.

17. • During the first day’s exposure, steam kills virtually all organisms except
bacterial spores and it stimulates spores to germinate into vegetative cells.
• During overnight incubation the cells multiply and are killed on second day.
• Again the material is cooled and a few remaining spores germinate only to be
killed on the 3rd day.
“This method also fails because thermophils and certain spores ( eg., some
anaerobes ) fail to germinate. A suitable medium for germination such as
broth is required”.
Tyndallisation or Intermittent sterilization…

18. AUTOCLAVE
STEAM UNDER PRESSURE:
* Principle: water boils when its vapour pressure equals that of the surrounding
atmosphere.
* Saturated steam has penetrative power. when steam comes in to contact with
a cooler surface it condenses to water and gives up its latent heat to that
surface .
*Reduction in volume sucks in more steam to the area and the process
continues till temperature of surface = steam. The condensed water ensures
moist conditions for killing the microbes present.
*Temperature: between 108 ° C and 147 °C (121 °C)
* Pressure: 15psi
* Duration: 20 mins
* Items: Dressings , instruments, gloves, laboratory ware, media and
pharmaceutical products

19. PRINCIPLE…..
Dry saturated steam
Meets cooler surface
Gets condensed into water
Denat. of proteins
Latent heat lib. Membrane dmg
16OO ml steam at 100 oC Leakage of cellular cont.
& at atmospheric pressure condenses Chromosomal dmg
into 1ml H2O → 518 cal heat Enzyme coagulation.

20. As the water molecules in steam become more energized, their
penetration also increases
Same principle is used in home pressure cooker.
It is important to note that sterilizing agent is moist heat but not the
pressure.

22. Settings for general wrapped items:
• Temp. - 121 degree C Pressure - 20 PSI
• Time -- 30 min Setting
Settings for bottled solutions:
• Always vent bottles to avoid bursting!
• Temp. - 121 degree C Pressure - 20 PSI
• Time -- 30 min Setting
Setting for "Flashing" an unwrapped instrument:
• Temp. – 132 degree C Pressure - 30 PSI
• Time -- 4-7 Min Setting
Recommended Cycles

23. This method can be used for a broad variety of items such as
instruments, clothing, glassware, cotton etc.
Limitations :
Plastic ware melts in high heat
Sharp instruments become dull and corrode
Many chemicals breakdown during the sterilization process, and
oily substances cannot be treated since they do not mix with
water.

24. Several types of steam sterilizers are in use:
• Laboratory autoclaves
• Hospital dressing sterilizers
• Bowland instrument sterilizers, and
• Rapid cooling sterilizers
(even the domestic pressure can be used as a
sterilizer).

25. Pre-vacuum Autoclave
• A new form of autoclave called the
Prevacuum autoclave has been
developed, which draws air out of
the chamber at the beginning of the
cycle. The major advantage of this is
minimal exposure.
• In the absence of air, steam is able
to penetrate to all instrument surfaces, including inside the narrow
lumens of hollow instruments such as dental handpieces and
scopes.

26. Unsaturated Chemical Vapour Sterilization
This system depends on heat, water and chemical combination for it’s efficacy
The temperature and pressure required is greater than that for autoclave
It is known as a Chemiclave
Instead of distilled water a solution of alcohol, formaldehyde, ketone, acetone
and water is used to produce the sterilizing vapor
Temperature : 1310C at 20 pounds pressure for 20 to 40 minutes

27. STERILISATION CONTROL
* For determining the efficacy of moist heat
sterlisation , spores of bacillus
stearothermophilus are used as the test
organism.
Chemical indicators , autoclave tapes and
thermocouples may also be used instead.

28. FILTRATION
To remove bacteria from heat labile liquids
-sera, sugar solutions & antibiotics.
Types:
a. candle filters:
i. Unglazed ceramic filters
ii. Diatomaceous earth filters
b. Asbestos filters:
c. Sintered glass filters
d. Membrane filters

29. Radiation
Ionizing
• X ray, gamma, beta rays.
• Use : plastics,culture
plates,catheters,tubes,
swabs
• Adv : large scale use.
• Disadv :sporicidial effect ?
Non ionizing
• Infra red, UV radiation
• Use: syringes,
catheters (IR)
entry ways/OTs/lab
(UV)
• Disadv: longer
wavelength hence poor
penetration

30. Chemical agents

31. I. Phenols
1.Carbolic acid/phenol:
• Mech of action:* membrane damage.
* protein precipitation
* protoplasmic poison.
Disadv:* highly caustic
* poor sporicidial.

32. 2.Hexachlorophene:
Uses: .skin disinfectant
.Presurgical showers for patients/surgeons.
.prophylaxis against staphylococcal
infection in nurseries.
Advantage: stays on the skin surface for longer time
disadvantage: absorption by skin barrier in neonates at
high concentrations

33. 3.CHLOROXYLENOL
• Non corrosive, non irritant
• 4.8 % + 9 % terpinol + 13 % alcohol 
DETTOL
4.CRESOL
• 3-10 times more active than carbolic acid
• 50% soapy emulsion  LYSOL

34. II. ALCOHOLS:
(mech of action: denaturation of bacterial protiens)
a. Ethanol
b. Isopropyl alcohol 70%-90% conc volatile
c. Methyl alcohol
used for quick drying
thermometers/trolley tops on physically clean
cabinets/incubators surfaces.
Disadvantage : . inflammable  caution during diathermy
. Mucus membrane irritant.
. Organic enviornment slows action.
. Promotes rusting.

35. III. Aldehydes
(active against amino group in protien molecule)
1.Formaldehyde:
bactericidial/sporicidial(?)/viricidial.
• Liquid form : formalin(37% soln)
10% formalin + 0.5% Na tetraborate used for clean
metal instrument….eg. Endoscope,dialysis equipment.
• Vapour form: fumigation of wards/corridors/ICUs
• Formaldehyde releasing agents:.noxythiolin(Rx peritonitis)
. taurolin

36. 2.Glutaraldehyde/Cidex (2% alkaline NaHCO3):
• Prolonged action
• Posseses high microbicidial activity against bacteria, spores,
yeasts, fungi, tubercle bacilli and
• Less toxic n irritant to the eyes & skin than formaldehyde
• Exposure time: > 10hrs.
catheters.
common uses .heat labile instruments polythene tubes.
. Bronchoscopes. endotracheal tube.
. Endoscopes.
. clean metal instruments.
. Face masks.

37. III Gases/vapour based disinfectants
1.Ethylene Oxide:ETO gas.
(action: alkylation of Amino-hydroxyl-sulphydryl groups in
bacterial protien)
• Advantage: readily absorbed in water/organic solvents,
rubber/plastics/oils.
• Disadvantage: . inflammable in >3% conc(mix with CO2).
. Mutagenecity/carcinogenic…toxic hazard.

38. 2.Formaldehyde:
procedure:
• windows & outlets are sealed.
• 150gms of KMnO4 added to 280ml formalin for every
1000cft.
• Considerable heat & vapours generated.
• Doors kept closed for 48hrs.
3. beta-Propiolactone / BPL( 0.2% ):
• More efficient than formaldehyde….but more
carcinogenic at the same time.

39. V. Biguanides:
Chlorhexidine:
• available as dihydrochloride,diacetate,gluconate.
• wide range of activity against gm+/- organisms.
• low activity against spores/viruses(Curd et al
1946).
• More active in a alkaline pH and activity reduced
in presence of soaps.

40. IV. Surface active agents
3 types:
• anionic  ordinary soaps.
• cationic  quats  cetrimide&benzalkonium chloride.
• non ionic
uses: wetting agents/emulsifiers/detergents.

41. Chemical agent Effectiveness against
Endospores Mycobacteria
Phenolics Poor Good
Quats None None
Chlorines Fair Fair
Alcohols Poor Good
Glutaraldehyde Fair Good

42. V. Dyes:
a) aniline dyes and b) acridine dyes
Used extensively as skin and wound antiseptics
(bacteriostatics in high dilution but of low
bactericidal activity).
Gm+ve>>Gm –ve
No activity against tubercle bacilli.
Lethal effects on bacteria are due to their
reactions with the acid groups in the cell.

43. VI. Halogens:
1) Iodine in aqueous and alcoholic solutions has
been used as a SKIN DISINFECTANT.
Active bactericidal agent with a moderate activity against spores,
tubercle bacillus and number of viruses. Compunds of iodine
( iodophores) are more active than aqueous or
alcoholic soln.
2) Chlorine and hypochlorites are markedly bactericidal.
They have a wide spectrum of activity against viruses.
* The organic chloramines are used as antiseptics for dressing
wounds.

44. VII Metallic salts:
Salts of silver, copper, and mercury are used as
disinfectants.
Protein coagulants and have the capactiy combine with
free sulphydyrl groups of cell enzymes.
Organic compounds, thio mersal, phenyl mercury nitrate
and mercurochrome are less toxic and are used as mild
antiseptics and marked bacteriostatics, limited
fungicidal and weak bactericidal activity.

45. MATERIAL METHOD
All suture materials (except
Catgut)
Autoclave , Glutaraldehyde
Catgut Ionising Radiation
Preservatives for gut sutures Isopropyl Alcohol
Surgical needles and suture
materials in manufacturing
unit
Gamma radiation
Rubber gloves, surgical
instruments
Autoclave
Forceps, scalpel, scissors Hot Air Oven
Disposable syringes Ethylene oxide
Operation theatres Fumigation with
formaldehyde

46. CLASSIFICATION OF INSTRUMENTS
• CRITICAL - objects which enter normally sterile tissue or the
vascular system or through which blood flows.
Scalpels, scalers, surgical forceps, burs, explorers, chisels etc
Steam (autoclave), dry heat, chemical strilization
• SEMICRITICAL - objects that contact mucous membranes or
non intact skin.
Impression trays, amalgam condensors, anesthesia equipment
Sterilization/high level disinfection
• NONCRITICAL - come in contact with intact skin but not
mucous membranes. Intact skin - barrier to most organisms.
BP cuff, restorative materials, varnish, liners, bed pans etc
Alcohols, phenols, iodophores, household bleach

47. UNIVERSAL PRECAUTIONS
• CONCEPT:
To address the inability of health care providers to specifically
identify all patients with communicable diseases.
THEORY:
protection of self , staff and patients from contamination by using
barrier techniques when treating all patients as if they all had a
communicable disease ensures that everyone is protected from those
who do have an infectious process.
COMPONENTS:
1. All doctors and staff who come in contact with patients blood or secrtetions ,
whether directly or in aerosol form , wear barrier devices including face mask eye
protection and gloves
2. decontaminating or disposing of all surfaces that are exposed to patient blood
tissues and secretions .
3. avoidance of touching and thereby contaminating surfaces ( eg: dental record ,
telephone, etc.,) with contaminated gloves or instruments.

48. PERSONAL BARRIER PROTECTION
GLOVES:
• All clinical personnel must wear treatment
gloves during all treatment procedures.
• After each appointment , or if leak is detected ,
remove gloves, wash hands and put on fresh gloves.
• Instead of attempting to wash gloved hands before
opening drawers or handling items adjacent to the
operatory, use tongs , a paper towel, or a food handler’s
over glove, to prevent contamination.
• All personnel with weeping or draining lesions that
could infect patients abstain from patient contact.

49. • Gloves that become penetrated or torn can
imbibe patient fluids and therefore should be
removed.
• Viruses have been found to penetrate not more
than one intact latex gloves out of hundred.
Double gloving prevents perforations of the
inner glove and therefore, adds protection.
• Latex gloves must have less than four percent
leak detectable water test. While handling sharp
instrument wear puncture resistant utility gloves.
• Nitrile latex gloves can be washed inside and
out, disinfected or steam autoclaved

51. PROTECTIVE MASKS AND HAIR PROTECTION.
• wear masks to protect against heavy spatter ,blood
droplets. Change the mask between every patient or
whenever it becomes visibly soiled or moist.
• masks with highest filtration are rectangular, folded
types used for surgeries.
• hair can trap heavy contamination hence should be
kept out of the treatment field by a protective head
cap.

52. PROTECTIVE OVER GARMENTS
• for protection of clothing and skin , sleeves
with knit cuffs that tuck under gloves are
preffered.
• Wearing contaminated garments home or out
of the clinical area should not occur.
• hot water up to 70 c or cool water containing
50 to 150ppm of chlorine provided by liquid
laundry bleach would provide more
antimicrobial action. Use of a hot air dryer and
/or ironing is also beneficial

53. SCRUB PROCEDURE
• The recommended scrub procedure for a particular operating
room is usually posted in the scrub area. The initial scrub
usually encompasses the following routine.
1. rinse hands and forearms with water, then wash with soap.
2. cleanse nails with an orange wood stick or nail cleanser
contained in scrub packs.
3. Start 10 minute scrub and work to an abundant lather, using
either brush or sponge. The palms, backs of hands, and fingers
are scrubbed first then the forearms. Scrub one hand and arm
and then the other.
4. when rinsing, raise both hands so that water will run down
and off at the elbows.
5. When the 10 minute scrub is finished , raise hands and prepare
to enter operating room.

55. PREPARATION FOR INTRAORAL
PROCEDURES
1. Make sure that all anesthetic equipment is cleared from the
operative site.
2. Prepare the peri-oral regions first starting at the corner of the
mouth and working outward to the cheek , once at the
periphery, do not return to the starting point.
3. With a freshly dampened sponge, repeat this process on the
other side of the face.
4. the inside of the mouth may be cleansed. Although the mouth
is not a sterile area and cannot be sterilized, some surgeons
prefer at least to sponge out the mouth prior to surgery
5. When the preparatory procedure is completed, the circulating
nurse will take the cup and sponge stick

56. PREPARATION FOR EXTRAORAL
PROCEDURE
• the night before surgery the patient should wash the area from
the level of the zygomatic arch superiorly to the clavicle
inferiorly.
• the preparation should extend from just past the midline to the
posterior auricular area.
• in the operating room, the area should be washed with surgical
soap for two to three minutes.
• wash soap off with gauze saturated with water.
• Repeat washing with surgical soap for about five minutes.
• Skin may then be covered with tincture of zephiran.
• The patient may be draped

58. DRAPING THE PATIENT
• after the preparation is completed, the patient is
draped.
• the simplest method of draping is the “ four towel
and thyroid drape” . Where thyroid drapes are not
available, a large body sheet may be used in
conjunction with a cystoscopy drape.
• In the technique , the towels are applied first then the
body sheet, and finally the cysto sheet.
• In both techniques , the only visible area left is the
operative site

61. STERILE TECHNIQUE:
1. when the scrubbing is completed, keep the arms and hands
raised.
2. when the gown and gloves are on, do not drop hands below
waist level or raise above the head.
3. Remember the back of the operating gown is not sterile. Do
not reach behind anyone.
4. When passing another gowned person, pass back to back.
5. when standing at the table, keep hands on sterile drape that
covers the patient (do not exert pressure because this may
interfere with respiration).
6. Do not touch mask or cap. If adjustment is necessary, ask the
circulating nurse.
7. Do not break the scrub ( take off gloves, etc.) until surgery has
been completed.

62. HBV RISKS FOR CLINICAL PERSONNEL
DATA RELATED:
1. Rate of cross infection is found to be 30%.
2. HBV is found in 1 of 100 to 500 persons in general
population.
3. Even only 1000³ virions per ml of blood of HBV is
capable of transmitting the disease
4. HBV is found to be resistant to dessication and
chemical disinfectants like alcohols , phenol, etc.,
5. Up to 90% of HIV infected patients have been infected
with HBV
Whether infected persons are symptomatic or not , they
can
transmit HBV infection .
6.. Mortality rates from HBV infection is 6.6 times to that of
HIV.
7. HBV is found in small concentrations in saliva and can be
transmitted by contamination of broken skin , mouth, or
eyes with blood contaminated saliva.

63. HIV RISK FOR CLINICAL PERSONNEL
DOCUMENTED DATA RELATED TO HIV :
Rate of cross infection is 0.3% .
1. unlike HBV , very low levels of HIV are found in
blood of infected patients.
2. in dried , infected blood 99% of HIV is found
inactivated in approx 90 minutes. But in wet
conditions virus may survive for two or more days.
3. HIV is killed by all methods of sterilization in less
than 2 minutes ( exception quarternary ammonium
compounds)
4. HIV can be transmitted by heavily splattered or
splashed blood contaminated fluids, but aerosols are
not found to transmit HBV or HIV .
5. Barrier techniques have great successful rates in
decreasing incidence of HIV infection.

64. PRECAUTIONS:
1. Follow universal precautions.
2. Protect eyes , mucosa , skin and hands from splatter and direct
contact with blood and blood contaminated body fluids during
dental treatments of all patients.
3. Precautions to minimize risks of injuries with sharp
instruments.
4. Minimize aerosols to minimize risk of secondary transmissable
respiratory infections like tuberculosis and cytomegalovirus.

65. NEEDLE STICK INJURY PROTOCOL:
1) Significant exposures:
a) contaminated needlestick
b) puncture wound from a contaminated sharp
dental instrument.
c) contamination of any obviously open
wound or mucous membrane by saliva, blood or
a mixture of both.
2) Exposure to the patients blood or saliva on the
unbroken skin is not considered significant.

66. 3) Protocol:
a) immediately clean the wound thoroughly
with soap and water.
b) have the sample of patients blood, drawn on
the same day and test it for HBV and HIV
c) the exposure recipient should also be tested
for anti HBV and anti body to HIV on the same
day of exposure.

67. POST EXPOSURE PROPHYLAXIS FOR HIV:
“No anti retro viral drug has been licensed”
These can be prescribed on an off label basis.
since their use for PEP is outside approved indications.
Recommended drugs- (emergency starter packs)
Zidovudine 250mg-300mg b.d + Lamivudine-150mg b.d.
+ Nelfinavir-1250mg b.d.(750mg tds)
other protease inhibitors:-
Ritonavir boosted Lopinavir
Saquinavir
Amprenavir
Duration: it should be started within 2-24hrs of exposure and not
beyond 48-72hrs. And should be continued upto 4weeks.

68. POST EXPOSURE PROPHYLAXIS FOR HBV
Patients antigen status recipient of exposure
1) HBsAg negative 1)HB vaccine, if not already
received
2) HBsAg positive 2a. Anti HBs positive recipient
no Rx
2b. HB vaccine recipient with
seroconversion no Rx necessary.
2c. HB vaccine without
seroconversion 1 additional dose of
vaccine
2d. Anti HBs –ve recipint:
HBIG starting within 48hrs after
exposure and HB vaccination started within
7 days.

69. Summary
• Sterilization methods are classified into physical and
chemical methods
• Autoclave is the most commonly used method for
sterilization
• Fumigation of clinics/OT/wards is done using
formaldehyde
• Cold sterilization is done using 2% glutaraldehyde
• Always use universal precautions/barrier technique for
all patients

70. References
• Textbook of microbiology- Ananthanarayan and
Paniker 7th edition
• Medical microbiology- Greenwood
• Clinical practices of dental hygienist- Wilkins 9th edition
• Contemporary Oral and Maxillofacial Surgery- 2nd
edition
• Textbook of Oral and Maxillofacial Surgery-
Gustav.O.Kruger 6th edition

71. THANK YOU