1. ‫بسم ا الرحمن الرحيم‬
STERILIZATION
Prof. Khalifa Sifaw Ghenghesh
Dept. of Medical Microbiology,
Faculty of Medicine, Tripoli University
Tripoli - Libya

2. ?What is Sterilization
• The removal of all forms of living
material.
• Important: First Objects to Be
Sterilized Should Be Cleaned by
Washing.

3. METHODS OF STERILIZATION
1. DRY HEAT
– Red Heat
– Hot - Air Oven:
• 160o/ 60 minutes
• 180o/ 20 minutes
2. MOIST HEAT:
– Tyndallization: > 100oC/ 30 minutes
On 3 Consecutive Days.
– The Autoclave: > Pressurized Steam.
• 121oC/ 1.1 bar for 15 minutes.
• 134oC/ 2.2 bar for 3 minutes.

6. • TESTS FOR AUTOCLAVE FUNCTION
– The Bowie-Dick Autoclave Tape Test:
– Browne's Tubes:
– Automatic Controls or Pen Records:
– Bacteriological Tests (Spore Tests):

7. • 2. IRRADIATION
• i. Ultra - Violet Radiation (UV):
– a. Not Recommended.
– b. Poor penetration in Air.
– c. Suitable to Reduce Microbial Counts
in Safety Cabinets.
• ii. Gamma - Ray Radiation
– Source: Cobalt 60.
– a. Lethal to All Forms of Microbial
Life.
– b. Used Commercially.

8. • 3. FILTRATION
– Bacterial Stopping Filters.
• 4. GASES
• i. Ethylene Oxide Gas:
– a. Ventilators.
– b. Toxic & Explodes When Mixed
with Air.
• ii. Formaldehyde:
– a. Rooms and Lab. Cabinets.

9. • 5. LIQUIDES:
– Disinfectants.
• i. Glutaraldehyde:
– a. Sterilizing Heat Sensitive Pieces
of Equipments.

10. Forms of Sterilization by Heat and Principle Uses.
_______________________________________________________________
Type of Heat
Use
_______________________________________________________________
DRY:
1. Red Heat.
Microbiological Loops. Incineration of Used
Lab. Culture Plates.
2. Hot - Air Oven.
Many Surgical & Dental Instruments but
Not
Fabrics or Rubber.
---------------------------------------------------------------------------------------------------------
MOIST:
1. Steam at 100oC
On 3 Consecutive Days.
2. Pressurized
Steam (Autoclave).
Some Bacteriological Media.
Most Surgical and Dental Instruments,
Fabrics & Dressings (If Wrapped); Most
Microbiological Media & Glassware.
_______________________________________________________________

11. Heat Content of Water and Steam
_______________________________________
Phase
Temp.
Heat Content (kJ/kg)
of
oC
Sensible Latent
Total
Water
Heat
Heat
Heat
----------------------------------------------------------------Liquid
100
419
0
419
Vapour 100
419
2257
2676
Vapour 121
509
2199
2708
Vapour 135
567
2160
2727
_______________________________________

12. • PROPERTIES OF STEAM
– i. Moisture content
– ii. Heat content
– iii. Penetration

13. PRESSURE STEAM STERILIZERS
1. Porous Load Sterilizers (Prevacuum type):
• Removal of air and heating of the chamber.
• Sterilization of the load.
• Removal of steam and drying of the load by
mechanical evacuation.
• Admission of filtered air to restoration
atmospheric pressure.

14. 2. Downward Displacement Jacketed
Sterilizers:
• Gradual displacement of air by incoming
steam while the chamber is heated to the
selected sterilizing temp.
• Sterilization of the textile packs for
30 min/ 121oc.
• Drying of the load by partial vacuum.
• Restoration of the chamber to
atmospheric pressure.

15. 3. Unwrapped Instrument and Utensil
Sterilizers:
• DSL autoclaves
4. Fluid Sterilizers:
• e.g. water, iv solutions, etc.

16. • Factors influencing sterilization
time for fluids:
– rate of heating of the chamber:
– type of container:
– viscosity of the liquid:
– volume of the liquid:
– trapped air:

17. "‫"بسم ا الرحمن الرحيم‬
DISINFECTION AND DISINFECTANTS
Prof. Khalifa Sifaw Ghenghesh
Dept. of Medical Microbiology,
Faculty of Medicine, Al-Fateh University
Tripoli - Libya

18. Disinfection
• The removal of most of the
pathogenic microorganism, but
often non-pathogenic or resistant
forms of pathogens remain.

19. Methods of Disinfection
• A. Cleaning
• Instruments with high risk organic
material >>
• Treat with strong disinfectant >>
Cleaning >> Sterile or dispose of.

20. B. Disinfection by Heat
i. Pasteurization
ii. Boiling water
iii. Flaming off alcohol
C. Physical Methods
• Ultrasonics
Ultrasonic vibration >
Disrupte microorganisms
e.g. Ultrasonic scalers.

21. D. Chemical Disinfectants
Denaturing protein or lipid
Act: Disrupting the biosynthetic pathways
I. Phenols
•
•
•
•
Clear phenolic solutions:
Black and White Phenolic Compounds:
Chloroxylenol: (Dettol)
Hexachlorophane: Pre-operative scrub

22. II. Halogenic Compounds
• Hypochlorites: Effective > HBV
• Iodine + Alcohol
Pre-operative skin antiseptic.
• Bovidone Iodine:
an anti-plaque agent.

23. III. Aldehydes
• Formaldehyde
• Gluteraldehyde
• Alcohol
-----------------------
Antiseptics
• Are bacteriostatic agents that can
be used on skin and mucosal
surfaces.

24. IV. Diguanides
• Chlorhexdine
0.5% + 70% alcohol >>> Skin
disinfectant
• Chlorhexidine gluconate
Treatment of oral candidosis + oral
ulceration

25. V. Quaternary Ammonium Compounds
• Cetrimide
VI. Organic Dyes
• e.g. gentian violet

26. • Factors Affecting the Effectiveness
of Disinfectants:
• Tests of the Proper Functioning of
Liquid Disinfectants:
" In-use" Tests.

27. Storage of Sterile Instruments
• Never store instruments in liquid
disinfectants.
Waste Disposal
Special Problems
• HBV, HCV and HIV (AIDS)

28. Sterilization and Disinfection
in Dentistry
• Sterilization >>> Autoclave.
• Dental instruments can and should be
autoclaved after each patient.
• Nozzles of air and water spray: ??