M2: Sterilisation & Disinfection Flashcards
Define Sterilisation
Removal or inactivation of all micro-organisms from an article including viruses, bacteria & fungi
Define Disinfection
Removal or inactivation of some micro-organisms from an article
Define Antiseptic
Substance which destroys or inhibits the growth of micro-organisms
(e.g. open wounds or abrasions)
Define Asepsis
State of being free from living organisms.
Define Cleaning
- Soil-removing process
- Removes high proportion of micro-organisms present
- Widely applied prior to sterilisation and disinfection.
What are the 4 main methods of sterilisation?
- Heat
- Irradiation
- Gas
- Filtration
Influencing factors for heat sterilisation (5)
- Temperature
- Time
- Number of organisms
- Species and spore-forming ability of the micro-organisms
- Nature of the contaminated material
What is moist heat?
- Used for cleaning instruments
- Highly effective (better than dry heat)
- Requires temps above 100 degrees
- Uses autoclave
Name some dry heat methods
- Incineration
- Red heat
- Heating
- Hot air steriliser
- Microwave ovens (not reliable)
Comment on the heat and time required between dry and moist air
With moist air you can use a lower temperature for a shorter time to sterilise
What is irradiation?
What is it used for?
- Ionising radiation including gamma rays, x-rays and accelerated electrons
- Used for commercial sterilisation of single-use items e.g. plastic syringes
What is the gaseous process of sterilisation?
What is it used for?
An example is ethylene oxide
- Highly penetrative and non-corrosive
- Used for commercial sterilisation of single use items.
What are sterilisation indicators used for?
- Used to determine whether sterilisation has occurred (e.g. inside autoclave)
How do biological sterilisation indicators work?
- Usually cultures of Bacillus spp
- After use, the strips are cultured in media and any growth is indicative of sterilisation failure
How do non-biological sterilisation indicators work?
Autoclave tape and Brownes’ tubes show apparatus reached correct temperature
What are the 5 main methods of disinfection?
- Moist heat
- UV Radiation
- Gases
- Filtration
- Chemicals
What factors influence chemical disinfection?
- Concentration
- Number, type and location of micro-organism
- Temp and pH of treatment
- Presence of external substance
What are the main classes of disinfectants
- Alcohols
- Aldehydes
- Biguanides
- Halogens
- Phenolics
- Peroxygenated compounds
- Surface-active agents
What are the 3 main sources of infection in the dental surgery
- Patients suffering from the infectious
disease - Patient in the prodromal stage of certain infections
- Individuals who are carriers of pathogenic micro-organisms
What are the 3 main sources of infection transmission in the dental surgery
- By direct contact of tissues with skin or body fluids
- By droplets containing infectious agents
- Via contaminated instruments which have not been rendered safe for reuse
What is autoclave?
What are the advantages pf this?
What are the disadvantages of this? (2)
- Steam under pressure
- Running cost is low
- Apparatus is expensive
- Rust possible
What is chemiclave?
What are the advantages pf this?
What are the disadvantages of this? (4)
- Various microbicidal substances at high temperatures, usually in vapour form
- Does not rust dental instruments
- Long cycle time
- Vapours may be harmful
- Machine need careful maintenance
- Chemical involved are expensive
What is hot air oven?
What are the advantages pf this?
What are the disadvantages of this? (4)
- Hot air used
- Very cheap to run
- Long cycle
- Not reliable even when fitted with circulatory fans
- Damages instruments
- Sterilisation cycles can be interrupted
