Theme 10 - Sterilisation

Question 1

How have antiseptics evolved?

Answer 1

• 3000 BC used pitch and tar - Egyptians used resins for embalming
• 1881 Koch devised first non pressure steam steriliser
• late 1800s surgical instruments design changed as antiseptic and aseptic techniques normal now
• 1968 - Earle Spaulding made reccomendations about disinfection and sterilising instruments according to use
• 1994 William Rutala worked with CDC to characterise and idea method of sterilisation

Question 2

Earle Spaulding’s 3 classifications of instruments and equipment

Answer 2

• critical
• semi critical
• non critical

Question 3

What is a critical instrument?

Answer 3

• penetrates mucous membranes or has contact with blood/saliva, bone and high risk of infection

Question 4

What is a semi critical instrument?

Answer 4

• contacts with mucous membranes
• doesn’t penetrate soft tissues

Question 5

What is a non-criticial instrument?

Answer 5

one that undergoes manual cleaning disinfection

Question 6

Define ‘decontamination’

Answer 6

the process of rendering an object or area free of danger from contaminants

Question 7

Define ‘disinfection’

Answer 7

• process of killing or removing most but not all viable organisms

Question 8

Define ‘sterilisation’

Answer 8

• saturated steam under pressure delivered at highest temp
• eliminates or kills all forms of life including transmissable agents such as viruses, bacteria and spores

Question 9

Chemical methods of disinfection

Answer 9

• liquids like alcohols, aldehydes, phenolic, halogens, surface active agent, dyes

Question 10

What is needed from disinfectant?

Answer 10

• kills microorganisms on inanimate object/surfaces
• inhibits growth/ germination of pathogenic microorganism
• fast acting even with bodily fluids
• easy to prepare and stable in light and heat
• easily penetrated without discolouring/damage
• inexpensive
• no unpleasant odour

Question 11

What do we use for surface disinfection?
What is disinfected?

Answer 11

• wipe sprays - acticohl solution (1:1000)
• chairs, lights, brakcet tables, spittoons, work surfaces, X-ray units, light curing units

Question 12

Why is the light curing unit disinfected not sterilised?

Answer 12

• too sensitive or large to sterilize

Question 13

What is used for skin disinfection?

Answer 13

• antiseptics anti microbial
• hand washing
• chlorhexidine mouth wash before surgery
• cleaning root canals, dry sockets

Question 14

Explain immersion

Answer 14

• liquid disinfectant
• 3-30 minutes
• for impressions, removable restorations like dentures, crowns
• washer disinfector pre sterilization

Question 15

2 methods of sterilization

Answer 15

• physical
• chemical

Question 16

Explain physical sterilization

Answer 16

• sunlight
• heat (dry heat, incineration, flaming, hot air OR moist heat autoclave)
• radiation

Question 17

Explain chemical sterilization

Answer 17

• liquid - formaldehyde or glutaraldehyde

Question 18

Uses of dry heat - hot air oven

Answer 18

• pre-packed sterile materials sensitive to moisture
• like cotton wool rolls, gauze, paper points, surgical instruments

Question 19

Cycle of dry heat - hot air oven

Answer 19

• 121 degrees for 6 hrs
• 160 degrees for 2 hrs
• 171 degrees for 1 hr

Question 20

How is the autoclave so effective?

Answer 20

• moist heat
• in the form of pressurised steam it’s the most reliable method of killing all bacterial life
• penetrates materials more rapidly than dry heat

Question 21

Types of autoclave

Answer 21

• type N - downward pressure
• Type S - vacuum
• type B - vacuum

Question 22

Uses of autoclave

Answer 22

• unwrapped items
• solid and hollow items
• porous loads like gowns and drapes

Question 23

Cycles of autoclave

Answer 23

• 121 degrees for 15 mins
• 134 degrees for 3 mins
• 30 mins total

Question 24

How does the autoclave cycle work?

Answer 24

• water boils and the vapour pressure equals that of surrounding atmosphere
• pressure of gas increases in enclosed vessel, temp increases too
• increase in temp causes water molecules in steam to become more energized
• saturated steam can penetrate materials (agent is the moist heat not the pressure)
• when steam contacts cooler surfaces it condenses to water and gives up latent heat to it
• reduction in steam sucks more steam into site and process continues until temp of objects is raised to temp of steam

Question 25

Chemical sterilization is also called …

Answer 25

cold sterilization

Question 26

How does chemical sterilization work?

Answer 26

• instruments immersed in glutaraldehyde solution
• up to 6hrs

Question 27

2 types of radiation used

Answer 27

• non-ionising
• ionising

Question 28

What is non-ionising radiation?

Answer 28

• low energy radiation
• produced by UV lamps

Question 29

What is ionising radiation?

Answer 29

high energy, gamma rays, x-rays

Question 30

Radiation sterilization is used in what?

Answer 30

industry for drugs and antibiotic sterilization

Question 31

Decontamination cycle

Answer 31

• stores used
• picked up
• cleaned and sorted
• washer disinfector
• inspection and protein testing
• sorting and packing
• sterilization
• packed on trollies

Question 32

What stages are added to sterilization of handpieces?

Answer 32

• stored
• cleaned
• washer disinfector
• packed
• sterilized
• SENT TO CURATOR
• cleaned
• washer disinfector
• packed
• RE-STERILIZED