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