Principles and Techniques of Instrument Processing and Sterilization Chapter 21

Question 1

Introduction

Answer 1

One of the most important
responsibilities of the dental assistant is
to process contaminated instruments
for reuse
 Instrument processing involves much
more than sterilization
 Sterilization is a process intended to kill
all microorganisms and is the highest
level of microbial destruction

Question 2

Classification of Patient Care
Items

Answer 2

These categories help determine which
sterilization methods best ensure the
safety of dental care workers and
patients
 Categories are based on the risk of
infection associated with their intended
use
 Classifications are used to determine
the minimal type of posttreatment
processing

Question 3

Classification of Instruments.1

Answer 3

Critical instruments
 Items used to penetrate soft tissue or bone
 Greatest risk of transmitting infection and
must be sterilized by heat
 Semicritical instruments
 Touch mucous membranes or nonintact skin
 Lower transmission risk
 Sterilized by heat or receive minimum high-
level disinfection if not heat tolerant

Question 3

Classification of Instruments.2

Answer 3

Noncritical instruments
 Contact only intact skin
 Low risk of infection transmission
 Cleaned and processed with EPA-registered
intermediate- or low-level disinfectant

Question 4

Personal Protective Equipment (PPE)

Answer 4

You must always use PPE when
processing instruments
 This includes utility gloves, mask,
eyewear, and protective clothing

Question 5

Transporting and Processing
Contaminated Patient Care
Items

Answer 5

The dental assistant may be exposed to
microorganisms through contact with
contaminated instruments or other
patient care items
 Exposure can occur through
percutaneous injury (e.g., needle sticks,
cuts) or contact with the mucous
membranes of the eyes, nose, or mouth

Question 6

Instrument-Processing Area

Answer 6

Should be centrally located in the office
to allow easy access from all patient
care areas
 Dedicated only to instrument processing
 Physically separated from operatories and
laboratory
 Not be part of a common walkway

Question 7

Instrument-Processing Area

Answer 7

Needs good air circulation
 Large enough to accommodate all
equipment and supplies
 The area should not have a door or
windows that open to the outside
because dust may enter the area
 Multiple outlets and proper lighting,
water, and an air line and a vacuum line
for flushing high-speed handpieces

Question 8

Contaminated Area

Answer 8

All soiled instruments are brought into the
contaminated area, the initial receiving area,
where they are held for processing
 Any disposable items that have not already been discarded
in the treatment room are removed from the instrument
tray and disposed of as contaminated waste
 Thorough cleaning should be done before all
disinfection and sterilization processes
 Removal of all debris and organic materials (e.g., blood and
saliva)
 The contaminated area contains clean protective
eyewear and utility gloves, counter space, a sink,
a waste disposal container, holding solution, an
ultrasonic cleaner, an eyewash station, and
supplies for wrapping of instruments before

Question 8

Instrument-Processing Area

Answer 8

A deep sink should have hands-free
control for instrument rinsing and (if
space permits) a foot-operated or other
hands-free trash receptacle
 The flooring should be an uncarpeted,
seamless, hard surface
 The size, shape, and accessories of the
instrument-processing area vary among
dental offices

Question 9

Workflow Pattern

Answer 9

Regardless of the size or shape of the instrument-
processing area, four basic areas govern the
pattern of workflow
 Processing of instruments should proceed in a
single loop, from dirty to clean to sterile to
storage, without ever “doubling back”
 If the instrument-processing area is small, you can
use signs that read:
 “Contaminated items only”
 “Precleaning area”
 “Cleaned items only”
 “Sterile items only”

Question 10

Preparation and Packaging Area

Answer 10

In this area, cleaned instruments and other dental
supplies should be inspected, assembled into sets
or trays, and wrapped or placed in packages for
sterilization
 The preparation and packaging area should consist of counter
space and storage space for sterilized instruments, fresh
disposable supplies, and prepared trays or instrument
cassettes
 Clean instruments are not sterile and could harbor
pathogens
 Instruments must be packaged and sterilized before they are
used on a patient

Question 11

Precleaning and Packaging
Instruments

Answer 11

Instruments may be precleaned in one
of three ways
 Hand scrubbing
 Ultrasonic cleaning
 Instrument-washing machine

Question 12

Holding Solution.1

Answer 12

 If instruments cannot be cleaned immediately
after a procedure, they should be placed in a
holding solution to prevent the drying of
blood and debris on the instruments
 The holding solution may be any noncorrosive
liquid
 A commercial enzymatic solution that partially
dissolves organic debris may be used
 Dishwasher detergent also makes a good
holding solution because it is low-cost, low-
foaming, and readily available
 It is neither cost-effective nor desirable to use
a disinfectant alone as a holding solution

Question 12

Holding Solution.2

Answer 12

The container must have a lid and must
be labeled with:
 A biohazard label (because of the
contaminated instruments)
 A chemical label (because of the
cleaner/detergent)
 The holding solution should be changed
at least twice daily, and even more
frequently if it becomes clouded
 Remember, a holding solution is
necessary only when contaminated
instruments cannot be processed immediately

Question 13

Hand Scrubbing

Answer 13

Hand scrubbing is the least desirable
method of cleaning instruments
because it requires direct hand contact
with the contaminated instrument

Question 14

More About Ultrasonic
Cleaning Solutions

Answer 14

 Do not use other chemicals such as plain
disinfectants in the ultrasonic cleaner
 Some disinfectants can “fix” the blood and
debris on the instruments, making subsequent
cleaning more difficult
 Specific ultrasonic solutions are available for the
removal of difficult materials such as cement,
tartar, stains, plaster, and alginate
 Refer to the instructions of the ultrasonic unit’s
manufacturer regarding the specific solution to
be used
 The ultrasonic cleaning unit should be labeled
with both a chemical label and a biohazard label
because it contains a chemical and

Question 14

Hand Scrubbing Precautions

Answer 14

 Wear goggle-type eyewear and puncture-
resistant gloves, as well as your protective
clothing
 Clean only one or two instruments at a time
 Use only a long-handled brush, preferably
one with a hand guard or wide surface
 Keep items above the waterline; fully
immersing them in a basin of soapy water
interferes with one’s ability to see the sharp
ends
 Allow instruments to air-dry or carefully pat
them with thick toweling
 Never rub or roll instruments while they are

Question 14

Commercial Cleaners

Answer 14

Ultrasonic cleaning solutions come in a
variety of sizes and types
 Packets (1 oz)
 Tablets
 Concentrate solutions
 Ready-mixed gallon containers

Question 14

Ultrasonic Cleaning

Answer 14

 Used to loosen and remove debris from
instruments
 Also reduces the risk of cuts and
punctures to the hands during the
cleaning process
 Puncture-resistant utility gloves, a
mask, protective eyewear, and a
protective gown should always be worn
when the ultrasonic cleaner is being
used
 Keep a set of tongs near the ultrasonic
unit; these can be used to remove

Question 14

Ultrasonic Cleaner

Answer 14

 Works by producing sound waves beyond
the range of human hearing
 Sound waves, which can travel through
metal and glass containers, cause
cavitation (formation of bubbles in liquid)
 Bubbles burst by implosion
 Instruments should be processed in the
ultrasonic cleaner until they are visibly
clean
 Time varies from 5 to 15 minutes,
depending on amount and type of
material on the instruments and the

Question 15

Ultrasonic Cleaning Solutions

Answer 15

Only use ultrasonic solutions that are
specially formulated for use in the
ultrasonic cleaner
 Some ultrasonic cleaning products have
enzyme activity
 Other ultrasonic cleaning products have
antimicrobial activity, which reduces the
buildup of microbes in the solutions with
repeated use
 Antimicrobial activity does not disinfect
the instruments; it merely prevents the
microorganisms from multiplying

Question 16

Care of the Ultrasonic Cleaner

Answer 16

The ultrasonic cleaning solution is
highly contaminated and must be
discarded at least
once a day or sooner if it becomes
visibly cloudy
 When the solution is being changed, the
inside of the pan and lid should be
rinsed with water, disinfected, rinsed
again, and dried
 All PPE should be worn while solutions
are being changed in the ultrasonic
cleaner

Question 17

Testing the Ultrasonic Cleaner

Answer 17

 If you notice that the instruments are not being
cleaned completely with processing in the
ultrasonic cleaner, the unit may not be
functioning properly
 To determine whether the ultrasonic cleaner is
working properly, hold a 5×5-inch sheet of
lightweight aluminum foil vertically (like a curtain)
half-submerged in fresh, unused solution
 Run the unit for 20 seconds, then hold foil up to
the light
 Surfaces that were submerged should be evenly
marked with a tiny pebbling effect over the entire
surface
 An area without pebbling of more than ½ inch

Question 18

Automated Washers/Disinfectors

Answer 18

Look and work similar to a household dishwasher
 Must be approved by the U.S. Food and Drug
Administration
 Use a combination of very hot recirculating water
and detergents to remove organic material
 After washing, the instruments are automatically
dried
 These units are classified as thermal disinfectors
because they have a disinfecting cycle that
subjects the instruments to a level of heat that
kills most vegetative microorganisms
 Instruments processed in an automatic
washer/disinfector must be wrapped and
sterilized before use on a patient

Question 19

Drying, Lubrication,
and Corrosion Control

Answer 19

Instruments and burs made of carbon steel
will rust during steam sterilization
 Rust inhibitors such as sodium nitrate and
commercial products can be used to help
reduce rust and corrosion
 An alternative to a rust inhibitor is to dry
the instrument thoroughly with the use of
dry heat or unsaturated chemical vapor
sterilization (discussed later), which does
not cause rusting

Question 20

Packaging Materials

Answer 20

Sterilization packaging materials and
cassettes are medical devices and
therefore must be FDA-approved
 It is of critical importance to use only
products and materials that are labeled
as “sterilization” packaging
 Never substitute products such as
plastic wraps, paper, or zipper-lock
freezer bags that are not registered for
this purpose
 Specific types of packaging material are
available for each method of

Question 21

Packaging Instruments

Answer 21

Before sterilization, the instruments should
be wrapped or packaged to protect them
from becoming contaminated after
sterilization
 When instruments are sterilized without
being packaged, they are exposed to the
environment as soon as the sterilizer door is
opened
 They can be contaminated by aerosols in the
air, dust, improper handling, or contact with
nonsterile surfaces
 Additional advantage to packaging
instruments is they can be grouped into

Question 22

Methods of Sterilization

Answer 22

 Sterilization destroys all microbial forms,
including bacterial spores
 Sterile is an absolute term; there is no “partially sterile”
or “almost sterile”
 All reusable items (critical and semicritical
instruments) that come into contact with
the patient’s blood, saliva, or mucous
membranes must be heat sterilized
 The three most common forms of heat
sterilization in the dental office are:
 Steam
 Chemical vapor
 Dry heat

Question 22

Sterilization of Unwrapped
Instruments

Answer 22

 An unwrapped cycle (sometimes called flash
sterilization) is a method for sterilizing
unwrapped patient care items for immediate
use
 The time for unwrapped sterilization cycles
depends on the type of sterilizer and the
type of item (i.e., porous or nonporous) to
be sterilized
 Unwrapped sterilization should be used only
under certain conditions

Question 23

Steam Autoclave Operation
Cycles

Answer 23

 Dental office steam sterilizers usually
operate in four cycles
 Heat-up cycle
 Sterilizing cycle
 Depressurization cycle
 Drying cycle
 Different manufacturers provide different
features
 Some have added a pre-sterilization vacuum
cycle to their units to remove any air pockets
from the chamber before steam enters the
chamber

Question 24

Steam Autoclave Sterilization

Answer 24

An autoclave is used to sterilize dental
instruments and other items by means of
steam under pressure
 Steam sterilization involves heating water
to generate steam, producing a moist heat
that rapidly kills microorganisms
 As steam fills the sterilizing chamber, the
cooler air is pushed from an escape valve,
which then closes and allows the pressure
to increase
 It is actually the heat, not the pressure,
that kills the microorganisms

Question 25

Packaging Instruments for
Steam Autoclave Sterilization

Answer 25

 Packaging material must be porous enough to
permit steam to penetrate to the instruments
inside
 The packaging material may be fabric but most
often is sealed film or paper pouches, nylon
tubing, sterilizing wrap, or paper-wrapped
cassettes
 One disadvantage of steam sterilization is that
the moisture may cause corrosion on some
high-carbon steel instruments
 Distilled water should be used in autoclaves
instead of tap water, which often contains
minerals and impurities

Question 26

Flash Sterilization

Answer 26

Rapid, or “flash,” sterilization of dental
instruments is accomplished by means of
rapid heat transfer, steam, and unsaturated
chemical vapor
 Flash sterilization may be used only on
instruments that are placed in the chamber
unwrapped
 Flash sterilization should also be used only
for instruments that are to be promptly used
on removal from the sterilizer
 It is always the best policy to use a method
of sterilization in which the instruments can
be packaged before use and remain

Question 27

Unsaturated Chemical
Vapor Sterilization

Answer 27

Chemical vapor sterilization is similar to
autoclaving, except that a combination
of chemicals (alcohol, formaldehyde,
ketone, acetone, and water) is used
instead of water to create a vapor for
sterilization
 OSHA requires a Safety Data Sheet
(SDS) on the chemical vapor solution
because of the chemicals’ toxicity

Question 28

Filtration and Monitoring
of Chemical Vapors

Answer 28

Newer sterilizers are equipped with a
special filtration device that further
reduces the amount of chemical vapor
remaining in the chamber at the end of
the cycle
 Older models can usually be retrofitted
 Formaldehyde monitoring badges,
similar to radiation monitoring devices,
are available for employees

Question 28

Advantages of Unsaturated
Chemical Vapor Sterilization

Answer 28

The major advantage of the chemical
vapor sterilizer is that it does not rust,
dull, or corrode dry metal instruments
 The low water content of the vapor
prevents destruction of items such as
endodontic files, orthodontic pliers,
wires, bands, and burs
 A wide range of items can be sterilized
routinely without damage
 Other advantages include the short
cycle time and the availability of a dry
instrument after the cycle

Question 29

Disadvantages of Chemical
Vapor Sterilization

Answer 29

The primary disadvantage is that
adequate ventilation is essential
because residual chemical vapors
containing formaldehyde and methyl
alcohol may be released when the
chamber door is opened at the end of
the cycle
 These vapors can temporarily leave an
unpleasant odor in the area and may be
irritating to the eyes

Question 30

Pressure, Temperature, and Time

Answer 30

 The three major factors in chemical vapor
sterilization are:
 Pressure, which should measure 20 psi
 Temperature, which should measure 131º C
(270º F)
 Time, which should measure 20 to 40 minutes

Question 31

Packaging for Unsaturated
Chemical Vapor Sterilization

Answer 31

 Standard packaging for chemical vapor
sterilization includes:
 Film pouches or paper bags
 Nylon see-through tubing
 Sterilization wrap
 Wrapped cassettes
 Thick or tightly wrapped items require longer
exposure because of the inability of the
unsaturated chemical vapors to penetrate as well
as saturated chemical vapors do under pressure
 As with autoclaving, closed containers (e.g., solid-
metal trays, capped glass vials) and aluminum foil
cannot be used in a chemical vapor sterilizer
because they prevent sterilizing agent from reaching instrument inside

Question 32

Dry Heat Sterilization

Answer 32

Operates by heating air and transferring that
heat from the air to the instruments
 This form of sterilization requires higher
temperatures than does steam or chemical
vapor sterilization
 Dry heat sterilizers operate at approximately
160º C to 190º C (320º F to 375º F),
depending on the type of sterilizer
 Advantage of dry heat: Instruments will not
rust if they are thoroughly dry before being
placed in the sterilizer
 Two types: Static air and forced air

Question 33

Static Air Sterilizers

Answer 33

Similar to an oven
 Heating coils are on the bottom of the
chamber, and the hot air rises inside by way
of natural convection
 Heat is transferred from the static
(nonmoving) air to the instruments in 1 to
2 hours
 Disadvantages include amount of time it
takes and errors due to incorrect
processing time
 The wrapping material must be heat
resistant

Question 34

Forced Air Sterilizers

Answer 34

Also called rapid heat transfer sterilizers
 Circulate the hot air throughout the
chamber at a high velocity
 This action permits rapid transfer of heat
energy from the air to the instruments,
reducing the time needed for sterilization
 Exposure time in a forced air sterilizer,
after the sterilizing temperature has
been reached, ranges from 6 minutes
for unpackaged items to 12 minutes for
packaged items

Question 35

Ethylene Oxide Sterilization

Answer 35

The use of ethylene oxide gas is a
recognized method of sterilization
 Carried out at low temperatures, which is an
advantage for plastic and rubber items that
would melt in heat sterilizers
 Requires 4 to 12 hours, depending on the
sterilizer model, and at least 16 hours of
poststerilization aeration is required to
remove the gas molecules bound to plastic
and rubber surfaces
 Ineffective on wet items
 Toxicity is possible if gas is not handled properly

Question 36

Liquid Chemical Sterilants

Answer 36

Some types of plastics, such as some
rubber dam frames, shade guides, and x-
ray film–holding devices, are damaged by
heat sterilization
 A liquid sterilant such as 2.0% to 3.4%
glutaraldehyde must be used for
sterilization of these items
 Glutaraldehyde requires 10 hours of
contact time; anything less than 10 hours
is disinfection, not sterilization
 Be sure you have an MSDS for these
products

Question 36

Sterilization Failures

Answer 36

Sterilization may fail when direct
contact for the correct time between the
sterilizing agent (chemical or steam)
and all surfaces of the items being
processed is insufficient
 Several factors can cause the
sterilization process to fail, including
improper instrument cleaning or
packaging and sterilizer malfunction

Question 37

Sterilization Monitoring

Answer 37

It is critical that dental instruments be
properly sterilized
 Because microorganisms cannot be seen
with the naked eye, the major difficulty in
sterilization is determining when an item is
sterile
 Currently, three forms of sterilization
monitoring are used
 Physical
 Chemical
 Biologic

Question 37

Physical Monitoring

Answer 37

Involves looking at the gauges and
readings on the sterilizer and recording
temperatures, pressure, and exposure
time
 Although correct readings do not
guarantee sterilization, an incorrect
reading is the first signal of a problem
 Remember that the reading reflects the
temperature in the chamber, not inside the
pack

Question 38

Process Indicators

Answer 38

 Process indicators (external) are placed
outside the instrument packages before
sterilization
 Examples: Autoclave tape and color-change
markings on packages or bags
 Process indicators simply identify
instrument packs that have been exposed
to a certain temperature; they do not
indicate duration or pressure
 Process indicators are useful in
distinguishing between packages that
have been processed and those that have

Question 38

Chemical Monitoring

Answer 38

Involves the use of a heat-sensitive
chemical that changes color when
exposed to certain conditions
 There are two types of chemical
indicators
 Process indicators
 Process integrators

Question 39

Process Integrators

Answer 39

Placed inside instrument packages
 They respond to a combination of
pressure, temperature, and time
 Process integrators are also known as
multiparameter indicators
 All sterilization factors are integrated
 Examples: Strips, tabs, or tubes of
colored liquid
 The advantage of placing integrators
inside each package is that penetration
of the packaging by the sterilizing agent
is ensured

Question 40

Limitations of Process
Integrators

Answer 40

Process indicators and integrators
provide immediate visual control of
sterilizing conditions
 They do not indicate sterility and are
not a replacement for biologic
monitoring

Question 41

Handpiece Sterilization

Answer 41

High-speed dental handpieces rotate at
speeds up to 400,000 revolutions per
minute (rpm)
 Blood, saliva, and tooth fragments, as
well as restorative materials, may lodge
in the head of the handpiece, where
they may be retained and transferred to
another patient
 Dental handpieces must be properly
cleaned and heat-sterilized

Question 41

Biologic Monitoring

Answer 41

Biologic monitoring (spore testing), is the
only way to determine whether sterilization
has occurred and all bacteria and
endospores have been killed
 The CDC, American Dental Association, and
Office of Safety and Asepsis Procedures
Research Foundation recommend at least
weekly biologic testing of sterilization
equipment
 Several states also require routine biologic
checks at weekly, monthly, or cycle-specific
intervals, such as spore testing every 40 hours of use or every 30 days

Question 42

Biologic Indicators (BIs)

Answer 42

Also known as spore tests, biologic
indicators (BIs) are vials or strips of paper
that contain harmless bacterial spores
(which are highly resistant to heat)
 Three BIs are used in testing
 Two BIs are placed inside instrument packs, and the
sterilizer is operated under normal conditions
 The third strip is set aside as a control
 After the load has been sterilized, all BIs are
cultured
 If the spores are killed (a negative culture),
the sterilization cycle was successful
 The culturing of the spore test is usually handled with the use of a mail-in monitoring

Question 43

Handpiece Flushing Techniques

Answer 43

 Flushing the handpiece is the best way
to remove debris from the head
 To flush a dental handpiece:
 Attach a pressurized handpiece cleaner to
the intake tube of the handpiece (where the
air passes through)
 Flush the head of the handpiece to remove
debris
 Blow out the handpiece using compressed
air to remove debris before sterilization
 Running coolant water from the dental
unit through the handpiece at chairside
is insufficient

Question 44

Handpiece Sterilizing Techniques

Answer 44

 Only steam sterilization and chemical vapor
sterilizers are recommended because
sterilization temperatures should not exceed
275º F (135º C)
 Handpieces should be packaged in bags,
wraps, or packs to protect them from
contamination before use
 Never run a handpiece “hot” out of the
sterilizer, and avoid rapid cool-downs, such as
running the handpiece under cold water
 If handpieces need to be cooled quickly after
sterilization, use an air fan to blow room-
temperature air over them