•Introduction
Definition
History
•Classification
Cutting instrument
Non cutting
•Cutting instrument
MATERIALS
Hardening and Tempering
Heat Treatments
Design
Shank angles
Nomenclature
Formula
Bevels
•Cutting instrument applications
Excavators
Chisels
•Sharpening
Stationary sharpening
Mechanical sharpening
•Instrument grasp
Modified pen. Inverted pen.
Palm and thumb.
Modified palm and thumb.
•Cleaning and Sterilization
•Non cutting instrument
Amalgam condenser
Mouth mirror
Others
Introduction
Definition :
It is hand-powered dental instruments.
History :
The early hand-operated instruments
characterized by:
Large, heavy handles and inferior metal alloys in the
blades.
cumbersome, difficult to use, and ineffective in many
situations.
there was no uniformity of manufacture or
nomenclature, Many dentists made their own hand
instruments in an effort to find a suitable
instrument for a specific need.
effective sterilization was a problem.
Designs of some early hand instruments
G.V. Black is credited with the first
acceptable nomenclature and classification
of hand instruments.
His classification system enabled both
dentists and manufacturers to communicate
more
clearly and effectively in regard to
instrument design and function.
G.V. Black
HAND
INSTRUMENT
cutting
excavators
Non cutting
chisels
others
Amalgam
condenser
ordinary
hatchets
straight
files
hoes
curved
scalers
Angle
formers
bin-angle
carvers
spoons
Enamel
hatchet
Gingival
margin trimmers
mirrors
explorers,
probes
others
MATERIALS
Hand cutting instruments are manufactured from two main materials.
carbon steel
Is harder than stainless
steel.
when unprotected, it will
corrode.
stainless steel
remains bright under
most conditions.
loses a keen edge during
use much more quickly
than does carbon steel
MATERIALS
Tungsten carbide inserts or blades to provide
more durable cutting edges (brittle). They may
be soldered to steel handles.
some instruments are made with carbide
to
provide more durable cutting edges.
MATERIALS
Other alloys of nickel, cobalt, or chromium are
used in the manufacture of hand instruments.
Stainless Steel
Carbon steel
MATERIALS
Hardening and Tempering Heat Treatments:
To gain maximal benefits from carbon steel or stainless steel,
the manufacturer must submit them to two heat treatments:
hardening and tempering .
Heat treatment Furnace
MATERIALS
The hardening heat treatment hardens the alloy,
but it also makes it brittle, especially when the
carbon content is high.
Heat treatment relieves strains and increases
the tempering toughness.
Heating or flaming of hand instruments
during dental use can alter the original
properties of the alloy and render it
unserviceable.
Design
Most hand instruments composed of
three parts :
a- Blade or nib
b-Shank
c-Handle
Design
a- blade
This is the working part of the instrument.
Begins at the point which terminates the
shank.
It is connected to the handle by the shank.
Each blade has a cutting edge which is the
working part of the instrument.
It is usually in the form of a bevel (acute
angle) that cuts into the tooth structure.
On non cutting instruments e.g. condensers
the part corresponding to the blade is called
the nib or face.
Design
b-shank
Connect the handle to the working end of
the instrument.
Normally smooth, round and tapered.
Have one or more angles to avoid twisting of
the instrument.
Hand instruments must be balanced and
sharp.
Balance allows for the concentration of
force onto the blade without causing
rotation of the instrument.
Design
Balance is accomplished by designing the
angle of the shank so that the cutting edge
of the blade must not be off axis by more
than 1-2 mm.
Shank angles:
Mon-angle, bin-angle, triple angle.
Instruments with small short blades may be
monangle
Design
Instruments with long blades may required
two or three angles in the shank to bring the
cutting edge near to the long axis of the
handle.
Such shanks are termed contra angled.
Design
c- handle(shaft)
It is the part grasped in the operator’s hand.
Perfectly straight, smooth or eight sided.
Serrated for better gripping and control of the
instrument.
Handles are in conjunction with the shank or
it may be separable.
Separate type is known as cone-socket
handle and allows for replacement of several
working ends e.g. mirrors and condensers.
Design
mirror
cone-socket handle (mirror)
nomenclature
Black classified all instruments by name
according to:
1. Function e.g. scaler, excavator.
2. Manner of use e.g. hand condenser.
3. Design of the working end e.g. spoon
excavator, sickle scaler
4. Shape of the shank e.g. mono-angle,
biangle, contra-angle.
•These names were combined to form the
complete description of the instrument e.g.
binangle spoon excavator.
formula
Hand cutting instruments have formulas
describing the dimensions and angle of
the working end.
These are placed on the handle using a
code of three or four numbers separated
by dashes or spaces (e.g. 10-85-8-14).
The first number indicates
the width of the blade in
tenths of a mm (e.g. 10 = 1 mm).
The second number primary cutting edge angle
measured from a line parallel to the long axis of
the handle in clockwise centigrade.
formula
Instrument shank and
blade design with formula.
formula
If the edge is perpendicular to the
blade,
this number is omitted resulting in a 3
numbers code.
The third number indicates the blade
length in mm (e.g. 8 = 8 mm).
The fourth number indicates the blade angle
relative to the
long axis of the handle in clockwise centigrade
e.g. (14)
Additional number on the handle is the
manufacturer’s identification number.
formula
Additional number should not
be confused with the formula
number.
Bevels
Most hand cutting instruments have on the end of
the blade a single bevel that forms the primary cutting
edge. Two additional edges,
Additional two secondary cutting edges that
extend from the primary cutting edge for
the
length
of the
blade.in 3 directions; facial and
This
allows
cutting
lingual walls of the proximal cavity.
Chisel blade design showing primary and secondary cutting edges.
Bevels
Bibeveled instrument have
two bevels that form the
cutting edge,
e.g. hatched excavator.
Bevels
Single beveled
instrument such as
spoon excavator
and gingival
margin trimmer are
used with lateral
cutting movement.
Bevels
Enamel hatchet also as a single
beveled instrument used with direct
cutting motion, a
planning or lateral cutting
designated for right and left to
the instrument formula.
Bevels
Right and left bevels
To determine this, the primary cutting
edge is held down and pointing away.
If the bevel appears on the right, it is in
the right instrument of the pair, when
used it is moved from right to left.
The opposite is true for the left
instrument of the pair.
One instrument is used for work on one
side of the preparation and the other for
the opposite side of the preparation.
Bevels
The cutting edge is perpendicular
to the axis of the handle
e.g. binangle chisel.
Instrument with slight blade curvature
e.g.Wedelstaedt chisel.
Applications can be classified into:
Hand cutting instrument
Excavators
-Removal of caries and
refinement of the internal parts
of the preparation.
Chisels
-Used primarily for cutting enamel.
CUTTING INSTRUMENT
APPLICATIONS
(1)Excavators
hatchets
hoes
angle formers
spoons
CUTTING INSTRUMENT
APPLICATIONS
Hatchet excavator
It has the cutting edge of the blade directed in the same
plane as that of the long axis of the handle and is bibeveled .
CUTTING INSTRUMENT
APPLICATIONS
Hatchet excavator
These instruments are used primarily on anterior teeth for
preparing retentive areas and sharpening internal line angles,
particularly in preparations for direct gold restorations .
CUTTING INSTRUMENT
APPLICATIONS
Hoe excavator
IT has the primary cutting edge of the
blade perpendicular to the axis of the
handle
CUTTING INSTRUMENT
APPLICATIONS
Hoe excavator
This type of instrument is used for planing tooth
preparation walls and forming line angles. It is
commonly used in Classes III and V preparations for
direct gold restorations.
CUTTING INSTRUMENT
APPLICATIONS
Hoe excavator
Some sets of cutting instruments contain
hoes with longer and heavier blades, with
the shanks contra-angled. These are
intended for use on enamel or posterior
teeth.
CUTTING INSTRUMENT
APPLICATIONS
Angle former excavator
It is mon-angled and has the primary
cutting edge at an angle (other than 90
degrees) to the blade. It is available in
pairs (right and left )
CUTTING INSTRUMENT
APPLICATIONS
Angle former excavator
It is used primarily for sharpening line angles and
creating retentive features in dentin in preparation
for gold restorations.
It also may be used in placing a bevel on enamel
margins
CUTTING INSTRUMENT
APPLICATIONS
Spoon excavator
Its blades are slightly curved, the shanks may be
bin-angled or triple-angled to facilitate
accessibility.
Spoon excavators
discoid
- the cutting edges are
circular.
cleoid
-the cutting edges are
claw like.
CUTTING INSTRUMENT
APPLICATIONS
binangled
spoon
tripleangled
spoon
CUTTING INSTRUMENT
APPLICATIONS
Cleoid spoon
CUTTING INSTRUMENT
APPLICATIONS
Discoid spoon
CUTTING INSTRUMENT
APPLICATIONS
(2)Chisels
straight, slightly
curved, or bin-angle
enamel hatchets
gingival margin trimmers
CUTTING INSTRUMENT
APPLICATIONS
straight, slightly
curved, or bin-angle
The straight chisel has a straight shank and blade, with
the bevel on only one side. Its primary edge is
perpendicular to the axis of the handle.
CUTTING INSTRUMENT
APPLICATIONS
straight, slightly
curved, or bin-angle
The shank and blade of the chisel also may be
slightly curved (Wedelstaedt design)
CUTTING INSTRUMENT
APPLICATIONS
straight, slightly
curved, or bin-angle
The shank and blade of the chisel
also may be bin-angled .
CUTTING INSTRUMENT
APPLICATIONS
straight, slightly
curved, or bin-angle
The force used with all these chisels is essentially
a straight thrust.
There is no need for a right and left type in a
straight chisel, since a 180-degree turn of the
instrument allows for its use on either side of the
preparation.
CUTTING INSTRUMENT
APPLICATIONS
straight, slightly
curved, or bin-angle
The bin-angle and Wedelstaedt chisels have
the primary cutting edges in a plane
perpendicular to the axis of the handle and
may have either a distal bevel or a mesial
(reverse) bevel.
CUTTING INSTRUMENT
APPLICATIONS
straight, slightly
curved, or bin-angle
The blade with a distal bevel is designed
to plane a wall that faces the blade's
inside surface
CUTTING INSTRUMENT
APPLICATIONS
The blade with a mesial bevel is designed to
plane a wall that faces the blade's outside
surface
CUTTING INSTRUMENT
APPLICATIONS
enamel hatchet
It is a chisel similar in design to the ordinary
hatchet excavator except that the blade is
larger, heavier, and is beveled on only one side
It has its cutting edges in a plane that is
parallel with the axis of the
handle.
CUTTING INSTRUMENT
APPLICATIONS
enamel hatchet
It is used for cutting enamel and comes as
right or left types for use on opposite sides of
the preparation.
CUTTING INSTRUMENT
APPLICATIONS
gingival margin trimmer
Similar in design to enamel hatchet except
the blade is curved.
Right and left types:
Right pair is for either a mesial or distal
gingival margins.
Left pair is for a mesial or distal margins
CUTTING INSTRUMENT
APPLICATIONS
gingival margin trimmer
CUTTING INSTRUMENT
APPLICATIONS
gingival margin trimmer
When the second number in the formula is 90100, it is used for distal gingival margins.
When this number is 75-85, the pair is used
to bevel the mesial margins.
100 and 75 pairs for steep margins for inlay
preparation while 90-85 for slight bevel in
amalgam preparations.
CUTTING INSTRUMENT
APPLICATIONS
gingival margin trimmer
Uses of GMT :
Beveling of the gingival margins of
proximoocclusal preparations.
Beveling of the axiopulpal line angle.
CUTTING INSTRUMENT
APPLICATIONS
gingival margin trimmer
Performing a gingival lock (reverse bevel),
placed on the gingival seat.
e.g. GMT 100 for the distal and GMT 75
for the mesial.
cutting instrument
sharpening
The cutting edge of the hand instrument
should always be kept sharp as dull
instruments may cause:
1. Loss of control.
2. More pain.
3. Prolonged time for the operative procedure.
4. Reduce the quality and precision of tooth
preparation.
cutting instrument
sharpening
Stationary sharpening stone e.g. Arkansas
stone, silicon carbide.
sharpening
Mechanical sharpener; moves at low
speed while the instrument is held at the
opposite angle and supported by a rest
i.e. easier and less time consuming.
Mechanical sharpener
There are four grasps used with the hand
instruments:
Modified pen.
Inverted pen.
Palm and thumb.
Modified palm and thumb.
With each grasp proper rest and guard is
important.
It is similar to that used in holding a pen except
that the thumb, index and middle fingers contact
the instrument while the tips of the ring and
little
fingers are placed on the working tooth as a rest..
The palm of the hand is facing away from the
operator.
pen grasp
Modified pen grasp
If the hand is rotated so that the palm
faces more toward the operator.
If is used in the lingual and labial surfaces
of anterior teeth.
inverted pen grasp
The handle of the instrument is placed on the
palm of the hand and grasped by all the
fingers while the thumb is free of the
instrument and rest on the nearby tooth of the
same arch.
Palm and thumb grasp
The same as in palm and thumb grasp
but the thumb is rested on the tooth
being prepared.
Used in the upper arch.
Modified palm and thumb grasp
A proper instrument grasp must include a firm
rest (support) to steady the hand during
operative procedures.
The support may be gained from hard tissue.
Soft tissue rest or too distant hard tissue rest
does not afford a reliable control.
Indirect rest may be gained by using the
index finger of the opposite hand to rest
on the shank of the instrument.
The operating hand rests on the opposite
hand which rests on stable oral structures.
Instrument guards
The use of interproximal wedges to
protect soft tissues from contact with
sharp rotary cutting instruments.
Cleaning and Sterilization
Cleaning and Sterilization
All instruments need to be cleaned and thoroughly
dried before they are sterilized.
Cleaning
Hand Scrubbing
Ultrasonic
Cleaning
Automated
Washer
1-Hand Scrubbing
Advantages
-Effective if performed properly
Disadvantages
-Increases chances for operator injury.
-Increases spread of contamination through splatter.
-Labor-intensive.
-Need proper care of scrub brush
2-Ultrasonic Cleaning
Advantages
-Safer than hand scrubbing.
-Effectively cleans all instruments .
Reduces chances for spread of
contaminants through splatter.
-Allows for more efficient use of staff
time
Disadvantages
-Microorganisms may accumulate in
cleaning solution.
-Ultrasonic cleaning will not remove
hardened Permanent cement.
(Solution: remove cement while it is
still soft.).
3-Automated Washer
Advantages
-Safer than hand scrubbing.
-Reduces chances for spread of contaminants of
contaminants through splatter and aerosols.
-Allows for more efficient use of staff time.
-Effectively cleans instruments.
Disadvantages
-Not all instruments are compatible with
automated washers.
-Please see manufacturer's instructions for detailed
requirements.
process by which an article, surface or medium is
freed of all living microorganisms.
-Most dental offices have a designated area for
instrument reprocessing that is separate from the
dental treatment room. This is ideal, since
cleaning, sterilizing and storing instruments in the
same room where the delivery of patient care is
provided increases the risk of crosscontamination.
-Some instruments and materials
are single use only.
- Single-use items should be
segregated in the operatory,
and those that are sharp
or otherwise pose a risk of injury
must be discarded into a sharps container .
-Items without risk, such as
a saliva ejector, can be thrown into the trash.
-To prevent accidental injury with the
contaminated instruments, special handling
should be used to transport the instruments to
the cleaning and sterilization area.
-Although heavy-duty gloves (utility gloves)
may feel more awkward than examination
gloves, they provide extra protection while
handling instruments during the cleaning,
rinsing, drying, packaging and sorting
procedures that take place during instrument
reprocessing
utility gloves
Sterilization
Steam pressure sterilization (autoclave)
Chemical vapor pressure sterilization
(chemiclave)
Dry heat sterilization (dryclave )
Ethylene oxide sterilization
-Sterilization with steam under pressure is
performed in a steam autoclave .
-For a light load of instruments, the time
required at 250'F (121° C) is a minimum of 15
minutes at 15 lbs of pressure.
-Time for wrapped instruments can be
reduced to 7 minutes if the temperature is
raised to approximately 273° F (134° C) to
give30 pounds of pressure.
An example of a steam pressure sterilizer (autoclave)
Advantages of
Autoclaves.
-Autoclaving is the most rapid and effective
method for
sterilizing cloth surgical packs and towel packs.
-Automated models are available.
-although they still can be misused or fail almost
as often as nonautomated ones; they must be
evaluated
with a biologic spore test monitoring system.
Disadvantages of autoclaves
-Items sensitive to the elevated
temperature can not be autoclaved.
-Autoclaving tends to rust carbon steel
instruments.
-Sterilization by chemical vapor under pressure is
performed in a Chemiclave.
-Chemical vapor pressure sterilizers operate at 270°
F (131° C) and 20 pounds of pressure.
-They are similar to steam sterilizers and have a
cycle time of approximately half an hour.
Advantages of Chemiclaves.
-Carbon steel and other corrosion-sensitive burs,
instruments, and pliers are said to be sterilized
without rust or corrosion.
Disadvantages of Chemiclaves.
- Items sensitive to the elevated temperature will be
damaged.
-Instruments must be lightly packaged in bags
obtained from the sterilizer manufacturer.
- Towels and heavy cloth wrappings of surgical
instruments may not be penetrated to provide
sterilization.
- Routinely use biologic spore test monitoring strips to
confirm heat penetration of heavy packs before use.
Chemical vapor pressure sterilizer (Chemiclave)
Is an excellent means of sterilization sharp instrument but rubber and plastic material can
not be sterilized by this method .
-Dry heat sterilizers for use in dental offices are available, but all that is necessary is an
oven that will maintain a temperature of
160°C(320°F)
-It imperative that all debris be removed from
an instrument before it placed in a dry heat
sterilizer .
*Holding period : 160°C(320°F),1 hour .
Advantages of this method
1-is an excellent means of sterilization
sharp instrument.
2-instrument not corrode or rust.
Disadvantages
1-a lower temperature or a shorter
period will not produce the desired
result .
2-The higher temperature of a dry-heat
sterilizer means that paper will scorch
and plastic will melt.
3-some hand pieces can not be sterilized
by this method
Cox rapid heat transfer dry heat sterilizer
-Ethylene oxide sterilization is the best
method for sterilizing complex instruments
and delicate materials.
-ethylene oxide gas is toxic for all viruses and
bacteria at room temperature on exposure for
8-10 hr at elevated temperature .
-this method requires rather expensive
equipment .
Room temperature ethylene oxide sterilizer
BOILING WATER
*Boiling water does not kill spores and cannot sterilize
instruments. However, heat can reach and kill blood
borne pathogens in places that liquid sterilants and
disinfectants used at room temperature cannot reach.
*Boiling is a method of high-level disinfection that has
been used when actual sterilization cannot be achieved
(e.g., in case of a sterilizer breakdown)
**Various new methods of sterilization are under
investigation and development.
-The microwave oven has major limitations for
sterilizing metal items, by either damaging the
machine or not reaching all sides of the instruments.
microwave oven
-Ultraviolet light is not highly effective against
RNA viruses such as HIV and is not very
effective against bacterial spores
Ultraviolet light
-Incomplete exposures of all surfaces
and poor penetration of oil and debris
are other limitations.
- Ultraviolet irradiation may be useful
for sanitizing room air to help control
tuberculosis bacteria .
1-After the instrument are sterilized, they are
placed in proper place in a dry condition .
2-The portions of dental cabinet designated for
hand instrument contain grooved glass or metal
trays.
3-These instrument containers must be kept in
clean and aseptic condition.
4-hey should also contain protective medium for
cutting edges of the instrument .
The purpose of this :
Sterilizing carbon steel instruments by
any of (cold disinfection, boiling water,
steam under pressure (autoclave) causes
discoloration, rust, and corrosion.
minimizing these problems are available.
1-electroplate the instrument. This affords
protection, except
on the blade, where use and sharpening remove
the plating.
2- use of rust inhibitors, which are soluble
alkaline compounds.
3-is to remove the instruments promptly at the
end of the recommended sterilizing period, dry
them thoroughly, and place them in the
instrument cabinet or on the tray setup.
Non cutting instrument
Amalgam condenser
Mouth mirror
others
It is a dental instrument used for compacting silver
amalgam while in a plastic state, used for restoring
teeth to a natural contour.
Condensers come in single- and double-ended
designs. They have various shaped and sized working
ends, which may be smooth or serrated.
Various Amalgam condensers
mouth mirror or dentist's mirror is an instrument
used in dentistry.
The head of the mirror is usually round, and the
most common sizes used are the No. 4 and No. 5.
A No. 2 is sometimes used when a smaller mirror
is needed, such as when working on back teeth
with a dental dam in place.
its most important functions are:
allowing indirect vision by the dentist .
reflecting light onto desired surfaces.
retraction of soft tissue.
A. Carvers.
After the amalgam is condensed, it must then be
carved to approximately the same original tooth
structure.
Carvers have sharp cutting edges that are used to
shape, form, or cut tooth anatomy into amalgam
restorations.
Carvers
B. Burnishers.
When the carving is complete, the dentist may use
burnishers.
used to
smooth and polish the restoration.
remove scratches left on the amalgam surface by a
carving instrument.
Burnishers
C. disposable brush
used with etching and bonding procedures
associated with composite resins is a
disposable brush with a reusable handle.
aiding in good infection control practices.
Disposable brush and handle.