dental instruments

Dental Instruments

*HAND*

Instruments Type

Contents Introduction : Definition & History Classification : Cutting instruments Non cutting Cutting instruments : Materials Hardening and Tempering Heat treatments Design Shank Angles Nomenclature Formula Bevels

Cutting instruments applications: Excavators Chisels Sharpening : Stationary sharpening Mechanical sharpening Instruments grasp : Modified pen . Inverted pen Palm and thumb Modified palm and thump Cleaning and sterilization Non cutting instruments : Amalgam condenser Mouth mirror Others

Introduction Definition : It’s hand –powered dental instruments .

History : The early hand – operated instruments characterized

by : 1- Large , heavy handles and inferior metal alloys in

the blades . 2- 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 instruments 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 enable both dentists and manufactures to communicate more clearly and effectively in regard to instruments design and function

G.V.Black

ClassificationHAND INSTRUMENT

Cutting Non cutting Excavators Chisels Others Amalgam condenser Mirrors

Explorers, Probes Others Ordinary Straight Files hatchets Hoes Curved Scalers Angle bin- carvers Formers angle Spoons Enamel Hatchet Gingival margin trimmers

A. Cutting Instruments,

*MATERIAL*

Carbon Steel Stainless SteelIs harder than stainless steel . Remains bright under most

conditions .

When Unprotected , it will corrode .

Loses a keen edge during use much more quickly than does carbon steel

Hand cutting instruments are manufactured from two main materials

* MATERIAL* 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 .

*MATERIAL*Other alloys of nickel , cobalt , or chromium

are used in the manufacture of hand instruments

Stainless steel Carbon steel

*MATERIALS*Hardening & Tempering Heat Treatments : To gain maximal benefits from carbon steel or

stainless steel , the manufacture must submit them to two heat treatments :

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 toughness , the tempering .

Heating or flaming of hand instruments during dental use can alter the original properties of the alloy and render it unserviceable .

DesignMost hand instruments composed of three

parts : a- Blade or nib b- Shank c- Handle

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.

B - shank Connect the handle to the working end of the

instrument.Normally smooth, round and tapered. DesignHave 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.

DesignBalance 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.

o 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

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)

NomenclatureBlack classified all instruments by name

according to:a) Function e . g . scaler, excavator .b) Manner of use e.g. hand condenser.c) Design of the working end e.g. spoon excavator,

sickle scaler nomenclature.d) Shape of the shank e.g. mono-angle, bi-angle,

contra-angle.e) These names were combined to form the complete

description of the instrument e.g. bi-angle spoon excavator.

FormulaHand 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).

Formula 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).Formula 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.

BevelsMost 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.

This allows cutting in 3 directions; facial and 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.

BevelsSingle beveled instrument such as spoon excavator and gingival margin trimmer are used with lateral cutting movement.

BevelsEnamel 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.

BevelsRight and left bevels 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.

BevelsThe cutting edge is perpendicular to the axis

of the handle, e.g. binangle chisel.

Instrument with slight blade curvature, e.g. Wedelstaedt chisel

Cutting instrument applications Applications can be classified into:

Hand cutting instrument

Excavators Chisels Removal of caries and Used primarily for refinement of the internal cutting enamel.

parts of the preparation.

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 .


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 .


Hoe excavator IT has the primary cutting edge of the blade

perpendicular to the axis of the handle


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.


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.


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 )


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


Spoon excavator Its blades are slightly curved, the shanks may

be bin-angled or triple-angled to facilitate accessibility.

Spoon excavators

Discoid Cleoid The cutting edges The cutting edges are circular. are claw like


Bin-angled spoon

Triple-angled spoon


Cleoid spoon


Discoid spoon


(2)Chisels

Straight, slightly curved, or bin-angle

Enamel hatchets

Gingival margin trimmers


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.


Straight, slightly curved, or bin-angle:

The shank and blade of the chisel also may be slightly curved (Wedelstaedt design)



The shank and blade of the chisel also may be bin-angled .


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.



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.



The blade with a distal bevel is designed to plane a wall that faces the blade's inside surface


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.


Enamel hatchet

It is used for cutting enamel and comes as right or left types for use on opposite sides of the preparation.


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


Gingival margin trimmer



When the second number in the formula is 90-100, 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.



Uses of GMT : 1. Beveling of the gingival margins of

proximoocclusal preparations.

2. Beveling of the axiopulpal line angle.



3. Performing a gingival lock (reverse bevel), placed on the gingival seat.

e.g. GMT 100 for the distal and GMT 75 for

the mesial.

SharpeningCutting instruments

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 instrumentSharpening

Sharpening equipment 1. Stationary sharpening stone e.g. Arkansas

stone, silicon carbide.

Sharpening2. 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

Instrument graspThere are four grasps used with the hand

instruments:1. Modified pen.2. Inverted pen.3. Palm and thumb.4. Modified palm and thumb. With each grasp proper rest and guard is

important

1. Modified pen graspIt 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

2. inverted 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

3. Palm and thumb grasp(grasp of power)

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

4. Modified palm and thumb graspThe 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

Instrument restrests : 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 guardsguards : The use of interproximal wedges to protect

soft tissues from contact with sharp rotary cutting instruments.

Cleaning and Sterilization


Instrument Cleaning and Sterilization

Cleaning All instruments need to be cleaned and

thoroughly dried before they sterilized .


Cleaning

Hand scrubbing

Ultrasonic cleaning

Automated washer

1- Hand ScrubbingAdvantages 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. Effectively cleans all instruments . Reduces chances for spread of contaminants of contaminants

through splatter and aerosols. Allows for more efficient use of staff time. Disadvantages Not all instruments are compatible with automated washers. Please see manufacturer's instructions for detailed

requirements.

Sterilization 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 cross-contamination.

o Some instruments and materials are single use only.

o 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 .

o Items without risk, such as a saliva ejector, can be thrown into the trash.

o To prevent accidental injury with the contaminated instruments, special handling should be used to transport the instruments to the cleaning and sterilization area.

o 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

SterilizationSteam pressure sterilization

( autoclave )

Chemical vapor pressure sterilization

Dry heat sterilization ( dryclave )

Ethylene oxide sterilization

1-Steam preasure strillization (autoclaving

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 no automated 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.

2-CHEMICAL VAPOR PRESSURE STERILIZATION (CHEMICLAVING )

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 )

3-Dry heat sterilization (dryclave)

Is an excellent means of sterilization sharpinstrument but rubber and plastic material can notbe 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 method1. 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

4-ETHYLENE OXIDE STERILIZATION-

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)

New methods of sterlization**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

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 .

Instrument storage in dental cabinet

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 :

1 •Prevent slinding into the ends of try as the drawer is opened and closed .

2 •It is important , when double-ended instrument are stored

3 •Protection of instrument from moisture or agent that cause rust or corrosion .

Effects of Sterilization 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

Non cutting instrument

Amalgam condenser

Mouth mirror

Others

1. Amalgam condenser 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

2. Mouth mirror 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.

4. others 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.

Disposable brush and handle.

Thank You

Done By : Ghadah SidqiAbrar Abdullah

G(3) , L(5) .

dental instruments

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