dentalhandinstruments-100306035258-phpapp02

•Instrument grasp Modified pen. Inverted

pen. Palm and thumb.

Modified palm and thumb.

•Non cutting instrument

Amalgam condenser Mouth mirror

Others

•Cleaning and Sterilization

•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

Introduction

IntroductionDefinition:

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 Non cutting

excavators chisels others

ordinary hatchets

hoes

Angle formers

spoons

straight

curved

bin-angle

Enamel hatchet

files

scalers

carvers

Amalgam condenser mirrors explorers,

probes

Gingival margin trimmers

others

Hand cutting instruments are manufactured from two main materials.

MATERIALS

carbon steel stainless steel

Is harder than stainless steel.

remains bright under most conditions.

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

when unprotected, it willcorrode.

MATERIALS

Tungsten carbide inserts or blades to providemore durable cutting edges (brittle). They maybe soldered to steel handles.

some instruments are made with carbide to

provide more durable cutting edges.

Stainless Steel Carbon steel

Other alloys of nickel, cobalt, or chromium are used in the manufacture of hand instruments.

MATERIALS

To gain maximal benefits from carbon steel or stainless steel, the manufacturer must submit them to two heat treatments: hardening and

tempering .

Hardening and Tempering 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

MATERIALS

Heating or flaming of hand instrumentsduring dental use can alter the originalproperties of the alloy and render itunserviceable.

Most hand instruments composed of three parts:

Design

a- Blade or nibb-Shankc-Handle

a- blade

This is the working part of the instrument.Begins at the point which terminates theshank.It is connected to the handle by the shank.

Each blade has a cutting edge which is theworking part of the instrument.It is usually in the form of a bevel (acuteangle) 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.

Design

Have one or more angles to avoid twisting ofthe instrument.Hand instruments must be balanced and sharp.

Balance allows for the concentration offorce onto the blade without causingrotation of the instrument.

Balance is accomplished by designing theangle of the shank so that the cutting edgeof the blade must not be off axis by morethan 1-2 mm.

Design

Shank angles:

Mon-angle, bin-angle, triple angle.

Instruments with small short blades may bemonangle

Instruments with long blades may requiredtwo or three angles in the shank to bring thecutting edge near to the long axis of thehandle .

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 theinstrument.

Design

Handles are in conjunction with the shank orit may be separable.Separate type is known as cone-sockethandle and allows for replacement of severalworking ends e.g. mirrors and condensers.

cone-socket handle (mirror)

mirror

Design

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. spoonexcavator, sickle scaler

nomenclature

4 .Shape of the shank e.g. mono-angle, biangle, contra-angle.

•These names were combined to form thecomplete description of the instrument e.g.binangle spoon excavator.

Hand cutting instruments have formulasdescribing the dimensions and angle ofthe working end .

These are placed on the handle using acode of three or four numbers separatedby dashes or spaces (e.g. 10-85-8-14).

formula

The first number indicatesthe width of the blade intenths of a mm (e.g. 10 = 1 mm).

The second number primary cutting edge anglemeasured from a line parallel to the long axis ofthe handle in clockwise centigrade.

Instrument shank and blade design with

formula.

formula

If the edge is perpendicular to the blade,this number is omitted resulting in a 3numbers code.The third number indicates the bladelength in mm (e.g. 8 = 8 mm).

formula

The fourth number indicates the blade angle relative to thelong axis of the handle in clockwise centigrade e.g. (14)Additional number on the handle is the manufacturer’s identification number .

Additional number should not be confused with the formula number.

formula

Additional two secondary cutting edges thatextend from the primary cutting edge for the length of the blade.

Most hand cutting instruments have on the end of the blade a single bevel that forms the primary cutting edge. Two additional edges,

Bevels

This allows cutting in 3 directions; facial andlingual walls of the proximal cavity.

Chisel blade design showing primary and secondary cutting edges.

Bibeveled instrument havetwo bevels that form thecutting edge,

e.g. hatched excavator.

Bevels

Single beveledinstrument such asspoon excavatorand gingival margin trimmer areused with lateralcutting movement.

Bevels

Enamel hatchet also as a single beveled instrument used with direct cutting motion, aplanning or lateral cutting designated for right and left tothe instrument formula.

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.

Right and left bevels

Bevels

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.

The cutting edge is perpendicular to the axis of the handle

e.g. binangle chisel.

Bevels

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

Applications can be classified into :

Hand cutting instrument

Excavators Chisels

-Removal of caries and refinement of the internal parts of the preparation.

-Used primarily for cutting enamel.

(1)Excavators

hatchets

hoes

angle formers

spoons

CUTTING INSTRUMENT APPLICATIONS




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



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 excavators

discoid cleoid

Spoon excavator

Its blades are slightly curved, the shanks may be bin-angled or triple-angled to facilitate accessibility.

-the cutting edges are circular.

-the cutting edges are claw like.



bin-angled spoon

triple-angled spoon



Cleoid spoon



Discoid spoon



(2)Chisels

enamel hatchets

gingival margin trimmers

straight, slightlycurved, 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.




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.




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 havethe 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



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 thehandle.



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




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 usedto bevel the mesial margins.

100 and 75 pairs for steep margins for inlaypreparation while 90-85 for slight bevel inamalgam preparations.




Uses of GMT:

Beveling of the gingival margins of proximoocclusal preparations.

Beveling of the axiopulpal line angle.




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 instrumentcutting instrument

sharpening

The cutting edge of the hand instrument should always be kept sharp as dullinstruments 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 instrumentcutting instrument

sharpening

Stationary sharpening stone e.g. Arkansas stone, silicon carbide.

sharpening

Mechanical sharpener; moves at lowspeed while the instrument is held at theopposite angle and supported by a rest

i.e. easier and less time consuming.

Mechanical sharpener

There are four grasps used with the handinstruments:Modified pen.Inverted pen.Palm and thumb.Modified palm and thumb.With each grasp proper rest and guard isimportant.

It is similar to that used in holding a pen exceptthat the thumb, index and middle fingers contactthe instrument while the tips of the ring and littlefingers are placed on the working tooth as a rest..

The palm of the hand is facing away from theoperator.

pen grasp Modified pen grasp

If the hand is rotated so that the palmfaces more toward the operator.If is used in the lingual and labial surfacesof anterior teeth.

inverted pen grasp

The handle of the instrument is placed on the palm of the hand and grasped by all thefingers while the thumb is free of theinstrument 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 firmrest (support) to steady the hand duringoperative procedures.

The support may be gained from hard tissue.

Soft tissue rest or too distant hard tissue restdoes not afford a reliable control.

Indirect rest may be gained by using theindex finger of the opposite hand to reston the shank of the instrument.

The operating hand rests on the oppositehand which rests on stable oral structures.

Instrument guardsInstrument guards

The use of interproximal wedges to protect soft tissues from contact with sharp rotary cutting instruments.

Cleaning and Sterilization




All instruments need to be cleaned and thoroughly dried before they are sterilized.

Cleaning

Hand Scrubbing Ultrasonic

Cleaning Automated

WasherWasher

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 timeDisadvantages

-Microorganisms may accumulate in cleaning solution.

-Ultrasonic cleaning will not remove hardened Permanent cement. (Solution: remove cement while it is still soft.).

3-Automated WasherAdvantages

-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 cross-contamination.

-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 glovesutility gloves

SterilizationSterilization

SteamSteam pressure sterilization ((autoclave)

Dry heat sterilization (dryclave )

Ethylene oxide sterilization

Chemical vapor pressure sterilization (chemiclave )

--Sterilization with steam under Sterilization with steam under pressure is performed in a steam pressure is performed in a steam autoclaveautoclave. .

-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 evaluatedwith 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 sterilizeinstruments. 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 thisThe 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, excepton 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 It is a dental instrument used for compacting silver amalgam while in a compacting silver amalgam while in a plastic state, used for restoring teeth plastic state, used for restoring teeth to a natural contour. to a natural contour.

Condensers come in single- and double-Condensers come in single- and double-ended designs. They have various shaped ended designs. They have various shaped and sized working ends, which may be and sized working ends, which may be smooth or serratedsmooth 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 brushC. disposable brushused with etching and bonding used with etching and bonding procedures associated with procedures associated with composite resins is a disposable composite resins is a disposable brush with a reusable handlebrush with a reusable handle . .

aiding in good infection control practices. aiding in good infection control practices.

Disposable brush and handleDisposable brush and handle . .

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