HAND INSTRUMENTS IN OPERATIVE DENTISTRY

By:- Dr Abhijeet D Khade

Nair Hospital Dental College,Mumbai

INTRODUCTION

The term “instrument” refers to a tool, device or implement used for specific purpose or type of work and is preferred in professional or scientific fields as precision items are generally required to perform specific procedures.

In order to perform, the intricate or detailed procedures associated with operative dentistry, the dentist must have a complete knowledge of the purpose and application of the many instruments required.

The instruments available. The purpose of the instrument. The position or manner of use. The application of the instrument.

HISTORY Most hand instruments of the mid 19th

century(1860’s) with large, heavy handles and inferior metal alloys in the blade, were cumbersome, awkward to use and ineffective.

These instruments had bone or ivory handles (effective sterilization was not possible).

There was no uniformity of manufacture and nomenclature.

Many dentists made their own hand instruments in an effort to find a suitable instrument for specific need.

Early hand instruments were grasped in the palm of the hand.

As cavity preparations refined and the access to various surfaces of teeth desired:-

- Grasp changed to pen grasp. - Instrument with large, straight blades modified to smaller, angled blades.

Dr. G.V. Black - Credited with the first acceptable nomenclature for and classification of hand instruments.

Dr. Arthur D. Black - Developed many of the instruments and techniques.

Dr. Charles E. Wood Bury - First to modify blacks instrumentation.

Designed 39 sets of Hand instruments for Class III cavity preparations & condensing points for building gold foil restorations.

Dr. Wedelstaedt - Developed Wedelstaedt chisel now referred to as “Curved Chisel”.

Dr. Waldon I. Ferrier – Developed a new set of instruments called ferrier set which were more refined and had uniform thickness on the cutting edge.

Dr. George Hollenback – Invented pneumatic condenser.

MATERIALS USED

Hand cutting instruments are manufactured from two main materials:

Stainless steel Carbon steel Some instruments are made with

carbide inserts to provide more durable cutting edge.

- Hard and wear resistant but is brittle too.

Stainless steel Chromium 18% Carbon 1% Iron 81- 81.4%

Adv.:- - Chromium in the alloy reduces the corrosion tendency by depositing an oxide layer on the surface of the metal. - Remains bright under most conditions.

Disadv:- - Maintaining the sharpness of the blade is a problem. - Loses a keen edge during much use.

Mainly used for working points and cement instruments.

Carbon steel Carbon 1 – 1.2% Manganese 0.2% Silicon 0.2% Iron 98.4 – 98.6%Adv.:-- Harder than stainless steel.Disadv:- - When unprotected, it will corrode.

Stellite Cobalt 65 – 90% Chromium 35% Trace amounts : tungsten, molybdenum and iron. Adv.:- - High resistance to acid - Hardness Use: Manufacture of mixing and inserting instruments.

Other alloys: Alloys of nickel, cobalt or chromium are used in the

manufacture of hand instruments.

PARTS OF HAND INSTRUMENTS

Handle/ Shaft Shank Blade with cutting

edge or Nib with face.

MANUFACTURING PROCESS

Blank steel is bent to the degree of angulation needed in the shank and blade.

The edges are milled to produce the cutting edge and structural design.

Martensitic type of stainless steel is used for manufacturing cutting instruments (high strength and hardness).

HEAT TREATMENT

HARDENING TREATMENT

The steel is heated to 1500 to 16000 F (8150 C) and then quenched in oil to harden the working edge.

Not more than 1 - 2mm of the tip is heated for hardening purpose, otherwise the instrument will lose its balance after sharpening.

Hardens the alloy, but it also makes it brittle, especially when the carbon content is high.

TEMPERING TREATMENT

Cutting edges are usually tempered to produce additional hardness and to remove some of the brittle properties.

To accomplish this, the tip is reheated at a lower temperature.

Quenched in solutions of oil, acid or mercury at 200- 4500C for 10 min.

This treatment relieves strains and increases toughness.

CLASSIFICATION I. ACCORDING TO STURDEVANT: Cutting (Excavators, Chisels and others) Non-cutting (Amalgam condensers, mirrors,

explorers, probes)

Excavator : -Ordinary Hatchets -Hoe -Angle former -Spoon excavator

CHISELS :-Straight chisel -Curved chisel or Wedelstaedt chisel -Bin angle chisel -Enamel hatchet-Gingival marginal trimmers

Others : -Knives -Files -Scalers -Carvers.

II. ACCORDING TO CHARBENAU

1. Cutting instruments

Hand - Hatchets - Chisel - Hoe - Excavator - Others

Rotary - Burs - Stones - Disk - Others

2. Condensing Instruments Pluggers

- Hand - Mechanical 3. Plastic Instruments

- Spatulas - Carvers - Burnishers - Packing Instruments

4. Finishing and Polishing

Instruments Hand

- Orange wood sticks - Polishing points - Finishing strips

Rotary - Finishing burs - Mounted brushes - Mounted stones - Rubber cups - Impregnated disk and wheels

5. Isolation Instruments

- Rubber dam frame Clamps Forceps Punch - Saliva ejectors - Cotton roll holders - Evacuating tip and equipments 6. Miscellaneous Instruments

- Mouth Mirrors - Probe - Scissors - Pliers - Others

III. ACCORDING TO MARZOUK:

1. Exploring or diagnostic instruments:

- Mouth mirror - Explorer or probe - Straight probe - Right angled probe - Arch shaped (Shepherds hook) - Interproximal (Back action) - Tweezers - Seperators - Cheek retractors - Air syringe2. Isolating instruments: - Cotton roll holder - Rubber dam - Saliva ejector - Suction apparatus

3. Hand cutting instruments: - Excavators - Spoon excavator - Cleiod - Discoid - Hatchet excavator - Hoe - Chisels - Straight chisel - Mono angle chisel - Bin angle chisel - Triple angle chisel - Special types of chisels or

modified chisels - Wedelsteadt chisel - Enamel hatchet - Gingival marginal

trimmer - Angle former

4. Restoring instruments: - Mixing instruments - Cement spatula - Agate spatula - Plastic carrying/ filling

instruments - Packing instruments - Amalgam carrier - Condensing instruments - Round condenser - Parallelogram condenser - Burnishing instruments - Ball shaped - Egg shaped - Conical shaped

- Carving instruments

- Hollenback carver - Diamond carver - Wards carver5. Miscellaneous

instruments: - Matrices and

retainers - Scissors

PARTS OF HAND INSTRUMENTS

Handle/ Shaft Shank Blade with cutting

edge or Nib with face.

HANDLE/ SHAFT

Length – 5.5 inches Diameter – 5.5 mm Available in various sizes and shapes

(small, medium & large diameter). Hexagonal or octagonal. Smooth, serrated or knurled. Knurled to facilitate control and to

increase the friction for hand-gripping. Instrument formula incorporated on it. Manufacturing kit number incorporated on

it. Handle is either continuous with shank or

separable.

SHANK Connects the handle to

the blade or nib. Smooth, round, tapered

and contrangled. Have one or more

bends to avoid the instrument from having tendency to twist in use where force is applied.

G.V.Black classified instruments depending on the number of angles in the shank as:-

Mon- angle Bin- angle Triple- angle Quaternary angle

DIFFERENT SHANK DESIGNS

NOMENCLATURE

In establishing a nomenclature for hand instruments, Dr G.V. Black prescribed four classes similar to biological classification:

ORDER: Purpose of the instrumentsSUBORDER: Position or manner of use CLASS: Form of working endSUB CLASS: Shape of the shank

Bin-angle hatchet push excavator.

BLADE

Functional end of the instrument that bears the cutting edge.

It is connected to the handle by the shank.

For non-cutting instruments, the part corresponding to the blade is termed “Nib”.

Working surface or the end of the nib is known as the “face”.

Cutting edge Beveled:- - Single beveled - Bibeveled - Triple beveled (1 primary and 2 secondary bevels). - Circumferentially beveled Regular bevel: - Distal to shaft Reverse bevel: - Mesial to shaft e.g. – Binangle chisel BLADE BEVELS

INSTRUMENT FORMULA GIVEN BY G.V.BLACK:

3 unit instrument formula: Cutting edge of the instrument is at a right angle to the blade.

a. First unit – Width of the blade in tenths of a millimeter.

b. Second unit – Length of the blade in millimeter.

c. Third unit – Angle the blade forms with the axis of the handle in centigrade.

Instrument formula of enamel hatchet.

4 unit instrument formula: Cutting edge of the instrument is at an angle other than a right angle to the blade.

a. First unit – Width of the blade in tenths of a millimeter.

b. Second unit - Angle the cutting edge forms with the axis of the handle in centigrade.

c. Third unit – Length of the blade in millimeter.

d. Fourth unit – Angle the blade forms with the axis of the handle in centigrade.

Example:- Gingival marginal trimmer & angle former.

Instrument formula of distal GMT

CENTIGRADE SCALE

MEASURING GAUZES

BOLEY’S GAUZE

MEASURING ANGLE OF THE BLADE AND CUTTING EDGE

Types of hand cutting instruments

Chisels:- - Cutting edge of the instrument

is at a right angle to the axis of the instrument.

- Used for planing or cleaving enamel.

1) Straight chisel:- - No bend in shank - Single beveled/ Triple beveled. - Minimal accessibility. - Used with push stroke or

lateral scraping action.

2) Mono angle chisel:- - Blade is shorter as compared

to straight chisel. - Single angle in the shank to

enhance the convenience form. - Used with push stroke or

lateral scraping action.

Hatchet:- - Cutting edge of the instrument is parallel to the axis of the instrument. - Cutting edge of the instrument is at right angle to the axis of blade. - Mono angled - Length of blade is very small - Bibevelled - Single ended - Used with push stroke Use:- - Preparing retentive areas on anterior

teeth. - Sharpening internal line angles in

DFG restorations.

Enamel hatchet:- - Cutting edge of the

instrument is parallel to the axis of the instrument.

- Cutting edge of the instrument is at right angle to the axis of blade.

- Binangle hatchet - Monobeveled - Single plane instrument - Paired instrument - Bevel on right side – Right

side instrument - Bevel on left side – Left side instrument

Used with push stroke (planing or direct cutting motion as well as lateral cutting motion).

Used for smoothening buccal and lingual walls of proximal box.

Used for breaking enamel of proximal box.

Used for smoothening gingival seat (lateral scraping motion).

Gingival marginal trimmer:- - Cutting edge of the

instrument is parallel to the axis of the instrument.

- Cutting edge of the instrument is at an angle other than a right angle to the blade.

- Modified hatchet - Binangle instrument - Monobeveled - Double plane instrument

(better lateral scraping efficiency/ scooping effect).

Spoon excavator:- - Modified hatchet. - Double ended instrument. - Binangle/ Triple-angle instrument. - Paired (right and left). - Double plane instrument. - Circumferentially beveled. - Cutting edge either

circular (discoid) or claw like

(cleoid).Use:- Spooning or scooping of softened carious material. - Carving amalgam or direct

wax patterns.

DIFFERENT SPOON EXCAVATORS

Other instruments:- Knives:- Finishing knives, Amalgam

knives, or Gold knives. Used for trimming excess restorative

material on the gingival, facial or lingual margins of a proximal restoration or trimming and contouring the surface of class V restorations.

Files:- Used for smoothening of overhanging

restorations (amalgam and gold).

Non cutting instruments Diagnostic instruments:-1) Mouth mirror:- - Is an instrument having a mirror head top and a detachable

handle. - Also called as odontoscope. Types:- A) Front surface:- - Is one where the reflecting surface is on the top of the

glass piece. - Gives better visibility. - Absence of intervening glass. - No double image. - Mercury coating on top is liker to be lost due to scratching. B) Rear surface (regular) - Reflecting surface is on the back surface of the mirror

lens. - Surface is less easily scratched. - Produces a double or ghost image.

C) Magnifying mirror (concave):- - Reflecting surface is on the front surface of the

mirror lens. - Produces magnified but slightly distorted image. - Concave surface mirror magnifies the image, requiring the clinician to learn to accommodate movement. - Concave mirror rarely used except for seeing

enlarged internal details of the cavity. - The instrument movements are smaller than the

clinician visual perception. - For endodontic surgeries.

D) Disposable mirror:- - Made of plastic.

Uses:- Indirect illumination. - Mouth mirror could be held at an angle to reflect the

light onto the working area. Retraction - Mirror head used to retract the patient’s lip or check

or tongue so that the clinician is able to view tooth

surfaces. Protects from injury. Indirect vision. Guard. Trans illumination. - Only maxillary and mandibular anterior teeth can be trans illuminated. Different sizes of mouth mirror:- No. 2 (5/8 inch) No. 4 (7/8 inch) No. 5 (15/16 inch)

FRONT SURFACE AND REAR SURFACE MIRROR

DIFRFERENT SIZES NO. 2,4,5.

2) Probe:- - Sharp pointed hand instrument used to

explore teeth and restoration surfaces in order to detect caries, overhanging edges and other defects.

- May be single-ended or double-ended. Uses:- - Exploring lesion - For detecting and assessing carious lesion

in the tooth - Detecting demineralized dentin. - Releasing debris from the tooth. - Removing slight excess fill up around cavo-surface margins - Identifying hypersensitive areas in the tooth - Assessing marginal fit of the restoration

Types:- - Straight. - Interproximal

probe - No.2 cow horn (arch explorer) - No.17 back action - No. 23 shepherd’s

hook - Orban –type

explorer

Different types of explorers

3) Periodontal probe:-

- Detect and measure the depth of periodontal pockets.

- In operative dentistry:- Used to determine the dimensions of instruments and of various features of preparations or restorations.

4) Forceps:- - Tweezers/ Cotton forceps - Hemostats - Articulating paper forceps Tweezers:- - Hand instrument with two narrow

and pointed, straight or curved beaks used to grasp small objects.

Consist of:- - 2 long arms. - Locking device. - 2 long arms joined at one end. - Other end remains apart.

Uses: - Useful in carrying things to and from mouth. - Carrying cotton rolls, cotton pledges, sponge

pellets to and around the cavity. - Carrying saliva soaked cotton rolls from the oral

cavity to the waste disposal unit.

Locking tweezer- May have a locking device to maintain the beaks

in a closed position until released. - This avoids the unnecessary anxiety of the operator at the possibility of slippage whatever is carried by the tweezer.

TWEEZERS ARTICULATING PAPER FORCEPS

HEMOSTATS

Restoring instruments:-1) Mixing instruments:- Cement

spatula Spatulas:- - Flat and wide nibs with blunt

edges. - Shank straight. - Different sizes and different

degrees of stiffness in their nibs to suit their various uses.

Made of ○ Stainless steel.○ Plastic.

- Doubles ended instrument. Blunt end – for manipulating

impression materials. Sharp end - for mixing

cements. - Used for manual mixing of

cements supplied as powder and liquid.

2) Plastic carrying/ filling instruments:-

It is an instrument used for carrying the mixed base cements which are in soft (plastic) stage or the restorative cement from a cement spatula to the cavity.

Usually one end is flat and other end is cylindrical.

Flat end is used for carrying the cement. Cylindrical end is used for manipulating and

positioning the cement. Made of: - Stainless steel

- Plastic Also can be plated with teflon to minimize

material adhesion.

TITANIUM NITRIDE INSTRUMENTS FOR PLACING AND SHAPING COMPOSITE

STAINLESS STEEL “PLASTIC” INSTRUMENTS

3) Packing instrument:-

Amalgam carrier:- Amalgam carrier is a stainless steel instrument used for carrying mixed amalgam to the cavity. Use:- -Hollow tip of an amalgam carrier is inserted into the mixed amalgam to pack the carrier with amalgam. -It is then carried into the cavity and plunger is pressed injecting cylindrical pellets of amalgam.

4) Condensing instruments. - To pack material into prepared cavity. - Types: A) Amalgam condenser

- Hand - Mechanical – Vibratory and Impact

type B) Gold condenser

- Hand - Mechanical.

Hand condenser:- - Are double-ended instruments with the

nibs (condensing tips) coming in different size

and shapes. - Force varies inversely with the area of the

face.

Nibs may be:- I) Of different shapes:- Round

Elliptical Diamond Triangular Parallelogram Rectangular

II) Sizes vary considerably; Large round condenser Small round condenser

III) Depending on working end; (condenser face).

Serrated – For spherical amalgam

Non-serrated (smooth) – For

admixed amalgam

DIFFERENT TYPES OF AMALGAM CONDENSERS

5) Burnishing instruments:- Hand instrument with rounded

edges used to polish or burnish the surface of metallic restorations by rubbing.

Burnishing is the process of rubbing usually performed to make a surface shiny or lustrous.

Double-ended. Nibs are spherical.

Ball shaped. Egg shaped. Apple shaped. Beaver tail shaped. Conical. Hour glass Fish tail. Bullet shaped etc.

DIFFERENT TYPES OF BURNISHERS Nibs are smooth-faced. Different angulations and curvature in their shank.

Amalgam burnishers - Small ball burnisher. - Beaver tail or egg burnisher. - Anatomic burnisher.

Other uses:- - Shape metal matrix bands so that they

impart more desirable contours to restorations.

- To “bend” cast gold near the margins to narrow the gap between the gold and the tooth (beaver tail).

6) Carving instruments:- - Hand instrument with a

blade or nib used to contour the surface of filling material in their plastic state, waxes, models and patterns.

e.g.- Hollenback carver (Knife- edged-elongated bibeveled)

- Diamond (Frahm’s) carver – Bibeveled cutting edge - Wards ‘C’ carver - Discoid- cleoid - Interproximal carver

Hollenback, Diamond and Wards - One blade is parallel to the long axis of the instrument and the other is perpendicular to the long axis of the instrument.

CLEOID (TOP) AND DISCOID (BOTTOM) CARVERS

DIFFERENT TYPES OF AMALGAM CARVERS

HAND INSTRUMENT TECHNIQUES Instrument grasps:- Definition:- These are the manners of holding the

instruments which if not held properly it will result in loss of efficiency and accumulation of unnecessary strain on the operator.

Adv:- Instrument can be held in different areas for maximum comforts of the operator.

- Better operator efficiency. Different grasps:- 1) Pen grasp (Not an acceptable

grasp) 2) Modified pen 3) Inverted pen 4) Palm and thumb 5) Modified palm and thumb

Used universally

Pen grasp:- - Instrument is held between thumb and first finger with middle finger below acting as a

support. - Either the third or third and fourth fingers are

placed on adjoining tooth as rest. - Position of middle finger is important – 1) For obtaining thrust 2) Preventing the instrument

from slippage during

manipulation. - It involves wrist movement. Adv:- -More flexibility of movement. -Less power. -Greatest versatility of movement. -More comfortable. -Limits application of pressure. Disadv:- Bracing is difficult because only the ring and little fingers are used.

Modified pen grasp:- - Permits greatest delicacy of touch. - Pads of thumb, index and middle finger contact the instrument, while the tip of the ring finger (or tips of the ring and little fingers) is placed on a nearby

tooth surface of the same arch as a rest. - The pad of the middle finger is placed near the “topside” of the instrument for good control and

cutting pressure. - The fingers and the thumb engage the instrument as

a grappling hook. - The base of the index finger and the tip of the

middle finger reciprocate, with the thumb placed midway between them. - The palm of the hand generally faces away from the operator. - Involves forearm which turns inward (pronates) or outward (supinates).

Adv:- - More effective - Controlled power to the instrument. Inverted pen grasp:- - The palm is rotated upwards with the

pad of the thumb and index fingers close to each other but the middle finger is farther down the shank.

- Used mostly for the tooth preparation utilizing the lingual approach on maxillary anterior teeth.

Palm and thumb grasp:- - The handle of the instrument is held between the palm and four fingers firmly with the tip of the thumb acting like a rest. - Power grasp. Adv:- - More control and precision. - Limited movement. - Enhance bracing (a forward thrust with the arm of wrist can be controlled by the

opposing action from the thumb, which is braced against the teeth). - Gives the possibility of applying pressure precisely.

Example: holding a hand piece for cutting incisal retention for Class III preparation on maxillary incisor.

Modified palm and thumb grasp:- - The handle of the instrument is held by all

four fingers whose pads press the handles

against the distal area of the palm, as well as the pad

and first joint of the thumb. - The rest is tip of thumb on tooth being

prepared or adjacent teeth. Adv:- - Most valuable aid in operating inside and

outside the mouth. - Allows greater ease of instrument

movement. - More control against slippage during thrust stroke compared to palm and thumb grasp. - Grasping the handle under the first joint of

the ring and little finger acts as a stabilizer. - More delicate manipulation.

PEN GRASP AND MODIFIED PEN GRASP INVERTED PEN GRASP

PALM AND THUMB GRASP MODIFIED PALM AND THUMB GRASP

Rest:-

Is to stabilize the hand and instrument by providing a firm fulcrum as movement are made to activate the instrument.

Is required for steady hand during operative procedures.

Adv:- A good finger rest prevents injury and

laceration of the gingiva and surrounding tissues.

The ring finger is preferred as finger rest.

When modified pen and inverted pen grasps are used, rests are established by placing the ring or ring and little fingers on a tooth (or teeth) of the same arch and as close to the operating site as possible (more reliable).

In palm and thumb grasp, rests are created by placing the tip of the thumb on tooth being operated on, or on an adjacent tooth, or on a convenient area of the same arch.

When it is impossible to establish a rest on tooth structure, soft tissue must be used (not reliable).

Finger rests classified Intra oral finger rest Extra oral fulcrumIntra oral finger rest:- 1. Conventional

Finger rest is established on the tooth surfaces

immediately adjacent to the working area. 2. Cross- arch

Finger rest is established on the tooth surfaces on

the other side of the same arch. 3. Opposite-arch

Finger rest is established on tooth surfaces on the

opposite arch (e. g:- mandibular arch finger rest for

instrumentation on the maxillary arch). 4. Finger – on – finger.

Finger rest is established on the index finger or thumb of the non operating hand.

Extra oral fulcrums. Two most commonly used- (1) Palm-up.

Palm-up fulcrum is established by resting the backs of the middle and ring fingers on the skin overlying the lateral aspect of the mandible on the right side of the face.

(2) Palm-down Palm- down fulcrum is established by

resting the front surfaces of the middle and ring fingers on the skin overlying lateral aspect of the mandible on the left side of the face.

Extraoral palm-up hand rest. Palm is facing out, away from the patient's face. 

Extraoral palm-down hand rest. Palm is facing in, toward the patient's face. 

SHARPENING HAND INSTRUMENTS

Sharpening is done by reducing the thickness of the metal at the cutting edge, while maintaining the angle and shape of the bevel.

DETECTION OF A DULL CUTTING INSTRUMENT 1) Visibility of a reflection off the cutting edge. Sharp edge – not reflect light Dull edge – reflect light/ presence of a “glint”. 2) Obvious irregularities in the cutting edge 3) Won’t shave thumb nail. 4) Won’t cut tooth structure.

Instruments with dull cutting edge causes:- - More pain - Prolong operative time - Less controllable - Reduce quality and precision in tooth preparation Goal of sharpening instrument - Maintain and restore a knife like cutting edge - Preserve the shape and proportional dimensions of the instrument - Increase work efficiency of the

instrument