HAND CUTTING INSTRUMENTS

CONTENTS

INTRODUCTION HISTORY CLASSIFICATION MATERIALS USED HEAT TREATMENT OF STEEL DENTAL INSTRUMENT GAUGE INSTRUMENT DESIGN IDENTIFICATION OF INSTRUMENT BEVELS OF INSTRUMENT

CUTTING INSTRUMENT METHODS OF CLEANING STERLISATION OF HAND INSTRUMENTS HAND INSTRUMENTATION TCHNIQUES SHARPENING OF HAND INSTRUMENT CONCLUSION REFERENCES

CONTENTS cont….

INTRODUCTIONTerm “instrument” refers ‘to a tool, device or implement used for a

specific purpose or type of work.’

They can be used to examine,clean,cut,& restore teeth. The two main types are-

a.Hand instruments-which include a large group of instruments that are hand held when used.

b.Rotary instruments- are operated in a handpiece which in turn is hand held.

Cutting instrument generally implies, unless otherwise specified ,a hand held instrument used to cut, plane, or cleave tooth structure during the prepration of a cavity to receive a restoration or other treatment.

HISTORY OF HAND CUTTING INSTRUMENTS

When Dr.Jonathen Taft wrote his book of operative dentistry in 1868,cutting procedures on tooth enamel and dentin were carried out using thick bulky chisels and excavators. They were heavy-handled made up of wood, ivory & inferior metals and were as wide as 1\4 inch at the cutting edge .

Chisel was used to gain entrance to the carious dentin which was then removed by the hand excavators .

Access to some interproximal lesions was gained by seperation of the teeth with an assortment of wedges or mechanical seperators.

They were made of stainless steel and were difficult to keep sharp , the problem was partly solved at the end of nineteenth century by the use use of carborandum discs and stones.

With their large heavy handles and inferior metal alloys in their blades they were cumbersome, awkward to use and ineffective in

many situations.

There was no uniformity of manufacturing or nomenclature.Many dentists made there own hand instruments for specific needs.

With the subsequent development of the dental handpiece in 1871 there has been a drastic decline in the use of hand instruments. The present trend is to use replaceable bladed or abrasive instruments held in rotary hand pieces.

classificationOperative dental instruments as classified by CHARBENEAU-

1.Cutting instruments- a) Hand -Hatchets -Chisels -Hoes -Excavators -others b) Rotary -Burs -Stones -Disks Others

2. Condensing instruments a) Pluggers -Hand -Mechanical

3. Plastic instruments a) Spatulas b) Carvers c) Burnishers d) Packing instruments

4. Finishing and polishing instruments a Hand -Orangewood sticks -Polishing points -Finishing sticks

b.Rotary -Finishing burs -Mounted brushes -Mounted stones -Rubber cups -Impregnated disks

5.Isolation instruments a. Rubber dam b. Saliva ejector c. Cotton roll holder d Evacuating tips

6. Miscellaneous instruments a. Mouth mirrors

b Explorers c Probes d Scissors e Pliers f others

By Marzouk1)Excavators

a. Hatchet b .Hoe c. Spoon d .Discoid e. Cleoid

2)Chisels

a .Straight chisel b .Monoangle chisel c. Binangle chisel d. Triple angle chisel

3)Special forms of chisels

a) Enamel hatchet b) Gingival margin trimmer c) Angle former d) Wedelstead chisel e) Offset hatchet f) Triangular chisel g) Hoe chisel

Classification by Sturdevant

Cutting instruments:-

a. Excavators -Hoe -Angle former -Ordinary hatchet -Spoon excavator

b. Chisels -Straight chisel -Curved chisel -Enamel hatchet -Gingival margin trimmer

c. Others -Knives -Files -Discoid -Cleiod •

Pickards Classification (Based on usage)

1) Examining the mouth and teeth-

a. Mouth mirrors b. Probes c. Scalers

2) Cutting teeth and removing caries a. Excavators b. Chisels, hatchets and hoes 3) Placing and condensing restorative materials

a. Plastic instruments b. Condensers or pluggers

4) Carving and finishing instruments

5) Miscellaneous

MATERIALS USED FOR HAND CUTTING INSTRUMENT

1) STEEL - -An alloy of chromium-15-23%, carbon-0.7-1.1% iron-balance -Chromium reduces the corroding tendency by oxide layer deposition on its surface

ADVANTAGES DISADVANTAGES

-Carbon steel - sharpness - if unprotected corrodes. -if dropped fractures easily. - more sensitive to chemicals.-Stainless steel -superior corrosion - looses keen edge during resistance in most condition .

2) MONEL metal – -An alloy of nickel-67% copper-28% iron-5% -Markedly resistant to acids and super heated steam

use, much more quickly .

2) Nichrome-

-An alloy of nickel-60-80%

chromium12-20%

iron-0-26%

ADV - can be subjected to high degree of temperature.

does not oxidize easily.

DISADV -but does not readily maintain a sharp edge.

3) STELLITE-

-An alloy of cobalt- 65-90%

chromium -10-35%

tungsten,molybednum,iron - small quantities.

ADV - high resistance to action of acids.

- higher strength maintains cutting edge.

- high melting point . 4)TARNO-

-An alloy of chromium.

-used for manipulation of cements.

Heat treatment of steel

Hardening heat treatment - steel is heated to 15000 c in oxygen free environment and quenched immediately by plunging into cold water. - In this state steel is extremely brittle.

Tempering - is the process of making steel tougher and less brittle. - steel is heated to 1760 C for one hour and then plunged into cold salt water (or) mercury.

Annealing -also called softening heat treatment. - is the process of heating steel to dull or incipient redness & cooling slowly.

Temperature with corresponding colours produced during heating of steel

TEMPERATURE COLOUR USE

217°C-232°C

243°C

258°C

266° C

279° -299°C

Light yellow

Medium yellow

Brown yellow

Brown purple

Blue

Enamel chisel,burnisher

Excavators,

Scalers

Condensers.

Saws,shanks of instruments.

Spring temper

PARTS OF HAND CUTTING INSTRUMENTS

Parts of instrument

DESIGN CHARECTERISTICS OF HAND CUTTING INSTRUMENTS

Hand instruments regardless of use are composed of 3 parts-

1) Handle/ Shaft-for grasping the instrument. factors to be considered while handle selection- a.weight- hollow-increase tactile transfer. -solid-increase hand fatigue. b.diameter- small-decrease control,

increase fatigue. - large-restrict movement in inaccessible areas

c.serrations- knurled-maximize control. smooth-increase muscle fatigue.

SHANK The shank serves to connect the handle to the working end of the instrument They are normally smooth, round and tapered. Any angulation in the instrument is placed at the shaft.

Two Types of instruments

A) If the handle, shank and blade are all made of one piece of steel, the instruments are known as long handled instruments.

B) If the shank and blade or nib are separate from the handle and are intended to be screwed into it the instrument is known as a cone socket instrument.

BLADE / NIB

The working end of the cutting instrument is called the blade whereas the working end of the non-cutting instrument is called nib. Face is the end of the nib or working surface. It maybe plain or serrated. Cutting edge is the working part of the instrument. It is in the form of a bevel with different shapes.

- Blade angle is defined as the angle between the long axis of the blade and the long axis of the shaft.

- Cutting edge angle is defined as an angle between the margins of the cutting edge and the long axis of the shaft.

INSTRUMENT FORMULA1st no. -Indicates the width of the blade or primary cutting edge in tenths of a mm.

-2nd no. -Indicates the primary cutting edge angle. -Measured from a line parallel to the long axis of the instrument handle in clockwise centigrade -If the edge is located perpendicular to the blade then it is omitted.

-3rd no. - Blade length in mm.

-4th no. -Indicates the blade angle, relative to the long axis of the . handle in clockwise centigrade.

Example -Binangle hatchet-15-8-12( 3 unit formula) -Distal GMT-12-92-10-8(4 unit formula)

Dental Instrument Gauge Boley gauge is valuable for measuring instrument blades

condenser points, drills, burs, teeth, in comparing measurements, in restoring angles of teeth , in selecting artificial teeth.

The smaller gradation on the principle bar are in mm used to measure the length of the blade.

Gradations of the smaller bar is in 1/10th of mm and is used to measure width of the blade.

Circular head has 100 divisions-centigrades for measuring angles.

Method:- Place the instrument handle on the principle bar of the gauge, parallel with the lengthwise line and while keeping the blade parallel with one of the gradations of the circular head. This gives the angle of the blade with the shaft in centigrades.

Instrument Design Direct cutting and lateral cutting instruments

a. Single planed instruments:

- Force is applied in the same plane as that of the blade and handle. - They have curves or angles in the shank but in the same plane as the handle. - Used for direct and lateral cutting.

b. Double planed instrument:

- In lateral cutting instruments the force is applied at a right angle to the plane of the blade and handle. - They have a curved blade and are called double planed instruments. - Used only for lateral cutting.

Example:- GMT and spoon excavator.

Contra-angling:-

-To gain access many instruments have the shank bent at one or more points. - Accordingly, the working point is moved out of line with the axis of the handle. If this occurs more than 3mm from the handle axis the instrument becomes out of balance in lateral cutting motion and the force will be required to keep it from rotating.

- To solve this problem the working end is kept within 3mm from the axis of the handle .This principle of instrument design is called contra-angling.

- In addition to balance contra-angling also provides better operating acess and a clearer view in the field.

INSTRUMENT BALANCE &SHARPNESS

Thinner cross-section more pressure

more efficient cutting

Proper balance optimal cutting with minimal effort

IDENTIFICATION OF INSTRUMENTS

DIRECT CUTTING INSTRUMENTS

When the instrument is held with the cutting edge down and pointing away from the operator and if the bevel appears on the right side it is a right instruments

LATERAL CUTTING INSTRUMENTS

When the instrument is held with the cutting edge pointing away ,the instrument having the curve of the blade directed to the right it is a right instrument

BEVELS OF INSTRUMENT

- Cutting edge at right angle to the long

axis of the shaft.

- They can be:

a.Distally bevelled -if the angle at the junction of the blade and the shank are observed and if primary bevel is not seen it is distally bevelled .

b.Mesial bevelled /Reverse bevel -

1 ) SINGLE BEVELLED INSTRUMENTS-

2) BIBEVELLED INSTRUMENT

Blade is equally bevelled on both

sides. Ex - ordinary hatchet.

3) TRIPLE BEVELLED INSTRUMENT They have two laterally placed bevels

along with the bevel on the working end.

Has additional cutting potential. Ex - angle former.

4 ) 4 ) CIRCUMFERENTIALLY BEVELLEDCIRCUMFERENTIALLY BEVELLED INSTRUMENTSINSTRUMENTS

Usually occurs in double-planed instruments where the blade is bevelled all along the periphery.

Ex spoon excavator ,discoid, cleoid

ADVANTAGES OF HAND CUTTING INSTRUMENTS

Self-limited in cutting enamel, cut only enamel undermined by the loss of enamel.

No vibration or heat accompanies the cutting, making it painless and with no adverse effects to tooth tissues.

Most efficient means of precise intricate cutting.

Create the smoothest surface of all cutting instrument.

The longest life span of all cutting instruments.

CUTTING INSTRUMENTS

EXCAVATORS-

Designed for excavation and removal of carious dentine and for sharpening of internal parts of cavities.

hatchet excavators hoe excavators spoon excavators discoid cleoid

A) HATCHET EXCAVATOR

It is a chisel-bladed instrument with blade and cutting edge in plane with the long axis of the handle

Instrument formula- 3-2-28

USES-

1. Primarily on anterior teeth for preparing retentive areas.2. Sharpening internal line

angles in class I ,III,V

cavities.3. For delicate cutting

within preparation.4. Removing hard caries.

B) HOE EXCAVATOR

Has a cutting edge that is at right angle to the handle , like that of a chisel but the blade angulation is greater than 12.5° and nearly approaching right angle.

Instrument formula -4 ½-1 ½-22 USES- 1.planning tooth preparation walls 2.defining line angles in cl-III,V in DFG

3.To remove harder varities of caries.

4.Heavy bladed with contra-angled shanks used for enamel of posterior teeth.

3) SPOON EXCAVATOR

It is a modified hatchet with the cutting edge ground to a semi-circular circumferential bevel sharpened to a thin edge.

Instrument formula:-

a. Binangle spoon- 13-7-14 b. Triple angle spoon- 15-7-14

.

Uses

a. Excavation of caries.

b . Used for carving amalgam & direct wax patterns.

4) DISCOID SPOON

- They have a blade which is circular in shape with cutting edge extending around the periphery except where it joins the shank.

Disc like in shape.

uses Round shape for reducing

excess material

5) CLEIOD EXCAVATOR

Claw like in shape. Essentially a spoon excavator

except that the blade is curved to a point.

Uses

a. For carving occlusal anatomy

of amalgam.

b. Excavating decay from area of

difficult access.

2)CHISELSAre primarily used for cutting enamel and dentine.

They are grouped as-

chisel enamel hatchet gingival margin trimmer angle former wedelstaed chisel off-set hatchet triangular chisel hoe chisel jeffery hatchet

CHISEL-Has a blade that is either aligned with the handle, slightly

angled or curved from the long axis of the handle ,with the working end at right angle to the handle.

They are 4 types-

a) straight chisel- (12-7-0) straight blade in line with the handle and the shaft

b) monoangle- blade is at an angle to the shaft.

monoangle

c) Binangle chisel- (10-7-8)

makes 2 angulations with the shaft

Uses to remove unsupported enamel rods.

d) Triple angled chisel –

makes 3 angles in its shank

Uses for cleaving and planing the cavit walls and floor.

ENAMEL HATCHET

Enamel hatchet is a chisel similar in design to the ordinary hatchet except the blade is longer, heavier and bevelled only on one side.

Instrument formula- 10-7-14.

Uses:-

a) For splitting or cleaving undermined enamel in proximal cavities.

b) Smaller sizes used for primarily for anterior teeth and larger for posterior teeth.

GINGIVAL MARGINAL TRIMMER

It is a modified hatchet but differs from hatchet in that

a. cutting is at an angle other than 90°

b. has a curved blade. c. is a double planed instrument.

Uses:-

a. 100 and 75 pairs used to prepare steep gingival bevels for inlays

and onlays.

b. 90 and 85 pairs used for beveling gingival margin of amalgam

preparation.

c. 90 to 100 used to bevel the distal gingival margin.

.

d. 85 to 75 used to bevel the mesial gingival margin.

e. For bevelling or roundening axiopulpal line angles.

f. Accentuate retentive grooves.

g. To give reverse bevels

Identification:-Distal GMT:-When the cutting edge makes an acute angle with the edge of the blade farthest from the handle, it is a distal GMT.

Mesial GMT:- The cutting edge makes an acute angle nearest to the handle.

Distal GMT

ANGLE FORMER

Introduced by Woodbury.

Made by grinding the bevel at an 80-85° angle with the shaft thus creating a pointed and linear cutting edge.

Uses:- a. To accentuate line angles and

point angles in internal outline form especially for gold restorations.

b. Used for giving bevels and retentive features.

Bayonet angle former:- When their working blades are offset from the long axis of the shaft they are termed Bayonet angle former.

WEDELSTAEDT CHISEL

Straight chisel with slight vertical curvature in its shank.

It is paired. If the bevel is on the side of the blade towards the

curvature of the shank it called as the mesial and vice versa.

Mesial beveled:- Push motion Distal beveled:- Pull motion

Uses:- a. Cleaving undermined enamel. b. Shaping walls.

Cutting motions:- a. Vertical b. Right c. Left

OFFSET HATCHET

regular hatchet except the whole blade is rotated a quarter of a turn forward or backward along its long axis.

Right and left pairs. The whole blade is rotated either forward or backward.

Uses:- 1. To create and shape specific

angulation of cavity walls. 2.Planning buccal & lingual

wallof posterior teeth.

TRIANGULAR CHISEL

• This chisel has a blade which is triangular in shape and the base of the triangle away from the shaft.

• Terminal cutting edge is like that of a straight chisel.

HOE CHISEL

• It is similar to the hoe excavator but has a

sturdier blade.

JEFFREY HATCHET

Similar to off angle hatchets but their blades are more nearly at right angles to the shaft.

It is of 3 types-(depending on the bevel angulation.) a. Inside cutting b. Outside cutting c. Square ended

Uses:- To prepare mandibular anterior

cavities from the lingual side of the teeth.

FILES

USES

1.for margination of restorations when knives and carvers do not suffice.

2.to trim excess restorative materials particularly at the gingival margins.

Nibs of the file can be:-

a. Foot shaped b. Parallelogram shaped c. Hatchet shaped

If serrations on the face of the nib are directed away from the handle it is used as a push file, if it is directed towards the handle it is a pull file.

KNIVES

Nibs carry knife edged faces on one side only.

Uses:- a) Used for trimming excess restorative

materials on the gingival, facial or lingual margins of proximal restoration.

b) Manipulation of restorative material inter proximally and gingivally.

c) Contouring the surface of class 5 restorations.

b. Wilson’s knife:- Nib is in a plane at at right angles to the shaft and so can be introduced inter proximally for proximal and gingival manipulation of restorative materials.

Examples:-

a. Black’s knives :- Nibs are almost at a right angle to the handle, with the cutting edge away from the handle in one set (push cutting) and towards the handle in one set (pull cutting).

c. Steins knife It has a trapezoid nib and is used for direct filling gold contouring and margination

METHODS OF CLEANING

Instruments that touch mucosa or penetrate tissue should be cleaned and then sterilized before reuse.

Two methods have been proposed:-

a. Hand scrubbing b. Ultrasonic cleaning Adv.-

1 to 9 times more effective.

COMPARISON OF CLEANING METHODSMETHODS ADVANTAGES DISADVATAGES

HAND SCRUBBING

1.Effective if performed properly

1.Enhances chances for operator injury.

2.Enhances spread of contamination through splatter.

3.Labour-intensive.

4.Need proper care of scrub brush

ULTRASONIC CLEANING

1.Safer than hand scrubbing.

2.Effectively cleans all instruments.

3.Reduces chances for spread of contaminants.

4.Allows for more efficient use of staff time.

1.Microorganisms may accumulate in cleaning solution.

STERILIZATION OF HAND INSTRUMENT

Accepted methods of sterilization are:-

Steam pressure sterilization (autoclave)

Chemical vapour sterilization (chemiclave)

Dry heat sterilization (dry clave)

Ethylene oxide sterilization

For wrapped instruments it can be at 134°C at 30lb of pressure for

7 min.

But sterlization by autoclaving of carbon steel instrument can cause

- discolouration

- rust

- corrosion

AUTOCLAVE For a light load of instruments the autoclave cycle is run at 121°C at 15lbs of pressure for 15 mins.

STEAM PRESSURE STERLIZER(AUTOCLAVE)

2) CHEMICLAVE

Chemical vapor pressure sterilizer operates at 131°C and 20 lb of pressure and has a sterilization time

of 30 min.

PRECAUTION-

Instruments should be absolutely dry when loaded or else sterilization will not be complete.

Chemiclave

DRY HEAT OVEN

Short cycle dry heat oven

- operates at 370-375°F with the sterilization time of - a.6 minutes for unwrapped

b.12 minutes for wrapped instruments

- It is a mechanical convection oven that circulates with a fan or a blower.

COX RAPID HEAT TRANSFER DRY HEAT STERLIZER

ETHELENE OXIDE STERLIZER

Best method for sterilizing complex instruments & delicate articles.

Operates at

a. elevated temperature below

100°C for several hours

b. room temperature but

overnight.

PRECAUTION

Plastic or porous material require areation for 24hours before safe use

NEWER METHODS UNDER INVESTIGATION

a. Microwave oven:- Limitations in sterilizing metal items

- Damaging effect on machine

- Not reaching all sides of the instrument.

b. Ultraviolet light:-

Limitations are

-Not effective against RNA viruses

(HIV) and bacterial spores

-Poor penetration of oil and debris.

METHODS

STANDARD STERLIZATION CYCLE

ADVANTAGES PRECAUTIONS SPORE TESTING

STEAM

AUTO - -CLAVE

20 min at 250°F (15psi)

1.Time efficient

2.Good penentration

1.Damages plastic or rubber handles.

2.Corrodes non stainless steel items.

3.Use of hard water may leave deposits.

BACILLUS STEAROTHERMOPHILUS, STRIPS,VIALS OR AMPULES.

CHEMIC -AL VAPOU-RS

20 min at 270°F

1Time efficient

2.Nocorrosion 3.Items dry quickly after cycle.

1.May damage rubber & plastic items.2Predry instruments or dip in special solutions .3.Provide adequate ventilation.

BACILLUS STEAROTHERMOPHILUS, STRIPS

COMPARISON OF HEAT STERLIZATION METHODS

METHODS

STANDARD STERLIZATION CYCLE

ADVANTAGES PRECAUTIONS SPORE TESTING

DRY HEAT OVEN

60-120min at 320°F

1.No corrosion.

2.Large capacity per cost

3.Items are dry after cycle

1.Longer sterlization time.

2.Door shouldn’t be open before cycle ends.

3.Predry instruments.

Bacillus subtilis strips

RAPID HEAT TRANSFER

12min at 375°F(for wrapped)

6min at 375 °F(for unwrapprd items)

1.No corrosion.

2.Short cycle.

3.Items are dry after cycle.

1.Door shouldn’t be open before cycle ends

2.Small capacity per cost.

3.Unwrapped instruments become contaminated after cycle.

Bacillus subtilis strips

There are 5 grasps used with hand instrument-

HAND INSTRUMENT TECHNIQUES

standard pen grip

- Instrument is held b/w thumb and index finger and medial part of

middle finger is used to control its movements

- not commonly used.

-most commonly used grasp.

- the pads of the thumb, index and middle fingers contact the instrument while the tip of the ring or little finger are placed on the near by tooth surface of the same arch as a rest.

2 MODIFIED PEN GRASP

- the pad of the middle finger is placed near the topside of the instrument and by this finger, working with wrist and forearm ,cutting and cleaving pressure is generated on the blade. - useful in mandibular arch

2 ) INVERTED PEN GRASP

Here the finger position are the same as modified pen grasp however the hand is rotated so that the palm faces more towards the operator.

Used mostly for tooth preparation of anterior teeth.

INVERTED PEN GRASP .Palm faces more towards operator.The rest is similar to that shown for modified pen grasp.

3 PALM AND THUMB APPROACH

• Handle is placed in the palm of the hand and grasped by all the fingers ,while the thumb is free of the instrument and the rest is provided by supporting the tip of the thumb on a nearby tooth

Palm – and thumb grasp.This grasp has limited use, such as preparing incisal retention in a class iii preparation on a maxillary incisor .The rest is tip of the thumb on tooth in the same arch.

Used when operating upon maxillary teeth.

Provides heavy force over a limited range of movement but with greater control than the pen grip.

4 MODIFIED PALM AND THUMB GRASP

Used when it is feasible to rest the thumb on the teeth being prepared or the adjacent teeth.

The handle of the instrument is held by all fingers whose pads press the handle against the distal area of the palm.

Used in maxillary arch, best adapted when approaching

from rear chair side position. Modified palm-and –thumb grasp. This modification allows greater ease of instrument movement and more control against slippage during thrust stroke compared to palm-and- thumb grasp .The rest is tip of thumb on tooth being prepared or adjacent tooth. Note how instrument is braced against pad and end joint of thumb.

RESTS AND GAURDSProper instrument grasp must include a firm rest to steady the hand

during the operative procedure.

a. Rests for modified pen or inverted pen grasp:- The ring finger is placed on a tooth or teeth in the same arch as

close to the operating site as possible.

b. Rests for palm and thumb grasp:- The tip of the thumb is placed on the tooth being operated on, on

an adjacent tooth or a convenient area of the same arch.

c. Indirect rests. Control gained by using opposite hand resting on a stable oral structure.

Gaurds:- They are used to protect soft tissues

from contact with sharp cutting or abrasive instruments.

SHARPENING OF HAND INSTUMENTS

• Instruments with dull cutting edges cause more pain, prolong operative

time, are less controllable and reduce quality and precision in tooth

preparation. It is therefore essential that all cutting instruments be

sharp.PRINCIPLES OF SHARPENING

a Done only after the instrument has been cleaned and sterilized.

b. Proper bevel angle and desired angle of the cutting edge to the blade should be maintained.

c. Light pressure against the stem should be used to minimize frictional heat.

d. Rest/guide should be used

e. Minimal material from the blade should be removed.

f. Unleveled side of the blade should be lightly honed.

g. After sharpening, the instruments have to be resterilized.

h. Sharpening stone should be kept clean and free of metal cutting.

SHARPNESS TEST

A. PLASTIC STICK TEST

Sharpness of an instrument can be tested by lightly resting the cutting edge on a hard plastic surface. If the instrument digs in during an attempt to slide the instrument forward over the surface the instrument is sharp, if it slides it is dull.

B. VISUAL INSPECTION

• To test sharpness instrument is held under a magnifying glass in bright light ,& rotated until the edge is facing the light

• If light is reflected of the edge then the instrument is dull

MECHANICAL TECHNIQUES

a. RECIPROCATING HONING SHARPNER

The blade is placed against the steady rest and proper angle of the cutting edge of the blade is established before starting.

Trace of metal debris on the face of a flat hem along the length of the cutting edge is indication that the entire cutting edge is contributing the hem.

b. HANDPIECE STONES

are used for instruments with curved blades, especially for inside curves of the blade.

-They are mounted silicon carbide and aluminium oxide stones with straight and contra-angled handpiece.

-

Disadv.:-

a. It is difficult to produce a flat cutting surface. b. Inconsistent results due to speed variables. c. Lack of rests and guides

The handpiece should be run at a low speed with the instrument held lightly in a modified pen grasp and the little fingers of each hand touching each other acting as a rest.

Overheating is avoided and the use of lubricant or coolant is desireable.

STATIONARY STONE TECHNIQUES

- Stone should be atleast 2” wide and 5” long - Most frequently used sharpening equipment consists of a block or stick of

abrasive material called stone. -Stationary stones are also called oilstones since oil is a commonly used

lubricant.

Available as:- a. Fine grit, for final sharpening b. Grained, for curved edges c. Cylindrical, for concave edges d. Tapered, for curved edges

Stones are made up of natural or synthetic materials like:- a. Arkansas stone (microcrystalline quartz) b. Silicon carbide c. Aluminium oxide d. Diamond

SHARPENING OF CHISELS, HATCHETS AND HOES

a. The instrument is held in modified pen grasp.

b. The blade is placed perpendicular to the stem.

c. The correct bevel is established.

d. The instrument is moved back and forth with the force from the shoulder coming along the stone or the stone is moved back and forth while maintaining a constant position.

SHARPENING OF DISCOID/CLEOID

Similar to excavator , to hone the flat inside surface of the blade ,a small cylindrical stone is passed back & froth over the surface.

SHARPENING OF GMT

• It requires more orientation of the cutting edge, palm

and thumb grasp is used for sharpening.

SHARPENING OF AMALGAM/GOLD KNIFE

• a. Blade is placed on the stone with the fulcrum of the blade and shank immediately over the edge of the stone.

• b. The blade is tilted to an acute angle with the stone, and the stroke is straight along the stone and towards the edge of the blade.

SHARPENING OF SPOON AND DISCOID EXCAVATORS

a. spoon is placed at the far end of the stone with the handle pointing towards the operator.

b. instrument is pulled along the stone towards the operator, the handle is rotated gradually away from the operator until it is pointing away from the operator at the end of the stroke.

c. same motion is repeated till the edge is honed.

d. To hone the flat inside surface of the blade, a small stone is passed back and forth over the surface.

Instrument maintenance cycle

5. DELIVERY

Place on intended work surface.

Open wrap and retain as sterile work surface cover.

Open cassette & place the lid under cassette bottom.

Inspect indicator strip & use

4. STERILE STORAGE

Place wrapped cassettes in storage area.

Cassettes can be stored upto 30 days, after that repackage in new wrop and sterliize.

1.CHAIRSIDE

After use,place instruments in procedural order.

Wipe off material debris.

Dispose of cotton goods.

Place lid on cassettte.2 CLEANING

Place detergent sol.&cassettes in ultrasonic unit

Place lid on ultrasonic unit.clean for 16min.

Remove cassettes..Rinse thoroughly under warm water.

Stand vertically to dry.

3.STERLIZATION

Open cassettes & inspect instruments visually.

Wrap instrument in autoclave & seal with monitor tape.

Place & process the cassettes

Instrument maintenance cycle

CONCLUSION

REFERENCES1.PRINCIPLES AND PRACTICES OF OPEERATIVE DENTISTRY-GERALD .T.CHARBENAU III EDITION.

2.OPERATIVE DENTISTRY MODERN THEORY& PRACTICES-M.A MARZOUK,A.L SIMONTON,R.D GROSS I EDITION.

3.FUNDAMENTAL OF OPERATIVE DENTISTRY CONTEMPORARY APPROACH-JAMES.B.SUMMIT,J WILLIAM ROBIN,RICHARD SCHWARTZ II EDITION

4.ART & SCIENCE OF OPERATIVE DENTISTRY-STURDEVANT, IV EDITION

5.OPERATIVE DENTISTRY-GILLMORE,LUND BALES,VERNETTI IV EDITION

6.ATLAS OF OPERATIVE DENTISTRY-WILLIAM .W .HOWARD, II EDITION

7.TEXTBOOK OF OPERATIVE DENTISTRY-BAUM ,PHILLIPS,LUND, III EDITION